United States Office of Air Quality EPA 456/K-01-001

Environmental Protection Planning and Standards July 2001

Agency Research Triangle Park, NC 27711

Air

EPA-456/K-01-001

July 2001

ULTRAVIOLET AND ELECTRON BEAM (UV/EB)

CURED COATINGS, INKS AND ADHESIVES

Prepared by

Clean Air Technology Center (MD-12)

Information Transfer and Program Integration Division

Office of Air Quality Planning and Standards

U.S. Environmental Protection Agency

Research Triangle Park, North Carolina 27711
ii

DISCLAIMER

This report has been reviewed by the Information Transfer and Program Integration

Division of the Office of Air Quality Planning and Standards, U.S. Environmental Protection

Agency and approved for publication. Approval does not signify that the contents of this report

reflect the views and policies of the U.S. Environmental Protection Agency. Mention of trade

names or commercial products is not intended to constitute endorsement or recommendation for

use. Copies of this report are available form the National Technical Information Service, 

U.S. Department of Commerce, 5285 Port Royal Road, Springfield, Virginia 22161, telephone

number (800) 553-6847.
iii

FORWARD

The Clean Air Technology Center (CATC) serves as a resource on all areas of

emerging and existing air pollution prevention and control technologies, and provides public

access to data and information on their use, effectiveness and cost. In addition, the CATC will

provide technical support, including access to EPA’s knowledge base, to government agencies

and others, as resources allow, related to the technical and economic feasibility, operation and

maintenance of these technologies.

Public Access and Information Transfer

INTERNET / World Wide Web Home Page

http://www.epa.gov/ttn/catc/

Communications

CATC Info-Line: (919) 541-0800 (English)

CATC/CICA Info-Line: (919) 541-1800 (Spanish)

FAX: (919) 541-0242

E-Mail: catcmail@epamail.epa.gov

Data Resources

& RACT/BACT/LAER Clearinghouse (RBLC)

Query, view and download data you select on 

- Source Specific Technology Applications

- Air Pollution Regulatory Requirements 

& CATC PRODUCTS

download technical reports, cost information and software 

Related Programs and Centers

& CICA - U.S.-Mexico Border Information Center on Air Pollution / 

Centro de Información sobre Contaminación de Aire Para la Frontera 

entre EE.UU. Y México

& SBAP - Small Business Assistance Program

& International Technology Transfer Center for Global Greenhouse Gasses
iv

ACKNOWLEDGMENTS

This technical bulletin was made possible through the diligent and persistent efforts of

Lyndon Cox, Senior Environmental Employee with the Clean Air Technology Center (CATC). 

Lyndon did an exceptional job identifying information sources, gathering relevant data and putting

this bulletin together. The CATC also appreciates the helpful and timely comments and

cooperation of the following peer reviewers:

Dr. Alexander Ross, RADTECH International North America

Paul Almodovar, Coatings and Consumer Products Group, Emission Standards Division, Office

of Air Quality Planning and Standards, Office of Air and Radiation, U.S. EPA

Rhea Jones, Coatings and Consumer Products Group, Emission Standards Division, Office of Air

Quality Planning and Standards, Office of Air and Radiation, U.S. EPA

Candace Sorrell, Emissions, Monitoring and Analysis Division , Office of Air Quality Planning

and Standards, Office of Air and Radiation, U.S. EPA

Charles Darvin, Emissions Characterization and Prevention Branch, Air Pollution Prevention and

Control Division, National Risk Management Research Laboratory, Office of Research and

Development, U.S. EPA

In addition, the CATC thanks the individuals, companies and institutions who supplied

information on Ultraviolet and electron beam curing technology used to prepare this Technical

Bulletin. Contributors are indicated in the REFERENCES section of this bulletin.
v

TABLE OF CONTENTS

TOPIC Page

DISCLAIMER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

FORWARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

TABLE OF CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

ACRONYMS USED IN THIS REPORT ................................... x

INTRODUCTION .................................................... 1

BACKGROUND ..................................................... 2

PART I: THE BASICS ........................................... 3

WHAT ARE UV/EB-CURED MATERIALS? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Review of Conventional Coatings, Inks and Adhesives ................... 4

UV/EB-Cured vs. Conventional Coatings, Inks and Adhesives ............ 5

WHERE ARE UV/EB-CURED MATERIALS USED? . . . . . . . . . . . . . . . . . . . . . . 6

DO UV/EB FORMULATIONS USE CONVENTIONAL RESINS?............ 9

HOW ARE UV/EB MATERIALS CURED? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

DO UV/EB-CURED MATERIALS NEED SPECIAL EQUIPMENT? . . . . . . . . . 12

Curing Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Printing and Roller Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Spray Painting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Other Application Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

PART II: THE DETAILS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

UV/EB RADIANT ENERGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

HOW IS UV/EB RADIANT ENERGY GENERATED? . . . . . . . . . . . . . . . . . . . 15
vi

TABLE OF CONTENTS (continued)

TOPIC Page

UV Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

EB Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

WHAT IS UV/EB IONIZING RADIATION? . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

HOW DEEPLY DOES IONIZING RADIATION PENETRATE? . . . . . . . . . . . 24

UV Ionizing Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

EB Ionizing Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

UV/EB-CURING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

HOW DO UV/EB COATINGS, INKS AND ADHESIVES FORM? . . . . . . . . . . 26

Free Radical Polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Cationic Polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Crosslinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

HOW DO PHOTOINITIATORS WORK? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

DOES PRODUCTION RATE DEPEND ON COATING THICKNESS? . . . . . . . 29

WHY HAS THERE BEEN GROWTH IN 3D CAPABILITIES? . . . . . . . . . . . . . . 30

HOW IS EXTENT OF CURING MEASURED? . . . . . . . . . . . . . . . . . . . . . . . . . . 31

IS THERE ANYTHING ELSE THAT AFFECTS CURING? . . . . . . . . . . . . . . . . 33

PART III: EMISSIONS, HEALTH AND SAFETY . . . . . . . . . . . . . 34

WHAT AIR POLLUTANTS ARE EMITTED FROM UV/EB-CURED

MATERIALS? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

VOC Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Fine Particulate Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

HAP Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Odorous Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Ozone and N02 Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
vii

TABLE OF CONTENTS (continued)

TOPIC Page

HOW ARE EMISSIONS FROM UV/EB-CURED MATERIALS MEASURED? . 36

WHAT ABOUT WORKER HEALTH AND SAFETY? . . . . . . . . . . . . . . . . . . . . 37

What Health and Safety Concerns Does UV/EB Radiant Energy Present? . . . 37

How Can Workers Be Protected Against UV/EB Ionizing Radiation? . . . . . . 38

What Health and Safety Concerns Do Hazardous Components In

UV/EB-Cured Materials Present? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

What About Worker Hygiene? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

COST CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

ARE UV/EB-CURED MATERIALS MORE EXPENSIVE THAN

CONVENTIONAL COATINGS, INKS AND ADHESIVES? . . . . . . . . . . . . . . . 46

SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

WHAT ARE THE ADVANTAGES OF USING UV/EB-CURED

COATINGS, INKS AND ADHESIVES? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

WHAT ARE THE DISADVANTAGES OF USING UV/EB-CURED

COATINGS, INKS AND ADHESIVES? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

GLOSSARY OF TERMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

APPENDIX A: ULTRAVIOLET AND ELECTRON BEAM RADIATION 

VS. RADIOACTIVITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

APPENDIX B: EXAMPLES OF UV/EB COATING AND INK USE . . . . . . . . . . . B-1

APPENDIX C: EPA METHOD 24: DETERMINATION OF VOLATILE 

 MATTER CONTENT, WATER CONTENT, DENSITY, VOLUME 

 SOLIDS, AND WEIGHT SOLIDS OF SURFACE COATINGS . . . C-1
viii

TABLE OF CONTENTS (continued)

TOPIC Page

APPENDIX D: DEFINITION OF VOLATILE ORGANIC COMPOUNDS (VOC) D-1

APPENDIX E: HAZARDOUS AIR POLLUTANTS (HAP) . . . . . . . . . . . . . . . . . E-1

FIGURES

1. General Domains of the Electromagnetic Spectrum from Gamma Radiation to 

Television and Frequency Modulated (FM) Wavelengths .............. . 5

2. UV Mercury Arc Lamp ........................................ 16

3. Microwave- Excited Bulb with Generator . .......................... 17

4. UV Light reflectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5. Spectrum of UV from a Mercury Vapor Lamp . . . . . . . . . . . . . . . . . . . . . . 19

6. Dichroic Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

7. Schematic of Electron Gun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8. Free Radical Polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

9. Cationic Polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

10. An Example of Crosslinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

11. Schematic of Optic Fiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

12. UV Coatings - Now used for Packaging Chocolates ................. 36

13. Examples of Safety Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

14. Presses with UV-Curing Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
ix

TABLES

1. UV/EB COATING, INK AND ADHESIVE APPLICATIONS . . . . . . . . . 7

2. RADIATION-CURABLE MONOMERS in 1991 . . . . . . . . . . . . . . . . . . 10

3. FAMILIES OF RADIATION-CURABLE MONOMERS IN 1999 . . . . . 11

4. PERMISSIBLE EXPOSURE LIMITS OF RADIATIONCURABLE MATERIAL IN 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5. PERMISSIBLE EXPOSURE LIMITS (PEL) FOR ORGANIC SOLVENTS 42
x

ACRONYMS USED IN THIS REPORT

3D Three Dimensional

ACGIH American Conference of Government Industrial Hygienists

AFP Association for Finishing Processes (an affiliate of SME)

AIM Architectural, Industrial and Maintenance

ASTM American Society of Testing Materials

C Centigrade

CAS Chemical Abstract Service

CATC Clean Air Technology Center

CD Compact Disk

CERCLA Comprehensive Environmental Response, Compensation and

Liability Act

CFR Code of Federal Regulations

cm Centimeter

cm2 Square Centimeters

cm3 Cubic Centimeters

DVD Digital Video Disk

EB Electron Beam

EPA U.S. Environmental Protection Agency

FDA U.S. Food and Drug Administration

FM Frequency Modulated

fpm Feet per minute

Gy Gray unit of energy absorption, equals one Joule per kilogram

HAP Hazardous Air Pollutants

hr Hour

HVAC Heating, Ventilating and Air Conditioning Equipment

in2 Square Inches 

IR Infrared

kg Kilogram

LAER Lowest Achievable Emission Rate

LEL Lower Explosive Limit
xi

MBTU Millions of British Thermal Units

mm millimeters

MSDS Material Safety Data Sheets

NCS New Chemical Substance

NFPA National Fire Protection Association

nm Nanometers

NTIS National Technical Information Service, U.S. Department of

Commerce

OSHA Occupational Safety and Health Administration

P2 Pollution Prevention

PEL Permissible Exposure Limit

PMN Premanufacturing Notice

R Roentgen

REM Roentgen Equivalents for Mankind

SAMPE Society for Advancement of Material and Process Engineering

SME Society of Manufacturing Engineers

Tg Glass Transition Temperature

TV Television

TWA Time Weighted Average

TSCA Toxic Substance Control Act

UV Ultraviolet

VOC Volatile Organic Compounds

WEELS Workplace Environmental Exposure Levels

Z Atomic Number
xii

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1

ULTRAVIOLET AND ELECTRON BEAM (UV/EB)

CURED COATING S, INKS AND ADHESIVES

INTRODUCTION

The use of ultraviolet and electron beam (UV/EB) cured coatings, inks and adhesives has

increased dramatically over the last decade. Currently, this pollution prevention (P2) technique

is used in a wide variety of coating, printing and unique product applications. This Clean Air

Technology Center (CATC) Technical Bulletin provides basic information on UV/EB

technology and how it has advanced since the Control Technology Center (CATC predecessor)

published "Radiation-Curable Coatings" (EPA-600/2-91-035) in 1991. 

Increasing numbers of coating and printing facilities are using or considering UV/EB

technology because it is effective and profitable for them to do so. In "Radiation-Cured

Coatings," three reasons were given for this: (1) a 75-90% energy savings; (2) a 50-75% savings

in floor space; and, (3) higher production rates. All three reasons are still valid and the

advantages may be even greater today. UV/EB-curing units are significantly more energy

efficient and compact than thermal drying/curing systems that are used with conventional

coatings, inks and adhesives. Also UV/EB-curing is extremely fast - almost instantaneous to a

few seconds at most. Because UV/EB systems emit only very small amounts of volatile organic

compounds (VOC; see Appendix D) and virtually no hazardous air pollutants (HAP; see

Appendix E), they generally require no add-on air pollution control equipment and are

considered environmentally friendly. In fact, the South Coast Air Quality Management District

in California classifies UV/EB coating and printing applications as “Super Clean Technology”

and has eliminated or minimized air pollution permitting procedures for facilities using this

technology.

UV/EB materials cure almost instantaneously when exposed to UV/EB radiant energy

(i.e., UV/EB radiation). Manufacturers of UV/EB equipment include shielding and safety

interlocks in their equipment that adequately protect workers from exposure to UV/EB radiant

energy. However, much confusion exists concerning worker safety. The term “radiation” has

been applied to many different types of energy sources that individually present significantly

different health and safety issues. For example, the term has been applied to nuclear radiation,

radioactivity, solar radiation, UV radiation, EB radiation, microwave radiation, fluorescent

lamp radiation, computer monitor radiation, television (TV) set radiation, TV and radio

broadcast radiation, and even illumination radiating from incandescent lamps. The unifying

attributes in all of these “radiation” sources are that energy (in some form) is emitted from a

source, propagated radially along a line-of-sight, and absorbed. However, the effects of these

various forms of “radiation” on humans are very different and depend on the type and source of

the energy. Because over-use and misuse of the term “radiation” has and continues to cause

confusion, we will use the term “UV/EB radiant energy” to describe the “radiation” that cures

UV/EB material. See the UV/EB Radiant Energy section of this report for more detailed
2

information on that topic. Additional information can be found in Appendix A, Ultraviolet and

Electron Beam Radiation vs. Radioactivity.

When we refer to UV/EB material in this Technical Bulletin we are speaking of UV/EB-cured

coatings, paints, inks, adhesives, and similar products in general. We use the name of the

specific type of material (e.g., coating, ink, etc.) when information pertains to only that

material. Trade-names are not used because they are not descriptive of the chemistry of the

materials involved and might be misconstrued as a recommendation.

To fully understand and appreciate UV/EB technology and its advantages we need to consider

organic chemistry, physics, engineering, manufacturing processes and cost accounting. This

Technical Bulletin tries to bring all of these perspectives together. 

BACKGROUND

Use of radiant energy cured coatings dates back at least 4,000 years. Ancient Egyptians used a

type of UV coating that cured when exposed to sunlight in preparing mummies (AFP/SME,

1986) 30 Also, an asphalt-based oil coating that polymerized upon exposure to solar radiation

was used by ancient Egyptians as a sealant for ships (Decker, 1987).30

In the modern era, scientific interest in developing UV/EB-cured systems began in the 1940's. 

At that time, the first patent was granted for an unsaturated polyester styrene printing ink that

polymerized under UV exposure. One of the first attempts at applying UV/EB-cured systems to

manufacturing was made in the late 1960's, but successful commercial application did not evolve

until the early 1970's. The publicized driving forces behind development of commercially viable

systems were the energy crisis of 1974 and growing environmental concerns about VOC

emissions resulting from conventional thermal-cure systems. However, the primary motivations

for use of UV/EB-cured systems were and still are improved product performance and increased

productivity.

Early applications of UV/EB-cured systems were limited to flat sheets, mainly in the wood

products and printing industries. Radiant energy cured processes of that time were limited by

the need for a line-of-sight energy source. Starting in 1974, UV-curable inks and varnishes

were used for decorating aluminum beverage cans. Improvements in plant engineering, such as

rotating conveyors, multiple UV sources and adjustments to curing equipment, have allowed

three-dimensional (3D) applications of UV/EB-cured materials. In addition, advances in

polymer science have provided a wide variety of UV/EB-cured materials that can exhibit

characteristics required by the end-user in specific applications.
3

PART I: THE BASICS

This section summarizes basic information on UV/EB materials, including their use and

application. A more comprehensive discussion of important technical, safety and regulatory

issues is presented in “PART II: THE DETAILS” section of this report. A number of terms are

introduced that may not be familiar to you. To help you, a glossary of terms is provided at the

end of this report. Terms included in the glossary are in BOLD print within the body of the

report. Acronyms also are used for many terms or complex names. A list of acronyms is

provided at the front of this report, immediately after the table of contents.

WHAT ARE UV/EB-CURED MATERIALS?

UV and EB materials cure (polymerize) when exposed to UV and EB radiant energy,

respectively. Virtually all components of a UV/EB formulation become a solid part of a cured

coating, ink or adhesive. Generally, only small amounts of VOC may be emitted. For UV/EB

materials, curing means the interaction of liquid molecules (monomers, oligomers and

photoinitiators) to form polymers. This curing process is known as polymerization. It forms

long molecular chains that are the carbon backbone for a polymer molecule. After

polymerization the UV/EB-cured material is a solid, consisting of pigments and polymer

molecules that may be tangled together and interconnected by crosslinks.

Conventional VOC/solvent borne and waterborne coatings, inks and adhesives use thermal

energy to evaporate volatile components (i.e., organic solvent/VOC and/or water) and to cure. 

As a result, most of the volatiles in a conventional coating, ink or adhesive are emitted to either

a control device or the atmosphere. Only the remaining non-volatile part in a conventional

material actually cures to form a final coating, printing or adhesive that remains on a substrate. 

Some degree of polymerization may take place in the cure of a conventional material. The

amount of polymerization that occurs during the cure of a conventional material (as opposed to

polymerization/prepolymer formation that occurs during the paint/ink/adhesive manufacturing

process) varies depending on the type of material. For example, virtually no polymerization

occurs when curing a conventional lacquer; however, polymerization would be a critical

process when curing a conventional urethane, epoxy, or acrylic. 

Since you are probably more familiar with conventional coatings, inks and adhesives and how

they are used, it may be helpful to compare UV/EB materials to conventional materials. So, we

will spend a little time here reviewing how conventional coating, ink and adhesive systems

work before elaborating on UV/EB coatings, inks and adhesives.
4

Review of Conventional Coatings, Inks and Adhesives

Conventional oil/solvent based and waterborne coatings, inks and adhesives are evaporative

systems. They use suitable partially pre-polymerized monomers (alkyd, acrylic, epoxy, silicone,

etc.) and pigments dispersed in a solvent. These pre-polymers must further polymerize and

cross-link during the cure to become solids. 

Conventional pre-polymers are formed by a chemical condensation reaction at elevated

temperatures. This reaction occurs at a chemical plant or coating, ink or adhesive

manufacturing facility, and not during the cure. Just before the pre-polymer gets long enough to

form a gel, the temperature is reduced and the pre-polymer is dispersed in either an organic

solvent or water. The organic solvent is usually VOC and often accounts for more than half of

the volume of liquid coating. Water accounts for a similar fraction of the volume of waterbased coatings. Some conventional coatings even contain HAP. 

When conventional materials are applied and the organic solvent or water evaporates, prepolymerized resin molecules are able to contact each other. Solidification of the coating occurs

as the pre-polymer further proceeds in its polymerization by a chemical reaction. This is a

relatively slow process because the temperature is now much lower than it was in prepolymerization and, in fact, it is a process that never ends. You may have observed that

conventional paints thicken in storage (even without evaporation), change their surface finish

and shrink over a period of years. 

For lacquers, solvent can be much more than half of the final volume of coating as applied. 

Lacquers simply solidify upon evaporation of the solvent. They are more fully polymerized

during their manufacture then other conventional coatings and no further polymerization is

needed when they are applied. However, there is no crosslinking and they melt or mar easily. 

They shrink from loss of solvent and not because of further polymerization.

Conventional materials must be applied with sufficient air flow (ventilation) to keep the solvent

concentration in air below a quarter of the Lower Explosive Limit (LEL). This is required by

the National Fire Protection Association (NFPA) and the Occupational Safety and Health

Administration (OSHA). For spray applications, air flow of either 100 feet per minute (fpm) or

60 fpm (for electrostatic deposition) through the area in which vapors are generated is required. 

In addition to explosion/fire safety issues, there also are health effects issues for humans that

breathe solvent vapors. 

Conventional materials use infrared (IR) radiant energy (i.e., heat) to cure. IR energy is

emitted naturally from everything. It is electromagnetic radiation with a wavelength between

1000 nm and 11,000 nm. Visible light is electromagnetic radiation with wavelengths from 400

nm to 700 nm. Microwaves are electromagnetic radiation with wavelengths in meters (See

Figure 1). IR energy is sensed as radiant heat and its wavelength is based upon temperature. 

Heat is used to evaporate organic solvent or water and to accelerate polymerization. 
5

Figure 1: General Domains of the Electromagnetic Spectrum from Gamma

Radiation to Television and Frequency Modulated (FM) Wavelengths

At ambient temperatures, evaporation and polymerization can take from hours to days. Thermal

ovens can reduce evaporation and polymerization time to minutes. However, thermal ovens are

bulky, take up considerable floor space, and consume large amounts of energy because they

must heat the air flow through the oven, in addition to heating the coating, ink, or adhesive and

substrate.

UV/EB-Cured vs. Conventional Coatings, Inks and Adhesives 

 

UV/EB materials consist of pigments and the same monomers and oligomers that react to form

polymers in conventional coatings, but without being subjected to pre-polymerization. 

Oligomers are created by joining about 3 to 5 monomer molecules, but this is not to be

confused with pre-polymerization. Acrylic groups or vinyl ether groups are reacted with

monomer and/or oligomer molecules in a UV/EB material, and become side-branching or

pendant groups to the carbon backbone. These are referred to as functional groups because

they are more reactive and, therefore, require less increase in energy to polymerize monomers

and oligomers. In addition, they are used to achieve desired properties and crosslinking

between polymer chains. 

