NBSIR 77-1399

Performance of A WaterThinned Polyurethane Seamless

Flooring System

McClure Godette

Paul Campbell

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D C. 20234

December 1977

Prepared for Division of Energy Building Technology and Standards

Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D.C. 20410

NBSIR 77-1399

PERFORMANCE OF A WATERTHINNED POLYURETHANE SEAMLESS

FLOORING SYSTEM

McClure Godette

Paul Campbell

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D C. 20234

December 1977

Prepared for Division of Energy Building Technology and Standards

Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D.C. 20410

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

ABSTRACT

This paper summarizes the work of a two-year project to evaluate the

performance of a recently developed flooring system. The flooring

system is a water-thinned polyurethane system proposed for use in high

traffic areas. The use of water as a solvent was intended to relieve

occupants of dwellings and applicators of seamless flooring systems of

the danger of exposure to toxic solvents and the discomfort of eye

and skin irritants during installation. The goals of this project were:

1. To evaluate by laboratory tests and field demonstrations

the performance and durability characteristics of a

water-thinned polyurethane seamless flooring system.

2. To compare the performance of a water-thinned polyurethane

system with solvent-thinned polyurethane systems and

other conventional flooring materials.

3. To recommend performance criteria for the selection of

water- thinned polyurethane seamless flooring systems.

The project was divided into two phases. In the first phase, laboratory

evaluation, conventional and modified methods of standard tests were

used to determine the level of performance of this newly developed

system and to characterize its durability under simulated in-service

conditions. Laboratory testing also provided for comparison of the

performance of the new system with that of conventional seamless

flooring systems.

i
In the second phase of the project, field demonstration, performance

of the system was observed under in-service conditions. Demonstration

of the system at 20 sites in various parts of the country, provided

many facets of in-service conditions under which flooring materials

must perform. In addition, it permitted NBS personnel and local

housing engineers to observe and record in-service performance of the

systems. This phase of the project was especially beneficial in that

local housing maintenance engineers, knowledgeable about the performance

of conventional flooring materials and skilled in their maintenance,

had an opportunity to evaluate the system under in-service conditions.

Data obtained from local maintenance engineers at the 20 demonstration

sites confirmed laboratory findings that the system did not compare

favorably with conventional seamless flooring systems for use in high

traffic areas.

Key Words: Water-thinned polyurethane system; solvent-thinned

polyurethane system; vinyl tile; laboratory findings;

field demonstration; maintenance engineers; service

conditions; high-traffic areas.

ii
Table of Contents

Page

1.0 Introduction 1

1.1 Background 2 1.2 Approach 3

1.2.1 Laboratory Evaluation 3

1.2.2 Field Demonstration 3

2.0 Laboratory Evaluation 6

2.1 Materials 6

2.1.1 Water-Thinned Polyurethane System 6

2.1.2 Solvent-Thinned Polyurethane System 6

2.1.3 Vinyl Tile 6

2.2 Preparation of Specimens 8

2.2.1 Seamless Flooring Systems 8

2.2.2 Vinyl Floor Tile 9

2.3 Test Methods and Results 9

2.3.1 Abrasion Resistance 9

2.3.2 Film Integrity 11

2. 3. 2.1 Tensile Strength 11

2. 3. 2.Elongation 12

2.3.3 Impact Resistance 12

2.3.4 Indentation 13

2.3.5 Dimensional Stability 13

2.3.6 Resistance to Solar Radiation 14

2.3.7 Resistance to Water Vapor 15

2.3.8 Resistance to Stain 17

2.3.9 Flame Spread 19

2.3.10 Smoke Generation 21

3.0 Field Demonstration 22

3.1 Preparation of Substrate 24

3.2 Application of System 24

3.3 Inspections by NBS Personnel 29

3.3.1 Preparation of Substrate 29

3.3.2 Application Process 30

3.3.3 Appearance of System 30

3.3.4 Appearance After Six Months 30

iii
Table of Contents (continued)

Page

3.3.5 Appearance After Ten Months 31

3.3.6 Maintenance 31

3.4

Evaluation of Local Maintenance Engineers 31

4.0 Summary of Properties and Recommendations 0

5.0 Recommended Interim Criteria for Water-Thinned 44

Polyurethane Systems

5.1 Resistance to Abrasion 44

5.2 Film Integrity 45

5.3 Impact Resistance 47

5.4 Indentation 48

5.5 Dimensional Stability 49

5.6 Resistance to Solar Radiation 49

5.7 Water Vapor Permeance 50

5.8 Resistance to Stain 51

5.9 Flame Spread 52

5.10 Smoke Generation 53

Acknowledgement 54

References 55

Appendix A Infrared Spectrum of Glaze Coat 56

Appendix B Thermogram of Water-Thinned Polyurethane System 58

Appendix C Manufacturer's Application Method 60

iv
Table Captions

Table 1 Desirable Properties of Flooring Materials for Use

in High-Traffic Areas

Table 2 Demonstration Sites for the Water-Thinned Polyurethane

Seamless Flooring System

Table 3 Test and Comparison Samples

Table 4 Comparative Performance of Three Flooring Systems

Table 5 Effects of Household Stains on Three Flooring Systems

Table 6 Flame Spread Values of a Water-Thinned Polyurethane

Flooring System

Table 7 Results of Smoke Generation Tests on Water-Thinned

Polyurethane Systems

Table 8 Evaluation of the Water-Thinned Polyurethane System

After 10 Months Service by Engineers at 18 of 20

Demonstration Sites

Table 9 Correlation Between Laboratory Tests and Field

Performance of the Water-Thinned Polyurethane

Seamless Flooring System

v
Figure Captions

Figure 1 Abrasion Test Apparatus with Abraser Wheels Being

Refaced on an Abrasive Disc.

Figure 2 Preparation of Substrate Using Heavy Duty Sander

Figure 3 Casting and Leveling of Vinyl Flakes

Figure 4 Addition of Vinyl Flakes to Attain Desired

Decorative Pattern

Figure 5 Removal of Excess Vinyl Flakes

Figure 6 Cigarette Burn and Chemical Staining

Figure 7 Multiple Staining of the Water-Thinned

Polyurethane System

Figure 8 Solvent and Rust Staining

Figure 9 Furniture Staining and Indentation

vi
SI CONVERSION UNITS

In recognition of the position of the United States as a signatory

to the General Conference on Weights and Measures, the metric SI system

of units have been used throughout this publication. However, in view of

the present accepted practice of using common U.S. units of measurement

for building technology in this country, appropriate conversion factors

have been provided in the table below. The reader interested in making

further use of the system of SI units is referred to:

NBS SP330, 1977 Edition, "The International System of Units"

NBS 380-76 ASTM Metric Practice Guide (American National Standard Z210.1)

The conversion factors for the units found in this report are as follows

Length

1 in = 0.0234 meter* (m)

1 ft = 0.3048 meter* (m)

Area

1 in^ = 0.000645 square meter S(m^)

1 ft^ = 0.0929 square meter (m^)

Mass

1 lb = 0.453 kilogram (kg)

*Exactly
Temperature

degree celsius t°C = 5/9(t°F - 32)

Pressure

1 psi = 6895 pascal (pa)

Mass/Time (Flow)

— 11. o

1 perm (23°C) = 5.745 x 10 kilogram/pascal second meter

(kg/Pa s m^)

Energy

1 inch - pound - force (in-lbf) = 0.1130 joule

viii
1.0 Introduction

During the past twenty years, solvent- thinned polyurethane systems

have been used extensively for seamless flooring in high-traffic areas

1 /*

of public buildings-r A typical polyurethane system consists of a primer or basecoat, an intermediate coat, vinyl chips and a clear glaze

coat. Traditionally, these systems have been used in bathrooms,

kitchens, laundry rooms and hallways. These areas require floor

finishes with high impact, stain, abrasion and mar resistance. In

many cases polyurethane systems are impermeable membranes for sealing

porous surfaces and for retarding the transfer of water and water

vapor. In brief, the solvent-thinned polyurethane flooring systems

are versatile, functional and durable. However, developing concurrently

with the use of the solvent-thinned polyurethane systems has been an awareness of their unpleasant odor and irritant nature. This has

created a demand in the flooring industry for information and education

on the hazards and safeguards relating to the solvents used in these

flooring systems.

Engineers in the Department of Housing and Urban Development (HUD)

indicated a need for a flooring system equal in performance to the

solvent-thinned polyurethane system, yet free of unpleasant odors and

irritating solvents. A response to this need was the development of a polyurethane system using water as a solvent instead of organic solvent.

This system was intended to retain the properties of the conventional

solvent-thinned systems while relieving occupants and applicators of

exposure to toxic and irritating solvents. At HUD's request, NBS

personnel have conducted an evaluation of this newly-developed system.

*Numbers represent references given at the end of this report.

1
1.1 Background

The purpose of this investigation was to collect and evaluate data

concerning the service performance of a water- thinned polyurethane

seamless flooring system and to develop performance criteria for

selection of such systems. The system was intended for use in hightraffic areas of public housing which may be frequently soiled and

subjected to impact and abrasion through occupant use. This report

on the performance of the newly developed system under laboratory and

in-service conditions is intended to be a guide for those engaged in

the design, specification and purchase of such materials.

