p.1 

OAR Box 1413 

Prepped by Ollie Stewart 

Document Number: 

79) 11-1-80 

Docket Number: 

A-94-52 

Printed 7/9/2008 3:11:24 PM Sheet 79 of 114 
D U C T I 0 N T 

A ^4-5 2 

JC~T-$Q 

The Why and How of 

Reducing Styrene Emissions 

A

lmost all composite molders use styrene-containing resins. Whether you're 

pultruding ladder rail, contact molding modular tub-and-shower units, polymer 

§ casting sinks, using RTM to mold hatch covers, making continuous panels, or compression molding automotive hoods, your process probably uses — and emits — styrene. 

Styrene plays two key roles in a resin system. Before curing takes place, ic reduces the vf 

viscosity ofthe polyester resin so that it can flow, wet the reinforcement, and be applied | 

to die mold. And during curing, styrene reacts to form the cross-links (chemical bonds) j 

between the polyester resin molecules. This cross-linking reaction transforms rhe resin J 

from a liquid to a solid material. /—-_ 

In this article, lets review the various technologies that are useful in reducing.the J 

amount of styrene that is lost from composite manufacturing pn 

Why reduce emissions? 

Why should you be interested in reducing die amounV-ofstyrenS/ihaNiribsc-frorn your f 

— — -JJ^QCK£ T ^ ~ | 

process? One obvious answer is — now don't be shy, we're all capitalists here^smoney.A 

Styrene is not free. It doesn't bubble up from a well in the back of your property (but call 

j|; me immediately if it does!). You pay for it. And if it evaporates and flies away out your j 

fe window, that's really your money floating away on the breeze 

Another important reason to reduce styrene losses from your process is protecting ' 

k the health of your employees. Under our industry agreement with OSHA, composite 

industry employers are required to limit exposure of workers to styrene to 50ppm (timeweighted-average over 8 hours; exposures up to lOOppm are permitted for no more than I 

• 15 minutes). Employers are encouraged to use engineering controls (ventilation) to keep 

exposures below these limits, but respirators may be used in some cases. Reducing the | 

by John Schweitzer 

Composites Fabricators Association 

12 Composites Fnbrictitio'iljune 1998 
P.3 

unt of styrene lost from your process 

reduce the resources needed to install 

operate ventilation systems, or the 

unt of time needed to manage respir programs. 

Even if you are already meeting the 

Dm limit, further reduction in styrene 

:s from your process may improve the 

cing conditions, morale, and quality 

roducts produced in your facility. 

And here's a heads-up on occupaal exposures. Very extensive epidemiical studies of composite industry 

cers did not show any relationship 

/een exposure to styrene and chronic 

th problems. However, recent 

irch with laboratory animals has 

;ested that styrene exposure may have 

rtory effects (that is, effects to nasal 

e, perhaps affecting the ability to 

cr odors). The industry is now 

cing to determine if this finding has 

relevance to humans. In any case, the 

among us will look to the day when 

istry scientists could recommend an 

i lower occupational exposure limit. 

A third reason to minimize the loss of 

:ne from your process is to reduce the 

ironmental footprint" of your facility, 

iicing styrene losses from your process 

mean that less styrene leaves your 

t. 

The science on styrene toxicology 

environmental fate clearly show that 

industry is not causing any significant 

ch risk or environmental damage, in 

amounts of styrene commonly 

ted by industry facilities. However, 

cing styrene losses from your process 

mean fewer odor complaints from 

• neighbors. It may also mean that 

are more-readily able to meet your 

's fence-line limit for styrene. And 

Iy, in areas with smog problems, 

:cing your styrene emissions will 

ce the contribution of your facility to 

problem, since styrene — like other 

2s — reacts in the atmosphere to help 

1 smog. 

