p.1 

OAR Box 1413 

Prepped by Ollie Stewart 

Document Number: 

22) 11-1-22 

Docket Number: 

A-94-52 

Printed 7/9/2008 3:11:21 PM Sheet 22 of 114 
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The advantages can be summarised as follows: 

Workers are exposed to lower styrene concentrations during processing 

Reduced styrene emission in the curing stage 

, Less pollution of the environment 

Reduction of the styrene emission is reached without affecting processibiiity and product properties 

Material savings are achieved because of low monomer evaporation 

No interlaminar adhesion problems; long curing times between consecutive lay-ups are possible 

Because of the lower styrene emissions new legislative requirements may 

be met with no or limited additional investments in ventilation, while 

purification of the exhaust air will not be necessary, 

in oruer to meet trie stringent MA-V vaiues u is nowever recomrnenoeu io pay 

attention to proper housekeeping, efficient ventilation, and using the right 

processing equipment. DSM Resins is witling to advise you on these aspects. 

DSM Resins continues its developments into resins with a low styrene emission 

during open-mould processing. Based on the technology which has been 

extensively described in this paper the range of resins for hand lay-up, spray-up 

and filament winding will be extended. This not only includes other ortho- and 

iso UP resins, but also the high performance bisphenol A and vinyl ester resins. 

Additionally, INSERT will be used to develop low styrene emission gelcoats. The 

preliminary results in this application area took very promising. 

ACKNOWLEDGEMENT 

The author thanks P. Dijkink and M. Luesken for their valuable contribution in 

developing the INSERT concept. 

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INTRINSIC STYRENE EMISSION REDUCTION TECHNOLOGY 

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A break-through in the reduction 

of styrene emission 

during open-mould processing 

Dr. A.J. de Koning R 

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JEC, April 1995 U 

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•flUG-15-1995 10=34 DSM RESINS 7068496777 P.03 

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'INSERT' Resins; a break-through in the reduction of 

styrene emission during open-mould processing 

Dr. A.J. de Konlng 

DSM Resins BV. Z-voffe, The Netherlands 

April 1335 

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ABSTRACT 

Health and environmental problems are receiving an increasing amount of 

attention. The workshop atmosphere as well as the ventilated air in the GRP 

industry are seriously affected by the styrene emission of unsaturated polyester 

resins. From a toxicological and performance point of view suitable alternatives 

are lacking, so styrene continues to be the monomer of choice in the unsaturated polyester and vinyl ester industry. 

During the fabrication of reinforced plastics composites one can distinguish 

between the processing stage (eg spraying and rolling) and the setting/curing 

stage when the resin is at rest. The well-known Low Styrene Emission (LSE) 

resins, which suppress monomer emission by the formation of a film across the 

surface of the laminate, are mainly effective in the setting/curing stage. During 

spraying and/or roll-out in open-mould processes, when the surface of the resin 

is continuously disturbed, emissions are hardly less than those of the base resin 

without a film forming additive. 

DSM Resins has conducted a very Intensive research program to specifically 

reduce the styrene emission in the processing stage. The effect of resin properties such as polymer structure, monomer content, molecular weight, viscosity, 

and reactivity on styrene emission have been thoroughly investigated. Through a 

basic understanding of the chemical- and physical phenomena of the evaporation 

process a new concept for resins with a reduced styrene emission has been 

developed. This concept has been called 'INSERT', meaning INtrinsic Styrene 

Emission Reduction Technology. The new Synolite 5500 series based on INSERT 

shows a reduction of the styrene emission in the processing stage of about 50% 

without detriment to the ease of fabrication and product properties. Mechanical 

characteristics, HDT and water resistance of the glass fibre reinforced products 

are consistent with those of typical UP resins. 

Through this emerging technology the use of Unsaturated Polyester resins in 

open-mould processing continues to have a viable future. Using these new resin 

systems may limit or even prevent additional investments in extraction and air 

purification to comply with the more stringent rules of legislation. 