Polymerization is actually a chain reaction, in which monomers or oligomers are added to a

backbone of carbon atoms. Each monomer or oligomer molecule is added as another link in the

chain, or as another vertebra in the carbon backbone. A polymer chain can be thousands of

monomer or oligomer molecules in length.
6

For UV/EB materials, polymerization actually is initiated by a compound included in the

formulation called a photoinitiator. A photoinitiator absorbs UV/EB radiant energy and

either forms free radicals or cations and anions. Until a photoinitiator receives UV/EB

radiant energy, a UV/EB-cured material does not have enough energy to initiate and complete

polymerization. Upon absorbing the UV/EB energy, photoinitiator molecules have enough

energy to split into either free radicals or cations and anions. These free radicals and cations

are energetic enough to create a polymer from monomers and oligomers. 

Free radicals produce a very fast reaction that occurs almost immediately and, for all practical

purposes, reaches completion. This results in a finished (cured) coating, ink or adhesive that is

almost completely polymerized and nearly ceases to polymerize further. Only trace quantities of

monomers, oligomers and photoinitiators remain trapped within the polymer after a free

radical reaction. These trace quantities may react with each other over time as they diffuse

through the polymer. However, this occurs very slowly.

When cations (Bronsted or Lewis acids) are formed, they generate more ions by spontaneously

breaking other photoinitiator molecules. These cations also initiate polymerization that can

spread, even in the absence of UV/EB radiant energy, after a UV/EB-cured material has

received enough radiant energy to start polymerization. These cationic photoinitiators cause

polymerization to occur somewhat more slowly; i.e., polymerization occurs in seconds. On

the other hand, being a chemical process, cationic polymerization can be completed in the dark

(without UV/EB radiant energy) once it has started. 

In 1991, UV/EB materials used volatile components, but these are no longer needed or used. 

UV/EB materials rarely use solvents. The only exception is to reduce viscosity and allow

application of a thinner coat (usually with adhesives) or to facilitate spray coating. Even when

a solvent is used with a UV/EB material, the amount of solvent and, therefore, the amount of

VOC emissions are generally much less than from conventional materials. In the typical case

where no solvent is used, only cure volatiles between 1-10% of the applied film weight might be

emitted. Usually cure volatiles are less than 5%. At this level, uncontrolled emissions are no

worse than that of a conventional operation equipped with very good emission capture and

control technology. However, no control technology is either needed or used with UV/EB

materials. 

WHERE ARE UV/EB-CURED MATERIALS USED?

UV/EB coatings, inks and adhesives are used in a variety of applications such as printing inks,

overprint varnishes, release coatings, primers, pigmented paints, clear topcoats, bonding

coatings for magnetic tape, bonding for abrasives, encapsulates, pressure sensitive adhesives,

and permanent bond adhesives.

5

 The list of applications keeps growing; therefore, any static

list of applications should not be expected to be complete. However, in order to appreciate the

extent to which UV/EB technology is being applied, a list of UV/EB applications compiled from
7

Envirosense 14 and the RadTech UV/EB-Curing Primer 23 is provided in Table 1. Examples of

UV/EB material applications can also be found in Appendix B.

TABLE 1: UV/EB COATING, INK AND ADHESIVE APPLICATIONS

INDUSTRY APPLICATION

AIM Coatings

(Architectural / Industrial /

Maintenance coatings

applied to protect from

corrosive environment)

metal and concrete structures

pipes

tanks

processing equipment

Aircraft primers

color coats

topcoats

Automotive Parts underbody paints

primers

color coats

topcoats

refinishing

Coil Coating Applied to coiled sheet metal that is used in:

 household appliance industries

 transportation industries

 construction industries

 container industries

Dental fillings

Electronics microelectronics photomasks

solder masks

notations on circuit board 

encapsulation of circuits or components

optical fiber coatings

compact disks (CDs)

digital video disks (DVD’s)

Flexible Plastics decals

decorative laminates

shrink film

magnetic recording media

abrasive films

release films
TABLE 1: UV/EB COATING, INK AND ADHESIVE APPLICATIONS

INDUSTRY APPLICATION

8

Highway coatings used to mark lanes 

coatings used to provide directional arrows on roadway

Leather finishes

topcoats

Machinery and Equipment farm equipment

construction equipment

electrical machinery

heating, ventilating, and air conditioning systems (HVAC) 

industrial machinery

computers

office equipment 

Marine ships

offshore platforms

other steel and aluminum structures 

Metal containers beverage cans

lids and closures

food cans

Optics eyeglass lenses

optical fibers

Paper and Paperboard record albums

folding cartons

juice cartons

magazines

paperback books

business forms

bank notes and money

release paper

abrasive coated paper

Rigid Plastics vinyl floor covering and tiles

bottles

credit cards

sports equipment

medical equipment
TABLE 1: UV/EB COATING, INK AND ADHESIVE APPLICATIONS

INDUSTRY APPLICATION

9

Textiles sizing

fill coats

topcoats

Wire magnet wire

Wood Furniture furniture

kitchen cabinets

doors

trim

moldings

Wood Products hardboard panels

plywood panels

particle board panels

hardwood flooring

door laminates

DO UV/EB FORMULATIONS USE CONVENTIONAL RESINS?

All coatings, inks and adhesives (i.e., solvent borne, waterborne, or UV/EB-cured), regardless

of curing method, use basically the same resins. However, the resins used with UV/EB-cured

material have been modified by including functional groups and photoinitiators that trigger

polymerization. For UV/EB materials, different performance properties have been gained by

using acrylics, methacrylates, epoxies, polyesters, polyols, glycols, silicones, urethanes, vinyl

ethers, and combinations of these. Structurally different monomers or oligomers may be

blended together to adjust properties of a final polymer. The composition of a formulation is

usually considered proprietary and, therefore, is usually referred to by a trademarked name

which does not normally reveal its composition. Table 2 shows monomers and oligomers that

were available in 1991. Either acrylic or vinyl ether functional groups are included in these

monomers to enable them to be cured by UV/EB radiant energy. 

The list of monomers and oligomers has grown to be quite large in 1999. See Table 3. This

listing is by generic types. Actual formulations are composed of these types of compounds in a

proprietary mix. The mix will be identified by a trademarked name that will give no clues as to

constituents. 
10

Table 2. RADIATION-CURABLE MONOMERS IN 1991 30

SYSTEM REACTIVITY OXYGEN

INHIBITION

DURABILITY EB

CURABLE

UV

CURABLE

Polyester/

styrene

Low High Poor No Yes

Acrylates High High Moderate Yes Yes

Thiol-polyene High Low High Yes Yes

Cationic

Epoxies

Medium Low Fair No Yes

Source: Decker, C. “UV-Curing Chemistry: Past, Present, and Future”, J. of Coatings Tech., 1987

Vrancken, A. “Market Trends for Irradiation Curable Coatings in Europe”, Radiation Curing V, 

Association of Finishing Processes of SME, Boston, 1980

HOW ARE UV/EB MATERIALS CURED?

UV/EB materials cure (change from a liquid to a solid) by a reaction that involves both

polymerization and crosslinking. UV-cured materials need UV radiant energy to polymerize

monomers and oligomers into a solid. EB-cured materials need EB radiant energy to

polymerize monomers and oligomers into a solid. There are many polymerization

mechanisms; however, currently only two polymerization mechanisms are used for curing

UV/EB materials: free radical polymerization and cationic polymerization. A free radical

cured UV material must be either very thin, clear, or both in order to let sufficient amounts of

UV radiant energy to (del) penetrate all the way through the material. A free radical cured EB

material can be filled, pigmented and thicker because EB penetrates more than UV. Cationic

photoinitiators, after UV/EB exposure, spontaneously form cations that trigger further cationic

polymerization. Once the cationic polymerization has been started, cationic reactions can

carry polymerization to completion in thicker, opaque materials, or even in the dark (i.e. after

radiant energy exposure stops).

In free radical polymerization, a monomer or oligomer joins with a free radical and, in

effect, forms a larger free radical. This larger free radical then acts upon another monomer or

oligomer and forms an even larger molecule, and so on. The process is a chain reaction (another

term used by chemists and physicists to mean a continuing reaction), that is endless until a

polymer molecule is terminated. Termination occurs when one polymer chain runs into the end

of another polymer chain, an oxygen atom reacts with the end of a chain, or a polymerization

becomes so nearly complete that further reactants are not available.
11

Table 3. FAMILIES OF RADIATION-CURABLE MONOMERS IN 1999

Acrylated Aliphatic Oligomers Cycloaliphatic Epoxides 

Acrylated Aromatic Oligomers Cyclohexyl Methacrylate

Acrylated Epoxy Monomers Ethylene Glycol Dimethacrylate

Acrylated Epoxy Oligomers Epoxy Methacrylates

Aliphatic Epoxy Acrylates Epoxy Soy Bean Acrylates

Aliphatic Urethane Acrylates Glycidyl Methacrylate

Aliphatic Urethane Methacrylates Hexanediol Dimethacrylate

Allyl Methacrylate Isodecyl Acrylate

Amine-modified Oligoether Acrylates Isooctyl Acrylate

Amine-modified Polyether Acrylates Oligoether Acrylates,

Aromatic Acid Acrylate Polybutadiene Diacrylate

Aromatic Epoxy Acrylates Polyester Acrylate Monomers

Aromatic Urethane Methacrylates Polyester Acrylate Oligomers

Butylene Glycol Acrylate Polyethylene Glycol Dimethacrylate

Silanes Stearyl Methacrylate

Silicones Triethylene Glycol Diacetate

Stearyl Acrylate Vinyl Ethers

Note: These monomers/oligomers were cataloged in 1999. These can be blended to achieve desired properties. These can

be combined with any of a similar number of types of photoinitiators. The photoinitiators tend to be aromatic molecules

that are more sensitive to UV or EB than the monomers and oligomers are.

Cationic polymerization is an ionic process that is not inhibited by oxygen and, therefore, can

cure in air without a nitrogen blanket. Cationic polymerization will continue after exposure

to UV/EB radiant energy source ceases. Therefore, the only concerns are to initiate cationic

polymerization and to store the product for a few seconds to allow for the cure to complete. 

UV/EB monomer and an oligomer molecules have functional groups that attach to the side of

a carbon chain. These also are referred to as pendant groups. Pendant groups aid in reducing

the energy that must be added to polymerize and to form crosslinks. Crosslinks interconnect

carbon chains and, as a result, provide greater mechanical strength, resistance to abrasion, higher

softening temperatures, and increased mar resistance. 
12

Polymerization and crosslinking are the critical processes that take place as a UV/EB material

cures. Free radical curing is very fast and may reach completion in a millisecond or less. 

Cationic curing is slower and may take a few seconds to reach completion. Fortunately, cations

are more stable than free radicals and endure much longer.

Monomer and oligomer molecules are initially short enough to be mobile and, therefore, are in

a liquid state. As polymerization progresses, polymer chains grow in length, become less

mobile, and form a gel. In the gel state, a polymer solidifies, but has no significant mechanical

strength. As polymerization continues, crosslinking occurs and the polymer gains mechanical

strength. A material is fully cured when polymerization and crosslinking processes are

virtually completed.

DO UV/EB-CURED MATERIALS NEED SPECIAL EQUIPMENT?

For the most part, the same equipment that is used to apply conventional coatings, inks and

adhesives can be used to apply UV/EB-cured materials, although they may be adjusted

differently. The only major difference is how these materials are cured. 

Curing Units

UV-curing units contain one or more UV lamps, a reflector for each lamp, a means of

dissipating heat from the lamps (which may be ventilating air flow), and shielding to protect

people from exposure to UV. All UV-curing unit manufacturers now include shielding as an

integral part of a curing unit.

An EB-curing unit contains an electron beam generator and shielding to attenuate x-rays that

are generated during the curing process. An EB-curing unit is heavier and larger than a UVcuring unit because it has more massive shielding to absorb x-rays. All EB-curing unit

manufacturers include such shielding as an integral part of a curing unit.

For both UV/EB-curing units, production rates are determined by the composition and applied

thickness of the UV/EB-cured material, intensity of radiant energy in the curing unit, and

amount of radiance that is absorbed. UV/EB materials cure almost instantaneously to within a

few seconds when exposed to the appropriate radiant energy. Compared to thermal dryers used

with conventional coating, ink and adhesive applications, UV/EB-curing units provide for a 75-

90% savings in energy, 50-75% savings in floor space, and higher production rates.

By contrast, for conventional coating, ink and adhesive applications, a thermal oven is used to

flash off organic solvent or water and to harden/cure the applied material enough for handling. 

The oven is insulated to minimize heat loss (other than to the air flow that passes through it). 

Air flow through a thermal oven must assure that the concentration of organic solvent does not

exceed one fourth of the LEL. Production rates are determined by the composition and applied
13

thickness of the conventional material, path length through the thermal oven, temperature, and

air flow. Oven temperature, air flow, oven size, and production rate are inter-related factors in

conventional processes. The temperature must be high enough to evaporate the solvent or water

and to harden the coating enough for handling, but must not damage the substrate or the

coating. Air flow must remove and dilute solvent vapors to prevent excess concentrations from

occurring. The size of the oven is based upon the time required to dry, harden, and/or cure a

conventional coating, ink or adhesive at the desired production rate. 

Printing and Roller Coating

Although printing presses and roller coaters that use UV/EB materials may differ in detail, they

are essentially the same as those that use conventional materials. The differences are mainly due

to the location, size and speed of the curing unit. For printing, UV/EB-curing units are often

mounted on a printing press after the application of each color. For roll-coating, the UV-curing

unit is a chamber with UV lamps arrayed to give the desired cure. 

Rollers and print transfer surfaces for UV/EB material applications can be identical to those used

for conventional coatings, inks and adhesives. UV/EB material losses only occur when colors

are changed, mist is emitted, or a roller must be cleaned. If a roller and its pan are covered to

prevent UV/EB radiant energy from reaching them, a UV/EB coating will not cure on or in

them. As a result, a roller and pan used with UV/EB materials can be left for over a weekend

and used again without cleaning. This can minimize both the loss of UV/EB material, as a result

of cleaning and use of cleaning solvents that might be VOC. 

Spray Painting

For spray coating, the same spray paint guns and related equipment used for conventional

coatings can be used for UV/EB coatings. Techniques for spraying viscous UV/EB paints

include: increased pressure to drive paint through spray gun nozzles; dilution with organic

solvent (VOC); dilution with water; or, some combination of heated spray paint guns and these

techniques. Viscosity in new UV/EB spray paints has been reduced, but still is higher than that

typically used for conventional paint spraying. Reactive diluents (i.e., diluents that become

part of the cured coating) reduce viscosity and are less toxic and volatile then they once were. 

However, because UV/EB paints tend to be more viscous, heated spray guns may be needed to

bring UV/EB paint viscosity close to that of conventional paints. New UV/EB coatings

significantly reduce or eliminate coating decomposition, fumes, and/or smoke aerosol problems

experienced in the past when using heated spray guns. If used, organic solvents must be flashed

off before the UV/EB cure, and generally increase VOC emissions that may need to be

controlled by add-on emission control technology. Water can successfully lower viscosity of

some UV/EB-cured coatings without introducing VOC.

40 However, when either an organic

solvent or water is used to adjust viscosity, additional drying time, space and energy is required.
14

The same paint spray booth used to apply conventional coatings can be used for UV/EB

applications. A paint spray booth where conventional coatings are applied must have positive

air flow through it to avoid accumulation of combustible or explosive vapors, and to carry VOC

and overspray away from workers. Because UV/EB paints contain little or no VOC (unless

VOC is used to adjust viscosity), overspray is the primary concern in UV/EB applications. As a

result, if VOC is not present, less airflow may be needed. Overspray in a UV/EB application is

carried to an overspray arrester (a kind of air filter) to protect workers. Overspray collected

from an arrester can be reused because UV/EB coatings retain their fluidity and do not dry out. 

However, if solvent was added to adjust viscosity, addition of solvent may be required before

reuse of captured overspray. 

Transfer efficiency for a particular spray application technique is about the same for both

conventional and UV/EB coatings. However, collection and reuse of UV/EB overspray can

improve the overall effectiveness of a coating operation; that is, the ratio of coating solids

applied on a substrate to the total amount of coating solids consumed improves because reusing

the UV/EB coating overspray reduces overall coating consumption. For example, when

transfer efficiency is about 50%, the overall effectiveness of a coating operation may improve

to about 95% with UV/EB coatings by using an arrester that captures 90% of the overspray and

reuse of that overspray. Similarly, electrostatic spray guns normally have a 90% transfer

efficiency, but the overall effectiveness of a coating operation using electrostatic spray guns can

be about 99% for UV/EB coatings when the Overspray is captured and reused.

Other Application Techniques

High speed spinners are used to apply UV/EB coatings in microelectronics. A photoresist

coating is applied to the center of a substrate, that is then spun to leave only a thin coat on the

substrate. The UV/EB photoresist coating may contain a solvent or be heated to reduce

viscosity, if necessary to control coating thickness. (Note: Conventional photoresist contains a

solvent that must evaporate to allow this thin film.) The UV/EB coating is then cured in

selected areas by exposure to radiant energy. The uncured areas are then washed away by

solvent to expose uncured areas to etching, doping to change the electronic properties, oxidation

to form insulators, or deposition of metal to form conductors. The coating is then stripped off

and another coating applied for the next step in the process.

Flow or curtain coating is used with objects that move through a flowing curtain of coating

(similar to a waterfall). This technique is used to advantage with UV/EB coatings because they

lack volatile ingredients. Volatile ingredients in conventional coatings would require

replacement to compensate for evaporation from the flowing curtain.
15

PART II: THE DETAILS

Now that you have a basic understanding of UV/EB coatings, inks and adhesives and how they

differ from conventional solvent borne and waterborne systems, you probably have some

insightful questions. In this section we attempt to answer those questions and provide details on

UV/EB technology and its application. 

UV/EB RADIANT ENERGY

In this section UV/EB radiant energy is discussed in detail. Topics cover UV/EB radiant

energy sources, UV/EB ionizing radiation and UV/EB radiation penetration. As previously

noted, there has been a lot of confusion about the term radiation and we have tried to use the

term UV/EB radiant energy to avoid this confusion. However, as we discuss certain topics the

term radiation will be used. As you read these sections, keep in mind that UV/EB radiation

and radioactivity are not the same, and should not be confused. The only connection between

UV/EB radiation and radioactivity is purely linguistic (i.e., both radiation and radioactivity

use the root radi- to describe radial propagation of energy by particles and electromagnetic

waves from a source). Refer to Appendix A, Ultraviolet and Electron Beam Radiation vs.

Radioactivity, for additional information.

UV radiant energy does not penetrate the skin, but can cause sunburn and tanning of the top

layer of skin - just like sunlight. UV radiation from curing units can be much more intense than

that from sunlight and can burn or tan the skin quicker. When UV sources are properly shielded,

eye irritation, skin tanning and sunburn do not occur. EB produces x-rays as high velocity

electrons change speed and are absorbed by air, an EB coating, ink, or adhesive, the substrate,

or an absorbing part of a printing press or coating apparatus. X-rays can and do penetrate

human tissue, but proper shielding of EB-curing units reduces this hazard to below background

levels. 

HOW IS UV/EB RADIANT ENERGY GENERATED?

Sources of UV and EB radiant energy are quite different. Therefore, each will be discussed

independently. In general, UV radiant energy sources have evolved for continuous and discrete

flat (2 dimensional) and 3D production, but EB has remained largely a continuous flat process

with only a few instances of use for discrete 3D production. 

UV Sources

UV radiant energy is often generated by electric arcs in medium-pressure (about two

atmospheres) mercury vapor arc lamps, as shown in Figure 2. These lamps are generally made

of quartz formed into a long cylindrical tube to provide uniform illumination over the width of
16

the web. The lamps also contain a gas, such as argon, that aids in ionizing mercury. When a

startup arc is operating, the mercury in the lamp has not yet fully vaporized and, for several

minutes, both the spectrum and intensity of radiation are changing. In addition, mercury vapor

arc bulbs have a very nonlinear current versus voltage characteristic. As a result, they require a

ballast - similar to fluorescent lamps, but at higher power. Various designs of these ballasts have

had their performance evaluated. There is truly no single answer for all applications, but ballast

selection is based on a tradeoff of cost, size, noise, and power.42 The length of the cylindrical

quartz tube with electrodes limits the width of the web that can be used. For mercury arc

lamps, this has a practical limit of about 5 feet. 

Figure 2: UV Mercury Arc Lamp

Microwave excited bulbs, another source of UV radiation, are filled with mercury vapor and an

easily ionized starter gas such as argon or xenon (See Figure 3). Light is produced by a plasma

which is generated by microwave radiation and, as a result, these bulbs do not have electrodes

penetrating the quartz envelope. Because these electrodes are absent, microwave excited lamps

are not subject to leakage or breakage around such electrodes. Consequently, microwave excited

lamps tend to last much longer than arc lamps. Because space is not required for electrodes,

microwave excited bulbs can achieve cures on very wide webs (up to six meters or 20 feet) and

conceivably more. Microwave excited lamps can be shaped to give more uniform 3D curing and

are not constrained to a long cylindrical geometry. Therefore, they can assume any shape that

the optical designers have in mind and that lamp manufacturers can make. Microwave excited

lamps may be used intermittently because they start up nearly immediately. They also can be

operated continuously. 

Recently, lamps have been developed which operate without elevated temperatures, are instanton, and produce a line spectrum in the near-UV which does not generate ozone.32
17

Figure 3: Microwave Excited Bulb with Generator

There are also xenon or argon arc lamps which use excimers to generate UV. These generate a

thermal plasma in xenon or argon gas which then excites an excimer. It appears that pulsed high

intensity radiance from these lamps can penetrate even better than a steady lower intensity

radiance from mercury vapor lamps. These arc lamps can be pulsed repetitively (strobed) to

give essentially continuous curing, or can be used for UV radiation which is required only

intermittently at a point (such as with hand-held sources). The rate and number of flashes can be

adjusted to give a required dose for curing. Hand-held UV point sources use much less power,

use a mirror to focus energy, and can use a wand or optical fiber to direct energy. Hand held

sources are used to splice optical fibers, bond lenses, bond items to printed circuit boards,

encapsulate small electronic components, or even bond artwork. These compact hand-held

sources produce less heat and consume less power with greater UV penetration than either

mercury arc lamps or microwave excited mercury vapor lamps.