This project included a laboratory evaluation of the properties of

the water-thinned polyurethane system and a comparison of those

properties with more conventional seamless flooring materials. In

addition, the laboratory evaluation was complemented by evaluating

the system at 20 demonstration sites in 10 HUD regions in various parts

of the United States. This in-service evaluation included field

inspections at four selected sites by NBS personnel and monitoring by

local maintenance engineers at each of the sites. Concisely, the

objectives of this project were:

1. To evaluate by laboratory tests and field demonstrations

the performance and durability characteristics of a water-thinned

polyurethane seamless flooring system.

2. To compare the performance of a water-thinned polyurethane

system with solvent-thinned polyurethane systems and other

conventional flooring materials.

3. To recommend performance criteria for the selection of

water-thinned polyurethane seamless flooring systems.

2
1.2 Approach

The project was conducted in two parts: 1) Laboratory evaluation,

and 2), Field demonstration.

1.2.1 Laboratory Evaluation

The water-thinned polyurethane system was evaluated in the

laboratory to establish its levels of performance in selected tests.

The following approach was used to identify those properties evaluated:

1. The purpose for which the material was to be used was defined and the service conditions were characterized.

2. Technical data on related materials for similar use were

reviewed and samples selected for comparison.

3. Suitable accelerated tests were identified to evaluate

properties related to user requirements and service conditions.

As a result of the above considerations, a list of properties

believed to be important to the performance of a flooring material in

public housing was drawn up (see Table 1).

1.2.2 Field Demonstration

In-use observation of the performance and durability of the new

flooring system was an essential part of the evaluation. For that

reason, the polyurethane flooring system was applied at 20 sites

(see Table 2) in 10 HUD regions of the United States. NBS personnel

coordinated the application of the system at the various sites,

assisted local housing maintenance engineers in the gathering of data,

and made periodic on-site inspections at four selected sites. The 20

sites provided a variety of substrates to which the system was applied;

revealed the effect of various environmental conditions and the

performance of the system in several locations of different buildings.

3
Table 1. Desirable Properties of Conventional

Flooring Materials for Use in Public

and Private Buildings

Property Requirement

Resistance to abrasion High

Film integrity High

Resistance to impact High

Resistance to indentation High

Dimensional stability High

Resistance to solar radiation High

Resistance to water vapor High

Resistance to stain High

Flame spread Low

Smoke generation Low

4
Table 2 Demonstration Sites for the Water-Thinned Polyurethane

Seamless Flooring System

1. Toledo, Ohio

2. Jeannette, Pennsylvania

3. Chester, Pennsylvania

4. Charleston, South Carolina

5. Birmingham, Alabama

6. Biloxi, Mississippi

7. New Orleans, Louisana

8. San Antonio, Texas

9. Little Rock, Arkansas

10. Phoenix, Arizona

11. San Francisco, California

12. Tacoma, Washington

13. Denver, Colorado

14. Kansas City, Missouri

15. Superior, Wisconsin

16. Chicago, Illinois

17. Detroit, Michigan

18. Boston, Massachusetts

19. Camden, New Jersey

20. Newark, New Jersey

5
2.0

Laboratory Evaluation

2.1

2.1.1 Materials

Water-Thinned Polyurethane System

At the beginning of this project, the water-thinned polyurethane

system to be evaluated (see Table 3) , was a new material which had

limited use as a flooring material. It was the only known commercially

available water- thinned system; however, at least one other water-thinned

polyurethane flooring system has become commercially available during

the course of this investigation. For purposes of characterization

and future reference, the infra-red spectrum of the water-thinned

polyurethane glaze coat is shown in Appendix A. A time-base thermogram

of the complete system is shown in Appendix B.

2.1.2

Solvent-Thinned Polyurethane Systems

(Comparison Samples)

Two solvent-thinned polyurethane seamless flooring systems (see

Table 3) which had been studied in a previous investigation [2] were

used for comparison purposes. Hereinafter, data given for the solventthinned system are an average of these two systems.

2.1.3

Vinyl Tile

The vinyl tile (see Table 3) selected as a comparison sample, is

a widely used vinyl tile comforming to Federal Specification SS-T-312,

Type III.

6
Table 3 Test and Comparison Samples

Water- Thinned Polyurethane Systems (Components)

A. Epoxy base coat (water-thinned)

B. Epoxy intermediate coat (same as in A)

C. Vinyl chips

D. Urethane top coat

Solvent-Thinned Polyurethane Systems (Components)

1. A. Epoxy base coat

B. Epoxy intermediate coat

C. Vinyl chips

D. Urethane top coat

2. A. Epoxy base coat

B. Urethane top coat

Vinyl Tile

Vinyl tile comforming to

Federal Specification SST-312, Type III

7
2.2 Preparation of Specimens

2.2.1 Seamless Flooring Systems

The preparation of each seamless flooring system followed the

procedure recommended by the manufacturer. Specimens were prepared on

two substrates:

1. Steel panels. Type R, Q panels (0.875 mm x 150 mm x 300 mm)

cold rolled, low carbon steel (ASTM D609, Type 1-B)

2. Plywood, (19 mm x 609 mm x 609 mm) conforming to Exterior

AC Grade, Species Group 1 (American National Standard A199. 1-1974,

Voluntary Product Standard PS 1-74)

After preparation, specimens were cured for seven days at 23+2°C

and 50+5% rh unless specified otherwise. Smaller specimens as required

for specific tests were made from these panels. Where free films of

the seamless flooring systems were required, a 0.075 mm film of

polyethylene was used as a release agent. The polyethylene was affixed

to the plywood board by a vinyl adhesive prior to application of the

seamless flooring system. After the seamless flooring system had

cured for 7 days, the system was peeled from the polyethylene as a free film.

8
2.2.2 Vinyl Floor Tile

Where necessary to satisfy a test requirement, vinyl tile was

affixed to plywood and metal panels (2.2.1) by adhesive as recommended

by the manufacturer.

2.3 Test Methods and Results

Tests were chosen to measure those physical properties which are directly related to the performance of flooring materials. Test

methods and procedures were intended to simulate conditions encountered

in use in public and private housing. The data obtained is presented

below and the tests are referenced in the interim performance criteria

of Section 5. The properties considered to be of greatest importance

for the intended application of water-thinned seamless flooring systems

were identified and evaluated as outlined below.

2.3.1 Abrasion Resistance

Flooring systems for high-traffic areas must resist wear and

retain their integrity during abrasion under heavy pedestrian traffic.

The abrasion resistance test was performed as described in Method

6192 of Federal Test Method Standard No. 141a [3]. Triplicate specimens

(100 mm x 100 mm) were taken from prepared steel panels (2.2) and

drilled with a center hole (6.25 mm). For each abrasion resistance

determination, a load of 1000 gm and abrasive calibrase wheels. No. CS-17,

k

were used with a Taber Abraser (Figure 1). Specimens were abraded

for 1000 cycles and the weight loss was recorded to 0.1 mg.

*Identif ication of commercial products is included only to adequately

specify the procedure. Identification does not imply recommendation

or endorsement by the National Bureau of Standards.

9
V

$*

10

Figure

1.

Abrasion

Test

Apparatus

With

Abraser

Wheels

Being

Refaced

On

An

Abrasive

Disc.
2.3.2 Film Integrity

2. 3. 2. 1 Tensile Strength

Tensile strength is of primary importance in any material that

may be subjected to stress and strain during service. The purpose of

this test was to determine the maximum load, in kilograms, and the

total elongation, in millimeters, up to the breaking point of the

flooring systems while increasing the strain at a constant rate.

Tensile strength measurements were made with a universal testing

machine on free films of the systems. Specimens were prepared as outlined in Section 2.2 except that the plywood board was coated with

polyethylene. Specimens were cut into a "dogbone" shape (25.4 mm wide

and 254.0 mm long) by die and removed as free films. Triplicate

specimens of vinyl tile were cut from squares of tile without substrate

backing. The thickness of each specimen was measured with a dial gauge

to the nearest 0.0025 mm.

The basic test method was as outlined in ASTM D882, Method B. The

specimen was mounted in the testing machine equipped with serrated grips

at a gauge length of 177.8 mm. Then the specimen was subjected to

tensile test at a crosshead speed of 5.0 mm/min. The tensile test

continued until a maximum load was obtained. Tensile strength was calculated by dividing the maximum load in kilograms by the original

minimum cross-sectional area in square millimeters. The average

strengths are reported for three specimens of each sample. The results

are shown in Table 4.

Table 4 shows that the tensile strength of the water-thinned system

was 11.8 megapascals. This value is considerably lower than the 34.3

megapascals for the solvent-thinned systems and 73.5 megapascals for

the vinyl tile.

11
2. 3. 2. 2 Elongation

Flooring materials require a moderate amount of elongation for

keeping stresses generated during service at relatively low levels.

The purpose of this test is to determine how much a flooring system

may be extended without losing its integrity.

While the specimens were being tested for tensile strength as specified above, the elongation was measured to the moment of rupture.

The percent elongation was calculated by dividing the elongation at

the moment of rupture by the original length and multiplying by 100.

Results of the determinations are seen in Table 4. The percent

elongation of the water-thinned system (1.7%) is considerably lower

than either the solvent-thinned system (3.3%) and vinyl tile (5.6%).

2.3.3 Impact Resistance

Flooring systems for use in high-traffic areas must resist the

effects of dragged, thrown or dropped objects. The purpose of this test was to determine the system’s resistance to cracking, chipping, flaking

and delamination under impact.

