p.1 

OAR Box 1413 

Prepped by Ollie Stewart 

Document Number: 

77) 11-1-78 

Docket Number: 

A-94-52 

Printed 7/9/2008 3:11:23 PM Sheet 77 of 114 
P.2 

echnically Speaking 

y Bob Lacovara 

'irector of Technical Services 

omposites Fabricators Association 

EPA AIR DOCKET 

ZD-X-7B 

deducing Emissions with Styrene Suppressants 

Ihe arsenal of styrene 

emissions reduction 

techniques for open 

molding includes low 

prene resins, controlled sprayg techniques, non-spray applittion, and the use of film 

rming agents, which reduce 

ie evaporation of styrene 

onomer. These film formers are called 

ipor suppressants or styrene suppresjits. Vapor suppressants are almost as old 

; the composites industry, but have 

ljoyed a re-birth of necessity, as a major 

nissions source reduction method for 

ie open molding industry. 

Vapor-suppressants are a class ofresin 

iditives typically based on aliphatic wax 

impounds, such as paraffin, although 

roprietary chemistries are used in high 

erformance formulations. The function 

f a vapor suppressant is to rapidly phase 

:parate from the resin, and form a film on 

ie surface of the curing laminate. The 

*axy film inhibits styrene evaporation, 

'hich results in reduced styrene emissions. 

Paraffin wax was originally used as an 

lir-dry additive" or 

rack-free additive" 

i assist in curing a 

iminate, or a postpplied gel coat 

arface, so it would 

e sandable. 

ypically, sanding a 

ured laminate will 

;sult in "gummingp" the sandpaper, 

while exposed to die oxygen in 

the atmosphere. The air inhibition, however, only occurs in a 

very thin layer at the surface of 

a laminate. The laminate may 

be very well cured, except for 

the boundary layer, which has 

been exposed to the atmosphere. This is particularly true 

for orthophthalic, isophthalic and vinyl 

ester resins. DCPD resins tend to air-dry 

on the surface and are less prone to air 

inhibition. The use of paraffin wax as an 

"air-dry" additive causes die surface to 

fully cure by excluding contact with the 

atmosphere. This results in a sandable 

surface. It was discovered that an incidental benefit of paraffin wax was that the 

film hindered styrene evaporation, 

tiirough the same mechanism of excluding contact with the atmosphere. 

Paraffin wax does have a downside -

die wax film can reduce the bond between 

laminates. The reduction in inter-ply 

adhesion can result in serious structural 

failure in case of delamination. However, 

more sophisticated suppressant formulaowever, once the 

surface gum" is 

emoved the 

iminate sands 

perfectly well. The 

eason for this is that 

nany polyester 

esins are air inhibted, meaning they 

lo not cure well 

6 Composites 

Interlaminar adhesion 

with parafin 

with advanced suppressant formulation 

dons incorporate adhesion promoters to 

enhance bonding of subsequent plies of 

laminate. Additionally, diere is a timing 

issue which .effects laminate adhesion. 

When using a vapor suppressant additive, 

diere is an ideal window of time for applying the following laminate over a cured 

laminate. That window may range from 2 

hours to 24 hours depending on the 

specific additive, resin type, laminate gel 

time, and ambient temperature cure 

conditions. Outside of die window, the 

laminate surface should be completely 

sanded to insure an adequate bond. 

Because adhesion is influenced by a 

number of factors, it is recommended that 

you conduct adhesion testing on your 

specific combination of materials and 

conditions. 

During the course ofthe CFA Styrene 

Emissions Test Project, the effects of vapor 

("Technically Speaking" continued on p. 42) 

*_:t_;_. _/7?*__7-i_.:,r, '" •'^-"— • • • '• .•.' "_' a ' ' " ", '.'_ V _ J 

Suppressant with adhesion promoter. 
•echnically Speaking (cont'd) 

P.3 

"Technically Speaking" continued fiom 36) 

ippressants were examined, to determine 

ie extent of emissions reduction. As a 

suit, an understanding of die function of 

ippressants has been developed. 