Addition of excimers to mercury vapor arc lamps, microwave excited lamps, or argon or xenon

filed arc lamps can generate more radiant output in selected near-UV or actinic portions of the

spectrum. For example, a Fusion UV Systems “D” filled bulb has an excimer that can produce a

broad spectrum with peak intensity at 370-380 nm. Excimers are excited dimers. These

molecules get excited, separate, and recombine while releasing energy in a given and sometimes

narrow band of wavelengths. Excimers can emit shorter wavelengths than that of photons used

to excite them. This happens because more than one photon can excite a dimer molecule to

cause it to separate, but only one photon is emitted when the molecule recombines. The

excimer is not consumed in this process. By comparison, the phenomenon of fluorescence

always produces longer wavelengths than that of an absorbed photon. Fluorescence is caused

by a molecule absorbing a photon and reradiating the energy at a defined longer wavelength.

Whenever mercury vapor or excimers are used, bulbs that have reached their end of life should

be disposed of properly. This may require crushing lamps to recover mercury, recycling of

quartz, capture of any excimers that may be hazardous pollutants, and recovery of electrodes.
18

Figure 4: UV Light Reflectors

A lamp is often backed by a semi-elliptical mirror to focus radiation and obtain the highest

intensity (See Figure 4). An ellipse has two foci. By placing a source at one focus, the image of

that source appears at the other focus. The reflected UV radiation is focused to achieve as

much intensity as possible because both wavelength and intensity play a role in curing. Intensity

is the energy flow or rate at which photons are being absorbed. More than one photon can be

absorbed by a molecule and the absorbed photon energies are available for ionization. This

allows other longer (del) wavelengths to play a part in curing too.

Lamps also can be backed by parabolic reflectors. As shown in Figure 4, parabolic reflectors

have only one focus that sends light from the focus as parallel rays away from the reflector. A

wide variety of dimpled reflectors and diffusing surfaces also are used where a sharp focus and

high intensity are not needed. All types of reflectors are used, but for different types of cures.

More than one UV lamp may be required in a UV-curing unit. The dose that objects (e.g., web

in printing, or furniture in a 3D cure) receive from UV lamps is determined by the power of the

lamps, intensity of radiation, absorption of radiation through an ink, coating, or adhesive,

absorption of the UV radiant energy spectrum by the photoinitiator, and the speed that objects

flow through UV radiant energy in a curing unit. In printing and web coating, web speed (rate

at which a substrate passes through a curing unit) determines production rate. Production rates

with UV-curing have been increasing as lamps become more efficient and powerful and as

advances in UV-cured material chemistry have enhanced polymerization.

The UV radiant energy source must be selected to match the absorption requirements of the

photoinitiator that the lamps are to activate. The source must also provide UV radiant energy

over the entire surface of the applied film, given the configuration of the product. Therefore,

the intensity of UV radiant energy must penetrate well enough to cure a UV ink, coating or

adhesive all the way through; the UV material must cure with the chosen photoinitiator; and,

the UV radiant energy source must be compatible with the photoinitiator and the shape of the

substrate. For all UV lamps, a large portion of their spectrum (See Figure 5) fails to match the

absorption of either the UV-cured material or the photoinitiator that is being used. Lamps and

excimers are selected on the basis that their output peaks at the wavelength of maximum

absorption of the photoinitiator. Lamps and excimers should be selected on the basis of their
19

Figure 5: Spectrum of UV From a Mercury Vapor Lamp 

 (having no excimer)

output of an emitted energy intensity peak that the photoinitiator absorbs, because the

photoinitiator is used to gain sensitivity and minimize the UV radiant energy dose required for

curing. When energy consumption must be addressed, the photoinitiator must be a concern.

UV is generally transmitted a short distance (up to 25-50 cm or 10-20 inches) through air or a

nitrogen atmosphere to minimize ozone formation. Because air and nitrogen are essentially

transparent to UV, and aerosol particles that would cause UV scattering are sparse, this distance

is not critical. Direct ozone and NO2 generation is not a problem if an oxygen-free nitrogen

blanket, an ozone-free lamp, or a quartz filter is used. Ozone-free mercury bulbs are made of a

type of quartz that strongly absorbs energy below 260 nm in wavelength.

Mercury vapor arc lamps can take several minutes to warm up. A shutter is usually provided to

protect the web and prevent fires during warm up. If there is no shutter, a printing or coating

line is kept running to prevent the web from melting or catching fire while the lamps warm up. 

A substrate or web that passes through a press or coater during bulb warmup becomes solid

waste with uncured UV ink or coating on it. This can be hazardous solid waste because the UV

ink and/or coating is not cured. It can be converted to solid non-hazardous waste simply by

exposing it to enough sunlight. A shutter that remains closed also can protect a stationary web

until mercury vapor arc lamps are warmed up and minimizes such waste. 

Both mercury vapor arc lamps and microwave excited lamps normally operate at about 800°C. 

IR radiant energy from each is proportional to their surface areas. Mercury vapor arc lamps

have over twice the surface area for the same UV radiance and, therefore, over twice the IR

radiant energy compared to microwave excited lamps. As a result, mercury vapor arc lamps

will cause a greater temperature rise in a substrate for the same UV dose. 
20

Figure 6: Dichroic Coatings

To prevent web damage from heat (highly focused IR radiant energy) and a fire hazard when a

web breaks or stops, UV-curing devices are usually equipped with one of the following: 

(1) deionized water in tubes to absorb IR radiant energy; (2) a dichroic optical system (See

Figure 6) (3) a shutter that automatically closes when the web stops; or (4) a cold light source. 

In option (1), flowing de-ionized water transmits UV while absorbing the IR. A dichroic optical

system (2) uses coatings on the reflector that transmit UV with much lower interference losses

than they do for IR radiant energy and, therefore, reduce incidental IR reaching the web. A

properly ventilated shutter (3) absorbs all radiation while the web is moving too slowly. In

option (4), the light source lacks any IR that would ignite a web. 

EB Sources

Electron guns are used to generate electron beams in a manner similar to a TV picture tube. 

These beams can be deflected, just like a beam that forms a raster on a TV screen or computer

monitor. A beam from these electron guns can be focused magnetically to create a small spot

that moves rapidly. Electron beams also may be generated by linear filaments and cathodes

that are then directed by electrostatic electrodes to form their image on a substrate, as in Figure

7. Multiple filaments or cathodes can be used when higher currents for higher production speeds

are required. 

An EB is capable of curing printing ink within a very short length of curing unit (excluding

those parts required for shielding and baffles), and has sufficient curing capability to allow high

web speeds. Older EB-curing units often had more production capacity than was needed. 

Because of the cost of shielding and handling high voltages, as well as improvements in EB

inks, coatings, adhesives and photoinitiators, there has been a trend to produce smaller

electron guns with lower voltages. Although Photoinitiators are frequently not needed for EB

cures, they have been used to cure thick films on three-dimensional objects with a lower EB

voltage. 
21

Figure 7: Schematic of Electron Gun

Early EB-curing units used with (and usually attached to) printing presses were relatively large

compared to UV-curing units because, EB units had to include much more shielding (some even

used concrete vaults to enclose a press). These early EB units had much greater production

(curing) capacity than early UV units and used up to10 MV to accelerate electrons. Current

state-of-the-art electron guns use about 35 kV in a package about 3 inches in diameter by 12

inches long. As a result of this substantial reduction in energy, current EB-curing units do not

require as massive a shield. Excess production capacity associated with EB in past years is

becoming smaller, and production capacity for both UV and EB is converging to a point

originally between the two techniques. In addition, greater efficiency in EB power use is

obtained by using cationic photoinitiators and has resulted in lower voltage sources. 

Electron beams are sensitive to the density of the gas between an EB source and an object to be

cured. An EB will ionize oxygen in air to create ozone and nitrogen oxide; therefore, a nitrogen

blanket is highly recommended to avoid nitrogen oxide and ozone formation. 

Electrons are slowed down by multiple impacts with gas molecules surrounding a substrate

(presumably nitrogen, but the same is true of oxygen). This causes an electron beam to

degenerate into a diffuse multiple scattering of electrons. Scattered electrons are much more

numerous than electrons in the original beam, because they result from an avalanche effect. 

Scattering occurs because nuclei are surrounded by numerous electrons that have the same mass

as electrons in the beam. To minimize this problem, a sealed evacuated space is provided from

the EB source to within a small distance from the substrate. A titanium foil window forms the

air-tight seal to maintain a vacuum for the evacuated space. 

Titanium is chosen for the window because: (1) it has a low atomic number (Z) and is a low

density metal that heats up by absorbing about half of the electrons in the beam, but does not

heat up enough to lose its strength; (2) it can be made as a foil that is thin enough to minimize
22

losses of electrons; (3) it is strong enough to allow a thin foil to hold against atmospheric

pressure, even when an electron beam is on; and (4) it is very corrosion resistant so it will not

readily oxidize when moderately heated. Until titanium foil could be made (circa.1970), there

was no suitable window material and, therefore, no energetic electron beam in air was possible. 

The electrons are directed at the foil window because they would lose too much energy going

through a thicker

metal wall. They would even lose too much energy by going through enough glass to provide an

adequate seal for a vacuum. 

When the electrons stream through the window, they encounter their first air or nitrogen

molecules and are scattered rather strongly. Nevertheless, an intact stream of electrons continues

for several millimeters (depending upon the initial velocity). This intact electron stream

becomes more and more diffuse as the distance becomes greater. After only a few centimeters,

the electron stream is scattered and diffuse. As the electron beam loses energy by impacts and

capture, it generates x-rays. Finally only ions remain, with x-rays radiating from where the

electron beam had been.

Electron beams are sensitive to the density of the gas surrounding the object to be cured and to

ionizing oxygen in air (oxygen ions create ozone). After passing through a foil window,

electrons are slowed down and scattered by impacts with molecular gases in air. As a result, a

foil window must be placed very near (~ 1 mm) to a material that is to be cured at atmospheric

pressure. 

Vacuum chambers have been built to EB-cure filament reinforced plastic objects.18 These

vacuum chambers are suitable for curing fiber reinforced composite objects that are small

enough to fit within a chamber. These chambers are also suitable for EB-curing of coatings on

the exterior of such objects. These chambers are not well-suited to continuous coating

applications as in either rotogravure printing or coating optical fibers. 

WHAT IS UV/EB IONIZING RADIATION?

Ionizing radiation is radiation that can ionize a molecule. Because all molecules are not

ionized by the same amount of energy, the question becomes what molecule? The term ionizing

radiation usually refers to the amount of radiation that will ionize oxygen in air; that is,

radiation with a wavelength shorter than 253 nm (this includes actinic UV radiant energy

generated in UV-curing systems and electrons and x-rays generated in EB-curing systems). 

UV/EB-cured inks, coatings and adhesives also contain other molecules that can be ionized by

radiation at these wavelengths. 

UV energy is selective in the molecules that it can ionize. On the other hand, EB energy ionizes

anything in its path until all electrons are absorbed. EB systems generate x-rays when the

electrons are absorbed. These x-rays also can ionize molecules. 
23

Ionizing radiation can even mean visible light if a photoinitiator that is sensitive to a visible

wavelength is used to ionize molecules. Even IR energy can ionize when it is intense enough to

set an object on fire.

Both UV and EB radiation have photons or particles that are energetic enough to break

molecular bonds. It is important to realize that photons of a given wavelength (or color if they

are visible) are all at the same energy level and that energy level increases as the radiated

wavelength gets smaller. The amount of energy in each photon is determined by the following

formula:

energy = hf = hc/

where h = Planck’s Constant

f = frequency

c = speed of light

 = wavelength

Intensity indicates the number of photons striking a detector per unit of time. Photons have

wavelength-defined energy until they are absorbed. Contrast this with the concept in quantum

physics that views photons as massless particles that are used as an alternative to wave behavior. 

Describing the phenomenon as both a wave and a particle is not logical. How can a particle be

everywhere a wave goes? How can a photon have only one energy, while a particle’s energy

varies. Yet both are used to describe the wave and particle characteristics of radiation. 

Knowing that this is the case, we now must deal with ionizing radiation that is used for

UV/EB-curing. 

OSHA does not include UV in its definition of ionizing radiation, although UV can ionize

oxygen in air when the wavelength is below 253 nm. From an EPA viewpoint, ionizing

radiation can be any wavelength shorter than blue light; therefore, ionizing radiation is any

wavelength shorter than 400 nm. It can be near-UV radiation (315 - 400 nm wavelength),

actinic or far-UV radiation (180 - 315 nm wavelength),1 x-rays (0.1- 40 nm wavelength), or

gamma rays (<0.1 nm wavelength). 

Some sources define ionizing radiation having wavelengths between 40 nm and 180 nm as UV. 

However, the ozone generation capability of electromagnetic waves with wavelengths under

253 nm and the difficulty in generating these waves greatly restricts use of these wavelengths for

curing UV/EB materials. 

Another definition of ionizing radiation splits the UV spectrum into parts. It defines UV-A as

315-400nm, UV-B as 280-315 nm, UV-C as 200-280 nm, and Vacuum UV as 100-200 nm. In

this scheme, UV-A is the lower wavelength limit for human vision, is transmitted by window

glass, and can increase pigmentation of tissues. UV-B is primarily erythrogenic energy; that is,

it will cause reddening of skin, increase pigmentation of tissue, and cause eye irritation. The

most common effect of UV-B exposure is erythema (sunburn) that generally appears within

three hours and becomes most severe about twelve hours after exposure. UV-C is filtered from
24

sunlight by ozone but, when man-made, has important sterilizing properties and other industrial

uses. Use of UV-C or Vacuum UV requires an oxygen-free atmosphere to prevent formation of

ozone.

Some materials need more energy to ionize than that supplied by a collision with one photon of

available radiation in a brief period of time and are, therefore, dependent on the intensity of

radiation for ionization. Intensity is the rate at which photons are absorbed. Even long

wavelength IR radiation can ionize molecules if it is sufficiently intense. However, IR

radiation is not usually considered ionizing radiation for curing because it either melts or

burns substrates. Only photons of shorter wavelengths and electrons actually have enough

energy to cause ionization of UV/EB-cured ink, coating and adhesive molecules to happen

without damaging a substrate. 

The intensity of UV is measured in Watts per square centimeter. Doses of x-rays and gamma

rays are measured in either Roentgens (1Roentgen; R = 100 ergs/gram) or the Roentgen

Equivalent for Mankind (REM, which is the integral over the whole spectrum of Roentgens

times the adsorption factor for human tissue).2 The dose of electron beams is measured in Gray

absorbed radiation units (1.0 Gy = 1.0 Joule/kg). 

HOW DEEPLY DOES IONIZING RADIATION PENETRATE?

UV Ionizing Radiation

UV radiant energy penetrates to only a shallow depth in a coating, ink or adhesive, clothing,

or human skin. Therefore, UV radiant energy is usually used for thin film applications such as

printing ink, pressure sensitive adhesives, permanent adhesive assembly, or some paints. UV

radiant energy is absorbed by pigments, monomers, oligomers and photoinitiator sensitive to

that UV wavelength to break molecular bonds. Air or nitrogen is essentially transparent to UV. 

However, an ink, coating or adhesive will deplete UV radiant energy within a shallow depth,

often less than a thousandth of an inch. 

EB Ionizing Radiation

In EB-curing, electrons have a limited range before scattering in air. They also have a limited

range (1 - 20 mm) within the material to be cured. This range is a function of the speed of the

electrons (usually measured in electron volts) at the surface of the material being cured, the

density of that material, and the atomic number (Z) of the molecules that make up the material. 

As EB voltage increases electrons move faster and, as electrons move faster, they penetrate more

deeply. For electrons and x-rays, higher Z materials have greater absorption potential because

an EB is attenuated by reacting with orbital electrons. Most nuclei in EB-cured materials have

about the same low capture cross-section for scattered electrons as they do for high energy
25

electrons. An EB ionizes (changes the electronic balance of) atoms and molecules that capture

it. Electrons in a beam lose energy to electrons that they impact and slow down. Electrons are

captured more readily (i.e., the capture cross-section is greater) when they are moving slower.

These fast moving electrons in a beam are retarded by impacts with the orbiting electrons of

atoms and the positive charge on the nuclei. This happens with air molecules as well as

molecules in the EB-cured material. Electrons that are impacted may either gain escape velocity

or go into larger orbits. Electrons that gain escape velocity are referred to as being scattered. 

Scattered electrons, and those that go into larger orbits, cause the atom to radiate energy as xrays. Scattered electrons impact other atoms and produce an avalanche of lower energy electrons

that replace electrons that were lost. 

As electrons in a beam slow down, they generate x-rays. These x-rays are called

brehmsstrahlung, which is a German word meaning “braking radiation” or “radiation caused

by retardation.” This results from the slowing of electrons, scattering of electrons, acceleration of

orbiting electrons, and cyclotron radiation are caused by larger electron orbits. Cyclotron

radiation produces a characteristic narrow band x-ray spectrum emission of brehmsstrahlung at

wavelengths that depend upon the particular capturing atoms. Low Z materials generate longer

wavelength x-rays that do not penetrate as much. Collisions with high Z materials tend to

produce more energetic x-rays that can penetrate more readily. Electrons that escape orbit

produce a broad spectrum of x-rays. All man-made x-rays are generated in this way.

The extent to which x-rays from EB radiation penetrate is related to the Z of the material, and

the density that is penetrated. X-rays generally penetrate lower Z materials to a greater depth. 

Higher material density places more atomic cross-sections along the trajectory, which causes a

greater attenuation. Attenuation is the term that is used to describe the amount that x-rays are

absorbed. X-rays resulting from older EB systems with significant excess capacity have required

a concrete vault or other appropriate shielding around the printing press to contain and attenuate

them.

Most substrates and EB-cured materials are composed of oxygen, hydrogen, carbon, and

nitrogen atoms. These are all low Z materials. Some pigments and additives contain high Z

materials, but the effect of these is mitigated by a thin film of material. Therefore, penetration of

low energy x-rays through the EB-cured materials and substrates is usually very great. When

higher Z atoms are excited by EB, a higher penetration x-ray is generated. These x-ray

generated photons also can ionize molecules in EB-cured materials, just as an electron beam

and UV radiant energy do more directly.

Because an EB will be absorbed and x-rays will be generated, x-rays will have to be attenuated. 

This is now done by insertion of dense heavy metal shields in a curing unit. It also can be done

by enclosing a press within a concrete vault. The walls of such a vault might be made thinner by

addition of insoluble heavy, metal salts as a filler.
26

UV/EB-CURING

In this section more details are provided on UV/EB coating, ink and adhesive formation,

photoinitiators, the relationship between film (applied coating, ink or adhesive) thickness and

production rate, 3D capabilities, measuring the extent of curing, and anything else that you need

to know about UV/EB-curing

HOW DO UV/EB COATINGS, INKS AND ADHESIVES FORM?

UV/EB materials cure (form a solid film) by polymerization and crosslinking. There are many

polymerization mechanisms; however, currently only two polymerization mechanisms are

used for UV/EB-curing: free radical polymerization and cationic polymerization. Except for

powder coatings, most UV/EB coatings start out as a liquid. UV/EB-cured powder coatings

start out as solid particles that are applied to a substrate, subjected to infrared radiant energy

(heat) to melt them, and then exposed to UV/EB radiant energy to polymerize the coating.

UV/EB radiant energy breaks the photoinitiator molecule in the UV/EB material by either

homolytic fission (to make free radicals), or heterolytic fission (to make cations and anions). 

This fission refers to breaking a molecule rather than an atom. (It does not mean the same thing

as the term used for nuclear reactions.) These free radicals and cations then combine with

monomer or oligomer molecules to form a polymer.

The properties of a polymer are the result of: (1) monomer and oligomer molecules that have

become part of the polymer chain; (2) crosslinking that is accomplished by pendant groups; and

(3) the length of the polymer chain before termination. A polymer molecule can be terminated

in one of three ways:

1. One chain bonds endwise to another, which creates a pair of electrons that will not react

further, or

2. An oxygen atom reacts with the free electron in a free radical and creates a pair of

electrons that will not react further, or

3. Polymer molecules limit the mobility of monomer molecules so that the reaction stops

due to the unavailability of reactants, and the free radical reaches the end of its lifetime.

The second termination mechanism is also referred to as oxygen inhibition. Note that this is

only an issue in free radical polymerization, not cationic polymerization. Oxygen inhibition

is avoided by blanketing the reaction area with dry nitrogen to exclude oxygen that would

otherwise be present in ambient air. The presence of oxygen molecules could cause polymer

chains to be terminated too short, or limit crosslinking. 

The types of monomers or oligomers define the structure of the polymer and, therefore, its

properties. The basic properties are modified by crosslinking that molecularly bonds the
27

Figure 8: Free Radical Polymerization

polymer chains together. 

While we might like to think that a time integrated dose of UV/EB radiant energy causes a

cure, intensity (the rate at which photon energy is absorbed) is also important. Molecules at the

surface (the topmost level) may receive 100 or more times the intensity of UV/EB energy as

molecules at the bottommost level adjacent to the substrate. As a result, adhesion failure may

occur if bottommost coating molecules do not receive enough radiant energy to cure.

Free Radical Polymerization

A free radical is a molecular fragment that has a single free valence electron (See Figure 8). 

Photoinitiators are unsaturated molecules (having aromatic or aryl carbon rings) that form free

radicals very readily. Valence electrons are unreactive when paired with another valence

electron; however, a single valence electron always seeks a second valence electron. A free

valence electron is formed by homolytic fission. This occurs when sufficient UV/EB radiant

energy is absorbed by the photoinitiator molecule. Homolytic fission means that both

fragments are free radicals with single electrons available. Free radicals exist for a limited

time and must find and react with monomers and oligomers within their lifetime. 

When a free radical captures an electron from a monomer or oligomer, that monomer or

oligomer becomes part of the free radical. A single valence electron is always left free after

this joining and this new expanded free radical reacts again and again as it forms a polymer. 

This is a chain reaction. In this way, monomers and oligomers form polymers that contain

long chains of monomer molecules.
28

Figure 9: Cationic Polymerization

Cationic Polymerization 

Cationic photoinitiators are unsaturated molecules that break apart by heterolytic fission under

UV/EB radiant energy to form cations and anions. Heterolytic fission means that the

fragments are different. Cation fragments initiate and sustain the polymerization process, as in

Figure 9. The anions do not contribute much to polymerization. The cations are either

Bronsted acids or Lewis acids. These strong organic acids are positive ions that either donate

protons or absorb electrons and are attracted to a cathode just as hydrogen ions are. The cations

also cause fission to continue until all available photoinitiator molecules have ionized. 