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•fiUG-15-1995 10:35 DSM RESINS 7068496777 P.04 

DSM Resins 

INTRODUCTION 

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The legislation in Europe with regard to styrene emission into the workplace and 

the environment has become more stringent in the last decade. Although longterm bioassays and epidemiological studies amongst more than 65,000 people 

who worked in their professional life in the polyester industry, do not show any 

conclusive evidence of carcinogenic effects related to styrene, the political 

pressure to reduce emissions is still on. There ar.e several reasons for that: 

• Upon exposure to styrene in concentrations welt above 50 ppm acute 

health effects such as skin and eye irritations as well as neurotoxic 

effects (narcosis) are known. These effects, despite the fact that they are 

completely reversible (i.e. the human body recovers without any adverse 

chronic health effects), negatively affects the human working conditions. 

• There is a general policy to reduce the emissions of volatile organic compounds (VOCs, a chief Ingredient in smog formation) into the environment. Styrene. however, has a short atmospheric half-life characteristic 

(2 to 5 hours). Its effect on the upper atmosphere and even at groundlevel in the formation of smog is minimal. 

The main source of styrene emissions is the polyester industry. About half of the 

UP resin volume is processed in open-mould techniques such as hand lay-up, 

spray-up, and filament winding. Hereby significant emissions occur; for instance 

during laminating approximately 5-7 % in weight of the resin is lost because of 

styrene evaporation. In industrial practice this may produce an exposure which 

is greater than the current MAC (Maximum Allowed Concentration) or TWA-TLV 

(Time Weighted Average • Threshold Limit Value). Moreover, the emission of 

styrene results in an increase in the material costs of production, and may 

negatively affect the mechanical properties of the product. 

The polyester industry, confronted with this serious problem, is intensively 

looking at technical possibilities to achieve a substantial reduction in the 

emission of styrene. This includes modifications of resins, process technologies, 

application techniques, work practices, and installation of add-on emission 

treatment devices. Although in ali these fields significant progress has been 

made the subject of this paper will be restricted to development of improved 

resins. 

Introduction of the well-known LSE (Low Styrene Emission) resins In the second 

half of the seventies was the first important step in combating styrene emission 

at the source. The LSE resins contain a small quantity of wax or paraffin that is 

just soluble in the resin. Upon evaporation of a limited amount of styrene the 

film forming additive separates and forms a thin layer on the surface of the 

polyester, thereby blocking further styrene emission. The problem of a poor 

interlaminar adhesion between consecutive applied laminate layers was over-

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flUG-15-1995 10=35 DSMRESINS 

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come by the addition of adhesion promotors in the second generation of LSE 

resins. These LSE resins, representing the state of the art in styrene emission 

reduction technology, are now used to a wide extent. 

The LSE resins, however, are only effective in the curing or static stage. In the 

preceding dynamic phase of spraying and roll-out the barrier paraffin film is 

continuously disrupted and therefore hardly active. As the major part of the total 

styrene emission takes place in the active laminating step of the process the 

overall efficiency of LSE resins is rather limited. 

n^M Orntin* t>.a -, « ...wijoiouw neiu tfirort to develop resins which also 

exhibit a reduced styrene evaporation in the dynamic phase of the process. 

These investigations have resulted in a new series of resins with a very low 

styrene emission during (and after) open-mould processing. 

RESIN DEVELOPMENT 

The target was to develop resins which during active lamination, the most critical stage of the contact moulding process, give off far less styrene. Several 

routes were explored: 

/. Alternative monomers. 

Although chemically (partial) replacement of styrene is a viable option, there are 

restrictions from physical, toxicological and economical points of view. Styrene 

remains the best choice as a monomer giving rise to polyesters which handle 

well, cure readily, and give products with good properties at a competitive price. 

2. Resins in which the solubility parameter of the unsaturated 

polyester matches that of styrene. 

Apart from the fact that the chemical possibilities to obtain such resins are very 

limited, the effect on styrene emission reduction was less than anticipated. 

3. Resins with a reduced styrene content. 

In a typical general purpose unsaturated polyester resin the percentage of nonvolatile polyester component is in the range of 55-60% and hence lhat of 

styrene monomer 40-45%. A decrease in the molecular weight of the unsaturated polyester results in a decrease in viscosity of the solutions in styrene and 

enables resins of a lower styrene content, and hence a lower evaporation rate, 

to be used. However, when starting from conventional polyesters no resins with 

a styrene content lower than 30-35 % can be produced with sufficient mechanical strength, chemical resistance, and workable viscosity. 

