p.1 

OAR Box 1413 

Prepped by Ollie Stewart 

Document Number: 

21)11-1-21 

Docket Number: 

A-94-52 

Printed 7/9/2008 3:11:21 PM Sheet 21 of 114 
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H\.fmm. 

THE EPOXY 

ALTERNATIVE 

WITH INCREASED OSHA AND EPA 

REGULATIONS AND RISING INSURANCE 

COSTS AFFECTING STYRENATED USERS, 

N O W IS THE TIME TO REVISIT EPOXIES. 

• by Gary R. Hovan/GLS Corporation 

A-

...- i 

'••^»t-k%m 

inee their introduction in 1948, epoxy resin 

systems have not been widely used in composites 

manufacturing outside of the aerospace industry. 

But now is the time to revisit epoxies. With 

increased OSHA and EPA regulations and rising 

insurance costs affecting styrenated resin users, 

the cost of doing business is constantly increasing. 

In a 1989 rulemaking, OSHA set the Permissible Exposure Limit (PEL) for styrene at 50 parts 

per million (ppm). The Eleventh Circuit Court of 

Appeals overturned that rulemaking in 1992, and 

the styrene PEL reverted back to 100 ppm. OSHA 

has established a hierarchy of controls to be used 

to meet the workplace PELs. Limited use of 

National Institute of Occupational Safety and 

Health (NIOSH) approved respirators is part of 

this hierarchy. OSHA will be revisiting the PEL 

issue in mid-1995. The results of this rulemaking, 

when finalized, may place added restrictions on 

the use of respirators for meeting workplace PELs. 

When the EPA's Clean Air Act of 1990 listed 

styrene as a hazardous air pollutant, the cost of 

doing business began an upward trend. If a 

business has the potential of being a 10-ton 

emitter of styrene, it will fall under the stringent 

regulations of Maximum Achievable Control 

Technology (MACT). A composites fabricator 

using as little as one drum of resin per day may 

be forced into this category. Lengthy permits as 

well as state-of-the-art technology for reducing 

emissions will be necessary. This could mean 

costly capital improvements such as incinerators 

and adsorption or biofiltration systems. Suddenly 

the cost of doing business increases dramatically. 

The resources and capital requirements to 

remain in compliance are not insignificant. If one 

takes into account these factors and views the 

total cost of using styrenated resins, then epoxy 

systems should be considered as a feasible 

alternative. 

Granted, epoxy resin systems are more 

expensive on a per pound basis versus styrenated 

polyester or vinyl ester resins. Epoxy resins have 

benefits that do not add to the cost of the process. 

Most significantly, epoxies do no* contain volatile 

or hazardous air pollutants. Their contribution to 

total emissions is negligible and a simplified air 

permit may be all that is required. From a worker 

exposure standpoint, most epoxy systems do not 

require special or mandated controls other than 

standard personal protective equipment. 

The performance of epoxy systems can 

overcome many of the costs associated with using 

less expensive polyester or vinyl ester resins. In 

marine applications, common concerns are 

secondary bonding and osmotic blistering. If 

these issues manifest themselves, resolutions are 

costly for marine fabricators and boat owners. 

Epoxy resins are extremely resistant to osmotic 

blistering, providing the benefits of lower warranty claims and more satisfied customers. Epoxy 

resins are also known for their outstanding 

adhesion which services to virtually eliminate 

secondary bonding problems. 

As a result of their superior fatigue and 

impact resistance, along with excellent fracture 

toughness, epoxies are the resin of choice in 

applications such as automobile leaf springs and 

water skis. These properties allow fabricators to 

reduce laminate schedules and produce less 

costly and lighter parts without a loss of performance. The performance of epoxies complements 

the physical properties of typical reinforcements. 

Most epoxy systems are non-flammable, 

thereby reducing the associated hazards of using 

flammable styrenated resin. One possible benefit 

is lower insurance premiums for plant facilities. 

Special handling and storage conditions are 

required for the organic peroxide and metal salt 

initiators used to cure polyester resins. These 

chemicals are not used to cure epoxy resins. 