Impact resistance was determined as described in ASTM D 2794,

Resistance of Organic Coatings to the Effects of Rapid Deformation

(Impact). Triplicate specimens (100 mm x 100 mm) were taken from

prepared steel panels (2.2) and impacted with a 0.9070 kilogram

cylindrical impact weight. The tests were performed with the coated

side up. The largest number of Joules at which failure (cracks around

the perimeter of the indentation) did not occur was determined.

Results of the impact tests are shown in Table 4. The impact

before failure of the water-thinned polyurethane system was 7.7 joules.

The impact before failure of the solvent-thinned polyurethane and vinyl

tile was 9.0 joules.

12
2.3.4 Indentation (Loading)

The ability of a flooring system to resist the effects of loading

is due in-part to its density and thickness. Flooring systems in a high-traffic area of public housing must resist indentation from loading

by heavy appliances and over-loaded chairs, tables and desks.

The apparatus used in this test was a hydraulic press. This method

of test consisted in permitting a load increased in increments of

6.4 x 10^ pascals to act for specific periods of time (five minutes)

upon a flooring system on steel panels (2.2). The force was applied

-4 2 through the flat-end of a cylinder having a head area of 6.5 x 10 m . The test panel rested on a steel platen and was removed after application

of successive increments of force and inspected for indentation. The

failure load was that load required to produce a visible impression

under the cylinder.

Table 4 shows the minimum loads required to make an indentation

in the three flooring systems. Indentation due to loading occurs at

5 approximately 8.2 x 10 pascals for the water-thinned polyurethane

system; the solvent-thinned system indents at approximately 11.7 x 10^

pascals and the vinyl tile at approximately 13.1 x 10^ pascals.

2.3.5 Dimensional Stability

The ability of a seamless flooring system to resist movement (flow

or slip) due to temperature changes depends on its cohesive strength

and strength of bond to the substrate. The purpose of this test was

to determine the extent of movement when the system was exposed to

relatively high temperatures.

Flow or slip was determined as described in 4. 7. 5.1 of Military

Specification D-3134F. Triplicate specimens (150 mm x 150 mm) of the

flooring systems were cut from steel panels (2.2), scribed, and placed

vertically in an oven at 70°C for five hours. The difference between

the distances from the scribed mark to the reference edge before and

13
after heating is a measure of flow or slip. The measurements were made

by suitable calipers to the nearest 0.0025 mm under the prescribed test

conditions

The movement (see Table 4), shown by the water-thinned polyurethane

system was 0.015 mm. Movements of the vinyl tile and solvent-thinned

polyurethane system were 0.003 and 0.004 mm, respectively.

2.3.6 Resistance to Solar

Radiation

Seamless flooring systems for use in areas exposed to sunlight

must resist solar radiation. Exposures to sunlight near windows and

in vestibules and other entrances may result in significant local changes

in color, and cause localized aging. The purpose of this test was to

determine the effects of solar radiation on the flooring systems.

Resistance to solar radiation was determined by exposing the

flooring systems to a xenon-arc radiant energy source in a weathering

machine equipped with a constant wattage transformer to operate a 6500 watt water-cooled lamp. The lamp contained an inner and outer

cylinder of borosilicate glass which filtered out all wave lengths

below 290 nanometers and above 1300 nanometers.

Triplicate specimens (100 mm x 100 mm) were taken from the plywood

panel (2.2) after curing for seven days. To determine color change,

the color of each specimen was measured before exposure with a color

difference meter. Specimens were then exposed to solar radiation at a black box temperature of 67+2 °C. After 24 hours, the specimens were

removed and stored at 23+2°C for two hours. Again, the color of each

specimen was determined, and the color change calculated as specified

in Method 6123 of Federal Test Method Standard 141a. Specimens were

also inspected for cracking, checking and peeling.

14
Color changes resulting from exposure in the xenon-arc weathering

machine are presented in Table 4. The greatest change occurred in the

vinyl tile, whereas the water-thinned system showed the least change.

2.3.7 Resistance to Water Vapor

In order for finish coats of flooring materials to remain

protective, decorative and functional, they must not be easily penetrated

or dissolved by water, dirt, dust and water vapor. The purpose of this

test was to determine the resistance of the finish-coat to the

penetration of water vapor.

The basic test method used is described in ASTM-E 96. Duplicate

specimens are prepared by application of the glaze coat, by draw-down,

•k to the highly permeable portion of penetration chart forms at a wet

film thickness of 0.250 mm. The specimens were then cured for seven

days at 23+2°C and 50+5% rh.

A disc (100 mm in diameter), cut from the chart with the cured film, was sealed over the mouth of a permeability cup containing a desiccant,

and placed in an atmosphere of 23+2°C and 50+5% rh. The assembly was weighed once every twenty four hours, and the results for the period

in which the gain in weight was linear with time were used to calculate

2 2

the rate, in kilogram/pascal-second-meter (kg/pa-svm ), of water vapor

movement through the membrane.

The permeabilities of the two glazed coats were 4.6 x 10

^

2 -10 2 kg/pa's*m for the solvent-thinned system and 1.2 x 10 kg/pa-s.

for the water-thinned system (see Table 4).

*Charts (Form HK) may be obtained from the Leneta Company, P.0. Box 675,

Ho-Ho-Kus, New Jersey.

15
Table 4

Comparative

Performance

of

Three

Flooring

Systems

in

co o o rH o CO o 50 • m 1—1 QJ • • . • X < . to I—

co

m CN o m 05 • co

d -h co rH is •H H > coi—

X)

0)d qj rH d d rH

•h

d o m 1 X. X 05 O o CN o o co H -u • • • • rH rH • I at m rH UO o CO 05 u tM m X X co d d

a; to 1*-. 50 > rH • • rH o rH O Pm rH

cnX qj QJ c d d

m o d -3 rH rH

•H 4-1 CM

OO I-"

m 1 00

X <u • • • • o o • H U o O o rH C'. rH rH 1—

i d in rH u to i—

X X

QJ rH

•u o CN CN d pm • • t£ 00 rH

/-~N

<50 S —\

CO

a)

w r\ /—V i—

<1 CO CN o w V4 0

to

p < d o CO o / N CO

tM 9k

X rd . o d qj 4J o ft o tM m bO dr o 4= d d /~N iH 4-1 tM QJ CO bO \ d O 1—

QJ rX

X CNI (M UM rH d QJ 1—

d 9k o |M a o d c S S 4J rH o 0 o d

<) CO

d

4M 0)

O •H 5_r

rH o

4J bO

d o <p\ oO d v-—

•H QJ o CO o X tM H co 0) rH

O •H bO

O

dd

N

d o 4-1 •H o 4-1 a d o o d -d rH >M a. rH CO I—

IH

O

d #5 bO

d

v—

XJ xj 14M tM bO 5^ dr d d 9K d d

^5 CO tM

d to o •H QJ bO

4-1 CO 4-1 4-1 X)

a QJ

Vm o U tM •H 0 d

d £

QJ I—

d QJ i—

d 0) o d 5-/ a i—

4-1 •H 0 o 1—

QJ o •u o d rd •H d 0 rC

>M rd CO £ d

X

d >5 £ 4-1 Pm bO '—y

4-1

d 4-1 rd QJ bO •H CO ^0 CO d. d

a) qj 0) •H 0) 5 (50 bO rH CO d tM d d d d QJ O O 4-1

9k

dd

d o tM •H dr CO

d

X rd o •H 4-1d o o o •H 4-1 d > QJ •H CO d 4-1 4-1 t—

CO )M tM

d bO

O

d tM •rH

d o o QJ

d

d 0) QJ CO

tM rH >H 0 o 9* XI 4-1

d

X o o •H rH 0 d

d QJ <3 CJ c_> Q w H H H

16
2.3.8 Stain Resistance

The appearance of a floor is often the greatest single factor

determining its useful life. To be useful, a flooring system must

resist the effects of shoe markings and exposure to common household

cleaners

Stain resistance of the flooring systems was, generally, determined

as described in ASTM D 1308, Effect of Household Chemicals on Clear

and Pigmented Organic Finishes. Glass vials (25.4 mm I.D., 12.7 mm

height) were sealed to the surface of the flooring systems with a polyurethane sealer. After 24 hours, 1 ml of the stain (see Table 5) was placed in the sealed ring and covered with a watch glass. Marks

by felt-tip pen were similarly covered. Sixteen hours later the watch

glasses were removed, the stains washed off and alteration to the

surface noted.

Table 5 identified the effect of each of seven stains on the three

flooring systems. The water-thinned polyurethane system was discolored

by four of the stains; vinyl tile was discolored by three, and the

solvent- thinned system was discolored only by one. The tendency of

the water-thinned polyurethane system to re-emulsify under standing

water would be a significant drawback in its use in high-traffic areas.