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1/ flUG-15-1995 10:35 DSM RESINS 

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Nevertheless. DSM Resins succeeded by special processing and formulating to 

produce a low viscosity resin with a styrene content of only 25%. having 

processing characteristics similar to standard UP resins. Moreover, the mechanical and physical characteristics of the cured products ressemble those of the 

classical UP's. 

The new proprietary technology, has been called 'INSERT'. INSERT is the 

acronym of INtrinsic Styrene Emission Reduction Technology. Through 'INSERT', 

emissions in both the dynamic and static phase of the production process can 

be reduced by 50%. 

When 'INSERT' Is combined with the well-known 'LSE' technology even further 

reductions in styrene emissions can be obtained in the curing stage. 

INSERT formed the basis for a new generation of resins suitable for open-mould 

processes such as hand lay-up, spray-up, chop-hoop, and filament winding. 

i 

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NEW PRODUCTS 

DSM Resins introduces the first resins in the new range of products. 

SYNOLITE 5520-1-1 

SYNOLITE 5520-P-1 

Pre-accelerated general purpose laminating resin. This 

thixotropic resin shows a good glass fibre wet out and 

is designed for use in general spray depositing work as 

well as roller and brush applications. The resin has a 

medium reactivity and shows a low peak exotherm 

upon curing. Because of 'INSERT' it exhibits a low 

styrene emission in both the dynamic and static phase 

of the production process. 

An 'LSE' version of Synolite 5520 with an even further 

reduction of the styrene emission in the curing phase. 

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The key feature of these new resins is a major reduction of the styrene emission, especially In the dynamic stage of the conversion process. The styrene 

evaporation of Synolite 5520-1-1 in the static or curing phase is also significantly 

lower than that of non LSE resins. However, to get the maximum result in total 

styrene emission reduction the use of an LSE version, Synolite 5520-P-1, is 

recommended. 

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Typical liquid resin properties 

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Property Unit Syn. 5520 Standard ortho 

UP resins 

General Reactivity 

purpose low medium 

Vise, at 23 *C 

Thix. index 

Styrene content 

Acid number 

Gel time 

Density (20 »C) 

mPa.s 

mg KOH/g 

min. 

kg/m1 

250-350 

2.2-3. 2 

25 

17-22 

13-18 

1120 

190-24 0 240-31 0 

2.5-3. 5 2.5-3. 5 

43 

22-27 

19-23 

1090 

42 

11-17 

20-25 

1100 

Table 1. Typical liquid resin properties of Synolite 5520 and (comparable) 

conventional ortho resins for open-mould processes. 

Despite the fact that Synolite 5520 only contains 25 % of styrene it has a very 

low viscosity suitable for hand lay-up and spray-up processing, and rapid fibre 

wet out. Viscosity and gel time can be tailored to the specific customer requirements. 

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Typical physical properties of cast unfilled resin 

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Property Unit Syn. 5520 Standard ortho 

UP Resins 

Reactivity 

low medium 

Tensile strength 

Tensile modulus 

Tensile elongation 

Flexural strength 

Flexural modulus 

Impact strength 

(Unnocched Charpy) 

HDT (ISO 75A) 

Barcol hardness 

MPa 

GPa 

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KPa 

GPa 

kJ/m» 

70 

3.0 

3.2 

115 

3.1 

7.0 

75 

44 

65 

3.4 

2.4 

95 

3.5 

8.0 

65 

44 

Table 2. Typical cured cast properties of Synolite 5520 and conventional 

ortho resins for contact moulding processes. 

Remarkably. Synolite 5520 exhibits mechanical properties that do not deviate 

from those of the well-known general purpose tesins. A special advantage 

offered by this resin is the low degree of shrinkage, resulting in less fibre printthrough. Because styrene gives the highest contribution to shrinkage reducing its 

content in the resin infiuenches this characteristic. As Synolite 5520 contains 

only 25% of styrene the volume shrinkage is 1.5-2.0 % less than that of 

conventional UP resins. 

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Typical properties df laminates (containing 30 % Chopped Strand 

Mat) 

1 Property 

. 