Therefore, once started, polymerization will spread throughout the UV/EB material. Unlike

free radical polymerization, cationic polymerization is an ionic reaction that cannot be

terminated by a reaction with oxygen molecules. Because anions are also formed, the overall

state of the polymer is neutral, even though polymerization occurs because cations are present.

Because cationic photoinitiators now exist, the list of potential applications that can be served

changes and expands. These cationic photoinitiators can be used to polymerize coatings that,

because of absorption, shadowing, or pigmentation, cannot receive enough radiant energy

throughout their depth. Once cationic polymerization starts, it will continue to completion,

even in the dark. 

Crosslinking

Crosslinking can result from either free radical polymerization or cationic polymerization. 

It occurs as part of polymerization when pendant groups on one chain connect with pendant

groups on another chain. Crosslinking produces mechanical hardness, resistance to melting,

resistance to mechanical deformation, greater strength, and mar resistance (See Figure 10).
29

Figure 10: An Example of Crosslinking

HOW DO PHOTOINITIATORS WORK?

Photoinitiators are unsaturated, aromatic, aryl compounds that are more sensitive to UV/EB

radiant energy than monomers and oligomers. Compared to monomers and oligomers,

photoinitiators represent a small percentage of the weight of a coating, ink or adhesive that is

being applied. Most absorption of UV/EB radiant energy in a UV/EB-cured material is

accomplished by a photoinitiator. 

Photoinitiator molecules fission (break apart) in predictable ways when they receive UV/EB

radiant energy. They either form free radicals or cations as fragments. Therefore,

photoinitiators play a critical role in initiating free radical or cationic polymerization in

UV/EB materials. The type of photoinitiator must be selected with care. The energy absorption

potential of a photoinitiator must be matched to the wavelength of peak radiant energy that is

generated by the UV/EB source in order for the photoinitiator to do its job properly. If radiant

energy is not sufficiently intense, a photoinitiator may not receive enough energy to form free

radicals or cations. Photoinitiators also are major absorbers of UV/EB radiant energy. 

DOES PRODUCTION RATE DEPEND ON COATING THICKNESS?

Coating thickness does affect production rate. Because the thickness of material applied by

spray and roller methods (>0.001 inch) are typically much greater than that of printing (<<0.001

inch), they require a larger dose of radiation to cure. Therefore, for a constant radiant energy

source, production rate must decrease as film thickness increases in order to provide adequate

exposure to radiant energy needed to cure the material. In reality, the intensity is adjusted to

cure the coating at the production rate. 

This is exacerbated by absorption of radiant energy by the UV material itself, because the

intensity of UV radiant energy will decrease severely with film thickness. This may be offset
30

with more intense UV. However, IR radiant energy (heat) is absorbed along with UV energy. 

Therefore, the limit in UV intensity is determined by the IR energy that is absorbed by the

substrate and coating.

Thin material applications (as used in printing and adhesive coating) can cure almost

immediately. Production rates for these applications can be much higher than for thicker

applications. Printing production speeds of over 1,000 feet per minute can be achieved with

complete curing in a UV-curing unit that is only a few feet long. 

Cure times for thicker applications using spray or roller techniques may be measured in seconds. 

3D fiber reinforced composite structures contain fibers that shadow much of the UV/EB coating

that bonds the fibers together. Curing a coating in this type of structure can require EB radiant

energy, cationic curing, or both. Cure time may be greatly extended, though 3D cures can be

accomplished in seconds.

WHY HAS THERE BEEN GROWTH IN 3D CAPABILITIES?

As previously stated, UV/EB-cured materials were first used in printing processes because this

technology is well suited to a thin coating of ink on a flat surface. UV/EB technology was also

well suited to coating sheet metal before it was coiled and flat wood product panels for the same

reasons. However, other applications arose, such as optical fibers, that were not flat. These 3D

applications have the ability to cast shadows that hide portions of the surface from the radiant

energy needed to cure the UV/EB material. By 3D capabilities we mean the ability to cure

coatings on 3D objects.

 Figure 11 shows a cross-section of an optical fiber used for transmission of digital signals and

the special coatings that are crucial to its performance. Without these coatings, fiber optics

could not be a long-distance medium. The innermost coating must have a low index of

refraction, and not absorb the wavelength of the laser that is being used to send the digital

signals. The next coating must provide strength. The outermost coating must strongly absorb

the wavelength that is being used to prevent “cross-talk” between fibers. The development and

availability of these UV/EB coatings were crucial to the success of fiber optic cable, because no

other technology could provide the rapid cure with 100% integrity. As a result, equipment and

UV/EB coating developers and manufacturers cooperated to produce this product and the other

products that use UV/EB materials.

Because efforts to minimize the effect of the shadow in 3D applications succeeded in optical

fiber manufacturing, the advancement of 3D capabilities in other applications became only a

matter of time. Currently the effects of shadows can be minimized for wood furniture and even

automobile bodies. This has been achieved by multiple radiant energy sources, dimpled

reflectors, and myriad other optical design techniques.
31

Figure 11: Schematic of Optical Fiber

Manufacturing plants now spray or roller coat UV sealers, primers, finish, and topcoats on

panels and furniture and rapidly cure these materials within 25°C of room temperature. 

Conventional coatings on a wood substrate can not be heated enough to cure in less than an

hour. Because the curing time is so short for UV materials, fine furniture manufactures use UV

coatings to avoid dust blemishes. In addition, because there are no flammable VOC to cause a

fire hazard, at least one insurance company has decreased the fire insurance premiums by 15%

where UV material are used.

Use of a computer guided UV optical fiber or laser has allowed layer-by-layer construction of

objects using a polymer. The polymer object that is formed can be either a model or the final

part. This technique is referred to as stereo lithography. This is done by retreating a platform

beneath the surface of a monomer or oligomer while a computer guided UV source operates

like a printer tracing a raster with the UV source “on” over the solid portion, and “off” over open

spaces or cavities in the structure of each successive cross-section. In this way, a scale model

(any scale including life size) of a complex part can be made - even body parts can be generated

from a CAT or MRI scan. This technique allows for troubleshooting of designs. It can even

allow surgeons to practice on life-size models of the patient.

HOW IS EXTENT OF CURING MEASURED?

The extent of a UV/EB coating cure has been measured by adhesion, solvent-rub, stain tests, ion

mobility, glass transition temperature, mechanical properties such as elastic modulus or tensile

strength, Taber abrasion, a fluorescent indicator, or by minimum volatility. The measure is

selected based on some performance measure that is germane to endurance, and no correlation

has been made between the various cure measurement techniques. A few of the main tests are

discussed here.
32

Adhesion of a coating is measured by the force per inch of edge that is peeled. When the

coating is liquid, this force is near zero. It becomes a finite amount as curing progresses. When

it approaches a maximum force, the slope of the peel force with increased UV/EB exposure 

approaches zero. Further exposure is said to overcure the material. Overcuring is thought to

accomplish further crosslinking between molecules and react some additional monomer.

Taber abrasion tests the resistance to abrasion. It is based on the use of a weight (250 gram, 500

gram, or 1 kilogram) bearing down on an abrasive disk while the specimen is rotated against it. 

The abrasive disk can be any of a large number of types, based upon the purpose for which a

coating is intended. 

Solvent-rub is a modification of abrasion that requires a specified solvent to be present. This

test measures the effect of the solvent on the cured coating. Presumably, an uncured or

shallowly-cured coating would be readily removed by the solvent. 

Ion mobility is measured by placing two electrodes on a coating, applying a voltage and

measuring the current. Both the amount of current and the time response to switching the

voltage on are measured. Both of these measurements provide diagnostics as to the ion mobility. 

Presumably, the ion mobility is least in an overcured coating. A minimum ion mobility that is

acceptable to the usage is specified.

Elastic modulus is based on the slope of the stress-strain curve. This test requires a specimen to

be coated for measurement of stress versus strain. Stress is the force per unit area to achieve the

strain. Strain is the elongation per unit length that results. A higher elastic modulus requires

more stress to achieve a given strain.

Tensile strength is the maximum stress that can be achieved before breaking. Typically, this

occurs when a discontinuity in the stress versus strain curve occurs.

Minimum volatility is measured by weighing a specimen of cured coating to determine weight

loss. Curing is done in increments with weight measurements at each increment. Between

increments, temperature can be elevated to drive off volatile ingredients. A minimum volatility

cure is the point at which weight loss reaches a minimum.

Glass transition is a property of the amorphous portion of a semi-crystalline solid. It is measured

as the temperature at which the solid changes from a glassy deformation to a rubbery

deformation. This is determined by measuring the elastic modulus at different temperatures, and

finding the temperature interval in which the glass transition to a higher modulus occurs. A

higher glass transition temperature (Tg) can be used as evidence of greater crosslinking. 

Alternatively, the minimum Tg can be specified and the elastic modulus is then determined at

that temperature to determine whether it is glass-like or rubber-like. 

The other methods are used less often because: they are more suited to research; are more

expensive; or take too long to obtain a result while production is running. While each method

ostensibly shows that curing is complete, the correlation of one method to another is seldom if
33

ever done. Whether food contact could or should be allowed is not determined by these tests

(with the possible exception of ion mobility).

IS THERE ANYTHING ELSE THAT AFFECTS CURING?

You may have noticed that we have hardly mentioned temperature. UV/EB materials cure

nearly instantaneously and cure even faster as temperature increases. Temperature is a measure

of the kinetic energy of molecules. If the temperature gets above a critical level (a different

level is critical for each UV/EB material) polymerization can occur in the absence of UV/EB

radiant energy. The temperature of UV/EB-cured materials needs to be kept between 60°F and

80°F to preclude depletion of inhibitors in the material. This temperature range usually is not a

problem, but air conditioning may be required in some cases.

Other factors are UV lamp variation during use, variations in power line voltage, oxidation

effects and infrared effects. All of these vary with time and the effect of each may be different. 

Therefore, we should recognize that the cure will vary as a combined effect of all of these

factors.

UV/EB materials can vary. To minimize variability, UV/EB-cured materials should not be

exposed to peroxides, iron particles, or other free radical sources. In addition, they should be

stored away from sunlight or other sources of radiant energy that could cause polymerization.

If a UV/EB-curing unit promoting free radical polymerization is exposed to atmospheric

oxygen or atmospheric oxygen invades a “nitrogen blanket” used in the process, oxygen

inhibition will occur. Oxygen can inhibit the curing of acrylics, polyesters, and styrenes. The

effects of oxygen inhibition may result in the use of a far greater dose of radiant energy than

expected to obtain a cure. This would be especially true if the “nitrogen blanket” were not

used. On a positive note, oxygen inhibition is intentionally used to retain tack in some pressure

sensitive adhesives.

Humidity can affect the curing time of UV/EB materials that use cationic photoinitiators. 

This effect differs for various coatings, coating thicknesses, coating permeabilities and water

vapor concentrations.38 In some cases, water can inhibit polymerization similar to oxygen

inhibition. This can be corrected by using an IR dryer or an extended dry nitrogen blanket.

Monomers, oligomers, photoinitiators, fibers, and pigments in a coating, ink or adhesive can

all absorb UV/EB radiant energy. The extent to which all of these materials absorb radiant

energy can inhibit curing of the material, especially in thicker applications. Fibers and pigments

can cast UV/EB shadows that prevent radiant energy from reaching monomers, oligomers, and

photoinitiators. Materials that contain cationic photoinitiators do not have this problem. 

Material containing cationic photoinitiators only have to receive enough radiant energy to

decompose the photoinitiator in the top layer and curing will be spontaneous after that.
34

PART III: EMISSIONS, HEALTH AND SAFETY

WHAT AIR POLLUTANTS ARE EMITTED FROM UV/EB-CURED MATERIALS?

UV/EB-curing is a very low emitter of air pollutants, but some emission do occur. This section

discusses potential emissions of VOC, fine particulate, HAP, odors, ozone and NO2.

VOC Emissions:

UV/EB-cured coatings, inks and adhesives have a reputation for being VOC-free, but they

actually do emit some cure volatiles that may be VOC. Although VOC emissions are extremely

low from many applications using modern UV/EB materials (i.e., VOC emissions can be less

than 1% of the weight of the coating, ink or adhesive used), cure volatile emissions for a typical

application usually are in the 1-5% range. (Note that no solvent diluent is used in the typical

case.) However, for a small number of applications, cure volatile emissions can approach 10%

of the applied film weight. Even at the 10% level, uncontrolled VOC emissions are no worse

than that of a conventional coating or printing operation equipped with good emission capture

and control technology. Typically, no add-on control technology is either needed or used with

UV/EB-cured materials.

UV/EB-cured materials are ready to use as provided by the manufacturer. No additives or

blending is required after the UV/EB-cured materials leave the manufacturer. The one exception

may be adding a solvent (VOC or water) to adjust viscosity in some spray or special

applications. UV/EB-cured materials will not dry up unless subjected to sufficient UV/EB

radiant energy. If diluents are present, uncured UV/EB coatings may simply become more

viscous as the diluent evaporates. However, normally VOC diluents are not present.

Acrylates have been measured at a concentration of approximately 10 ppm in the space

immediately above a coating (a headspace measurement) during cure. Concentrations of VOC

in the same space were even lower.28 Concentrations in a subsequent emission stream would tend

to be even lower as a result of mixing and dilution with air in the exhaust stream. Such small

emission concentrations are the desired goal of add-on emission control technology used with

conventional processes, but they can be achieved by using UV/EB-cured coatings, inks and

adhesives without a add-on emission control device. 
35

EXAMPLE: Calculation of VOC Emissions

Source type: Printing 

Application: Overcoating a 5 foot Web running at 1000 feet/minute

Coating characteristics: 0.8% specific gravity

Film thickness: 100 microns 

VOC emissions: 1% of the film weight as applied 

In this example, the source would produce 0.000163 pounds of VOC per square foot, or about

1.0 pound of VOC per 6,124 square feet. One pound of VOC would be emitted from

overcoating 100% of a 5 foot web for 1.2 minutes at 1,000 feet/minute. This would provide a

maximum of 72 pounds of VOC per hour, 576 pounds per 8 hour shift, or 52 tons per year per

shift. In most cases UV/EB technology would qualify as a Lowest Achieved Emission Rate

(LAER) technology. (LAER is required by the Clean Air Act on new and modified major

sources locating in areas that are not attaining National Ambient Air Quality Standards.) In

comparison, a conventional overcoating operation using VOC solvent would emit 2,600 - 3,600

tons per year of VOC for the same level of operation. 

Note that the previous calculation was based on the amount of material that actually is applied to

the substrate. In reality, some losses due to misting, spills, splatter, transfer efficiency, etc.

may occur. Therefore, it would be preferable to use the mass of the total amount of UV/EBcured material (coating, ink, etc.) that is consumed when calculating potential emissions from

UV/EB printing and/or coating processes. 

Fine Particulate Emissions:

When UV/EB materials are used on high speed printing presses and roll coaters, they will emit

some mist. Mist is generated when UV/EB material that is between rollers and substrate

rapidly separates in high speed applications. (Conventional materials also would mist if they

were applied at as high a speed.) Misting of UV/EB ink in high speed printing has been

measured at between 1% and 50% of the ink consumed. Many of the droplets were found to be

under 2.5 m (PM-2.5). Where misting is severe, users and suppliers can work together to

minimize the problem. 

HAP Emissions:

Unless HAP solvents are added, UV/EB coatings are HAP-free (i.e., do not contain any a HAP

listed in Appendix E). However, fine droplets in mist generated by high speed rollers (see

above) may contain toxic chemical compounds. You should check Material Safety Data Sheets

(MSDS), review the HAP list, and/or contact the supplier to determine to what extent toxicity is

an issue with a particular UV/EB-cured material.
36

Figure 12: UV Coatings -- Now Used for

Packaging Chocolates

Odorous Emissions:

Overall, the UV/EB-cured material used today have much less of an odor problem then material

used 10 years ago. In fact, restaurant menus, packages for fine perfumes and boxes for

chocolates can now be printed and coated with UV/EB (See Figure 12). However, UV/EB

materials have historically emitted some objectionable odor, some even after curing. Odor

generating UV/EB materials containing amines or sulfur compounds should be avoided where

odor is an issue. 

Ozone and NO2 Emissions:

Each form of ionizing radiation can ionize oxygen and generate ozone. Also, there is suspicion

that NO2 can be generated, too. However, total emission of ozone and NO2 are relatively small

and should not significantly affect concentrations of these pollutants in the atmosphere. 

Equipment manufacturers have reduced the potential for ozone and NO2 generation from

processes that use UV/EB radiant energy. Nitrogen blankets exclude air from the

polymerization areas and, therefore, exclude oxygen as a reactant in these areas. However, air

ventilation is used to remove heat from UV lamps; therefore, these pollutants still can be

generated. Quartz filters that strongly absorbs wavelengths below 260 nm (the wavelengths that

form ozone) can be used to reduce ozone generation. 

HOW ARE EMISSIONS FROM UV/EB-CURED MATERIALS MEASURED?

VOC content of coatings is measured by EPA Reference Test Method 24. This method can be

found in Title 40, Code of Federal Regulations, Part 60, Appendix A. For your convenience,

Method 24 is provided in Appendix C of this report. Section 3.2 of Method 24 addresses nonthin-film UV Radiation-cured Coatings. This method is based on an American Society for

Testing Materials (ASTM) test method (D 5403-93). If the amount of UV coating or ink as

applied to the sample substrate is less than 0.2 grams (based on manufactures recommended
37

film thickness) and the area of the sample substrate is equal to or greater than 35 in2 (225 cm2 )

then the coating is considered a thin-film UV radiation-cured coating for determining

applicability of ASTM D 5403–93. No test method is specified for thin-film UV coatings, inks

or adhesives or any EB-cured materials. 

In considering and evaluating the modifications to Test Method 24 that eventually added

procedures for testing non-thin-film UV coatings, minimum VOC content was found when a

resin was UV-cured well beyond the manufacturers recommendation.16 The supporting paper

evaluating this modification did not state whether the recommended cure was intended for an

oxygen-free atmosphere, or whether an oxygen-free atmosphere was used. Because it made no

mention of a nitrogen blanket to exclude air from the curing process to minimize oxygen

inhibition, we assume that one was not used. Oxygen inhibition of a cure in atmospheric air

would explain the need for a higher UV dose (i.e., the amount of UV radiant energy required to

complete the cure and assure minimum VOC emissions). The report also stated that lamp output

power in the test apparatus was not measured, and that there is no easy relationship between the

power input level and UV light output at the specific wavelengths that cause a coating to cure. 

Therefore, low lamp output at the desired wavelength also could have increased the cure time. 

Manufacturers of UV radiant energy cured materials believe that Method 24 overstates VOC

emissions because it subjects a cured UV material to excessive heat (110 +/- 5°C) after a cure. 

Manufacturers suggest that excessive heat causes a UV coating to decompose and that a

resultant loss of coating mass is being reported as VOC. EPA is aware of these concerns, but

has no plans to revise the test method or develop a new method at this time. 

WHAT ABOUT WORKER HEALTH AND SAFETY?

There are three major worker health and safety issues that need to be addressed: (1) potential

exposure to UV/EB radiation; (2) potential exposure to hazardous components that are part of

UV/EB-cured materials; and (3) hygiene to protect workers. This section will discuss all of

these issues and significant changes and improvements made over the past ten years to minimize

potential hazards. 

What Health and Safety Concerns Does UV/EB Radiant Energy Present?

UV radiant energy is ultraviolet light. This is the same type of ultraviolet light that is

received from the sun. It cannot penetrate the skin, but can cause sunburn and tanning of the top

layer of skin or can cause eye irritation. When properly shielded, UV does not cause even these

to occur.

EB radiant energy consists of high velocity electrons and subsequent x-rays. Electrons are

generated in an accelerator or gun that projects them toward the coating, ink or adhesive and

the substrate. Electrons generate x-rays as their speed is retarded in these materials, and by any
38

molecules between the EB source and the target film and substrate. Manufacturers of this EB

equipment install shielding to reduce x-radiation to below background level.

According to OSHA regulations (Code of Federal Regulations (CFR) part 1910.96), no

employer shall possess, use, or transfer sources of ionizing radiation (OSHA’s definition

excludes UV) in such a manner as to cause any individual to receive, in any quarter of a calendar

year, more than:

Whole body, head and trunk, active blood-forming organs, or gonads.......1.25 REM

Hands and forearms, feet and ankles........................................................18.75 REM

Skin of whole body.....................................................................................7.5 REM

An individual can receive a dose greater than this if:

1. During any calendar quarter the dose equivalent of the whole body does not exceed 3

REM.

2. The dose equivalent to the whole body when added to the accumulated dose equivalent to

the whole body shall not exceed 5(N-18) REM, where N equals the individuals age in

years.

3. The employer maintains past and current records which show that the addition of such

dose equivalent will not cause the individual to exceed the above tabulated amounts.

Additional limitations may exist in the form of local, state, or subsequent federal regulations. It

is the responsibility of the employer to determine what regulations apply and to assure that

employees are not exposed to ionizing radiation that exceeds statutory and regulatory limits.

How Can Workers Be Protected Against UV/EB Ionizing Radiation?

The principal means of protection from all ionizing radiation is shielding. This shielding is

integrated into UV/EB-curing equipment in most cases. In the event of UV leakage, clothing is

a backup to shielding and wearing full sleeved and full legged garments is recommended. Eye

protection with side-shields is also recommended for the same reason. 

With near-UV, far-UV, and actinic radiation, shielding consists of opaque barriers and baffles. 