The final important reason you 

ild reduce styrene emissions is that it 

increase your credibility among your 

loyees and your community. As 

lical processors, composite molders 

inevitably face some (probably 

arranted) skepticism about their 

mirmenr to fully protect workers and 

hbors. An aggressive program to 

imize styrene emissions, when 

•fFlow applicators and pressure-fed rollers 

Controlled spray 

Covered wet areas — pultrusion 

49% 

23% 

60% 

properly managed and communicated, 

will help build trust between you and 

your employees and community. 

How to reduce emissions 

There are basically only two ways you can 

reduce the amount of styrene lost from 

your composite molding process: use less 

styrene, or prevent exposure ofthe styrene 

to air. Emission reduction technologies 

included in the use-less-styrene group are 

low-styrene resins and filled resin systems. 

The second, prevent-exposure-to-air 

group includes low-emitting resin application technologies, suppressants, 

controlled spray, airflow management, 

and closed-molding processes. 

Low-styrene resins 

One way for some molders to minimize 

the loss of styrene from their process is to 

use resins formulated with less styrene. 

Resin suppliers offer a variety of resins 

with lower styrene content, many of 

which were formulated to meet the 

requirements for California's SCAQMD 

Rule 1162 and similar regulations. 

Some of the low-styrene resins are 

made with special shorter-chain polyester 

molecules that permit lower styrene 

content while still maintaining workable 

viscosity and other properties. Other 

low-styrene resins employ vinyl toluene, 

p-methyl styrene, or other non-styrene 

monomers; these other monomers have 

lower vapor pressures than styrene, so less 

of the material evaporates when exposed 

to air. And some low-styrene resins are 

made with combinations of short-chain 

polyesters and low-volatility monomers. 

While the use of low-styrene 

resin sounds like is should be relatively 

painless, this technology is not for everyone. First, for many molding processes, 

such as pultrusion, compression molding, 

and even flow-coater application of resin 

to an open mold, reducing the styrene 

content ofa resin may not result in significant reductions in emissions. 

Further, reducing the styrene content 

ofa resin means that it is a different resin. 

It will likely have different glass wetting 

ability, filler loading capacity, gel times, 

viscosity, and rheological properties. 

Using low-styrene resin may require that 

you employ different formulas, application technologies, and roll-out procedures. 

And products molded using lowstyrene resins will have different chemical 

and physical properties. Styrene, after all, 

is primarily a reactive monomer, not a 

solvent. Changing the amount of styrene 

in a resin, or changing the type of 

monomer used, will change the properties 

of the product, sometimes unacceptably. 

In some cases, it's possible that the 

use of a low-styrene resin will actually 

increase emissions, if, for example, longer 

roll-out is needed to wet the glass, or if 

more resin is needed to offset decreased 

physical properties. 

Still, molders — especially open 

molders using traditional spray application of resin or gel coat — should work 

with low-styrene systems to see if the use 

of these materials decreases emissions 

while still allowing acceptable processing 

and product performance. Many of the 

molders required ro use the 1162-style 

low-styrene resins were able to overcome 

initial processing problems, and today use 

these materials and enjoy the benefits of 

lower styrene emissions. 

Fillers 

A second way to reduce styrene emissions 

is to use less resin. This might mean 

engineering a product so that it uses only 

as much resin as needed to provide the 

required properties, but more often this 

approach means adding an inert filler to 

the formula. Fillers reduce the amount of 

resin needed (thereby reducing styrene 
P.4 

usage and consequently emissions), while 

possibly increasing produa stiffness or fire 

resistance (depending on the type of filler 

used). 

Typically, processing and product 

performance requirements will determine 

what type and how much filler can be 

used. Some suppressants, and some of die 

new non-spray application technologies, 

may not be compatible widi filled systems. 

Low-emitting resin application 

technologies 

While the emission reduction technologies discussed above work by decreasing 

the amount of styrene used to make a 

product, the technologies described in 

this and the following sections work by 

reducing die contact of styrene with air. 

If you wanted to reduce die amount 

of water evaporating from a puddle, what 

would you do? Well, you could obviously 

mop up some of die water, so there would 

be less to evaporate. This would be analogous to rhe use-less-styrene technologies 

described above. 