Tensile strength 

Tensile modulus 

Flexural strength 

Flexural modulus 

Water absorption 

(ISO-R-175) 

after 24 hours 

after 7 days 

after 21 days 

Unit 

MPa 

GPa 

KPa 

GPa 

% 

% 

Syn. 5520 

100 

7.6 

180 

7.0 

0.10 

0.25 

0.40 

standard 

UP Resins 

ortho 

Reactivity. 

low medium 

105 

7.9 

180 

7.2 

125 

8.0 

205 

7.4 

0.10 

0.30 

0.45 1 

Table 3. Typical laminate properties of Synolite 5520 in comparison to those 

of standard ortho resins. 

Also the laminate properties of Synolite 5520 are in accordance with those of 

general purpose laminating resins. Because ofthe low styrene content of the 

resin the peak exotherm is well controlled enabling the production of relatively 

thick laminates in one step. 

The water absorption of the laminates does not exceed that of currently 

available (LSE) resins which are Lloyd's and Det Norske Veritas (DNV) approved. 

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In table 4 the minimal technical requirements are defined for Lloyd's. Det Norske 

Veritas. (DNV), and the classification type 1120 according to DIN 16946. 

Whan 

values of Synolite 5520, as presented in table 2 and 3, it is evident that our 

new laminating resin, easily meets the requirements of the marine specifying 

authorities. Tests are underway to get the official approvals. 

From these results it is evident that no technical concessions have to be made 

for this new range of resins with a low styrene emission during open-mould 

processing. 

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Tensile strength 

Tensile modulus * 

Tensile elongation 

Flexural strength 

HOT (IS0-75A) 

Barcol hardness 

Laminate 

Tensile strength 

Tensile modulus 

Flexural strength 

Flexural modulus 

MPa 

GPa 

* 

MPa 

•c 

2.0 

55 

40 

45 

3.0 

1.5 

62 

35 

MPa 

GPa 

MPa 

GPa 

75 

4.S 

145 

4.5 

80 

7.0 

130 

6.0 

OIN 16946 

Type 1120 

60 

2.0 

110 

55 

Table 4. Minimal technical requirements for cast resin and laminate properties according to Lloyd's, DNV and DIN 16946. 

Styrene emission 

A lot of non-resin related factors have an influence on the styrene emission, 

such as ambient temperature, speed of air flow over the resin or laminate, mould 

geometry, type of spray gun, time of processing, laminate thickness and gel 

time. Moreover, background emissions may be present which in case of direct 

styrene detection measurements may give wrong results. In order to draw valid 

conclusions it is therefore of utmost importance to conduct the experiments 

under identical working conditions. 

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1. Laboratory scale experiments 

A first and quick screening to investigate whether or not a new resin exhibits a 

lower styrene emission than the reference materia), is through the determination 

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RUG-15-1995 10:3? 

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of the static weight loss of the uncatalysed resin. 

This type of measurement is very simple. 50 grams of the UP resin is poured 

onto a tin dish with a diameter of 13.5 cm, giving a polyester layer with a 

thickness of approximately 3 mm and a surface of 143 cm1. The filled dish is 

placed on a balance and the weight loss is followed in time. The styrene 

emission is expressed in g/ma. 

These measurements were done at 23 °C in a closed thermostated space with a 

well defined constant air flow. In figure 1 the static styrene emissions of a 

standard UP resin, a standard LSE resin, Synolite 5520-1-1 (ISERT). and Synolite 

5520-P-1 (the LSE version of Synolite 5520-1-1) are compared. 

150 

E 100 f 

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Standard UP / 

INSERT^. 

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..*** —-•••uiiiiliuiiiiniilllllillllllllim'IIIIW 

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UMSERT-LSE 

10 f20 30 

Time (min) 

-t40 50 

Figure 1. Static styrene emission of uncatalysed laminating resins; standard 

UP, standard LSE, INSERT (Synolite 5520-1-1). and INSERT-LSE 

(Synolite 5520-P-1.) 

For the standard UP resin the styrene loss is linear over the 50 minutes period. 