Baffles are needed because UV radiation can readily scatter from sub-micron aerosols and

become a diffuse glow reflected and re-radiated from aerosols and surfaces. UV can scatter

much more readily than visible light can, because its wavelength is shorter and sub-micron

aerosols in air can readily scatter UV. These aerosols are invisible (too small to be seen)

because they fail to efficiently scatter visible light. Multiple baffles are needed to reduce the

leakage produced by this scattering before it reaches human tissue. OSHA allows up to 1

milliwatt/square centimeter of near-UV radiation for exposure times over 16 minutes. OSHA

allows only up to 0.1 milliwatt/square centimeter of actinic radiation for 8 hour exposures.1

 
39

Unlike UV with coexisting visible wavelengths, electron beams and x-rays have no visible

component to alert a human being to their existence. Because human genes (just like the

photoinitiator, monomer, and oligomer molecules) are sensitive to molecular breakage under

ionizing radiation, workers need to be shielded from EB radiation. Ideally, radiation intensity

should be reduced to near background radiation level by shielding. The background radiation

level is the intensity of x-ray and gamma radiation that would exist if no radiation source

(except for trace sources of naturally radioactive materials) were close enough to affect the

radiation intensity. There are many of these low-level natural sources (such as wood, wood-fiber,

paper, metals, and masonry) and therefore the background level can never reach absolute zero. 

At wavelengths of x-ray and shorter, scattering becomes pronounced and there is no truly

opaque material. The mass of a shield will attenuate (reduce) the intensity of radiation that

penetrates that shield, as will the atomic number (Z) of the material Higher Z materials

attenuate penetrating radiation more than low Z ones of equal mass. However, the first solid to

be encountered by radiation should be a low Z material, both to minimize generation of x-rays

and to absorb x-rays that are generated from the higher Z materials that are encountered later in

a multiple layer shield. 

X-ray and shorter wavelengths are usually shielded by lead, other heavy metals, concrete, or

distance. In the absence of shielding, radiation intensity is reduced by the square of the distance

between the source and the point of the measurement. Obviously, nobody can afford to place an

operator a kilometer or even a hundred meters away from a source just to attenuate the intensity

and limit the dose they receive. Shielding which places a high-Z mass between a source and a

person is used to attenuate (reduce or weaken) x-rays within a reasonable distance. This

shielding must include baffles to limit leakage of scattered or re-radiated x-rays because even air

molecules and aerosols can scatter x-rays. The effectiveness of shielding must be tested by

measuring the radiation level to assure that radiation leakage is near background levels while

an electron beam is operating. 

What Health and Safety Concerns Do Hazardous Components in 

UV/EB-Cured Materials Present?

The toxicity of constituents that are vapors and gases are determined from the MSDS that are

required to be supplied with a coating. According to OSHA regulation 1910.1000:

E = C(a) T(a) + C(b) T(b) +.....C(n) T(n) divided by 8

Where: 

E is the exposure in terms of effective concentration.

C is the concentration during any time period T where the concentration remains consistent.

T is the duration in hours of the exposure at concentration C.
40

The value of E shall not exceed the 8-hour time weighted average specified in Subpart Z of 29

CFR Part 1910 for the substance involved. Table Z-1 (which is too large to insert here) gives

the permissible exposure limits (PELs) which are 8-hour time weighted averages (TWAs) unless

otherwise noted. A “C” designation on concentration in the table denotes a ceiling limit on the

concentration.

When monomers, oligomers and photoinitiator have become part of a polymer, they no

longer have the toxicity that they previously had. Therefore, the UV/EB radiant energy can be

considered as transforming the composition of a liquid material and thereby changing its

toxicological properties. This transformation generally reduces toxicity by making the

contribution of each component to overall toxic dosage unavailable. 

Monomers that were used with acrylic functional groups over 20 years ago were toxic at a 

dose of milligrams per kilogram of body weight. Everything is toxic, it just depends on the

dose. You can be killed by ingesting even pure water or table salt if the dose is large enough. 

Acrylates in use today have a greatly increased toxic dose (which means a lower toxicity) when

compared to monomers and photoinitiators used in the past. However, these formulations

should still be used with adequate hygiene (safety precautions). Table 4 lists some allowable

emissions that were found in 1991.

Additional compounds could have been listed in Table 4, but no PEL standards were available

for them in 1991. These unlisted compounds include: acetophenone, benzophenone,

caprolactone acrylate, 2,2 dimethyltrimethylene acrylate, epoxy acrylate,

ethoxyethoxyethacrylate, ethoxyethyl acrylate, 2 ethylhexyl methacrylate,

glycerolpropoxytriacrylate, hexandiol acrylate, methylcarbamoyloxyethyl acrylate,

pentaerythritol triacrylate, trimethylolpropane triacrylate, trimethylolpropane

tri(3-mercaptopropionate, tripropyleneglycoldiacrylate, n-vinyl pyrrolidone. The fact that there

were no standards available indicates the infancy of UV/EB materials in 1991.

Table 4 Permissible Exposure Limits of Radiation-Curable Material in 1991

Compound 8 hour time averaged permissible exposure limit (PEL)

1,4 divinyl benzene 10 ppm

2-ethylhexyl acrylate 50 ppm

hydroxypropyl acrylate 0.5 ppm *

phenyl glycidyl ether 10 ppm

styrene 100 ppm

vinyl cyclohexene dioxide 10ppm

Note: * - There were no federal standards available, values recommended by American Conference of Government Industrial

Hygienists (ACGIH). OSHA determined the PEL.
41

Ten years ago, many photoinitiators were VOC and leached out after polymerization.

30

Because these photoinitiators also were toxic, they were undesirable and not allowed to contact

food. As a result, new photoinitiators were developed that replaced the old ones. These new

photoinitiators have a lower toxicity in an uncured state and become an integral part of the

polymer molecule. Therefore, toxic compounds can no longer migrate or leach out. After

polymerization they are no longer separate and toxic molecules. 

The Toxic Substance Control Act (TSCA) of 1977 gave EPA broad authority to assess risks to

human health. Most of the radiation-curable materials were subject to TSCA. Section 5 of

TSCA required manufacturers or importers of a new chemical substance to submit a 

Pre-Manufacturing Notice (PMN) for a new chemical substance (NCS) 90 days prior to its

manufacture or import. During the 90 day period, EPA had to decide whether or not the NCS

presented an unreasonable risk. In 1991, questions about acrylic material caused few if any

acrylates to clear the PMN step of the regulatory process. This inhibited the development of

acrylates and also inhibited the development of alternatives. However, a study by the Specialty

Acrylates and Methacrylates Panel of the Chemical Manufacturers Association changed that

situation. Based on that study, the EPA’s position changed and the EPA no longer automatically

considers newer acrylates and methacrylates as significant health risks. However, if a new

acrylate is structurally similar to a substance for which EPA has positive toxicity data, EPA

may regulate that substance on the basis of its potential risk. This change in EPA policy has

helped to introduce new acrylates and methacrylates, especially those with higher molecular

weight. Therefore, the toxicity of UV/EB-cured monomers, oligomers and photoinitiators are

much less of a concern today then they were in the past. 

The American Industrial Hygiene Association has published Workplace Environmental

Exposure Levels (WEELs) for several monomers used in UV/EB-curable coating technology.1

Table 5 shows the PELs for organic solvents that could be used for cleanup or dilution.

When applying a coating by spray painting, about 50% of the coating is carried away in air

flow as overspray. This amount of overspray can be as small as 10% if electrostatic deposition

is used. This is true of both conventional paints and UV paints. The conventional and UV

paints can have a comparable toxicity prior to curing. However, all of the overspray of a

conventional paint must be disposed of, because it has flashed off its volatile components

(mainly the VOC) and changed its viscosity. The UV paint that is captured by the arrester can

be reused because it typically contains no volatile solvent and, therefore, has not changed its

viscosity.

Paint overspray arresters (filters in the air exhaust from a paint spray booth) capture 90% to

99% of the overspray droplets. Reuse of overspray droplets that drain off of a UV/EB paint

overspray arrester can increase the overall effectiveness of a spray coating operation. Various

types of paint overspray arresters, when used with conventional paints, allow droplets with

aerodynamic diameters from 3 to 7 microns or less unimpeded passage. However, a filter to

capture droplets down to 1 micron in diameter could be used with UV paints. This is practical

because drainage from the filter in a UV process can be reused and the cost realized, as a 
42

TABLE 5: PERMISSIBLE EXPOSURE LIMITS (PEL) FOR ORGANIC SOLVENTS

Compound 8 hour time weighted average permissible exposure limit (PEL)

n-butoxyethanol 50 ppm

butyl acetate 150 ppm

n-butyl glycidyl ester 50

butyl lactate 5 ppm *

p-tert-butyl toluene 10 ppm

carbon tetrachloride 10 ppm

di-isopropyl ether 500 ppm

n,n dimethylacetamide 10 ppm

dipropylene glycol methyl ether 100 ppm

dipropyl ketone 50 ppm

2 ethoxyethanol 200 ppm

2 ethoxyethyl acetate 100 ppm

ethyl acetate 400 ppm

ethyl butyl ketone 50 ppm

ethyl ether 400 ppm

sec-hexyl acetate 50 ppm

isophorone 25 ppm

isopropanol 400 ppm

isopropyl acetate 250 ppm

mesityl oxide 25 ppm

methyl acetate 200 ppm

methylal 1,000 ppm

methyl alcohol 200 ppm

methyl n-amyl ketone 100 ppm

methyl n-butyl ketone 100 ppm

methylcyclohexane 500 ppm

methyl ethyl ketone 500 ppm

5-methyl-3-heptane 25 ppm

methyl isoamyl ketone 50 ppm

n-propyl alcohol 200 ppm

propylene glycol monomethyl ether 100 ppm *

1,1,2,2-tetrachloroethane 5 ppm

tetrahydrofuran 200 ppm

toluene 200 ppm

xylenes 100 ppm

* Note: No Federal Standard, value recommended by ACGIH
43

result of the greater pressure, would be less than the cost of the paint saved. 

To minimize potential exposure to uncured UV droplets that do pass through the arrester, a UVcuring unit should be installed on an arrester exhaust. If a UV-curing unit is used to cure the

droplets that pass through the filter before they are exhausted to the atmosphere, the aerosol in

the exhaust air would not be toxic. In addition, the cured exhaust stream would be less likely to

mark a neighbor’s roof than an aerosol from a conventional spray booth.

A paint overspray arrester is typically removed when it is “fully loaded” with uncured

conventional paint. “Fully loaded” means that a filter has too great a pressure drop when

passing the required air flow. In addition to a “fully loaded” filter (and the paint it contains),

paint that has drained off the overspray arrester must be considered. When a conventional paint

is used, this drainage cannot by reused because it has flashed off its volatile components and is

more viscous than the sprayed paint. Therefore, with conventional paints, a greater amount of

waste must be handled and this poses a greater threat of adverse health effects. This threat of

adverse health effects can be minimized by using and reusing UV paint.

The aerosol emission of mist was noted in 1991 as “monomer emissions”, for which the

quantity 

and composition of emissions were to be researched. It has since been discovered that this

aerosol or mist is emitted not only from spray guns, but from rollers and printing presses

(especially high speed operations). Misting varies from 1% to 50% of the total consumed

UV/EB coating or ink. If misting is a problem, the equipment, process and materials suppliers

can work with operators to minimize emissions.

Conventional coatings can range from 40% to 80% solvent by volume. This solvent is

frequently a combination of VOC. Ingredients in conventional coatings that cause health effects

include HAP, VOC, and pigments. HAP include ingredients that are toxic, neurotoxic, and

carcinogenic. UV/EB materials essentially do not contain VOC or HAP (Currently available

UV/EB coatings may have HAP as a very minor ingredient that becomes part of the polymer). 

Some pigments have displayed toxicity.

Currently available UV/EB coatings emit only 1% - 5% by weight, while older coatings could

emit up to 10% as curing volatiles. These values are based on Method 24 results. Method 24

bakes the coating after the cure to drive off any residual VOC, but this may cause some

decomposition to occur.

What About Worker Hygiene?

Hygiene is the procedure that is followed to keep from getting injured, sick, or otherwise having

health problems. It is contrasted with therapy, the procedure followed to recover or to get well

after you have gotten injured, sick, or developed a health problem. Hygiene is safety

precautions. Therefore, it is a good idea to follow good hygiene, even though you may not agree
44

that it is necessary, or understand why it is required. 

Several regulations or laws have been enacted, including the Federal Hazard Communication

Standard, plus federal, state, and local laws and regulations requiring workmen to be informed

of risk factors in a job. Parts of these standards regulate product warning labels, MSDS,

worker education, and training. These standards should help you understand why hygiene needs

to be practiced, why specific hygienic practices are required, and how to communicate hygiene

requirements to employees. 

Although UV/EB-curable materials, in their modern form, have not been in use long enough to

demonstrate long-term toxic effects, some older UV/EB materials have demonstrated short-term

toxic effects. These short-term effects have abated somewhat with development of less toxic

materials over intervening years since these effects were observed. 

Because the same base monomers and oligomers are used in conventional coatings, inks and

adhesives for painting or printing, UV/EB materials are subject to the same conventional

painting or printing hygiene with some additions. Some of these additional safety precautions

are attributed to the acrylic group (or other functional group) which has been attached to an

UV/EB-curable molecule. An acceptable risk of occupational contact dermatitis (inflammation

of the skin and mucous membranes) and eye irritation can be achieved with proper protective

clothing, proper handling procedures of UV/EB-curable materials and proper shielding from

UV/EB radiation. Contact dermatitis also may be caused by an allergic reaction to a substance

in a UV/EB material that is only present in trace amounts.

It is important to remember that UV/EB-curable materials remain spreadable and not necessarily

in one place until they are cured or cleaned up. They do not evaporate, cure, or dry up like

conventional materials do. They may travel based on contact, first from a contaminated site and

then on contact to any other site. Equipment touched by contaminated gloves will remain

contaminated and a source of exposure until it is either exposed to UV/EB radiation or cleaned

up. 

UV/EB-curable materials should never be allowed to come in contact with the eyes. For eye

protection, safety glasses, goggles, or a full face shield should always be worn when handling

any chemicals or solvents (See Figure 13). This was especially true of older UV/EB chemicals,

but you should use this precaution even though newer UV/EB chemicals cause less eye irritation

and are less toxic. 

You should never look directly at UV lamps or strong reflections, even with eye protection. All

eye protection materials should have side shields and absorb sufficient UV light to prevent

unintentional exposure and the resulting eye irritation.1

 

You should never adjust UV or EB shielding without qualified supervision.1

 

You should always eat or drink in a designated lunch area, and never in the work area. You

should be alert to any contamination of this area and avoid such contamination. You should also

wash thoroughly before touching any food or drink.24 You should apply a barrier cream after

eating and before returning to work. 
45

Figure 13: Examples of Safety Equipment 

Direct skin contact with all coatings, inks and adhesives should be avoided.1

 Always wash

hands thoroughly before using restroom facilities. Barrier cream should subsequently be

reapplied after washing hands and before returning to work.24 Barrier creams should be applied

to clean skin before exposure and not applied after exposure. Barrier creams can protect against

material that might penetrate through defects in the protective equipment. 

Typically, fabric or non-woven long sleeved and full leg clothing or coveralls are worn. Rubber

gloves should always be worn when direct contact with radiation curable materials is possible. 

It is appropriate to use the same hygiene for UV/EB materials that you would use for a solvent,

a corrosive chemical, or a toxic chemical. Wearing protective clothing for a full shift may also

require that air temperature be controlled to allow workers to remain comfortable. Use of a

rubber apron or rubber suit is appropriate when there is a possibility that you could be splashed

with solvent, corrosive, or toxic material. Shoes must provide full foot coverage. Rubber boots

should be worn when there is danger of a spill or when walking where a solvent or toxic

material has spilled. 

Contaminated leather objects (shoes, belts, etc.) should be discarded because they cannot be

decontaminated. Always change work clothes before leaving the plant. Never wear the work

clothes or the work shoes away from the plant. 

Contaminated clothing can be laundered at a commercial laundry, but not in a home laundry. 

After cleaning, they may be worn again. Heavily contaminated clothing should be discarded.24

Rags used for clean up should immediately be placed in a container for either disposal or

laundering and should never be placed in your pocket.1

Some coatings use monomers and amine photoinitiators that may have strong odors. Vapor

inhalation is usually an odor problem, but could also become a toxicity problem. Therefore,

ventilation for odor control is strongly advised. Although odoriferous amines are falling out of
46

use, ventilation should also be used for mist aerosols, ozone, and HAP that might result when

UV/EB radiation cured materials are applied and cured. Odors can reach concentration levels

that require controls for the comfort and, perhaps, health of workers.

Misting occurs in high speed presses, at liquid ink transfer points, when paints are sprayed and

during application with high speed rollers. Mist is an aerosol that is probably toxic and possibly

carcinogenic. Misting forms deposits in UV lamp enclosures. Such deposits reduce UV output

and increase heating within an enclosure. Electrical arcing can occur at lamp electrode contacts

as a result of powder accumulating due to misting. This can cause slower curing speeds and

result in higher operating costs. Deposits must be removed from ovens and lamp enclosures

with a mild detergent to avoid these problems. 

The droplet size of mist aerosol is often smaller than 3 microns, but can be larger for sprayed

paints. In both cases, its existence is well-known. Since uncured UV/EB materials have a

toxicity, prudence would require that you not breathe this aerosol. A suitable filter mask or

supplied air mask is recommended when there is no ventilation. If an aerosol has been cured by

sufficient exposure to UV or EB radiant energy, it no longer is toxic. Operations that produce

such aerosols or mists should be enclosed and well ventilated. Ventilation should carry air to an

ultraviolet light source or sunlight to cure a UV coating or ink aerosol, because droplets are

frequently too small to be filtered out. Such aerosols should not be emitted after sundown unless

cured by a curing unit before being emitted. Aerosols can also form in a fire, or with

uncontrolled polymerization of bulk materials. A mask providing fresh air or an organic vapor

respirator should be worn under such potential exposure conditions.1

Make sure that you do not exceed the allowed exposure to ionizing radiation. While the OSHA

definition only applies to x-rays, care must be taken to assure that workers do not receive a UV

dose that would irritate either their skin or eyes. 

COST CONSIDERATIONS

ARE UV/EB-CURED MATERIALS MORE EXPENSIVE THAN CONVENTIONAL

COATINGS, INKS AND ADHESIVES?

Conventional coatings, inks and adhesives can emit 50% to 80% of their volume as VOC. This

VOC evaporates and is carried away by ventilating air flow from application processes and/or

from thermal ovens that dry and cure this material. VOC emissions from UV/EB-cured

materials are much less, ranging from 1% to 10% of the weight of the UV/EB material. 

Typically, VOC emissions from most UV/EB material applications are less than 5% of the

applied material weight. Also note that virtually every component in a UV/EB-cured material

becomes part of the cured coating ink or adhesive, but only 20%-50% of a conventional

material (i.e., the resin and pigments, not the solvent) becomes applied coating solids. Less

gallons of UV/EB material are needed to cover the same amount of area at the same film

thickness. Therefore, the best way to compare the cost of UV/EB and conventional materials is

on a solid film basis instead of cost per gallon. 
47

More effective use of UV/EB-cured materials (based on reuse of overspray) can make UV/EB

operations more cost effective then conventional operations. In addition, more cost savings

result when using UV/EB technology as a result of lower energy requirements, reduced floor

space, increased productivity and absence of add-on control equipment. Overspray of UV/EB

materials can be effectively captured and reused because they generally lack volatiles, and will

not cure unless exposed to UV/EB radiant energy. If recirculation of UV/EB material is a

viable alternative, the cost of UV/EB materials could actually be about 30% - 60% of the cost of

a conventional coating on a comparable solid film basis (this is for material cost only).

The cost of “as applied” UV/EB-cured coatings is about 15% greater than conventional coatings

on a per gallon basis. However, as noted above, over half of a conventional coating evaporates

and does not become part of the final cured coating. Because UV/EB-cured coatings have only

a 1 to 10 % loss, they cost about 45 % less than conventional coatings per square foot on a solid

film basis. The 1991 CTC report stated that UV/EB coatings cost as much as four times the cost

of conventional coatings on a per gallon basis, and twice as much on a solid film basis. Over

the past 10 years these differences are no longer valid because of reductions in price of UV/EBcured materials. When higher production rates (along with a resulting reduction of inventory

in-process), lower energy consumption and reduced floor space requirements are considered,

economic considerations greatly favor UV/EB over conventional coating technologies in most

cases. Similar economic advantages are found in the printing industry.

Higher production rates for UV/EB processes are based on shorter (faster) cure time. Shorter

cure times result in smaller curing units (compared to conventional thermal dryers) that require

less floor space (See Figure 14). Also, there may be additional space savings because UV/EBcured products do not require conditioning time in storage. For conventional processes that use

thermal ovens, product exiting an oven may have to be held for several hours (8 to 24 hours or

possibly more) in storage if conditioning of the substrate is necessary (e.g., to reduce

brittleness after a paper substrate has been subjected to heat and drying in an oven). This

conditioning often requires storage at controlled temperature and humidity. This type of storage

is not needed for products after UV/EB-curing. Therefore, UV/EB processes may have an

additional space and productivity advantage over conventional operations that require product

conditioning after exiting a thermal oven.

As an example, consider two printing lines with 10 foot wide webs and operating at 1,000 feet

per minute. One printing line uses UV technology and print leaves the curing unit completely

cured. The other printing line uses conventional technology and print leaving the oven is

sufficiently cured (i.e., it will no longer smudge). In this comparison, the conventional material

must reach that point in 6 seconds in an oven that extends 100 feet. This may be optimistic. The

conventional process may have to run slower than this, but we will assume that the conventional

material will cure sufficiently in 6 seconds. By comparison, the UV cure will take a fraction of a

second and the UV-curing unit only takes up100 square feet. The thermal oven will need to use

1,000 square feet (10 x 100) of rental floor space at $0.50 per square foot per month ($6.00 per

square foot per year), for a total of $6,000 per year. The UV-curing unit will use only 100

square feet (10 x 10), and the rental cost is $600 per year.
48

Figure 14: Presses With UV-Curing Units

For the same example, energy consumption for a thermal oven is 1.5 MBTU/hr plus blowers at

56 kW. We will assume that natural gas consumption will be at $3.00 /MBTU and electric

consumption will be at $0.07/kW-hr. If the plant operates 300 days per year for two shifts, the

total energy cost for the thermal oven would be $21,600 per year and the cost of electricity for

the blowers would be $18,816 per year. In comparison, the UV-curing unit would use 5.6

kW/lamp times 12 lamps times $0.07/kW-hr to cost $22,579 per year and ventilation would cost

$336 per year on the same basis.