But what if you needed die water (like 

we need styrene to provide those crosslinks)? Well, you could reduce die surface 

area of the water by covering the puddle 

with a plastic sheet or by scooping the 

water into a bucket. This is analogous to 

the minimize-exposure-to-air technologies. 

For example, the various nonatomized application technologies like 

pressure-fed rollers and flow-applicators 

(also called flow coaters) work to reduce 

emissions by minimizing die contact of 

resin to air. In traditional spray application of resin, very small "atomized" 

droplets ofresin travel from the spray gun 

to the mold — or to the floor, walls, or 

filters ofthe spray booth! — creating very 

high surface areas of wet resin, and consequently high emissions. By contrast, 

flow-applicators deliver streams ofresin to 

the mold, rather than atomized droplets; 

the applied resin has a much lower surface 

area and therefore lower emissions. And 

with pressure-fed rollers, there is not even 

a stream of resin. 

Another low-emitting resin application technology is resin impregnation, 

where glass mats are mechanically fed 

through a resin bath, and then applied to 

the mold. Again, there's no spray (or 

stream) of resin through the air, and more 

of the resin is delivered to the mold. 

Of course, these technologies have 

14 Composites Fabricationl]\ine 1998 

their limitations. None can practically be 

used for gel coat, since this material needs 

to be applied in a very uniform layer that 

can be accomplished only with atomized 

spray. Pressure-fed rollers may not transfer resin to the mold fast enough to keep 

up with production in many shops, and, 

like resin impregnation, are not useful 

with chopped roving. Flow-applicators 

may have problems with filled resin 

systems, although suppliers are working 

to overcome this limitation. And 

Suppressants have to be 

matched to the resin system 

employed, and they may not 

work as effectively with filled 

resin systems. 

pressure-fed rollers and flow-applicators 

may require additional roll-out to satisfactorily wet glass. 

Despite the potential limitations, 

however, these technologies promise 

significant emission reductions over the 

traditional spray application of resin, and 

are finding increasing acceptance in the 

industry. Any molder using atomized 

spray application ofresin should give flow 

applicators, pressure fed rollers, and resin 

impregnators a serious look 

Suppressants 

A second way of reducing contact of resin 

with air is through the use of suppressants. These materials, which are typically 

waxes, form a layer on the surface of the 

resin while it is curing. This layer reduces 

the evaporation of styrene. 

Suppressants work only when the 

resin is left undisturbed, so that the layer 

of wax can be formed on the surface. 

During resin application and roll-out, 

fresh resin and styrene is continuously 

exposed to the air, and suppressants are 

not effective in reducing emissions. In a 

typical spray-up/roll-out/curing process, 

however, about one-quarter of che 

1 

emissions comes from the curing stage, 

and suppressant can be very effective in 

reducing diese emissions. 

Suppressants have to be matched to 

the resin system employed, and they may 

not work as effectively with filled resin 

systems. Resin and suppressant suppliers 

can help select the most effective combinations of materials. 

Finally, with suppressants, molders 

have often found diat diey need to sand or 

grind die surface of parts if additional 

laminate layers are to be applied after 

curing. This problem with "secondary 

bonding" is because the waxy suppressanc 

layer on the surface of the part, which 

reduced styrene evaporation during curing, 

can later act like a release agent and prevent 

adequate bonding between the laminate 

and die subsequentiy applied resin. 

Controlled spray 

For the atomized spray application of 

resin or gel coat, the use of a controlled 

spray program is one ofthe most effective 

ways of reducing the surface area of the 

wet resin, thereby reducing contact of 

resin with air, and consequently reducing 

emissions. A controlled spray program 

consists of three components: 

• proper calibration of spray guns, so 

that the lowest tip pressure that still 

delivers an adequate fan pattern is used 

(higher pressures result in much more 

"misting" of resin and evaporation of 

styrene); 

• training operators to handle spray guns 

and apply resin using techniques 

designed to minimize overspray; and 

• use of containment flanges at mold 

perimeters, which prevent the deposition of high surface area resin layers 

on the floor and walls. 