The styrene evaporation speed of the INSERT resin, Synolite 5520-1-1, is significantly lower. The styrene loss versus time plot slightly deviates from the 

linear behaviour. As the mechanism of INSERT can be explained through the formation of intermolecular interactions this is in line with expectations. The 

standard UP and Synolite 5520 have similar viscosities despite the fact their 

styrene content differs considerably, viz. 43 and 25 % on total resin weight, 

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respectively. 

When the LSE technology is applied to Synolite 5520 the lowest styrene 

emission curve is obtained. After 20 minutes more or less the same emission 

level has been reached with the standard LSE-UP resin, however its emission 

curve clearly differs. In case of the Standard LSE resin the film formation of the 

LSE additive is complete within a few minutes after which the styrene evaporation virtually stops. The barrier on Synolite 5520-P-1 on the contrary, develops 

gradually in time. Maybe this less abrupt film formation, leaving more room for 

air inhibition at the surface, is the reason for the good interlaminar adhesion of 

laminates involving a lapse of 24 hours between the first and second layer. 

Although these simple laboratory experiments give an indication of how effective new developments may be, the real proof of course has to come from 

styrene concentration measurements during actual moulding. 

2. Spray-up experiments 

The following test was devised by DSM Resins to simulate lamination in a 

workshop. In the spray-booth of our Technical Centre in Zwolie a series of 

garden ponds was made with different resins as matrix. The production process 

consisted of three spraying and consolidation steps (total operation time 15 

minutes) followed by the curing phase. The spray-up technique was chosen 

because it is known that more than half of the total styrene emission takes place 

in the dynamic phase of this application process. 

Continuous monitoring of the evaporated styrene was done using a photoionisation detector directly inside the stack on top of the spray-booth while the 

extraction fans were running. For reliability of these experiments it was of 

paramount importance that they were conducted under identical circumstances. 

All experiments were done in duplicate. Three different resins, all having a gel 

time of 35 minutes, were selected. The UP resins were a standard orthophthalic 

spray-up resin, an LSE version of the previous resin, and the newly developed 

Synolite 5520-P-1. 

For clarity the process has been 'mathematically' divided into three stages, viz. 

the cumulative spraying operation (1), the total time of consolidation (2), and 

the laminate curing (3). This was done to get an insight of the styrene evaporation of the different process phases on the total emission. The results of the 

experiments are presented graphically in figure 2. 

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INSERT-LSE 

Standard-LSE 

Standard-UP 

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The following conclusions can be drawn: 

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Figure 2. Comparison of a standard UP resin, Standard LSE resin, and 

INSERT LSE Resins (Synolite 5520-P-1) by measurement of atmospheric styrene during the production process. 

About two thirds of the total styrene emission occurs in the dynamic 

phase. However, it must be noted that this ratio is dependant on the type 

of product and the gel time of the resin. 

Only in the curing phase does the LSE resin give a lower styrene emission 

than the standard resin. The film forming additive is not active during 

spraying and roll-out of the laminate. 

12 

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RUG-15-1995 10:38 DSM RESINS ••/UbfcWybVVY r.14 

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•' • The styrene emission of Synolite 5520-P-1 in the static phase ts compa-

• rable to that of the LSE resin. 

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At the moment several field trials at customers are in progress to reaffirm the 

results of styrene emission reduction in practice. 

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Interlaminar adhesion studies 

Resins containing film forming additives, in particular the first generation LSE 

resins, have built up a bad reputation in the market place with regard to poor 

interlaminar adhesion. Since Synolite 5520-P-1 contains an LSE additive to 

obtain the optimum reduction in styrene emission, its effect on secondary 

bonding was thoroughly studied. 

13 

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The INSERT resin gives 50% less styrene emission than both the standard I 

and the LSE resin in the dynamic phase of the process. • 

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A series of laminates were made by laying-up four layers of 450 g/m2 chopped 

strand mat together with each resin and leaving this for a defined period to cure 

before a further four layers of glass mat and resin were applied. The surface of . 