In summary, the cost of operating a conventional printing line in the example would be $6,000 +

$21,600 + $18,816 = $46,416. The cost of operating the UV printing line would be $600 +

$22.579 + $336 = $23,415. This is a savings in operating cost for the UV line over the

conventional line of at least $23,001 ($46,416 - $23,415), or about 50% for this hypothetical

example. 

The capital cost of a thermal oven is significant. The capital cost of a UV-curing unit is almost

trivial by comparison. Even an EB-curing unit should cost less.

As previously indicated, UV/EB-cured coatings, inks and adhesives cure rapidly and can go on

to the next finishing operation in the production process immediately. The only exception (at

this time) is if cationic photoinitiators are used. Cationic curing takes a few seconds compared

to almost instantaneous cures when using free radical photoinitiators

The cost of add-on emission control technology for conventional solvent (i.e., VOC) based

coatings, inks and adhesives can be from $250,000 to over $3,000,000. UV/EB-cured coatings

have minimal VOC emissions; therefore, add-on controls are not required. The capital and
49

operation and maintenance costs of the emission controls needed for conventional applications

should be included in any comparative cost analysis.

When UV/EB materials are used, fire insurance premiums should be reduced due to the lack of

inflammable VOC. (One insurance company reported a 5% reduction). The absence of

inflammable VOC at facilities using UV/EB technology should reduce accidents that lead to fire

or explosion.

Protective equipment and safety measures that must be used with UV/EB materials are typical of

the chemical, printing, painting, and coating industries in general. Although there may be some

variation in safety precautions between facilities that use UV/EB materials compared to

conventional materials, the variations should not greatly influence cost. 

The actual costs for implementing UV/EB technology for a particular operation will vary with

time and circumstances. Actual cost estimates should be obtained for each facility and process at

the time a change is being considered. The net cost of a change to UV/EB-cured technology

usually allows payback within two years.

SUMMARY

WHAT ARE THE ADVANTAGES OF USING UV/EB-CURED 

COATINGS, INKS AND ADHESIVES?

L Cures Fast - Runs at higher rates and cures in a shorter time than evaporative coatings.

L Low Energy Consumption - Uses much less energy to cure than evaporative coatings.

LCompact Design - Uses much less floor space than conventional evaporative coatings.

L Low Emissions - Less emissions without controls than most conventional evaporative

coatings systems with emissions controls.

LRegulatory Advantage - Easily meets most regulatory requirements and eliminates some.

L Cost Effective - Reduces initial costs and payback times. No conditioning required.

L Produces High Quality Finish - Used for quality furniture, magazines, microelectronics.

L Ready-to Go - Materials supplied ready to use - no blending/mixing required.

L Reusable/Recyclable - No volatiles lost in application, can be reused immediately.

L Cures in Curing Unit - Does not cure on equipment, can be left over a weekend.
50

L Less Worker Exposure to HAP/VOC - Absence of HAP/VOC in UV/EB materials.

L Less Flammable - Greater safety, lower fire insurance premiums.

L Able to Recycle Product - Paper from UV/EB products can be recycled, even to higher grade

WHAT ARE THE DISADVANTAGES OF USING UV/EB-CURED 

COATINGS, INKS AND ADHESIVES?

 Misting/Overspray - Spray and high speed roller and printing applications can produce

aerosol that can be inhaled.

 Aerosol Toxicity - Aerosol is uncured, toxic, and will not go away without cleanup.

 Worker Hygiene/Sensitization - Similar to other processes, but different. Has different

results.

 Workplace Contamination/Cleanup - Contamination will persist and spread until cleaned up.

 Persistent in Environment - Uncured material will persist in shade.

 UV/EB Radiant Energy - Can injure if used improperly.

 Customer Resistance - Historic risk of not meeting need. This may now be past.

CONCLUSIONS

1. UV/EB-cured coatings, inks and adhesives are widely used and are expected to be more

widely used as people become more familiar with this material and developers produce new,

safer, and better coatings, inks and adhesives to apply to specific objects or substrates.

2. Toxicity of UV/EB-cured coatings has gone from very toxic to only mildly toxic. Further

advances in toxicity reduction are anticipated. Conventional coatings are considered mildly

toxic. Cured coatings of all types are usually free of toxicity.

3. Use of UV/EB-cured coatings, inks and adhesives requires good hygiene in handling and

disposal of waste. This hygiene is similar to what is already used in the coating, printing, and

chemical industries. However, each situation requires somewhat different equipment. 

4. Using UV/EB radiant energy to cure instead of heat to evaporate VOC from coatings and

inks reduces energy consumption, fire hazard, need for control technology, in-process product

storage requirements, floor space needs and, probably, insurance premiums. These reductions

should provide potentially significant economic benefits.
51

REFERENCES

1. Safety and Handling of UV/EB-curing Materials, R. Golden, Journal of Coatings

Technology, Vol. 69 No. 871, August 1997, pp 83-89

2. Occupational Safety and Health Administration (OSHA) Standards 29CFR No. 1910.1096,

Ionizing Radiation

3. AP-42, Clearinghouse for Inventory and Emission Factors, Environmental Protection

Agency, Chapter 4 Section 9, General Graphic Printing

4. Stork Sheds Light on UV Inks, D. Lanska, Converting Magazine, June 1997

5. Acrylate Formulations for a Solventless Magnetic Tape Manufacturing Process; M. Ellison,

J. Huh, A. Power, J. Purse, and D. Nikles, Proceeding of the Polymeric Materials Science and

Engineering, American Chemical Society, pp 115-116

6. Ultra Low Voltage Curing of Acrylic Hot Melt PSA’s, R. Ramharack, R. Chandran, S. Shah,

D. Hariharan, J. Orloff, and P. Foreman, Adhesives Age, December 1996, pp 40-43

7. Deco-Chem Education Center

www.decochem.com/educntr.htm

8. Coating Types and Curing Characteristics, Small Business Environmental Assistance

Program

sbeap.niar.twsu.edu/docs/pntch2.html

9. Electron-beam Curable Structural Adhesives. Part 1: Study of acrylic resins for adhesive

applications, N. Cadinot, B. Boutevin, AJ. Parisi, D. Beziers and E. Chataignier, International

Journal of Adhesion and Adhesives, Volume 14 Number 4, 1994, pp 237-241

10. Design for the Environment, Flexography Project, Focusing on Flexo Inks,

 EPA 744-F-95-006, February 1996

11. Coating Alternatives Guide, CAGE

cage.rti.org/altern_data.cfm?id=radcure&cat=summary

12. European Coatings Net: New Coating Technologies for Wood Products, M. Tavakoli, S.

Riches, J. Shipman, and M. Thomas

www.coatings.de/articles/tava/TAVA.htm

13. Alternatives to Solvent-Borne Coatings, University of Illinois at Urbana-Champaign

nuclear.hazard.uiuc.edu/packets/coatings/alternat.htm
52

14. Guide to Cleaner Technologies: Organic Coating Replacements, R. Joseph, O. Stanley, C.

Danick, L. Melgery, Envirosense/Environmental Protection Agency

es.epa.gov/program/epaorgs/ord/org-coat.html

15. Polyallyl Glycidal Ether Resins for Very Fast Curing High Performance Coatings,

 J. Knapczyk, Solutia Inc.

www.coatings-solutia.com/docs/TechPubs/211x.htm 

16. Volatile Organic Compounds from Electron Beam Cured and Partially Electron Beam

Cured Packaging Using Automated Short Path Thermal Desorption, V. Das, J. Manura, T.

Hartman, Scientific Instrument Services Application Note No.79

www.sisweb.com/referenc/applnote/app-79.htm

17. Advanced Electron Beam Curing Systems and Recent Composite Armored Vehicle

Results, D. Goodman, C. Byrne, G. Palmese, 42nd International SAMPE Symposium, May 1997 

18. E-Beam Processing of Composite Structures, R. Vastava, 42nd International SAMPE

Symposium, May 1997

19. Layer by Layer E-Beam Curing of Filament Wound Composite Materials with Low Energy

Beam Accelerators, F. Guasti, N. Kutufa, G. Mattacari, E. Rosi, SAMPE Journal, Vol.34 No.2,

March/April 1998

20. Low Energy Electron Beam Curing for Thick Composite Production, F. Guasti and E. Rosi,

Composites - Part A: Applied Science and Manufacturing, Vol. 28 No.11, 1997, pp. 965-969 

21. Toughened Epoxy Resins Cures by Electron Beam Radiation, C. Jahnke, G. Dorsey, S.

Havens, V. Lopata, 28th International SAMPE Technical Conference, November 1996

22. Electron Curing of Epoxy Resins: Initiator and Concentration Effects on Curing Dose and

Rheological Properties, V. Lopata, M. Chung, C. Jahnke, and S. Havens, 28th International

SAMPE Technical Conference, November 1996

23. UV/EB-curing, Primer 1, RadTech International North America, 1995

24. UV-curing Technical Information, Health Safety and the Environment

www.uvcuring.com/uvguide/chap4_8/chap4_8.htm

25. Coatings R&D, Paint and Powder Magazine Online, Dr. Harvest L. Collier, University of

Missouri-Rolla www.ippmagazine.com/news/0499col3.htm

26. UV, EB and Aqueous Coatings: Technical Basics, Elmer W. Griese, GATFWorld,

May/June 1998

27. Radiation Curing in the Printing Industry, CEPE Position Paper of June 1997

www.cepe.org/RadCurePS0697.html
53

28. Volatile Organic Compounds from Electron Beam Cured Packaging Using Automated

Short Path Thermal Desorption, V. Das, J. Manura, T. Hartman, PittaCon99 Meeting, Orlando,

FL, March 1999

29. UV Systems – Technology and Technique, R. Stowe, Fusion Systems at the National

Association of Graphic and Product Identification Manufacturers, Coronado Island Marriott

Resort, CA, October 25-28 1998

30. Radiation-Curable Coatings, Control Technology Center, U.S. Environmental Protection

Agency, April 1991

31. Characteristics and Performance of Radiation Curable Powder Coatings, S. UddingLouwrier, E. Sjord de Jong, R. Baijards, RadTech Proceedings, April 19-22 1998, Chicago, pp

106-111

32. Excimer UV Lamps - The real cold alternative in UV-curing, Dr. A. Roth, M. Honig,

RadTech Proceedings, April 19-22 1998, Chicago, pp 112-116

33. UCB Chemicals Corporation/Radcure - An Overview, M. Philips, D. Nack, RadTech

Proceedings, April 19-22 1998, Chicago, pp 120-124

34. Waterbased radiation-curable systems - newest investigations, W. Reich, P. Enenkel, E. 

Keil, M. Lokai, K. Menzel, w. Schrof, RadTech Proceedings, April 19-22 1998, Chicago, pp

258-265

35. Radiation Curable Binder Matrices of Interest in Manufacturing Energetic Materials, S.

Stiles, Dr C. Clark, RadTech Proceedings, April 19-22 1998, Chicago, pp 266-284

36. Characterization of Radiation Curable Formulations Using a Fluorescence Monitoring

Technique, R. Buehner, pp 337-347

37. New Developments in Fluorescence Probe Technology for Cure Monitoring, K. Specht, R. 

Popielarz, S. Hu, d. Neckers, RadTech Proceedings, April 19-22 1998, Chicago, pp 348-355

38. The Effect of Moisture on the Cationic Polymerization, P. Hupfield, S. Hurford, J. 

Tonge, pp 468-475

39. Low Viscous Maleate/Vinyl Ether Resins as Reactive Diluents In Conventional Acrylate

Based Wood Coating Formulations For UV-curing, E. Meij, A. Dias, L. de Cocq, pp 585-589

40. Water Thinnable UV-Curable Coatings, M. Bernard, RadTech Proceedings, April 19-22

1998, Chicago, pp 590-596

41. UV Lamp Performance Over Time, S. Siegel, RadTech Proceedings, April 19-22 1998,

Chicago, pp 685-691
54

42. A Performance Comparison of Electronic vs. Magnetic Ballast for Powering Gas-Discharge

UV Lamps, E. Persson, D. Kuuisisto, RadTech Proceedings, April 19-22 1998, Chicago, pp

692-700

43. Deinking Trials for RadTech International, Beloit Corporation, Pittsfield Research Center,

Pittsfield, Mass., January 1992

44. Personal communication, Gary Jones, Graphic Arts Technical Foundation, January 31, 2000
55

GLOSSARY OF TERMS

Acrylate(s) An organic salt (an ester) produced by the reaction of acrylic

acid with an organic molecule. It is any molecule that has an

acrylic radical attached to it.

Actinic UV Actinic or far-UV (both terms mean the same thing) is the UV

radiant energy between 180 - 315 nanometers in wavelength. It

is used mainly for sterilization. Also see UV Radiant Energy.

Adhesive(s) Specialty coating designed applied to a material to make it cling

or stick fast to another surface (e.g., the coating applied to make

pressure sensitive tape and labels).

Arrhenius Acid(s) S. Arrhenius of Sweden defined an acid as a hydrogen ion

donor. Since the hydrogen ion is a proton and a neutron, this is

very close to a Bronsted acid. Also see Lewis acid.

Atomic Number (Z) The number of protons in the nucleus of each atom of an

element. The atomic numbers for naturally occurring elements

range from 1 to 89. Man-made elements exist above this range.

Brehmsstrahlung In German, Brehmsstrahlung is literally retarding or braking

radiation. Brehmsstrahlung is the energy lost in the elastic

impact of electrons, or the energy lost when an electron goes

from a larger orbit to a smaller orbit. It is radiated as x-rays.

Bronsted Acid(s) J. N. Bronsted of Denmark defined an acid as a proton donor. 

This definition allows an organic radical or a zeolite to be

included with the acids. It replaced the concept of a hydrogen

ion donor for chemicals that do not hydrolyze or generate

hydrogen ions. See also Arrhenius acids, Lewis acids

Catalyst(s) There are two types of catalysts, heterogenous and

homogenous. Both affect the rate of chemical reactions. A

heterogenous catalyst is a substance within another phase (solid,

liquid or gas). A homogeneous catalyst is a substance within

the same phase. Heterogenous catalysts do not enter into the

reaction, but homogeneous catalysts may enter into the

reaction.

Cationic/Cationic

Polymerization

A positive valence ion that is attracted to the cathode in

electrolysis. A cationic photoinitiator is one that decomposes

under UV/EB radiant energy or from Bronsted Acids to form

cations that cause polymerization to occur by an ionic

mechanism.

Coating(s) A protective, adhesive, or decorative film applied in a layer to a

surface. The coating can be applied as either a liquid or a solid.
56

Crosslinking The interconnecting of one polymer molecule with another by

molecular bonds. Crosslinking raises the glass transition

temperature and gives mechanical strength and abrasion

resistance to the polymer. 

Diluent(s) A low viscosity chemical that is added to a mixture to reduce

overall viscosity. This includes reactive diluents that become

part of the polymer molecule upon polymerization. Reactive

diluents may be VOC prior to polymerization, but cease to be

VOC after polymerization

Dimer(s) Two identical molecules link together to form one molecule. 

An example is a hydrogen peroxide molecule which is two

hydroxyl radicals linked together.

Electromagnetic Wave(s) Radially propagating energy in the form of photons or waves,

traveling away from a source. These photons or waves are

characterized by wavelength or frequency, amplitude, intensity,

and quantum parameters. Wavelength is the speed of

propagation divided by frequency. Amplitude of a wave is a

measure of the strength of the energy. Intensity is measured as

the rate at which the energy is absorbed.

Electron Beam (EB)

EB Radiant Energy

Electron beams are produced by a high potential gradient

between electrodes. When the gradient is high enough,

electrons stream from the negative electrode. A positive

electrode having a hole in the middle attracts the electrons. 

Because an electron has mass, electrons that are directed toward

the hole continue through as an electron beam.

Excimer(s) An excimer is an excited dimer. It is a molecule that is split

apart by photons. It gives a defined spectrum of

electromagnetic energy when the dimer reassembles. If two or

more photons caused the split, the emitted spectrum can even

be at a shorter, more energetic wavelength.

Far UV See Actinic UV

Fluorescence The phenomenon of a single photon exciting a molecule and

causing that molecule to emit a longer wavelength.

Free Radical / Free

Radical Polymerization

A free radical is a molecular fragment having a single unpaired

electron. It causes polymerization by transfer of an electron

from a monomer molecule. When this transfer occurs, the free

radical and the monomer molecule become one. This new

molecule is a larger free radical that can then transfer an

electron from still another monomer molecule. This process

can continue in a chain reaction that will form a seemingly

endless polymer molecule (one composed of many monomers).
57

Functional Group(s) A radical that has been attached to a monomer or oligomer

molecule. A functional group causes a molecule to become

excited more easily in the presence of free radicals and radiant

energy. The most commonly used functional groups are the

acrylic, methacrylic, vinyl ether, and methoxyacrylic radicals.

Gray A unit of absorbed radiant that is equal to one Joule per

kilogram.

Hazardous Air Pollutants

(HAP)

A list of 189 chemicals identified in the Clean Air Act

Amendments of 1990 as Hazardous Air Pollutants. See

Appendix E

Ionizing Radiation Radiation that can ionize a molecule. The term usually refers

to the amount of radiation that will ionize oxygen in air; that is,

radiation with a wavelength shorter than 253 nm (this includes

actinic UV radiant energy generated in UV-curing systems and

electrons and x-rays generated in EB-curing systems).

Infrared (IR)

IR Radiant Energy

Electromagnetic radiant energy that is emitted by any body

above absolute zero in temperature. It is absorbed and sensed as

heat. It is emitted as a spectrum, which shifts its peak to shorter

wavelengths as the temperature increases. The non-luminous

portion of that spectrum is in the range from 700 to ~11,000 nm.

Ink(s) A pigmented fluid or paste that is used as a writing fluid or the

visible result in printing. 

Lewis Acid(s) G. N. Lewis defined an acid as a electron pair acceptor. See

also the Arrhenius Acid and Bronsted acid definitions.

Monomer(s) A molecule that self-assembles into a polymer. Each monomer

is another vertebra in a polymer’s carbon backbone. The types

of monomer that are available will define the properties of a

polymer. Monomer molecules are named for their chemical

structure (e.g., epoxy, polyester, urethane, silicone, etc). 

Near-UV UV radiant energy between 315 nm and 400 nm. Also see UV

Radiant Energy.

Nitrogen Blanket Nitrogen gas that covers the substrate like a blanket to exclude

oxygen in the ambient atmosphere. It is used to avoid ozone

generation, nitrogen oxide generation and oxygen inhibition of

polymerization.

Oligomer(s) A group of 3 to 5 monomer molecules that have been joined

together to form a larger molecule. It behaves as a monomer

would, but is usually less toxic.
58

Overspray The solids potion of a coating from a spray applicator which

fails to adhere to the part being sprayed or coated. UV/EB

overspray may be droplets of liquid because virtually all of the

UV/EB material can become a solid. 

Oxygen Inhibition The premature termination of a polymer molecule caused by the

reaction of oxygen molecules with free radicals. When

polymerization is terminated prematurely, polymer molecules

are shorter and perform differently. 

Photoinitiator(s) A compound that forms free radicals or cations when subjected

to UV/EB radiant energy. A photoinitiator is sensitive to a

specific wavelength of radiant energy. Photoinitiators now

become part of the polymer that is formed. 

Photon(s) According to quantum theory, a hypothetical massless particle

that is used to explain some aspects of an electromagnetic

wave. In quantum theory, the electromagnetic wave and the

particle are the same.

Polymer(s) A chain of many monomer molecules linked together. This

chain can be thousands to millions of monomers long. The

polymer chain tangles and bonds to other polymer chains. 

Commonly, a polymer is known as a plastic.

Polymerization The process that forms a polymer from monomers and

oligomers. 

Radiation Energy (in some form) emitted from a source, propagated

radially along a line-of-sight, and absorbed. However,

depending on the type and source of the energy, the effects of

radiation on humans are very different

Radical An ionized portion of a molecule. Normally these are anions

and cations, depending upon whether they have a surplus or

deficiency of electrons.

Radioactivity A property of some atoms in which electromagnetic energy is

emitted. The energy comes from an unstable ratio of neutrons

to protons in the nucleus of these atoms. The nucleus will either

spontaneously fission or fuse to reduce the energy. This occurs

spontaneously and the energy is radiated away as gamma rays,

x-rays, or other particles. Half of the atoms having such

identity will fission or fuse within a well defined half life. 

Reactive Diluent(s) see Diluents

Resin(s) A term used interchangeably with polymer.
59

Roentgens (R) A unit of absorbed radiation. One Roentgen equals 100 ergs

per gram.

Roentgen Equivalent for

Mankind (REM)

A unit of absorbed dose for the human body. It is expressed in

Roentgens (see above). It is the absorbed dose over the

spectrum up to 100 nm. Since the REM is an integral (the sum)

of all these wavelengths multiplied by the absorption at that

wavelength, there are no conversion factors from other

measurements. 

Solvent A liquid used in a paint, coating or ink to dissolve or disperse

film-forming constituents and to adjust viscosity. It evaporates

during drying/curing and does not become part of the dried film.

Substrate The surface to which a coating is applied.

Three-Dimensional (3D) Any object that has length, width, and depth dimensions. Such

objects are capable of casting a shadow over some portion of

their surface. With regard to UV/EB technology, this refers to

the ability to minimize the effect of such shadows to provide for

curing of the entire coating.

Toxic Dose The lethal dose for 50% of laboratory animals (rats) that

ingested the substance. It can also refer to the concentration that

if inhaled leads to 50% death of laboratory animals.

Transfer Efficiency The ratio of the amount of coating solids deposited onto the

surface of the coated part to the total amount of coating solids

used.

Ultraviolet (UV) 

UV Radiant Energy

That portion of the electromagnetic spectrum between 180 nm

and 400 nm. This can be broken into near-UV (315 nm - 400

nm) and far-UV or actinic (180 nm - 315 nm). It can also be

broken into UV-A ( 315 nm - 400 nm), UV-B (290nm -315

nm), and UV-C (220nm - 290 nm). Near-UV, UV-a, and UV-B

are used for curing UV materials. Sunburn is caused by UV-A

and UV-B. Actinic UV or UV-C is used for sterilization. 