17
Table 5

Effects

of

Household

Stains

on

Three

Flooring

Systems

Water

temporary whitening;

appearance

recovered

on

drying no effect no effect

•HH 44 4-) 3 1 3 CJ o 3

44 4)

O 03

O 3 •H r4 CO 3 o-i 3 04 3

<u 0-1 04 44

03 3 3 1o a) CD 3 44 M e 3 3 CJ 3 o *H •r-l O 3 O 3 3 3 3 04

1-1 -3 4-1 4-J 04 3 o CD 3 3 s

.3 4-J 44 3 3 m O C3 3 O -H O 0) O 3 •H 3 O-l 3 oo 3

cn o 0-1 04 44

P-( 03 3 3

CD 44 3

4-1 o

03 *H CJ

O 3

03 3 O 3 3 04 H 4-1 3 04 3 4-i 3 3

033 4-J 4-J 44

03aO ^.3 3

+J

O 3 O 3 >4 00 *H

CD 3 04 3 04 3 -H 3 3 0-1 04 > H 44 S 3 3 3 3

03 3

4-1 44

01 3

CJ CJ 04 •H O 3 O 3

0-1 3 3 04 3 04 o 4-1 4-1 04 U 3

QJ 3

033

03 3 3 3 3 •H 3 43 3

•H

H rH

w -3 1 •H H H 4J H C/J | 3

>H 3-i 3 rH

CO 3 >

4-1 *H 3 3 o •H S </) >

18
* 2.3.9 Flame Spread

Interior finishes in residences are recognized as contributors

to fire deaths. For this reason, it is advisable to characterize all

new and innovative materials for their contribution to flame spread.

The purpose of this test was to determine the surface flammability of

the water-thinned polyurethane flooring system.

The flame spread test method used was ASTM E-162, "A Standard

Method of Test for Surface Flammability of Materials Using A Radiant

Heat Energy Source" [4]. Test specimens were prepared on plywood board

as outlined in section 2.2. Flame spread tests determine a flame spread

index number which reflects the rate of flame propagation over the

surface of the material.

An inclined 150 mm x 450 mm specimen of the material is situated

in front of a radiant heat source (300 mm x 450 mm panel). Ignition

is induced near the upper edge and the flame front progresses downward.

A factor derived from the rate of progress of the flame front (ignition

properties) and another relating to the rate of heat liberation by

the material under test are combined to provide a flame spread index.

As shown in Table 6, the average flame spread value for the waterthinned polyurethane system was 416. Published reports [5], [6] revealed

flame spread values of 70 and 129 for vinyl tiles; 200 and 240 for

solvent-thinned polyurethane systems.

*Testing conducted by Program for Fire Control Construction,

National Bureau of Standards Center for Fire Research.

19
Table 6 Flame Spread Value of a Water-Thinned Polyurethane Flooring System

Specimen

No.

Polyurethane

Coating

Thickness mm

Plywood

Thickness mm

Measured * Density Flame Spread

kg/nP Fs Q Is

1

2

0.78

0.78

18.76

18.75

592.7 19.62 20.3 398

592.7 23.74 19.2 437

416 Avg.

*Fs = Flame spread factor

Q

= Heat evolution factor

I = Flame spread index

s

20
2.3.10 Smoke Generation

The smoke generated by an interior finish should be a primary con- sideration in assessing life safety of the interior of a dwelling.

The purpose of this test was to determine the smoke generation

characteristics of the water-thinned polyurethane flooring system.

The smoke generation test method used is described in NBS TN 708,

"Interlaboratory Evaluation of the Smoke Density Chamber Test Method','

Appendix II, by T.G. Lee, December 1971 [7], Test specimens were

prepared in 28 mm by 75 mm by 75 mm size on 19 mm AC Grade, Species

Group I plywood. The system was subjected to smoke generation tests

by measuring the progressive attenuation of a light beam passed through

the smoke aerosol within the enclosed smoke chamber. The smoke level

is reported in terms of specific optical density, a dimensionless

attenuation coefficient which defines the amount of smoke accumulated

from a specimen of unit surface area in terms of its photometric

obscuration over unit path length within a chamber of unit volume [7].

4 2 The test consists of a thermal irradiation exposure of 2.5 x 10 W/m

normal to the exterior surface of the test specimen, and was performed

under both flaming and nonflaming (smoldering) conditions. To induce

open flaming, a small pilot natural gas diffusion flame is applied

at the base of the specimen.

Specific optical density, Ds, is a property of a specimen of given

thickness, and represents the optical density measured over unit path

length (L) , within a chamber of unit volume (V), produced from a specimen

of unit surface area (A). Thus:

Ds = D (- V

AL

-) « V

AL

r i 100 i [log — ]

*Testing Conducted by Program for Fire Control Construction Center for

Fire Research, National Bureau of Standards, Center for Fire Research.

21
where T = percent light transmission, and D is normally referred to as -1 3

"optical density'.' For the test chamber, V = 5.0 x 10 m , A = 4.2 x

-3 2 -1

10 m , and L = 9.0 x 10 m. The change in Ds with time depends only

on the thickness of the specimen, its chemical and physical properties

and exposure conditions [7],

In the testing of flooring, the complete system and underlayment

were tested. This procedure was followed because the underlayment has

been found to have a significant effect upon small scale test results

for flooring.

Test results indicated that the specimens produced more smoke in

the non-flaming mode than in the flaming mode, and that the optical

density (smoke) levels were still increasing at the end of the twenty

minute test duration in two of the tests (see Table 7). Several gaseous

components and their concentration in parts per million are also given

in Table 7.

3.0 Field Demonstration

Although the laboratory tests discussed in the foregoing sections

may give information on the physical characteristics of flooring systems,

and the uniformity of a particular sample, they cannot predict the

performance of any one system under all possible conditions of service

life. Therefore, where possible, it is advantageous to test the

performance of the systems in service.

HUD officials, in concurrence with local housing authorities,

selected twenty sites for application of the water-thinned system for

in-service tests. At least one site (see Table 2) was located in each

of the ten HUD regions throughout the country. Selection of the

particular dwellings was fortuitous in that it provided for application

of the system over the following common substrates: 1) asphalt tile,

2) concrete, 3) wood, 4) vinyl asbestos tile, and 5) vinyl tile.

Application of the system at the twenty sites was carried out by a

22
Table 7

Results

of

Smoke

Generation

Test

on

Water-Thinned

Polyurethane

Systems. • co

mm 00 OH r^* •>d- HO OH £

COo r^.

m

m rH CN rH rH

hJ rH rH rH rH rH rH rH rH o o o o m 00 n

CvJ CN

Z-N /'—

o 00

CJ CN rH

V-/ 'w/ c o m o CN rH

•H CN /"“s 4J o co cn

CC) CO CN rH k X N-/

4-1 Pu a ex

cu

CJ CN

m

O

C • O cn cn o c z \ CJ -H + CN CN s o CN rH

CO z 'w'

ctf * O a)E O nO

T3 *H rH

a) fr> z

4J <j rH rH

Cfl 33 CN rH O s-/ '—

•HT3CM <d- hJ rH

CJ Z“N PC O 00

CN

'w/

Z-N

O • 6 'H H >, P3 3 14-4 Ctf 4-1 2 H-

£; *H CJ % H o hO

m CO HO r*.m OH

•H CJ -H CO CJ CN cn hO HO o OH 00 X <U 4-1 C

V-/ rH CN rH rH <r

m

co

a a, <u E S co o o o

00e

•HE

0£ aj

CU

C rH • •

!-4 -H CM 00 00 3 e 1 > >

co nJ e P-* [H Ph < z z z < O rH o

CX p4 z X II ii W pH z

nd tn

a) 4-1 k •Ho") 3 co E

CO c m

rt a) 4>0 in

a) o S

-X

CO

CO

a)

_ cn § cn

u rH

•H.eH

nd

QJ a) s s e

•H -c g

hC

J CO 00

H (U CO c m

cu 1 4 <U • H • 0

rHa

k

cu It

k CN 0 rH 03 E 4J H (5 0 >h

cfl cO 0 <U i—1 3 rH

CO 3 X CO Pn

O P-i

23

NOTE:

(t)

Indicates

smoke

levels

were

still

increasing

at

the

end

of

the

twenty

minute

test

duration.
professional applicator who was well established in the seamless

flooring industry, and who had experience in application of the waterthinned seamless flooring system.

A record of the application and performance of the system was obtained from the maintenance engineer at each of the twenty sites.

This data was supplemented by on-site inspections at four of the

sites by NBS personnel. The evaluations by local housing maintenance

engineers were very important because they are experienced in floor

maintenance and familiar with the needs of the tenants. The format

shown in Table 8 was used by both, NBS personnel and local maintenance

engineers to evaluate the system.

3.1 Preparation of Substrate

The average time required to prepare the substrate at each of the

twenty sites was four and one-half hours. This included one employee

skilled in the application of seamless flooring systems and one helper

provided by the local housing authority. Typical equipment involved

a mechanical sander, putty knife, broom and mop. Degreasing and wax

cleaners were also available. The average area coated ranged from

2 42 to 47 meters. Typical substrate preparation procedures are shown in Figure 2. The failure most frequently noted in this phase of

the program was an uneven substrate which later showed through the

system.

3.2 Application of the System

Application of the system was by a skilled applicator assisted

by the local housing maintenance employee. The average application

time, including a drying time of about two hours between coats, was twenty hours. Application equipment included a mixer, vacuum cleaner,

trowel, brush, roller and three pairs of shoes - including one pair of

golfing shoes which provided minimal adhesion to the applied system

(see Figures 3-5).