] the bottom laminate layer was either glass-rich or resin-rich. ; 

The laminates were subjected to the classical peel test, and the more advanced , \ 

Double Cantelever Beam test (European Group on Fracture proposal for interla- . 

minar fracture toughness testing of composites - March 1990). J ; 

The peel test gives a good Qualitative impression of the secondary bonding, 

while • according to internal investigations - the DC8 test provides the most reliable Quantitative results. Both the short beam flexural test (ISO 4585) and lap 

shear test (ASTM 3163) which were also evaluated were less discriminating 

between a good and bad interlaminar adhesion. The DCB test determines the 

energy that is required for the crack propagation of a specimen in which 

delamination Is initiated through a film placed between the laminate layers during 

moulding. The required energy to obtain a certain crack length, divided by the 

surface area of the crack, is a measure of the interlaminar adhesion. 

The INSERT resins have been compared with standard polyesters containing no 

wax or paraffin, and LSE resins. Laminates based on Synolite 5520-P-1 give an 

excellent interlaminar adhesion. Even after a lapse of one week crack propagation energy values of > 85% than that ofthe reference wet-on-wet made 

laminate were obtained. These values correspond to those of the ortho UP resins 

without film former. The conventional LSE resins, however, showed lower 

results. A laminating interval of 24 hours already resulted in a reduction of the 

secondary bonding by 30-40 %. This was the case both with DSM and competitive resins which were evaluated. 

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-AUG-15-1995 10:36 DSM RESINS 706649677? P.15 

DSM Resins DSM t $ 

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The DCB test thus indicates a good secondary bonding for laminates based on 

Synolite 5520-P-1. The DCB values of Synolite 5520-1-1 (non LSE) resin and 

Synolite 5520-P-1 do not differ. In the peel test the laminate layers based on the 

INSERT resins were only peeled off with considerable effort and with a lot of 

fibre tear from the surfaces. 

CONCLUSION 

DSM Resins has launched the first in a new generation of polyester resins for 

open-mould processing techniques. These resins feature low styrene emissions 

not only in the static or curing stage but also during lamination, while maintaining the physical properties of existing high-standard products, especially with 

regard to product performance and interlaminar adhesion. 

Both laboratory studies and actual workshop evaluations prove that the new 

resins have reduced monomer loss into the workplace and hence into the 

surrounding environment. 

Synolite S520-I-1 is a pre-accelerated thixotropic polyester resin specially 

designed for hand lay-up, spray-up. and chop-hoop applications. Through the 

application of a new technology. INSERT, a styrene emission reduction of 

approximately 50% is achieved without the use of paraffins or waxes as 

filmformers. 

SynoUte 5520-P-1 contains additionally an LSE additive. However, in combination with INSERT no problems with respect to interlaminar adhesion are encountered. 

* i 

These resins are commercially available at a small premium when compared to 

standard products. Although the resins are thus somewhat more expensive 

significant savings may be gained in lower cost extraction systems and the 

avoidance of air purification techniques. Moreover, bearing in mind that the 

customer has actually paid the price of resin for the styrene that evaporates, 

savings are also obtained through the reduction in the loss of initial styrene. 

14 

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AUG-15-1995 10:38 DSM RESINS 706849677? P.16 

DSM Resins DSM & 

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The advantages can be summarised as follows: 

Workers are exposed to lower styrene concentrations during processing 

Reduced styrene emission in the curing stage 

.. Less pollution of the environment 

Reduction of the styrene emission is reached without affecting processibility and product properties 

Material savings are achieved because of low monomer evaporation 

No interlaminar adhesion problems; long curing times between consecutive lay-ups are possible 

Because of the lower styrene emissions new legislative requirements may 

be met with no or limited additional investments in ventilation, while 

purification of the exhaust air will not be necessary, 

in oruer io meet trie stringent IVIMC vaiues it is nowever recornrnenoeo io pay 

attention to proper housekeeping, efficient ventilation, and using the right 

processing equipment. DSM Resins is willing to advise you on these aspects. 

DSM Resins continues its developments into resins with a low styrene emission 

during open-mould processing. Based on the technology which has been 

extensively described in this paper the range of resins for hand lay-up. spray-up 

and filament winding will be extended. This not only includes other ortho- and 

iso UP resins, but also the high performance bisphenol A and vinyl ester resins. 

Additionally, INSERT will be used to develop low styrene emission gelcoats. The 

preliminary results in this application area look very promising. 

ACKNOWLEDGEMENT 

The author thanks P. Dijkink and M. Luesken for their valuable contribution in 

developing the INSERT concept. 

16