Volatile Organic

Compounds (VOC)

Any compound of carbon, excluding carbon monoxide, carbon

dioxide, carbonic acid, metallic carbides or carbonates, and

ammonium carbonate, which participates in atmospheric

photochemical reactions. This includes any such organic

compound other than those that the Administrator of EPA has

determined to have negligible photochemical reactivity.

See Appendix D
60

Web Any fabric, paper, plastic film, metallic foil, coiled sheet metal,

or other products which are flexible enough to be unrolled from

a large roll, coated by blade, roll coating, or rotogravure as a

continuous sheet and, after cured, rerolled

X-Ray(s) Electromagnetic radiation having a wavelength ranging from

0.1 nm to 40 nm. X-rays have a relatively low absorption, and

therefore pass through solids. The attenuation (reduction) in

intensity varies with the mass along that path, the atomic

number of the material along the path, and the wavelength of

the x-ray. Some high Z materials can reduce the x-ray to

background levels with only a short path. 
A -1

APPENDIX A

ULTRAVIOLET AND ELECTRON BEAM RADIATION 

VS. 

RADIOACTIVITY

Radiation is a very broad term. It can refer to the emission of rays of heat, light, radio waves,

or sounds; however, it can also may refer to the emissions of rays by a radioactive substance. 

Ultraviolet (UV) and electron beam (EB) radiation are not the same as radioactivity and

should not be confused. Hopefully this appendix will help you understand the difference. Niels

Bohr’s concept of the atom (i.e., a nucleus of protons and neutrons surrounded by orbiting

electrons) is the basis for this appendix. We do not need to go any deeper into the realm of

atomic structure.

RADIOACTIVITY

Radioactivity is a property of atoms that have an unstable ratio of neutrons to protons in their

nucleus (i.e., have more than the minimum energy in the nucleus). Because these atoms have

more energy than atoms with a stable nuclide (i.e., a favorable ratio of neutrons to protons),

these atoms are unstable. The nuclei of these atoms spontaneously divide (fission, when the

number of protons is greater than 82, which is the atomic number of lead) or combine (fusion,

when the number of protons is less than 82) with well-defined half-lives. These fissions and

fusions cause emission of electrons, alpha particles (two protons and two neutrons, a helium

nucleus), beta particles (a positron or an electron), neutrons, protons, x-rays, and gamma rays. 

The half-life is defined as the time for half of the atoms to undergo either fission or fusion. 

Half-lives range from almost instantaneous to millennia. 

Fission or fusion of these atoms can be greatly accelerated when they are bombarded by neutrons

from a chain reaction. This happens when neutrons are sufficiently conserved within a critical

mass. As far as we know, a critical mass occurs only in man-made nuclear reactors and in nature

in the core of each star and planet. Even the Earth has a radioactive core and, therefore, we

cannot totally avoid all radioactivity. 

There are naturally occurring radioactive isotopes of elements (atoms having a defined atomic

number, but having various atomic weights). These isotopes exist in trace quantities and are

radioactive. UV/EB radiation does not change the concentration, rate of reaction, or number of

such isotope atoms. Therefore, UV/EB radiation does not change naturally occurring

radioactivity. UV/EB radiant energy does not make atoms radioactive.

Gamma rays are not used for curing UV/EB materials because they require much more shielding

to attenuate the intensity of radiation to near background radiation levels. 35
A -2

UV/EB RADIATION 

UV/EB radiation refers to electromagnetic energy moving radially (i.e., radiating) from a

source. This energy is normally transmitted over a line of sight, but it experiences scattering

when it strikes an object. Ultraviolet radiation exists in sunlight and is emitted, very weakly,

by radioactive materials (except when they undergo a chain reaction - as in the sun or Earth’s

core - and elevate their temperature). Our principal natural source of ultraviolet radiation is

sunlight. 

The energy of a photon is inversely proportional to its wavelength. Scattering is a function of

wavelength and the size of the object that produces scattering. When the diameter of an object

(scatterer) is less than a tenth of the wavelength of the radiant energy, scattering is negligible. 

When the size of the scatterer becomes comparable to or larger than the wavelength of the

radiated energy, scattering is enhanced. You can see an example of this with visible light in a

smoky room. Visible light rays (400-700 nm wavelength) go radially as directed until they

strike a scatterer (e.g., a smoke particle of about 1000 nm) that scatters the radiation. Each

scatterer acts like a point source in scattering waves of radiation and, therefore, each scatterer

appears to be a luminous source. All wavelengths of radiation behave like this, regardless of

the source. X-rays have a short enough wavelength that even oxygen and nitrogen molecules

become scatterers like the smoke described above.

Electron beams are composed of particles (electrons) that collide with other electrons and

scatter, too. Electrons do not actually collide with electrons, but repel each other in close

encounters that resemble collisions. Electron beams, in scattering electrons and impacting

nuclei, generate x-rays similar to those emitted from radioactive materials, but these x-rays (like

medical x-rays) cease to be emitted when the electron beam is turned off. 

CONCLUSION

Since UV/EB radiation does not supply neutrons, the UV/EB-cured material does not have any

change in radioactivity or half-life. Therefore, the only connection between UV/EB radiation

and radioactivity is purely linguistic. Both radiation and radioactivity use the root radi- to

describe radial propagation of energy by quantum particles or electromagnetic waves.

We hope that this clarifies more misconceptions than it may cause, for as Alfred North

Whitehead once said, “All truths are only half-truths.” This is true because the human mind

cannot understand or accept whole truths. We all function on half-truths that we can understand. 

We can act intelligently only when we have the capability to understand what we are doing.
B -1

APPENDIX B

EXAMPLES OF UV/EB COATING AND INK USE

ABRASIVES

Abrasives can be permanently bonded instantly. This eliminates an energy-intensive 8 hour or

longer curing that is required for conventional evaporative coatings under controlled

temperature and ventilation. It also eliminates storage of a day’s production under these

controlled conditions. UV-cured abrasives are instantly ready for use.

DENTISTRY

Dental fillings are another application area. After preparing a tooth, a suitably sized lump of

oligomers, photoinitiators, pigments and fillers is mixed and inserted into a clean dry hole in

the tooth. After insertion and molding, an intense UV light source (with readily apparent visible

light) is directed at it by a wand. In about a minute the UV and visible light cures the filling and

the person can use their teeth immediately after finishing operations are completed. While this

seems slow, it is a much faster cure than silver amalgam fillings. The use of a radiation-cured

dental filling has an additional benefit in that it avoids ingestion of mercury from silver amalgam

fillings. 

FIBER REINFORCED PLASTICS

Coatings have also been used as the cement to hold fibers or particles together. These fiberreinforced-polymer items are used to construct 3D objects. Penetration of EB radiation

becomes a significant factor when coating depth is over 1 centimeter. These thick applications

have been cured by EB either in a vacuum chamber or with a cationic photoinitiator. In these

types of applications, coatings are not limited to a surface, but also may be found on interfaces

at any depth within the object.

FOOD PACKAGING / MENUS

Ten years ago strong odors associated with some monomers and photoinitiators precluded their

use with foods and perfumes. This has been overcome to a large extent, by purification to

eliminate malodorous impurities, using a less odiferous photoinitiator, or using other

alternatives to odiferous additives, monomers, or oligomers. These deodorized materials have

made both printing and overprint coatings suitable for packages for fine perfumes, chocolates,

and food, and even for restaurant menus.23
B -2

MAGNETIC MEDIA

Printing of magnetic media by orienting magnetic particles of a coating to lock magnetic

domains of particles in a preferred position before EB-curing has benefitted the high density

floppy disk and tape manufacturing industry. EB-curing also allows a more durable surface

after bonding. Such coatings must be applied in a clean room to control coating thickness,

insure surface smoothness, and to eliminate dust particles. EB-curing allows these needs to be

easily met. 

MICROELECTRONICS

In the microelectronics industry, electron beams have been focused and used to trace circuits on

coated substrates. Alternatively, UV has been used to cure a coating through a mask. The

coating (which is referred to as a photoresist) is cured by the focused EB along a path where a

substrate must be protected from the next step in the process. The coating is then “developed”

by washing any uncured resin away with a solvent. This leaves uncured parts of the substrate

unprotected from reagents used to subsequently etch, deposit a dopant (an atomic species that

changes the electronic properties of the substrate), or deposit metal conductors. It has been

found that for very sharp demarcation of edges of a cured polymer, a coating thickness has to

be no thicker than the width of a line on the microelectronics. Microelectronics now uses lines

only 0.18 microns wide. This thin layer of monomer is applied by diluting or heating the

coating to reduce viscosity and then spreading it by high-speed spinning of the substrate to

centrifuge most of the coating away. The substrate is usually a sliced and polished section of a

purified silicon ingot (called a boule`) about 4 inches in diameter. 

To be able to use UV, the wavelength must be shorter. This is referred to as extreme UV. This

process requires a thin film that can be either UV-cured through a mask, or EB-cured along a

path. For a UV cure, UV radiant energy must be at a wavelength that the photoinitiator can

adsorb and that delineates a clear image (edge), even if the path is obstructed. For an EB cure,

EB radiant energy must be focused to a spot no larger than the finest line that must be

produced. This produces an EB that cures the thin film instantly at low voltage.

After the cured coating has performed its function of providing a mask for reagents, the cured

polymer is stripped off and another thin coating of photoresist is applied before the next step of

the process is performed. This is repeated several times when an integrated circuit is created. 

Integrated circuits are used as central processor units, as memory, as programmable gate arrays,

and as various logic components that are used on circuit boards to make digital circuits. 

On printed circuit boards, features such as solder masks, notations, encapsulates and conformal

coatings all use a thicker UV/EB-curable coating than that used in making integrated circuits.

Although curing of UV/EB coatings on circuit boards is fast, it is not as rapid as EB-curing for

microelectronics (extremely rapid). However, the time required for curing microelectronics is

per unit length along the track within the mask, while curing for circuit board coatings occurs all

at once. 
B -3

OPTICAL FIBERS

3D techniques have been applied to cure coatings on optical fibers. The inner coating on

optical fibers has a low index of refraction that redirects light (the signal) back into the fiber. An

overcoat for these fibers provides abrasion resistance and adds to mechanical strength. An

optically absorbent final coating prevents undesirable “crosstalk” between fibers. Without these

radiation-cured coatings, long distance optical fiber communications could not have come into

existence. 

PRESSURE SENSITIVE ADHESIVES

Use of UV/EB coatings with pressure sensitive adhesives is seldom advertised. Pressure

sensitive adhesives are used to bond metallization to wrappings, for tapes and labels, and to

laminate. Advantages include: (1) use of single-component materials that can be dispensed with

automated equipment; (2) long open time without losing volatile ingredients; (3) fast cures after

dispensing; (4) low energy requirement for curing; and (5) ability to be used on temperature

sensitive substrates such as paper and plastic films. 

PRINTING

UV/EB coatings had their start in printing and many terms from printing are generically used -

such as web that refers to a continuous flexible substrate that is unrolled, passes through the

printing press and drying ovens, and is then re-rolled. Radiation-cured printing inks are used

for lithographic, rotogravure, screen, and flexographic printing.3,4 All of these types of printing

are in a state of rapid evolution with former distinctions between them becoming blurred. As a

result, any generalization may have already become obsolete. For example, flexography has

historically used a low viscosity ink. While UV/EB-cured inks are more viscous than the

traditional flexographic inks, UV/EB-cured inks are used in flexography anyway. UV/EB

radiation-cured inks allow printing presses to have web speeds of 400-1000 feet per minute.

The advent of ultraviolet lasers has allowed UV-curing of photopolymer printing plates without

need for a negative transparency. The ultraviolet laser is computer controlled, and can be used

to make any number of identical plates at any number of sites. These plates can then make

identical impressions on any number of presses. This eliminates the need for printing plates that

can make a million impressions and adds to the capacity to reproduce images. 

RELEASE COATINGS

Release coatings are usually silicones applied to plastic or paper. Silicone resin producers

worked with equipment producers and flexible packaging printers to produce desired UV/EB

radiation-cured release coatings. Labels and double-sided tapes with pressure sensitive

adhesive coatings are normally placed on a release coating until they are applied.
B -4

SPRAY COATING

UV/EB-cured paints are suitable for spray-coating and can realize up to 99% overall

effectiveness in applying a coating to a substrate when capture and reuse of overspray are

considered. Coatings have been applied to materials that are porous (such as wood or ceramics)

or impervious (such as plastics or metal). This overall effectiveness is significantly greater than

that for conventional coatings because captured UV/EB droplets can be reused. This can be

done because UV coatings can have essentially zero VOC content and do not cure unless

exposed to an appropriate radiation source.

VINYL FLOORING

Vinyl floor coatings are second only to paper coatings in use of UV/EB-cured coatings.

Premium grade no-wax vinyl flooring uses a UV/EB topcoat consisting of two layers. The first

layer is a barrier coat to seal the vinyl and provide better adhesion for the final layer. The final

layer is an abrasion resistant coating to improve wear characteristics.

WOOD PRODUCTS

UV wood product coatings have been used for a long time. They were used first to coat panels

with polyester resins. Acrylic and urethane-acrylic coatings have since been used on panels for

greater durability. Further developments have included 3D cure of sealers and primers for wood

furniture. UV radiation curing of topcoats for fine furniture allows a shorter cure time (a few

seconds) with fewer dust flaws in the wet surface. 

The example given for emissions in the 1991 reference is now outdated. The use of VOC as

thinners in furniture coatings is now obsolete. In 1999, wood furniture used water thinned UVcured coatings, monomer thinned UV-cured coatings, heat and reactive diluents when

temperature alone could not sufficiently control viscosity. 
C -1

APPENDIX C



EMISSION MEASUREMENT TECHNICAL INFORMATION CENTER

NSPS TEST METHOD



(EMTIC —24, 9/11/95)

 

Method 24 - Determination of Volatile Matter Content,

Water Content, Density, Volume Solids, and

Weight Solids of Surface Coatings

1. APPLICABILITY AND PRINCIPLE

1.1 Applicability. This method applies to the determination of

volatile matter content, water content, density, volume solids,

and weight solids of paint, varnish, lacquer, or related surface

coatings.

1.2 Principle. Standard methods are used to determine the

volatile matter content, water content, density, volume solids,

and weight solids of the paint, varnish, lacquer, or related

surface coatings.

2. APPLICABLE STANDARD METHODS

Use the apparatus, reagents, and procedures specified in the

standard methods below:

2.1 ASTM D 1475-60 (Reapproved 1980), Standard Test Method for

Density of Paint, Varnish, Lacquer, and Related Products. 

2.2 ASTM D 2369-81, Standard Test Method for Volatile Content of

Coatings. 

2.3 ASTM D 3792-79, Standard Test Method for Water Content of

Water Reducible Paints by Direct Injection into a Gas

Chromatograph. 

2.4 ASTM D 4017-81, Standard Test Method for Water in Paints and

Paint Materials by the Karl Fischer Titration Method. 

2.5 ASTM 4457-85 Standard Test Method for Determination of

Dichloromethane and 1,1,1-Trichloroethane in Paints and Coatings

by Direct Injection into a Gas Chromatograph (incorporated by

reference--see §60.17).

2.6 ASTM D 5403-93 Standard Test Methods for Volatile Content of

Radiation Curable Materials (incorporated by reference--see

§60.17).
C -2

Eq.

3. PROCEDURE

3.1 Multicomponent Coatings. Multicomponent coatings are

coatings that are packaged in two or more parts, which are

combined before application. Upon combination a coreactant from

one part of the coating chemically reacts, at ambient conditions,

with a coreactant from another part of the coating. To determine

the total volatile content, water content, and density of

multicomponent coatings, follow the procedures in section 3.8. 

3.2 Non Thin-film Ultraviolet Radiation-cured Coating. To

determine volatile content of non thin-film ultraviolet 

radiation-cured (UV radiation-cured) coatings, follow the

procedures in Section 3.9. Determine water content, density and

solids content of the UV-cured coatings according to Sections

3.4, 3.5, and 3.6, respectively. The UV-cured coatings are

coatings which contain unreacted monomers that are polymerized by

exposure to ultraviolet light. To determine if a coating or ink

can be classified as a thin-film UV cured coating or ink, use the

following equation:

where:

A = Area of substrate, in2

, cm2.

C = Amount of coating or ink added to the substrate, g.

D = Density of coating or ink, g/in3 (g/cm3)

F = Manufacturer’s recommended film thickness, in (cm).

If C is less than 0.2 g and A is greater than or equal to 35 in2

(225 cm2) then the coating or ink is considered a thin-film UV

radiation-cured coating for determining applicability of 

ASTM D 5403-93. NOTE: As noted in Section 1.4 of 

ASTM D 5403-93, this method may not be applicable to radiation

curable materials wherein the volatile material is water. For

all other coatings not covered by Sections 3.1 or 3.2 analyze as

follows:

3.3 Volatile Matter Content. Use the procedure in ASTM D 2369-

81 to determine the volatile matter content (may include water)

of the coating. 

3.3.1 Record the following information:

W1 = Weight of dish and sample before heating, g.

W2 = Weight of dish and sample after heating, g.

W3 = Sample weight, g.
C -3

3.3.2 Run analyses in pairs (duplicate sets) for each coating

until the criterion in Section 4.3 is met. Calculate the weight

fraction of the volatile matter (Wv) for each analysis as

follows:

Wv = (W1 - W2)/W3 Eq. 24-2

 

Record the arithmetic average (Wv).

3.4 Water Content. For waterborne (water reducible) coatings

only, determine the weight fraction of water (Ww) using either

ASTM D 3792-79 or ASTM D 4017—81. A waterborne coating is any

coating which contains more than 5 percent water by weight in its

volatile fraction. Run duplicate sets of determinations until

the criterion in Section 4.3 is met. Record the arithmetic

average (Ww).

3.5 Coating Density. Determine the density (Dc, kg/liter) of

the surface coating using the procedure in ASTM D 1475-60. Run

duplicate sets of determinations for each coating until the

criterion in Section 4.3 is met. Record the arithmetic average

(Dc).

3.6 Solids Content. Determine the volume fraction (Vs) solids

of the coating by calculation using the manufacturer's

formulation.

3.7 Exempt Solvent Content. Determine the weight fraction of

exempt solvents (WE) by using ASTM Method D4457-85 (incorporated

by reference--see §60.17). Run a duplicate set of determinations

and record the arithmetic average (WE).

3.8 To determine the total volatile content, water content, and

density of multicomponent coatings, use the following procedures:

3.8.1 Prepare about 100 ml of sample by mixing the components in

a storage container, such as a glass jar with a screw top or a

metal can with a cap. The storage container should be just large

enough to hold the mixture. Combine the components (by weight or

volume) in the ratio recommended by the manufacturer. Tightly

close the container between additions and during mixing to

prevent loss of volatile materials. However, most manufacturers

mixing instructions are by volume. Because of possible error

caused by expansion of the liquid when measuring the volume, it

is recommended that the components be combined by weight. When

weight is used to combine the components and the manufacturer’s

recommended ratio is by volume, the density must be determined by

section 3.5.

3.8.2 Immediately after mixing, take aliquots from this 100 ml

sample for determination of the total volatile content, water

content, and density. To determine water content follow
C -4

section 3.4. To determine density, follow section 3.5. To

determine total volatile content, use the apparatus and reagents

described in ASTM D2369-81, sections 3 and 4, respectively

(incorporated by reference, and see §60.17) the following

procedures:

3.8.2.1 Weigh and record the weight of an aluminum foil weighing

dish. Add 3+1 ml of suitable solvent as specified in ASTM

D2369-81 to the weighing dish. Using a syringe as specified in

ASTM D2369-81, weigh to 1 mg, by difference, a sample of coating

into the weighing dish. For coatings believed to have a volatile

content less than 40 weight percent, a suitable size is

0.3 + 0.10 g, but for coatings believed to have a volatile

content greater than 40 weight percent, a suitable size is

0.5 + 0.1 g.

NOTE: If the volatile content determined pursuant to

section 5 is not in the range corresponding to the sample size

chosen repeat the test with the appropriate sample size. Add the

specimen dropwise, shaking (swirling) the dish to disperse the

specimen completely in the solvent. If the material forms a lump

that cannot be dispersed, discard the specimen and prepare a new

one. Similarly, prepare a duplicate. The sample shall stand for

a minimum of 1 hour, but no more than 24 hours prior to being

oven fried at 110 + 5°C, for 1 hour. 

3.8.2.2 Heat the aluminum foil dishes containing the dispersed

specimens in the forced draft oven for 60 min at 110+5°C. 

Caution -- provide adequate ventilation, consistent with accepted

laboratory practice, to prevent solvent vapors from accumulating

to a dangerous level.

3.8.2.3 Remove the dishes from the oven, place immediately in a

desiccator, cool to ambient temperature, and weigh to within

1 mg.

 

3.8.2.4 Run analyses in pairs (duplicate sets) for each coating

mixture until the criterion in section 4.3 is met. Calculate Wv

following Equation 24-2 and record the arithmetic average.

3.9 UV-cured Coating's Volatile Matter Content. Use the

procedure in ASTM D 5403-93 (incorporated by reference--see

§60.17) to determine the volatile matter content of the coating

except the curing test described in NOTE 2 of ASTM D 5403-93 is

required.

4. DATA VALIDATION PROCEDURE

4.1 Summary. The variety of coatings that may be subject to

analysis makes it necessary to verify the ability of the analyst

and the analytical procedures to obtain reproducible results for
C -5

the coatings tested. This is done by running duplicate analyses

on each sample tested and comparing results with the withinlaboratory precision statements for each parameter. Because of

the inherent increased imprecision in the determination of the

VOC content of water-borne coatings as the weight percent water

increases, measured parameters for water-borne coatings are 

modified by the appropriate confidence limits based on betweenlaboratory precision statements.