Special handling and storage are not 

required to keep epoxy resins within specification. The longer shelf life eliminates the need to 

dispose of material that may gel prematurely. This 

stability also lends itself to reliable lot-to-lot 

consistency. 

Epoxy resin systems are available as direct 

Composites FabricationlVthiuary 1995 
-•> • • •"•» . 

P.3 

s.*g$&zi --• \<&\, *" "4 ^' ' .- I'^AEporyxaminatipg Resi«n !

"'^'S.:E£S;Ei m^mmmmm m. 

Epoxide Equivalent Wieig/if (g/g equivalent) 

Viscosity (cP at 77°F) 

Flash Poi'nf Seta flash (°F) 

S/ic//Li/e 

166-177 •yi-M^l&s 

•3000-4500 ;.

:

i,r$^j&;Z 

>300 ' y-ti$*0?-' 

1 year minimum,.;:.'$•%'' 

V Coring Agent (CA) 

•„-.•'".'• •• :*.•'

 ! '.S3SV tf&^M*'"-' 

Amine Equivalent Weight (g/g equivalent) •' 

Viscosity (cP at 77°F) 

Flash Poi/ifPMCC(°F) 

Shelf Life 

58-62 

7-12 

255 

1 year minimum 

Cure Accelerator 

Viscosity (poise at 77°F) 

ShelfLtfe 

40-60 

1 year minimum 

- Mixed System Properties 

Mix Ratio, Resin/CA parts by wt., (parts by vol.) 

Resin/CA Blend Viscosity (cP at 77°F) 

100/35 (100/43) 

400-600 

Reactivity 

Accelerator Level (parts by wt./100 parts resin) 

Cup Gel Time 210g. (minutes at 75°F) 

1 

200 

2 

99 

3 

75 

4 

55 

5 

45 

replacements for polyester or vinyl ester resins 

used in spray up and hand lay up processes. The 

properties for a typical epoxy resin laminating 

system are as shown above in the chart. 

This resin system offers low 

viscosity without the use of 

modifiers or reactive diluents thus 

keeping the odor very low. 

Similar to polyester resins, the gel 

time can be varied by changing 

the level of the accelerator to 

compensate for seasonal changes 

of temperature. Fabricators can 

deliberately adjust the pot life to 

accommodate the needs of the 

operation. The accelerator can be 

left out for vacuum bagging with 

moderate heat cures or more can 

be added for quick room temperature cures. 

All thermoset resin systems 

will benefit from a post cure to 

develop ultimate physical properties. Epoxies are no different and a mild post cure 

is recommended for consistent product performance independent of seasonal shop temperatures. Making provisions for post curing may 

represent a capital investment for some facilities. 

The cost and energy of post curing can be 

substantially less than the cost of incinerators or 

Epoxy resin 

systems are 

available as direct 

replacements for 

polyester or vinyl 

ester resins used in 

spray up and hand 

lay up processes. 

biofiltration. A relatively cost effective method for 

post curing is to use intrinsically safe heat lamps 

that can be lowered directly into the mold. More 

efficient enclosed systems can effectively pay for 

themselves with energy savings. 

Faster cure rates and greater 

through-put as well as reduced 

energy consumption can be 

realized. The leading suppliers of 

epoxy resins continue to develop 

systems that fit the needs of 

composites fabricators. 

The trend toward increasing 

regulations for composites manufacturers suggests a thorough 

review of all options. The benefits 

of using epoxies such as negligible 

emissions, superior physical 

properties, and high quality 

finished parts cannot be overlooked. When the total cost of 

using styrenated resins is examined, epoxy resin systems become 

an increasingly attractive alternative. A 

Special thanks to Gary A. Hunter, Senior Technical Associate, Shell Development Company, 

Houston, TX, and Nancy Dehmlow, Vicefresidenl 

of Health, Safety, and Environment, GLS Corporation for their input. 

10 Composites Fabrication/February 1995