. Film formation only occurs when the 

surface is in quiescent state, that is, 

when not being disturbed by resin 

transport or by manipulating the 

surface with laminating tools. The 

implication is that the suppressant is 

only effective during the static (quiescent) curing phase of the emissions 

profile. (Fig 1) 

2. Vapor suppressants produce a large 

emissions reduction from the curing 

phase ofthe emissions cycle. (Fig. 1) 

3. Suppressants vary in effectiveness with 

different combinations of suppressant 

and resin formulation. 

4. Suppressing action varies with resin 

styrene content, with high styrene 

ppm) 

s 

o 

i 

Application Phase 

\ RolK)ut 

\ Phase 

Lugo Suppressant Effect 

" -_-»_____^^ Static Curing Phase 

Time 

iStyrei 

Content 

% Weight 

33% 

44% 

49% 

t-Vapor 

Suppressed Emissions 

%ResinWt 

4.6% 

7.5% 

9.3% 

:". Vapor 

Suppressed Emissions 

% Resin Wt 

2.8% 

3.1% 

3.6% 

Emissions 

Reduction 

-39% 

-59% 

-61% 

fc 

-ft. 

J *! 

lable 2 .{.fl 

Resin Styrene 

Content 

% Weight 

33% 

44% 

49% 

.Atomized Spray Application (Chopping) 

Non-Vapor 

Suppressed Emissions 

% Resin Wt 

8.2% 

11.5% 

14.0% 

Vapor 

Suppressed Emissions 

% Resin Wt 

5.2% 

8.0% 

9.2% 

% 

Emissions 

Reduction 

-37% 

-30% 

-34% 

resins exhibiting greater overall reductions dian low styrene resins. (Tables 1 

&2) 

The differences in emissions reduction between manual application and 

spray application are a result of the 

emissions profiles of these two processes. 

(Tables 1 & 2). In the case of spray application, a large portion of emissions is lost 

during die spray transfer process. Once 

the resin is on the surface ofthe reinforcement, spray application shares the same 

profile as manual application. Because the 

vapor suppressant is not effective during 

the spraying stage, emissions for this 

portion of the profile are virtually the 

same as a non-suppressed system. 

However, once the resin is less disturbed, 

and finally undisturbed, the suppressant 

begins to take effect. With manual application, styrene loss is less during the transfer stage, therefore the proportion of 

emissions reduction on the back-end of 

die process is greater. 

The other evident fact is that with 

manual application, higher styrene 

content resin exhibits a greater proportional reduction in emissions. It appears 

that once the suppressant film is formed 

on the resin surface, emissions are about 

the same for both high and low styrene 

resins. The high styrene resin emits more 

styrene during the transfer stage and 

during roll-out, so the actual amount of 

emissions is higher, but the proportional 

decrease is also greater. The result is that 

high styrene resins reap a greater benefit 

from vapor suppressants than low styrene 

resins in manual application. In spray 

application the differences are blurred 

across the range of styrene contents, most 

likely due to the influence of the magnitude of emissions during the spraying 

phase. 

During recent testing, flow applicators have produced emissions profiles that 

are similar or better than manual application. The combination of a flow chopper 

("Technically Speaking" 

continued on p. 35) 

Composites Fabricationl)une 1998 
P.4 

Section 112(d) is the heart of Tide III. 

.d) directs EPA to establish emission 

dards for each category or subcategory 

jurces listed under 112(c). It allows 

. to set different standards for different 

s of sources widiin a category. 

And now we finally get to MACT. 

ion 112(d) requires that the emission 

dards (i.e., NESHAPs) established 

er this section shall require "the 

imum degree of reduction in 

•sions of the [HAPs] diat [EPA]... 

rmines is achievable... through the 

ication of [control technology]..." 

ce, "Maximum Achievable Control 

inology." 