4.2 Analytical Precision Statements. The within-laboratory and

between-laboratory precision statements are given below:

 Within- Between- 

 laboratory Laboratory

 

Volatile matter content, Wv 1.5% Wv 4.7% Wv

Water content, Ww 2.9% Ww 7.5% Ww

Density, Dc 001 kg/liter 0.002 kg/liter

4.3 Sample Analysis Criteria. For Wv and Ww, run duplicate

analyses until the difference between the two values in a set is

less than or equal to the within-laboratory precision statement

for that parameter. For Dc run duplicate analyses until each

value in a set deviates from the mean of the set by no more than

the within-laboratory precision statement. If after several

attempts it is concluded that the ASTM procedures cannot be used

for the specific coating with the established within-laboratory

precision, the Administrator will assume responsibility for

providing the necessary procedures for revising the method or

precision statements upon written request to: Director, Emission

Standards and Engineering Division, MD-13, Office of Air Quality

Planning and Standards, U.S. Environmental Protection Agency,

Research Triangle Park, NC 27711.

4.4 Confidence Limit Calculations for Waterborne Coatings. 

Based on the between-laboratory precision statements, calculate

the confidence limits for waterborne coatings as follows: To

calculate the lower confidence limit, subtract the appropriate

between-laboratory precision value from the measured mean value

for that parameter. To calculate the upper confidence limit, add

the appropriate between-laboratory precision value to the

measured mean value for that parameter. For Wv and Dc, use the

lower confidence limits, and for Ww, use the upper confidence

limit. Because Vs is calculated, there is no adjustment for this

parameter.
C -6

5. CALCULATIONS

5.1 Nonaqueous Volatile Matter.

5.1.1 Solvent-borne Coatings.

 Wo = Wv Eq. 24-3

where: Wo = Weight fraction nonaqueous volatile matter, g/g.

5.1.2 Waterborne Coatings.

 Wo = Wv - Ww Eq. 24-4

5.2 Weight Fraction Solids.

 Ws = 1 - Wv. Eq. 24-5

where: Ws = Weight solids, g/g.
D -1

APPENDIX D

Definition of Volatile Organic Compounds (VOC)

As of 2/25/99

40 CFR 51.100(s) - Definition - Volatile organic compounds (VOC)

"Volatile organic compounds (VOC)" means any compound of carbon, excluding carbon

monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium

carbonate, which participates in atmospheric photochemical reactions. 

(1) This includes any such organic compound other than the following, which have been

determined to have negligible photochemical reactivity: 

 methane

 ethane

 methylene chloride (dichloromethane)

 1,1,1-trichloroethane (methyl chloroform)

 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113)

 trichlorofluoromethane (CFC-11)

 dichlorodifluoromethane (CFC-12)

 chlorodifluoromethane (HCFC-22)

 trifluoromethane (HFC-23)

 1,2-dichloro 1,1,2,2-tetrafluoroethane (CFC-114)

 chloropentafluoroethane (CFC-115)

 1,1,1-trifluoro 2,2-dichloroethane (HCFC-123)

 1,1,1,2-tetrafluoroethane (HFC-134a)

 1,1-dichloro 1-fluoroethane (HCFC-141b)

 1-chloro 1,1-difluoroethane (HCFC-142b)

 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124)

 pentafluoroethane (HFC-125)

 1,1,2,2-tetrafluoroethane (HFC-134)

 1,1,1-trifluoroethane (HFC-143a)

 1,1-difluoroethane (HFC-152a)

 parachlorobenzotrifluoride (PCBTF)

 cyclic, branched, or linear completely methylated siloxanes

 acetone

 perchloroethylene (tetrachloroethylene)

 3,3-dichloro-1,1,1,2,2-pentafluoropropane (HCFC-225ca)

 1,3-dichloro-1,1,2,2,3-pentafluoropropane (HCFC-225cb)

 1,1,1,2,3,4,4,5,5,5-decafluoropentane (HFC 43-10mee)

 difluoromethane (HFC-32)

 ethylfluoride (HFC-161)

 1,1,1,3,3,3-hexafluoropropane (HFC-236fa)
D -2

 1,1,2,2,3-pentafluoropropane (HFC-245ca)

 1,1,2,3,3-pentafluoropropane (HFC-245ea)

 1,1,1,2,3-pentafluoropropane (HFC-245eb)

 1,1,1,3,3-pentafluoropropane (HFC-245fa)

 1,1,1,2,3,3-hexafluoropropane (HFC-236ea)

 1,1,1,3,3-pentafluorobutane (HFC-365mfc)

 chlorofluoromethane (HCFC-31)

 1-chloro-1-fluoroethane (HCFC-151a)

 1,2-dichloro-1,1,2-trifluoroethane (HCFC-123a)

 1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxy-butane (C4F9OCH3)

 2-(difluoromethoxymethyl)-1,1,1,2,3,3,3-heptafluoropropane ((CF3)2CFCF2OCH3)

 1-ethoxy-1,1,2,2,3,3,4,4,4-nonafluorobutane (C4F9OC2H5)

 2-(ethoxydifluoromethyl)-1,1,1,2,3,3,3-heptafluoropropane ((CF3)2CFCF2OC2H5)

 methyl acetate and perfluorocarbon compounds which fall into these classes: 

 (i) cyclic, branched, or linear, completely fluorinated alkanes, 

 (ii) cyclic, branched, or linear, completely fluorinated ethers with no

unsaturations, 

 (iii) cyclic, branched, or linear, completely fluorinated tertiary amines with no

unsaturations, and 

 (iv) sulfur containing perfluorocarbons with no unsaturations and with sulfur

bonds only to carbon and fluorine. 

(2) For purposes of determining compliance with emissions limits, VOC will be measured by

the test methods in the approved State implementation plan (SIP) or 40 CFR Part 60, Appendix

A, as applicable. Where such a method also measures compounds with negligible photochemical

reactivity, these negligibly-reactive compounds may be excluded as VOC if the amount of such

compounds is accurately quantified, and such exclusion is approved by the enforcement

authority. 

(3) As a precondition to excluding these compounds as VOC or at any time thereafter, the

enforcement authority may require an owner or operator to provide monitoring or testing

methods and results demonstrating, to the satisfaction of the enforcement authority, the amount

of negligibly-reactive compounds in the source's emissions. 

(4) For purposes of Federal enforcement for a specific source, the EPA shall use the test methods

specified in the applicable EPA-approved SIP, in a permit issued pursuant to a program

approved or promulgated under Title V of the Act, or under 40 CFR Part 51, Subpart I or

Appendix S, or under 40 CFR Parts 52 or 60. The EPA shall not be bound by any State

determination as to appropriate methods for testing or monitoring negligibly-reactive compounds

if such determination is not reflected in any of the above provisions.

Note to reader: This has been formatted to make it easier for the user to read.
E -1

APPENDIX E

HAZARDOUS AIR POLLUTANTS (HAP)

This appendix contains the original list of hazardous air pollutants from the Clean Air

Act Amendments of 1990 followed by a list of final and proposed modifications to the list.

HAP LIST FROM THE CLEAN AIR ACT AMENDMENTS OF 1990

CAS Number Chemical Name

75070 Acetaldehyde

60355 Acetamide

75058 Acetonitrile

98862 Acetophenone

53963 2-Acetylaminofluorene

107028 Acrolein

79061 Acrylamide

79107 Acrylic acid

107131 Acrylonitrile

107051 Allyl chloride

92671 4-Aminobiphenyl

62533 Aniline

90040 o-Anisidine

133221 Asbestos

71432 Benzene (including benzene from gasoline)

92875 Benzidine

98077 Benzotrichloride

100447 Benzyl chloride

92524 Biphenyl

117817 Bis(2-ethylhexyl)phthalate (DEHP)

542881 Bis(chloromethyl)ether

75252 Bromoform

106990 1,3-Butadiene

156627 Calcium cyanamide

105602 Caprolactam (See Modification) 

133062 Captan

63252 Carbaryl

75150 Carbon disulfide

56235 Carbon tetrachloride

463581 Carbonyl sulfide
E -2

CAS Number Chemical Name

120809 Catechol

133904 Chloramben

57749 Chlordane

7782505 Chlorine

79118 Chloroacetic acid

532274 2-Chloroacetophenone

108907 Chlorobenzene

510156 Chlorobenzilate

67663 Chloroform

107302 Chloromethyl methyl ether

126998 Chloroprene

1319773 Cresols/Cresylic acid (isomers and mixture)

95487 o-Cresol

108394 m-Cresol

106445 p-Cresol

98828 Cumene

94757 2,4-D, salts and esters

3547044 DDE (See technical note) 

334883 Diazomethane

132649 Dibenzofurans (See technical note)

96128 1,2-Dibromo-3-chloropropane

84742 Dibutylphthalate

106467 1,4-Dichlorobenzene(p)

91941 3,3-Dichlorobenzidene (See technical note)

111444 Dichloroethyl ether (Bis(2-chloroethyl)ether)

542756 1,3-Dichloropropene

62737 Dichlorvos

111422 Diethanolamine

121697 N,N-Diethyl aniline (N,N-Dimethylaniline) (See technical note)

64675 Diethyl sulfate

119904 3,3-Dimethoxybenzidine (See technical note)

60117 Dimethyl aminoazobenzene

119937 3,3'-Dimethyl benzidine (See technical note)

79447 Dimethyl carbamoyl chloride (See technical note)

68122 Dimethyl formamide
E -3

CAS Number Chemical Name

57147 1,1-Dimethyl hydrazine (See technical note)

131113 Dimethyl phthalate

77781 Dimethyl sulfate

534521 4,6-Dinitro-o-cresol, and salts

51285 2,4-Dinitrophenol

121142 2,4-Dinitrotoluene

123911 1,4-Dioxane (1,4-Diethyleneoxide)

122667 1,2-Diphenylhydrazine

106898 Epichlorohydrin (l-Chloro-2,3-epoxypropane)

106887 1,2-Epoxybutane

140885 Ethyl acrylate

100414 Ethyl benzene (See technical note)

51796 Ethyl carbamate (Urethane)

75003 Ethyl chloride (Chloroethane)

106934 Ethylene dibromide (Dibromoethane)

107062 Ethylene dichloride (1,2-Dichloroethane)

107211 Ethylene glycol

151564 Ethylene imine (Aziridine)

75218 Ethylene oxide 

96457 Ethylene thiourea

75343 Ethylidene dichloride (1,1-Dichloroethane)

50000 Formaldehyde

76448 Heptachlor

118741 Hexachlorobenzene

87683 Hexachlorobutadiene

77474 Hexachlorocyclopentadiene

67721 Hexachloroethane

822060 Hexamethylene-1,6-diisocyanate

680319 Hexamethylphosphoramide

110543 Hexane

302012 Hydrazine

7647010 Hydrochloric acid (See technical note)

7664393 Hydrogen fluoride (Hydrofluoric acid)

7783064 Hydrogen sulfide (See Modification) 

123319 Hydroquinone
E -4

CAS Number Chemical Name

78591 Isophorone

58899 Lindane (all isomers)

108316 Maleic anhydride

67561 Methanol

72435 Methoxychlor

74839 Methyl bromide (Bromomethane)

74873 Methyl chloride (Chloromethane)

71556 Methyl chloroform (1,1,1-Trichloroethane)

78933 Methyl ethyl ketone (2-Butanone)

60344 Methyl hydrazine

74884 Methyl iodide (Iodomethane)

108101 Methyl isobutyl ketone (Hexone)

624839 Methyl isocyanate

80626 Methyl methacrylate

1634044 Methyl tert butyl ether(See technical note)

101144 4,4-Methylene bis(2-chloroaniline)(See technical note)

75092 Methylene chloride (Dichloromethane)

101688 Methylene diphenyl diisocyanate (MDI)

101779 4,4¬-Methylenedianiline

91203 Naphthalene

98953 Nitrobenzene

92933 4-Nitrobiphenyl

100027 4-Nitrophenol

79469 2-Nitropropane

684935 N-Nitroso-N-methylurea

62759 N-Nitrosodimethylamine

59892 N-Nitrosomorpholine

56382 Parathion

82688 Pentachloronitrobenzene (Quintobenzene)

87865 Pentachlorophenol

108952 Phenol

106503 p-Phenylenediamine

75445 Phosgene

7803512 Phosphine

7723140 Phosphorus (See technical note)
E -5

CAS Number Chemical Name

85449 Phthalic anhydride 

1336363 Polychlorinated biphenyls (Aroclors) 

1120714 1,3-Propane sultone 

57578 beta-Propiolactone 

123386 Propionaldehyde 

114261 Propoxur (Baygon) 

78875 Propylene dichloride (1,2-Dichloropropane) 

75569 Propylene oxide 

75558 1,2-Propylenimine (2-Methyl aziridine) 

91225 Quinoline 

106514 Quinone 

100425 Styrene 

96093 Styrene oxide 

1746016 2,3,7,8-Tetrachlorodibenzo-p-dioxin 

79345 1,1,2,2-Tetrachloroethane 

127184 Tetrachloroethylene (Perchloroethylene) 

7550450 Titanium tetrachloride 

108883 Toluene 

95807 2,4-Toluene diamine 

584849 2,4-Toluene diisocyanate 

95534 o-Toluidine 

8001352 Toxaphene (chlorinated camphene) 

120821 1,2,4-Trichlorobenzene 

79005 1,1,2-Trichloroethane 

79016 Trichloroethylene 

95954 2,4,5-Trichlorophenol 

88062 2,4,6-Trichlorophenol 

121448 Triethylamine 

1582098 Trifluralin 

540841 2,2,4-Trimethylpentane 

108054 Vinyl acetate 

593602 Vinyl bromide 

75014 Vinyl chloride 

75354 Vinylidene chloride (1,1-Dichloroethylene) 

1330207 Xylenes (isomers and mixture)
E -6

CAS Number Chemical Name

95476 o-Xylenes (See technical note) 

108383 m-Xylenes (See technical note) 

10642 p-Xylenes (See technical note)

Antimony Compounds 

Arsenic Compounds (inorganic including arsine) 

Beryllium Compounds 

Cadmium Compounds 

Chromium Compounds 

Cobalt Compounds 

 Coke Oven Emissions 

Cyanide Compounds1

 Glycol ethers2

Lead Compounds (See technical note) 

Manganese Compounds 

Mercury Compounds 

Fine mineral fibers3

 (See technical note)

Nickel Compounds 

Polycylic Organic Matter4

 (See technical note)

Radionuclides (including radon)5

Selenium Compounds

NOTE: For all listings above which contain the word "compounds" and for glycol ethers, the

following applies: 

Unless otherwise specified, these listings are defined as including any unique chemical substance

that contains the named chemical (i.e., antimony, arsenic, etc.) as part of that chemical's

infrastructure.

1. X'CN where X = H' or any other group where a formal dissociation may occur. For example

KCN or Ca(CN)2

2. Includes mono- and di- ethers of ethylene glycol, diethylene glycol, and triethylene glycol

R-(OCH2CH2)n -OR'

where

n = 1, 2, or 3

R = alkyl or aryl groups

R' = R, H, or groups which, when removed, yield glycol ethers with the structure:

R-(OCH2CH)n-OH. Polymers are excluded from the glycol category.(See Modification)

3. Includes mineral fiber emissions from facilities manufacturing or processing glass, rock, or

slag fibers (or other mineral derived fibers) of average diameter 1 micrometer or less.
E -7

4. Includes organic compounds with more than one benzene ring, and which have a boiling

point greater than or equal to 100 °C. 

5. A type of atom which spontaneously undergoes radioactive decay. 

Technical Note: Minor editorial/technical issue - call (919) 541-5347 for details.
E -8

Modifications To The 112(b)1 Hazardous Air Pollutants

Authority for modifications:

Section 112 of the Act contains a mandate for EPA to evaluate and control emissions of

hazardous air pollutants. Section 112(b)(1) includes an initial list of hazardous air pollutants

that is composed of specific chemical compounds and compound classes to be used to identify

source categories for which the EPA will promulgate emissions standards. The listed categories

are subject to emission standards subsequently developed under Section 112. The EPA must

periodically review the list of hazardous air pollutants and, where appropriate, revise this list

by rule. In addition, any person may petition EPA under Section 112(b)(3) to modify the list by

adding or deleting one or more substances. A petitioner seeking to delete a substance must

demonstrate that there are adequate data on the health and environmental effects of the substance

to determine that emissions, ambient concentrations, bioaccumulation, or deposition of the

substance may not reasonably be anticipated to cause any adverse effects to human health or the

environment. To demonstrate the burden of proof, a petitioner must provide a detailed

evaluation of the available data concerning the substance's potential adverse health and

environmental effects, and estimate the potential exposures through inhalation or other routes

resulting from emissions of the substance.

Modifications:

Glycol Ethers - Proposed

On January 12, 1999 (FR64:1780), EPA proposed to modify the definition of glycol ethers to

exclude surfactant alcohol ethoxylates and their derivatives (SAED). This proposal was based on

EPA's finding that emissions, ambient concentrations, bioaccumulation, or deposition of SAED

may not reasonably be anticipated to cause adverse human health or environmental effects. EPA

also proposed to make conforming changes in the definition of glycol ethers with respect to the

designation of hazardous substances under the Comprehensive Environmental Response,

Compensation, and Liability Act (CERCLA). The proposal reads as follows: 

"The definition of the glycol ethers category of hazardous air pollutants, as established by 42

U.S.C. 7412(b)(1) includes mono- and di-ethers of ethylene glycol, diethylene glycol, and

triethylene glycol R-(OCH2CH2)n-OR' Where: 

n= 1, 2, or 3 

R= alkyl C7 or less, or phenyl or alkyl substituted phenyl 

R'= H, or alkyl C7 or less, or carboxylic acid ester, sulfate, phosphate, nitrate, or

sulfonate." 

Methyl Ethyl Ketone(MEK) - Notices of Review

Hazardous Air Pollutant list - Methyl Ethyl Ketone(MEK); receipt of a complete petition

to delist Citation: 64 FR 33453; Date: 06/23/99
E -9

Caprolactam

 On July 19, 1993, EPA received a petition from AlliedSignal, Inc., BASF Corporation, and

DSM Chemicals North America, Inc. to delete caprolactam (CAS No. 105-60-2) from the

hazardous air pollutant list in Section 112(b)(1), 42 U.S.C., Section 7412(b)(1). A Notice of

Receipt was published (58FR45081, August 26, 1993) noting that the data filed were adequate to

support decision making. After a comprehensive review of the data submitted, the EPA

published a proposal to delist caprolactam (60FR48081, September 18, 1995). In order to help

address public concern, on March 13, 1995, EPA executed two detailed agreements with

AlliedSignal concerning the Irmo, South Carolina manufacturing facility and another facility

located in Chesterfield, Virginia, copies of which are included in the public docket for this

rulemaking. AlliedSignal agreed that, if caprolactam was delisted pursuant to the proposal,

AlliedSignal would install emissions controls which EPA believed would be equivalent to the

controls which would have been required had EPA issued a standard to control these sources

under Section 112. The agreed emissions controls are incorporated in federally enforceable

operating permits for the affected facilities, and will be in place years earlier than controls would

have otherwise been required. In addition, AlliedSignal has agreed to establish a citizen advisory

panel concerning the Irmo facility in order to improve communications with the community and

to assure that citizens have an ongoing role in implementation of the agreed emission reductions.

The public requesting a public hearing. On November 28, 1995, the EPA published a notice of

public hearing and an extension of the comment period (60FR58589). After considering all

public comments, the EPA published a final rule delisting caprolactam (61FR30816, June 18,

1996).

 All information associated with this rule making is located in Docket Number A-94-33 at the

Central Docket Section (A-130), Environmental Protection Agency, 401 M St. SW.,

Washington, D.C. 20460. phone 202-260-7548, fax 202-260-4400, email

a-and-r-docket@epamail.epa. gov. The docket includes complete index to all papers filed in this

docket, a copy of the original petition, comments submitted, and additional materials supporting

the rule. A reasonable fee may be charged for copying. The docket may be inspected in person

between 8:00 a.m. and 4:30 p.m. on weekdays at EPA's Central Docket Section, West Tower

Lobby, Gallery 1, Waterside Mall, 401 M St., SW, Washington, D.C. 20460.

Hydrogen Sulfide

A clerical error led to the inadvertent addition of hydrogen sulfide to the Section 112(b) list of

Hazardous Air Pollutants. However, a Joint Resolution to remove hydrogen sulfide from the

Section 112(b)(1) list was passed by the Senate on August 1, 1991 (Congressional Record page

S11799), and the House of Representatives on November 25, 1991 (Congressional Record pages

H11217-H11219). The Joint Resolution was approved by the President on December 4, 1991.

Hydrogen Sulfide is included in Section 112(r) and is subject to the accidental release

provisions. A study (see citation below) was required under Section 112(n)(5).
E -10

Hydrogen Sulfide Air Emissions Associated with the Extraction of Oil and Natural Gas,

EPA-453/R-93-045, (NTIS publication # is PB94-131224, $36.50 hard copy, $17.50

microfiche).

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EPA 456/K-01-001

Clean Air Technology Center

ITG, ITPID, OAQPS

MD-12, U.S. EPA

RTP, NC 27711

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Research Triangle Park, North Carolina 27711

July 2001

Final

This document is a Technical Bulletin which is intended to enlighten the state air

pollution authorities about a relatively new technology. This document defines UV/EB coatings, explains why they are important, explains how the technology works, what degree of

pollution prevention is afforded, what industries could use UV/EB coatings, and the cost

analysis of using UV/EB coatings. It even describes stereolithography, which makes a part

out of a coating. UV/EB coatings were previously called UV/EB radiation cured coatings, but

"radiation" has been dropped from the name because it is a term that is used too freely.

UV/EB cured coatings are used in many applications, and should become useful in more when

the results and risks of using them are fully understood. The intent is to make them fully

understandable.

Release Unlimited, Available from NTIS

5285 Port Royal Rd.

Springfield, VA 22161

Unclassified

Unclassified

Air Pollution Control, Pollution

Prevention, Volatile

Organic Compounds,

Hazardous Air Pollutants

Ultraviolet and Electron Beam (UV/EB) Cured Coatings, Inks,

and Adhesives CATC/ITPID/OAQPS/OAR/EPA

Clean Air Technology Center

coatings, inks, adhesives, ultraviolet, electron

beam, electromagnetic radiation, mercury vapor

lamps, organic polymers, free radical polymerization, cationic polymerization, polymer, curing,

cure of conventional coatings, visible spectrum,

extreme ultraviolet, ozone