24
25

Figure

2

Preparation

of

Substrate

Using

Heavy

Duty

Sander
26

Figure

3

Casting

and

Leveling

of

Vinyl

Flakes
27

Figure

4

Addition

of

Vinyl

Flakes

to

Attain

Desired

Decorative

Pattern

and

Subsequent

Overcoat

by

Glaze

Coat.
28

Figure

5

Removal

of

Excess

Vinyl

Flakes
The skill of the applicator was reflected in the number of vertically

protruding chips. Horizontal arrangement of the chips is due, in part,

to the skill of the applicator in applying the glaze coat. Protruding

chips frequently inhibit pedestrian foot movement and contribute to

uncomfortable walking conditions.

The major shortcoming of the system evident from this phase of the

program was the number of glaze coats required to obtain adequate

wearing thickness. A minimum of three glaze coats was applied at each

site. The manufacturer's "Approved Application Method" is included

in Appendix C [8].

3.3 Inspections by NBS Personnel

Through arrangements by officials of the Department of Housing and

Urban Development, and with the cooperation of the local housing

authorities, field inspections were made at sites in the following

cities

1 . Boston, Massachusetts

2. Camden, New Jersey

3. Chester , Pennsylvania

4. Newark, New Jersey

At each site, discussions were held with staff and field engineers

on 1) preparation of the substrate; 2) application of the system;

3) performance of the systems; and 4) comparison of the performance of

the system with the performance of other flooring materials.

3.3.1 Preparation of Substrate

1. Preparation of the substrate is critical

2. The preparation process is laborious and tedious

2 3. Average preparation time for 42 to 47 meters was 4.5 hours

4. Equipment required:

a. heavy duty sanding machine,

29
b. commerical vacuum cleaner,

c . mixer , and

d. three pairs of shoes, including one pair

of golfing shoes.

3.3.2 Application Process

1. Base coat may be brushed, rolled or troweled.

2. Application time, including two hours drying time

between coats, was approximately twenty hours

for 46. 5m^.

3. Several coats of glaze coat were required to provide

an adequate wearing thickness.

4. Good ventilation was required during application

and drying of the system.

5. Although the system was thinned with water, an unpleasant

odor presisted.

6. Surface preparation, application and curing of the

system required a minimum of four-day occupant vacancy.

7. Chips occasionally protruded above the glaze coat.

3.3.3 Appearance of System

1. The gloss was low, a higher gloss was desired.

2. Overall appearance of the system was good.

3. An outline of irregularities in the substrate showed

in several locations ("telegraphing").

4. At least one high spot was visible at each site.

3.3.4

Appearance After Six Months

1. Stains were noted.

2. A cigarette burn was evident.

3. Changes in color of the system were noted,

4. Chips protruded in several spots.

30
3.3.5 Appearance After Ten Months

1. Discoloration was evident.

2. Dusting of the finish was observed.

3. Numerous stains were noted (see Figures 6-9).

4. Abrasion was evident in high-traffic areas.

5. Several indentations were noted.

6. Overall appearance was judged fair to poor.

7. Dirt was embedded in the surface of the system.

3.3.6 Maintenance

1. Required daily sweeping because of tendency to dust.

2. Stained easily.

3. Stains were difficult to remove.

Data obtained from on-site inspections by NBS personnel were

similar to those recorded in laboratory tests and reinforced the

conclusion, drawn from laboratory tests, that the water-thinned

polyurethane system was not suitable for use in high-traffic areas. Major factors contributing to this conclusion were the system's

tendency to: stain; indent; wear; embed dirt; and discolor.

3.4 Evaluation by Local Maintenance Engineers

The local maintenance engineers at the twenty demonstration sites

contributed much to the evaluation of the water-thinned system. Their

responses to contacts by phone and periodic questionaires provided

current information on the performance of the system at each site. After

ten months, a final questionaire was forwarded to the engineer at each

of the twenty sites. Of the twenty forms forwarded, eighteen were

returned. A summary of the final assessments provided by the local

engineers is shown in Table 8.

31
32

Figure

6

Cigarette

Burn

and

Chemical

Staining

of

the

Water-Thinned

Polyurethane

System
33

Figure

7

Multiple

Staining

of

the

Water-Thinned

Polyurethane

System
1

34

Figure

8

Solvent

and

Rust

Staining

of

the

Water-Thinned

Polyurethane

System
35

Figure

9

Furniture

Staining

and

Indentation

of

the

Water-Thinned

Polyurethane

System
Table 8 Evaluation of the Water-Thinned System

After 10 Months Service by Engineers at

18 of the 20 Demonstration Sites.

*

1. Overall appearance

Good 38

Fair 50^

16

2. Discolored

Yes 42

No 48

16

3. Uniform gloss

Yes 57

No 2j*

15

4. Embedded dirt

Yes 64

No 3j>

18

5. Worn

Yes 29

No 71

18

6. Telegraphing of substrate

Yes 21

No 79. 18

7. Cracks

Yes 20

No 80

18

8. Shrinkage

Yes 14

No 86

18

9. Uniform color

Yes 79

No 21

18

10. Lifting from substrate

Yes 24

No 7_6 *Percentage of 18 respondents who rated the system as shown. xg

**Total number responding to this issue.

36
Table 8 (continued)

Service Percentage

1. Sweeping required

Daily 86

Weekly 0

Other 0

16

2. Waxing required

Daily 0

Weekly 20

Other 0

“4

3. Dirt removed

Easily 42

Not so easily 58

18

Comparison with more conventional flooring materials

(e.g., tile, linoleum, and solvent seamless systems)

1. Water-thinned seamless systems

Preferred . 20

Not preferred 80^

18

2. Wears

Faster 27

Slower 20

Same .40

16

3. Stains

More easily 40

Less easily 27

Same 0

12

4. Requires more maintenance

Yes 53

No 15

Same 0

12

5. Discolors more readily

Yes 40

No 20

Same _0_

11

6. Indents more easily

Yes 63

No 33

Same 0

17

37
Table 8 (continued)

Service Percentage

1. Rough to walk on Yes 7 No 93

;s

2. Protruding Chips

Yes 14

No M

18

3. High spots

Yes 7 No

18

4. Wear resistance

Good 57

Fair 29

Poor

18

5. Stains

Few 54

Several 21

None 20.

17

6. Indents

Yes 64

No 36

18

7. Scuffs

Heel marks 29

Furniture movement 5]^

16

8. Water spots

Yes 14

No 86

18

9. Obvious color change

Yes 29

No n

18

10. Other comments

Would not recommend for use in heavy traffic

areas 40

7
Table 8 (continued)

Service Percentage

7. Retains buff more easily

Yes 27

No A 7 Same 13

16

8. Scuffs more easily

Yes 53

* No 21

14

9. More suitable for needs of tenants of

public housing

Yes 27

No AO

Same 20_

16

39
In reviewing this table, it should be kept in mind that the system

had been in use for a relatively short period of time (ten months) . This represents only a small fraction of the intended service life

(approximately 8 years) of the flooring system. Exemplary in-service

performance in the test sites would have been an essential requirement

for acceptance as a system for use in high-traffic areas. This was not

the case, 80 percent of the engineers who evaluated the system in the

field preferred more conventional types of flooring systems. Other

characteristics that were not in the satisfactory range, as judged by

a majority of the engineers, were: 1) embedded dirt, 2) stains,

3) indentations, 4) maintenance requirements, 5) scuffs, and 6) dirt was difficult to remove. These observations of the in-service

performance of the system was consistent with the conclusions based

on the laboratory results (see Table 9). Thus the flooring cannot

be considered suitable for use in high-traffic areas such as those

in which it was tested.

4.0 Summary of Properties and Recommendations

Laboratory evaluations, visits to field demonstration sites and

assessments by field engineers were used to determine the suitability

of a water-thinned polyurethane flooring system for use in high-traffic

areas of public housing.

Laboratory tests were used to determine values of performancerelated properties by subjecting the sample to simulated in-use

conditions. These tests relied upon a close following of visual

changes and measurement of physical alterations within the system.

These physical changes were readily detected and measured. Similar

tests were carried out on solvent-thinned polyurethane systems and

vinyl tile. It was concluded:

1. The water-thinned polyurethane flooring system is not

suitable for use in high-traffic areas.

40
Correlation

Between

Laboratory

Tests

and

Field

Performance

of

the

Water-Thinned

Polyurethane

Seamless

Flooring

System

41

Percentage

of

18

respondents

who

rated

the

system

as

shown.
2 . The performance of the water-thinned system, as determined by

laboratory evaluation, correlated well with on-site

evaluations at 20 demonstration sites.

3. The weight loss of the water- thinned system when abraded by

a Taber Abrader was greater than the solvent-thinned

polyurethane system and vinyl tile.

4. The tensile strength of the water- thinned polyurethane was

least of the flooring materials tested.

5. The elongation of the water-thinned polyurethane system was considerably less than either the solvent-thinned system or the vinyl tile.

6. Exposure of the water- thinned system to seven household

materials resulted in severe staining.

7. The maximum impact before the water-thinned system cracked

was less than either the vinyl tile or the solvent-thinned

polyurethane system.

8. The water-thinned polyurethane system indented at a considerably lower force than either the vinyl tile or the solvent-thinned polyurethane system.

9. The water-thinned polyurethane showed a greater tendency

to flow than either the solvent-thinned system or the

vinyl tile.

10. The vinyl tile showed the greatest change in color due to

solar radiation, the water-thinned polyurethane the least.