EPA is allowed to take into consideracosts, environmental impacts, and 

gy use when determining what is 

evable. However, 112(d) tells EPA 

the standard for new sources shall not 

•ss stringent than the emission control 

sved in practice by the best controlled 

lar source. And the standard for exist-

>ources shall not be less stringent than 

iverage emission limitation achieved in 

rice by the best performing 12% of 

ing sources (or for the best performing 

sources for categories or subcategories 

. fewer than 30 sources). These 

imum stringency levels (or "MACT 

:s") are set without regard to cost or 

r impacts. Congress assumed that, 

. other facilities are using the controls, 

they are by definition feasible and achievable. This simple assumption, and EPA's 

derivation of die floors for composites, is 

causing us no end of trouble; more about 

that next month. 

Section 112(e) tells EPA to establish 

these standards according to a schedule. 

EPA is to promulgate all standards by 

November 15, 2000. (There's that pesky 

November 15 again.) The RP/C 

NESHAP was originally scheduled for 

promulgation in 1997, but was recently 

moved to November 15, 2000 to allow 

EPA more time to collect data. 

Section 112(f) directs EPA to revisit 

the MACT standards and issue additional 

regulations if the MACTs are not sufficiently protecting the public health. 

112(f) is known as the "residual risk" 

provision. 

Section 112(g) requires MACT for 

new, reconstructed, and modified sources, 

even if EPA has not yet promulgated the 

appropriate MACT standard. You may 

recall a lot of heat and noise about 112(g) 

a few years ago. In its first proposed rule 

to implement 112(g), EPA classified 

styrene as a carcinogen, and required caseby-case MACT and permit revisions for 

many of the day-to-day operational 

changes commonly made in the composites industry (like changing to a new spray 

gun). The composites industry was instrumental in getting EPA to limit case-bycase MACT requirements to construction 

of new sources and reconstruction of existing sources (where 50% or more of a 

source is replaced). And EPA decided not 

to classify styrene or other HAPs as part of 

the 112(g) rule. 

For industries where it is not possible 

to enforce an emission limitation, Section 

112(h) allows EPA to establish MACT as a 

design, equipment, work practice, or 

operational standard. Under die RP/C 

MACT, many parts of the indusny will be 

required to employ certain equipment 

designs, materials, or work practices, rather 

than comply with emission limitations. 

There are several other parts of 

Section 112(112(k), fbr example, requires 

EPA to limit emissions from non-major 

sources to reduce cancer risk in urban 

areas), but they don't have much to do 

with MACT. 

Next month: EPA's development of 

MACT for composites. O 

chnically Speaking" continued from 42) 

vapor-suppressed resin has produced 

.sions in the range of 1 -2% of resin 

;ht, which is extremely low. The flow 

pper has an advantage over bucket 

brush hand lay-up - the flow chopper 

ster. The faster the resin is transferred 

he laminate the lower the emissions, 

itionally, chop is generally easier to 

rate and roll-out than chopped strand 

, so both the resin application stage 

the roll-out stage are truncated, 

lting in lower emissions. 

Should you use a vapor suppressant? 

The answer is a qualified yes. Is secondary 

bonding an issue for your products? If you 

are fabricating "one shot" laminates, or if 

structural bonding is not an issue, you are 

free to use almost any type of suppressant. 

However, if you are fabricating products, 

which use multiple laminates and have 

structural requirements, you should 

approach suppressants cautiously. You 

must select a suppressant that is effective 

with your specific resin system. 

Additionally, you must have procedures in 

place, which specify laminate timing 

and/or sanding schedules. 

By working closely with your resin 

supplier, yor .an take maximum advantage of spec. t iig a vapor suppressant 

that has the required adhesion characteristics, and is effective in reducing 

emissions. While styrene suppressants 

are not suitable for all applications, they 

can offer real emissions reduction 

benefits in a wide range on molding 

situations. O 

5