Actually, controlled spray can fit into 

both of our general emission reduction 

technologies: a controlled spray process 

uses less resin and styrene — because 

more if ir is delivered to the mold — and 

it minimizes the exposure ofresin to air. 

While implementing a controlled 

spray program will require employee training (including regular refresher training) 

and some modification of molds (to add 

the flanges), die investment will be quickly 

recovered through savings in resin use and 

improved housekeeping. Honestly, everyone doing atomized spray application of 

resin or gel coat should be using controlled 

spray. For more information about this 
P.5 

hnology, call CFA and ask for a copy of 

: Controlled Spray Handbook. 

rflow management 

: has a limited ability to hold styrene 

.or, and once this limit is reached, no 

ire styrene will evaporate, unless the 

rene-laden air is replaced with fresh air. 

in theory, allowing a styrene-laden 

er of air to remain at the resin surface 

i reduce styrene evaporation. 

In practice, airflow must be reduced 

very low levels to achieve any real 

pact on styrene evaporation. The CFA 

:ing program showed that reducing 

low across wet open molds did not 

lificantly reduce emissions in open 

lding, probably because airflow can 

: be practically reduced enough over an 

:n mold. 

In other processes, however, emission 

uctions of up to 60% can be achieved, 

ting has shown significant emission 

uctions from the use of covers or 

losures over wet process areas in 

trusion, continuous lamination, and 

C compounding. And tests with 

trusion lines have shown emission 

ictions just by reducing general venti-

>n flows. 

Of course, users of this technology 

st still comply with occupational 

osure limits. The enclosures 

irioned above typically allow access to 

process only through hand-sized 

rs ("hand-ways" rather than "mans"). And general ventilation can be 

iced only if. occupational exposure 

Is are still below the required levels. 

Finally, air flow management — 

ugh the use of lids or covers — is also 

effective in reducing emissions from 

i mixing, storage, and transfer vessels. 

sed molding 

last technology that we'll consider for 

cing styrene loss from a process is 

:d molding, which includes vacuum 

molding, resin infusion, RTM, and 

pression molding. These technolozzn have very low emissions. 

However, process economies often 

ely limit the application of these 

lologies. Compression molding is 

jle only when large production runs 

eeded (say, 50,000 automotive hoods 

'ear), and where the capital is availto pay for the large presses and 

>lex molds. Vacuum bag molding 

and resin infusion, however, are often 

useful and economically feasible for 

products made with open molding, 

especially where high volume production 

is not needed. And while RTM (resin 

transfer molding) does require special 

molds and other equipment, the investment is much less than that required for 

compression molding. 

Conclusion 

Several technologies are proven and available for reducing emissions of styrene 

from composite manufacturing processes. 

While most have some limitations, almost 

every composite manufacturer will find at 

least one that will work with his process. 

And the improved working conditions, 

reduced environmental footprint, and 

goodwill to be gained from workers and 

neighbors, make the effort to investigate 

and use these technologies a good investment, ft 

John Schweitzer is the Composites 

Fabricators association's Senior Director of 

Government Affairs. 

If you'd like to join 

this elite group... 

it is possible. 

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1-800-978-3733 

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and the industry. 

MARQUIS SPAS 

ATTBAR, INC. 

K§R&L INDUSTRIES, INC. 

AMTECH CORPORATION 

CUSTOM FIBERGLASS & VACUUM FORMED PARTS 

G€A 

Thermal and Energy 

Technology Division 

CEA Thermal-Dynamic 

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Dynamic Fabricator* 

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TiBe/tWInc. 

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GATC 

Gate Precast Company 

fR€€S. IMC 

Samford • Shreveport, LA 71103 • Phone:(318)424-2654 

Fax: (318) 424-967*5 • Visit us on the web at www.freesinc.com 

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