11. The water vapor permeance of the glaze coat of the water-thinned

polyurethane system was considerably higher than that of the

solvent-thinned polyurethane system.

12. The flame spread index of the water-thinned system was greater than that reported in the literature for conventional

vinyl tile.

42
As a result of the foregoing evaluations, properties of the waterthinned polyurethane system were further compiled and summarized as follow:

Property

Abrasion resistance

Tensile strength

Impact resistance

Indentation

Resistance to staining

Permeability

Characteristic

Low

Low

Low

Low indentation resistance

Low

Subject to penetration by

water and water vapor.

The above characteristics were confirmed in field inspections

of four sites, and by HUD maintenance engineers at 18 of the 20 sites

where the system was applied. For example, evidence of wear, stain,

indentation, color change, and embedded dirt were observed at the

four sites. Other problems such as the long occupant-vacancy time

required for application of the system were noted. Many engineers and

tenants expressed a desire for a higher gloss finish, and remarked

about the number of glaze coats required. At least three applications

of the glaze coat were required. Thus, the cost-benefit of the system

is affected adversely by the number of glaze coats necessary to obtain

sufficient thickness to provide adequate wear resistance. Another

observation was the pungent odor during application of the system.

In many cases, forced ventilation was used.

Evaluations by engineers and other staff members at the various

sites confirmed laboratory and field inspection findings. Eighty

two percent of those who made the final evaluation preferred other

flooring materials to the water-thinned system.

43
Past histories have shown solvent-thinned polyurethane seamless

flooring systems and vinyl tiles to perform well in the use for which

the water-thinned flooring was being considered. Therefore, these two

systems were selected as comparison samples. Thus, reasonable criteria

of acceptance of the water-thinned flooring are that it should meet or exceed the performance levels of the other two types of flooring in

appropriate laboratory tests. Since in most laboratory tests, it fell

far short of the level of performance for the solvent-thinned polyurethane

seamless flooring and vinyl tile, the water-thinned flooring did not

appear to be an adequate substitute for the other types. However, it was desirable to assure by field tests that this conclusion was not

due to laboratory tests having been set at unreasonable high levels.

Although data indicate that the water-thinned system is not the

most suitable flooring material for high-traffic areas, it may be

adequate for other applications such as wall coatings in bathrooms,

hallways, recreational and food service areas.

5.0 Recommended Interim Criteria for

Water-Thinned Polyurethane

Systems

Laboratory test results presented in Section 2 and data obtained

from in-service performance provide the basis for the following interim

criteria for water-thinned polyurethane systems for use in high-traffic

areas. Water-thinned polyurethane systems for use in high-traffic areas should perform as well or better than the comparison floor samples

evaluated in this report. On that basis, the following criteria were

developed. The criteria are preliminary and may need to be updated

as additional information becomes available.

5.1 Resistance to Abrasion

Requirement

Flooring systems should have long service life even when exposed

to abrasion from heavy pedestrian traffic.

44
Criterion

When tested as outlined below, the average weight loss of

triplicate specimens shall not exceed 55 milligrams.

Test

Triplicate specimens are prepared by applying the system to

100 x 100 mm solvent-cleaned No. 21 gauge cold rolled steel according

to the manufacturer’s directions. The system is cured for seven days

at 23 + 2°C and 50 + 5% rh. Then a 6.25 mm diameter hole is drilled

in the center of each steel square to permit mounting in the abrasion

tester.

The initial weight of each square specimen is determined to the

nearest milligram and the specimens are mounted as directed in Method

6192 of Federal Test Method Standard 141a. Using CS 17 calibrase

wheels with a load of 1000 grams on each wheel, the specimen is

abraded for 1000 cycles, and its weight loss determined.

Commentary

Flooring systems are subjected to abrasion from occupant traffic.

Flooring systems intended for use in high-traffic areas should be

highly resistant to wear.

The expression of abrasion resistance as milligrams of weight loss

per number of cycles establishes a meaningful comparison by which

flooring systems can be rated. The system evaluated in this report

would not be rated suitable for use in high-traffic areas.

5.2 Film Integrity

Requirement

Flooring systems should be able to resist the stress and strain of

pedestrian traffic and environmental changes during their service life.

They should remain intact under stresses expected in service.

45
Criterion 1 - Tensile Strength

When tested as outlined below, the average tensile strength of

triplicate specimens shall not be less than 34.3 mega pascals.

Test

The basic test method shall be as outlined in ASTM-D882, Method B. Specimens are prepared by applying the coating according to the manufacturer’s instructions to a plywood board coated with polyethylene.

Specimens are cut into a "dogbone" shape (25.4 mm wide and 254.0 mm long)

by die and removed as free films. The thickness of each specimen is

measured with a dial gauge to the nearest 0.001 mm.

The specimen is next mounted in the testing machine equipped with

serrated grips at a gauge length of 177.8 mm. Then the specimen is

subjected to tensile test at a crosshead speed of 5.0 mm/min. The

tensile test continues until a maximum load is obtained. Tensile

strength is calculated by dividing the maximum load in kilograms by

the original minimum cross-sectional area in square millimeters. The

average strengths are reported for three specimens of each sample.

This test is designed to determine the tensile properties of various

flooring systems. Good tensile strength is of basic importance in any

material that may be subjected to stress and strain during its service

life.

Criterion 2 - Elongation

When tested as outlined below the percent elongation of the

flooring system shall not be less than 3% of its original length.

Test

The method of test shall be the same as outlined above. The

percent elongation is calculated by dividing the elongation at the

moment of rupture by the original length and multiplying by 100.

46
Commentary

The criterion was selected to ensure that the selected flooring

systems are suitable for application in areas which may be subjected

to dimensional changes or deformation.

5.3 Impact Resistance

Requirement

Flooring systems selected for use in high-traffic areas must

withstand intentional abuse in addition to the accidental impacts that

normally occur.

Criterion

When tested as outlined below, the flooring system shall not crack,

chip or flake at an impact of 9.0 Joules.

Test

Impact resistance shall be determined as described in ASTM-D2794,

Resistance of Organic Coatings to the Effects of Rapid Deformation

(Impact). Triplicate specimens (100 mm x 100 mm) are taken from

prepared steel panels (Type R, Q Panels, 0.875 mm x 150 mm x 300 mm,

cold rolled, low carbon steel), and impacted with a 0.9070 kilogram

cylindrical impact weight. The test is performed with the coated

side up.

Commentary

Flooring systems such as vinyl tile are capable of withstanding

impacts of 9.0 Joules. In view of the satisfactory performance of

vinyl tile and solvent- thinned polyurethane systems, their performance

was selected as the minimum criterion for impact.

47
5.4 Resistance to Indentation

Requirement

Flooring systems should be resistant to indentation by furniture,

equipment and other heavy articles that are likely to be in contact

with the floor for long periods of time.

Criterion

Flooring systems shall be free of visible indentation when a pressure of 1.3 megapascals is applied uniformly over an area of

6.5 x 10"4 m^ for 5 minutes.

Test

Triplicate specimens are prepared by applying the system to

100 x 100 mm, solvent -cleaned, No. 21 Gauge cold-rolled steel according

to the manufacturer's directions. After curing seven days at 23 ± 2°C

and 50 ± 5% rh, the specimens are placed in a hydraulic press capable of

indicating to the nearest 68,940 pascals. The cylinder against the

finish shall be 6.5 x 10~4 m^. The force shall be maintained for five

minutes, the specimen removed and inspected for indentation.

Commentary

Flooring systems usually experience most severe indentation from

furniture. Frequently, the design of furniture support legs result in

the concentration of heavy loads in small areas of flooring. This

criterion is to ensure that flooring systems are not marred by forces

resulting from over-loaded furniture and appliances. Need for this

criterion was frequently demonstrated in the field by indentations

from tables, chairs and other appliances.

48
5.5 Dimensional Stability

Requirement

Flooring systems in high-traffic areas should remain functional

and decorative when exposed to changes in temperature.

Criterion

When tested as outlined below, the average movement (flow) of

triplicate specimens shall not be greater than 0.004 mm.

Test

Triplicate specimens are prepared by applying the system to

150 x 150 mm, solvent-cleaned, No. 21 gauge cold-rolled steel according

to the manufacturer’s directions. After curing seven days at 23 + 2°C

and 50 + 5% rh, the specimens are scribed and placed vertically in an oven

at 70°C for five hours. The difference in distance between the scribed

mark and reference edge before and after heating is a measure of flow

or slip. Measurements shall be made to the nearest 0.003 mm.

5.6 Resistance to Solar Radiation

Requirement

Flooring systems should retain their original appearance after

expected exposure to solar radition.

Criterion

When the flooring system is subjected to solar radiation as outlined below, the change in color shall not be greater than 2 NBS

units.

Test

Specimens are exposed to a xenon-arc radiant energy source in a weathering machine equipped with a constant wattage transformer to

operate a 6500 watt water-cooled lamp. The lamp contains an outer

and inner cylinder of borosilicate glass which filters out all wave

lengths below 290 nanometers and above 1300 nanometers.

49
Triplicate specimens (100 mm x 100 mm) are taken from cured samples

on plywood. The plywood (19 mm x 609 mm x 609 mm) conforms to Exterior

AC Grade, Species Group I (Voluntary Produce Standard PS 1-74, American

National Standard A1971-1974). After curing seven days, the color of

each specimen is measured before exposure with a color difference meter.

Specimens are exposed to solar radiation only, at a black box temperature

of 67 + 2°C. After 24 hours, the specimens are removed and stored at

23 + 2°C and 50 + 5% rh for two hours. Again, the color of each

specimen is determined, and the color change calculated as specified

in Method 6131 of Federal Test Method Standard 141a.

Commentary

This criterion was selected to ensure retention of the original

appearance accepted by users of flooring systems. Flooring systems

are generally exposed to solar radiation at windows, vestibules and

door entrances.

5.7 Water Vapor Permeance

Requirement

Flooring system should be resistant to permeation by water and

water vapor.

Criterion

Where flooring systems are required to be resistant to the transmission of water vapor, the glaze coat of the system shall not have

-11 2 a water vapor permeance greater than 4.6 x 10 kg/Pa* s*m .

Test

Triplicate specimens are prepared by application of the glaze coat

to the highly permeable portion of penetration chart forms at a wet

film thickness of 0.175 mm. The specimens are cured for seven days

at 23 + 2°C and 50 + 5% rh.

50
A disc (100 mm in diameter) cut from the chart with the cured film

is sealed over the mouth of a permeability cup containing 30 gms of

calcium chloride and placed in an atmosphere of 23 + 2°C and 50 + 5% rh.

The assembly is weighed once every 24 hours, and the results for the

period in which the gain in weight is linear with time is used to

calculate, in pascals, water vapor movement through the membrane.

Commentary

The sealing of moisture-laden flooring substrates by flooring systems

of low permeability may cause cracking, flaking and peeling of the

flooring system. The above criterion provides guidance in the

selection of systems suitable for application to areas where the

exclusion of water vapor is desired.

5.8 Resistance to Stain

Requirement

Flooring systems selected for use in high traffic areas should

maintain their original appearance even after prolonged exposure to

household materials.

Criterion

When tested as outlined below, the flooring system shall not

wrinkle, blister or discolor.

Test

Stain resistance of the flooring system shall be determined as described in ASTM-D1308, Effect of Household Chemicals on Clear and

Pigmented Organic Finishes. Glass vials (25.4 mm I.D., 12.7, height)

are sealed to the surface of the flooring system with a polyurethane

sealer. After twenty-four hours, 1 ml of coffee, mustard, tea, shoe

polish and water are placed in separate sealed rings and covered with

a watch glass. After sixteen hours the watch glasses are removed,

the stains washed off and alteration to the flooring system noted.

51
Commentary

Flooring systems for use in high-traffic areas must resist attack

by most common household stains. Systems that resist the action of

such stains are likely to have longer useful service life and reduced

maintenance costs. This criterion is intended to identify flooring

systems which are able to resist common household stains. Performance

of the system in the field demonstrated the need for a stringent

requirement for stains in high-traffic areas.

5.9 Flame Spread

Requirement

Flooring systems shall provide resistance to the spread of fire.

Criterion

When tested as outlined below, the flame spread index shall not

be greater than 200.

Test

The method of test shall be in accordance with the procedure

specified in ASTM E-84.

Commentary

This criterion is intended to provide the user a surface finish

resistant to the spread of fire. The criterion is in accordance with

the HUD Minimum Property Standards (MPS) [9] within the living unit

except for the kitchen space. Areas where exposure to fire are more

likely, and exit areas, where the degree of resistance to fire may

determine the time that the occupants of a building have to leave a residence, usually have more strict flame spread requirements.

52
5.10 Smoke Generation

Requirement

If in a fire, flooring systems should not yield specific optical

densities of smoke and combustion product levels of gaseous components

which are hazardous to occupants of buildings.

Criterion

When tested as outlined below, materials that yield combustion

product levels greater than the upper limits listed by Gross et.al.

[10], given below, shall be classified as "potentially hazardous'.'

Hazardous Combustion Product Levels

Concentration in PPM

a. CO

b. HC1

c. HCN

d. NO + N0

2

Test

The method of test shall be as "Interlaboratory Evaluation of the

Appendix II, by T.G. Lee, December

10,000

1,000 - 2,000

200 - 300

200

described in NBS TN 708,

Smoke Density Chamber Test Method','

1971 [7].

Commentary

The above levels were based on levels represent a potential danger

a short term exposure period. These

to life when exposed 2 to 5 minutes.

53
Acknowled gement

Acknowledgement Is gratefully extended to the local housing

authorities at the 20 sites and to their staff without whose patience,

cooperation, and advice the field demonstration could not have been

conducted.

We thank George Erickson of the Department of Housing and Urban

Development for his contribution in locating the 20 field demonstration

sites and for making initial contacts with each of the responsible

housing authorities.

54
References

1. Larson, L.M., Tweet, D.E., "Alkyds and Polyesters Readied for

Market Entry," Modern Paint and Coatings, Palmerton Publishing Co.,

Inc., New York, N.Y. 10001.

2. Campbell, P.G., Post, M., Godette, M., Roberts, W ., "Final Report - Radiant Heating in Seamless Flooring - A Feasibility Study". NBS

report in press.

3. "Paint, Varnish, Lacquer, and Related Material; Methods of Inspection,

Sampling and Testing", Federal Test Method Standard 141a, September,

1963. Copies may be obtained from Superintendent of Documents,

U.S. Government Printing Office, Washington, D.C. 20402.

4. "A Standard Method of Test for Surface Flammability of Materials

Using a Radiant Heat Energy Source," ASTME 162, Annual Book of

ASTM Standards, Part 14, pp 500-511.

5. Ferguson, J.B., "Summary of Flame Spread and Smoke Generation

Tests Conducted for Operation Breakthrough". NBS Report NBSIR

73-228.

6. Benjamin, I., Gross, D. "Naval Shipboard Fire Research Criteria

Final Report, Phase 1, Evaluation of Fire Test Requirements.

NBS Report 10159.

7. Lee, T.G., "Inter laboratory Evaluation of the Smoke Density Chamber

Test Method", National Bureau of Standards Technical Note 708,

Appendix II, December, 1971, (Superintendent of Documents, U.S.

Government Printing Office, Washington, D.C. 20402).

8. "U.S. Department of Housing and Urban Development Housing

Management Transmittal Notice No. 2". HMG 74828.

9. Minimum Property Standards for Multifamily Housing, FHA No. 2600,

U.S. Department of Housing and Urban Development, February, 1971,

(Superintendent of Documents, U.S. Government Printing Office,

Washington, D.C. 20402).

10. Gross, D., Loftus, J.J., Lee, T.G., and Gray, V.E., "Smoke and

Gases Produced by Burning Aircraft Interior Materials", Building

Science Series 18, National Bureau of Standards, February, 1969,

(Superintendent of Documents, U.S. Government Printing Office,

Washington, D.C. 20402).

11. Wolf, W.C., Roberts, R.E., "Durability and Maintenance as Related

to the Selection of Flooring", NBS Technical Note.

55
APPENDIX A

56
57

Figure

1

Infrared

Spectrum

of

the

Glaze

Coat

of

the

Water-Thinned

Polyurethane

System.
APPENDIX B

58
SAMPLE : D

_ RUN N

59

Figure

1

Time-Based

Thermogram

of

the

Water-Thinned

Polyurethane

Seamless

Flooring

System
APPENDIX C

60
Manufacturer's Approved Application Method

1. Introduction . If the applicator has complied with the recommenda-

* tions outlined in Chapter 3 , Job Set-Up, and Chapter 4, Surface

Preparation, he is now ready for installation of the system in a well lighted and adequately ventilated area. The substrate is

thoroughly cleaned, and adjacent areas prepared for the installation

of the system.

2. Application of Base Coat

a. The first step in the installation of the system is the

application of the base coat. This material is a twocomponent emulsion epoxy. The purpose of this material

is to "weld" the system to the substrate, establish a background color, and act as a barrier coat to block off

the possible bleed-through of any latent contamination

* in the substrate. Reference should be made to Figure 2,

the chart, to ascertain the amount of material to mix.

You will note that the containers are marked with appropriate nomenclature and are also marked "A" and "B'.' Be sure that the materials in both containers are thoroughly mixed prior to measurement of the amount needed

for the installation. Equal parts of A and B should be

mixed together to achieve the total gallonage required.

Do not mix more material than can be easily applied

within one hour. The emulsion is manuf acturered with one component white and one component with a bluish tint.

This is designed to help the applicator see that the

components are thoroughly mixed. If the base coat is

to be tinted to match a predominant flake color, the

first coat of base coat should be applied as received and

the second base coat applied at the color desired. This

will aid in making sure that all areas have the minimum

of two base coats.

*For complete details see reference [8].

61
b. A Universal tint or colorant must be used to achieve

color and only colorants supplied or recommended by the

material manufacturer should be used in the base coat.

It is a wise precaution to disperse the colorant in a small container of water prior to adding the tint, being

sure that the materials are again well blended to disperse the colorant so that you will not have streaks in

the applied coating. A powered mixer is helpful. These

are available with propellers mounted on various length

shafts that fit into standard electric drills.

c. Plastic containers are preferable , as they are economical

and easily cleaned. They may be used over and over again.

d. If_ the base coat is to be sprayed , request specific instructions from the manufacturer. Follow the manufacturer's

recommendations closely and beware of "dry spray',' as this

will often happen when spraying a floor area. Dry spray

may be caused by atomizing pressure that is too great, but

may also be caused by fanning at irregular distances and by

holding the gun too far from the substrate. This is frequently done on floor jobs, due to the nature of the work.

The applicator is advised to exercise caution in this

respect

e. When the application is by roller , a medium nap paint roller

will suffice, and cut-in may be by brush. For ease of application, potable water may be added to the mixed material.

This should never exceed 6% by volume of the entire mix. The

material should be worked into the substrate by pressure on the brush or roller and adequate coverage made to insure

hiding and an even film over the substrate. Any material left over should be discarded.

62
3. Second Base Coat . With proper ventilation and heat, the installation should be ready for the second base coat within an hour,

following the same procedure as described above. Tinting should

be done as closely as possible to the desired shade. From this

point on, the applicator should use cleated shoes or booties (with

the former preferable) to avoid transmitting contamination to the

dry but not cured coating. Following the procedures outlined

above, apply the second base coat in as even a film as possible.

When completed, the entire area should have two full coats of

base and be of an even color.

4. Decorative Flakes . While the second base coat is drying (or

before starting the application), the decorative flakes should

be mixed to the desired mixture or pattern. This may be achieved

either by weight or by volume, the latter being the more prevalent method. If a blend, as an example, calls for four parts

beige, two parts white, and one part brown, this may be weighed

or measured in drums, buckets, cups, or any available container.

Bear in mind that one pound of flakes will finish 0.9 to 1.3 square

meter of floor area, but that at least 25% more flakes will be

needed to achieve the desired effect. The surplus flakes may

be used again on other installations. Mix the flakes well and

have them adjacent to the installation area. Gallon-size buckets

make excellent containers for broadcasting flakes into the wet

material. Be sure to note on your records the ratio of colored

flakes mixed, as you may need this information at a later date.

5. Chip-In Urethane Coat

a. After the second base coat is thoroughly dry , you are now

ready to apply the chip-in urethane coat. The prime

purpose of this coating is to receive the decorative

flakes and weld them into a smooth esthetically acceptable

monolithic film. This material is a one-component urethane

emulsion that is milky in appearance, but will dry into a

63
clear film. When this material, into which you will distribute or broadcast the mixed flakes, is applied in an exceedingly thin film in some areas and in near puddles

in others, each section would hold or retain flakes in

proportion to the amount or thickness of the coating.

This would cause the finished surface to end up with a splotchy or uneven color. It is, therefore, important

that the first coat of chip-in urethane be applied in as even a film as possible.

b. lf_ the application is by spray , follow the suggestions

given previously in regard to the spraying of the base

coat

c. Medium to short nap roller covers should be used to apply the chip- in urethane coat. An acceptable brush will

suffice for cutting in the edges and to coat hard-toreach areas. Be sure that you brush on the same amount

of material as will be rolled on so that your colors will

be even and uniform throughout the job. Your cleat ed

shoes will now prove their worth and allow you to walk

on the freshly applied coating. After cutting in by

brush, roll on the chip-in urethane coat as evenly as possible and then cross roll the area. This rolling at

90° to the initial roll will help you maintain an even

coat devoid of puddles and roller edge marks. Do not

press hard on the roller when cross rolling, and do not

coat more area than you can effectively cover with flakes

while the urethane chip-in coat is wet and receptive.

Power devices are available for the broadcasting of flakes;

but distribution by hand is very satisfactory, and remains

the most widely used method. Distribute the flakes as evenly as possible over the substrate, making sure to

have no voids or holidays. Oblique lighting will show up areas too lightly covered with flakes by reflecting the

64
lights or showing "shiny" areas. Cover one area completely

before moving to another, and always leave 100 to 150 millimeters of wet edge without flakes so that when you coat

the adjoining area with the chip-in urethane coat, you can tie in the areas. Occasional flakes will fall into the

wet area, and the advantage of the clear chip-in urethane

coat will be readily apparent when you "freshen up" the

wet edge. You may now go directly over the flakes scattered

into the wet material and upon the edge of the fully

chipped area without destroying the esthetics. If flaking

into a colored coating, this would not be possible, as streaks would possibly occur in the floor. When broadcasting

the flakes, fine particles settle to the bottom of the container. Be sure not to put these into one small area,

but sprinkle these small particles over a large area,

preferably an area already chipped with the larger flakes.

d. With proper ventilation and heat, the urethane chip-in

coat should be sufficiently dry within an hour to con- tinue the operation. Sweep the floor surface with a clean stiff-bristled broom to remove excess particles,

paying particular attention to corners and hard-toreach areas where there may be an accumulation of flakes.

Follow this procedure with a thorough vacuuming of the

area. Check the wheels of your vacuum cleaner to be^ sure you do not bring contamination into the installation.

e. While waiting for the chip-in urethane coat to dry , it

would be a good time to clean up tools and equipment that

will no longer be needed on the job. Brooms, vacuum

cleaners, flakes, etc., will no longer be required. Application tools may be cleaned (see Figure 2, the chart,

under "Clean-up" for method of cleaning) and stored for

future use, and the entire installation readied for appplication of the glaze coats.

65
6. Final Coats

a. The final coats to be applied are referred to as glaze

top coats and are consecutive coats of the same water

dispersed urethane used as the chip-in coat. This material is a one-component urethane emulsion that is

milky in appearance but will dry into a perfectly clear,

tough, durable film with a velvet finish that will

effectively resist abrasion.

k

b. Refer to Chapter 3 , Job Set-Up to be sure you have

located your fans and lights correctly, as it is most

important at this stage of the installation. Consult

Figure 2, the chart, referring to coverage data on the

water dispersed urethane glaze coat. Bear in mind

that you must now exercise care as the glaze will magnify greatly any foreign substance. The applicator is

further cautioned that the glaze must never be allowed

to accumulate into a thicker film than that achieved

by rolling the material on with a short nap roller.

If this material is to be sprayed, follow manufacturer's

recommendations closely and pay particular heed to

instructions. Apply approximately 0.064 millimeters

of dry film.

c. Start of application (coatings system). Upon start of

application, cut in with a brush and apply the glaze by

the roller in an even film over a small area. Do not

work the roller any more than necessary, and cross roll

lightly to be sure of even distribution. When completed,

flush your roller and brush thoroughly with water and

dry with clear, absorbent cloth on paper. They will now

be in good condition for your next coat.

*For complete details see reference 8.

66
For best results use a new white short nap roller with

a long-handled applicator. The use of a colored roller

is not recommended as the color may bleed out.

The urethane glaze is used as received. Nothing need be

or should be added. Pour a line of urethane glaze across

the width of the application area and roll in one direction

to cover the area completely. Apply at a rate of approximately 23.2 to 27.9 square meters per gallon. Pour additional

glaze as necessary until the area is completely glazed.

Apply the glaze as thinly as in painting but be sure

to cover the entire area, especially the edges. The use

of a paint brush may be necessary at edges and in corners.

Allow the first coat to dry until tack free, approximately

1/2 hour. The second coat may be applied as soon as the

first coat is dry enough to walk on using plastic footwear

or plastic bags over your feet. A slight elasticity is

normal but no footprints will remain if the glaze has

adequately dried.

Apply the second coat of urethane glaze along the length

of the application area, at right angles to the direction

of the first coat. Roll out the second coat in one direction filling in and evening streaking in the first

coat.

Allow the second coat to dry until track free.

Apply the third coat of glaze at right angles to the

second coat, etc.

67
d. Subsequent coats may be applied as soon as the preceding coat

is completely dry to the touch. A minimum of three glaze

coats is recommended. These coats impart the wearing

quality of the seamless coating.

68
NBS-1 1 4A (REV. 7-73)

I

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 77-1399

2. Gov't Accession

No.

3. Recipient’s Accession No.

4. TITLE AND SUBTITLE

Performance of a Water-thinned Polyurethane Seamless

Flooring System

5. Publication Date December 1977

6. Performing Organization Code

7. AUTHOR(S)

M. Godette, Paul G. Campbell

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Division of Energy Building Technology and Standards

Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D. C. 20410

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

This paper summarizes the work of a two-year project to evaluate the performance of a water- thinned polyure thane seamless flooring system. The goals of this project

included: 1) To evaluate by laboratory tests and field demonstrations the performance

and durability characteristics of a water-thinned polyurethane seamless flooring

system; 2) To compare the performance of a water-thinned polyurethane system with

solvent-thinned polyurethane systems and other conventional flooring materials; and

3) To recommend performance criteria for the selection of water-thinned polyurethane

seamless flooring systems.

The project was divided into two phases, laboratory evaluation and field demonstration. Data obtained from local maintenance engineers at the 20 demonstration sites

confirmed laboratory findings that the system did not compare favorably with con- ventional flooring systems for use in high traffic areas.

17. KEY WORDS (atx to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Water-thinned polyurethane system; solvent-thinned polyurethane system; vinyl tile;

laboratory findings; field demonstration; maintenance engineers; service conditions;

- hlRh traffic...

re,as..,

'

18. AVAILABILITY Unlimited

I

1 For Official Distribution. Do Not Release to NTIS

n Order From Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402, SD Cat. No. C11

fxl Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS 21. NO. OF PAGES

(THIS REPORT)

78

UNCLASSIFIED

20. SECURITY CLASS 22. Price (THIS PAGE)

UNCLASSIFIED $6.00

USCOMM.DC 29042- 74
i