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Cray Valley cuts VOCs from gel-coat
Cray Valley cuts VOCs fkom gel-coat The European market for gel-coat may be about to change, not necessarily because of any need for improved performance, but because of the need to meet ever increasing demands for reduced styrene emissions. Cray Valley has been at the forefront of developments regarding LSEresins and is now ready to announce its low VOC gelcoats, says Jeff Humberstone. The term low volatile organic compound (VOC) best describes the new gel-coat developed and not the term low styrene emission (LSE). Cray Valley has chosen low VOC because the real objective with gel-coats is to reduce the emissions during application. The emissions during applicaSTANDARD LOWVOC tion are linked directly to IS0 the amount of VOC in the FIGURE I: Styrene levels in gel-coat formulations. product, i.e. the level of styrene. By cutting the styrene content from 31% to 20% This technology originates whilst maintaining or improving all from CCP, Cray Valley’s sister company in the USA and has already other properties, Cray Valley has been available there since 1992. managed to make a real reduction The time is now right for Cray without replacing styrene with any Valley to launch the product in other organic compounds.
Reinforced Plastics October 1996
q ‘*
Europe and so we are presently scaling up production of the low VOC gel-coat. The product has been well researched, tried and tested since 1992 in both the sanitary and marine market. CCP saw an opportunity for a low VOC gel-coat and after lengthy development work trying out several replacement/ semi-replacements for styrene it introduced its present low VOC gel-coat. The choices we had were to either replace the styrene or reduce it. After considering the alternatives it was decided that the best option was to reduce the styrene content rather than replace one monomer
0034-3617/96/$15.00 Copyright01996, Published by Elsevier Science Ltd. Au rights reserved.
Cray Valley
with another compound.
cuts VOCs from gel-coat
product in terms of styrene loss during this stage. Figure 4 shows how data in Figure 3 relate to the actual VOC loss as a percentage of the overall formulation.
organic
Figure 1 shows the reduction in the level of styrene, comparing the standard Iso system with the new low VOC gelcoat. This reduction in styrene content has not been to the detriment of other properties. In fact the advantages of the low VOC gel-coat over the standard gel-coats include: reduced monomer loss; superior weathering properties; increased cured film thickness (less shrinkage); less odour; increased elongation; and maintained ease of use. The reduction in monomer loss is achieved in two stages. Firstly we have to consider the loss during application i.e. spraying, and secondly the loss during the curing stage. The loss of monomer during application is linked to the styrene content in the gel-coat formulation, degree of atomization, air flow, overspray and type of spray equipment, etc. Our tests indicate that the low VOC gel-coat can reduce the styrene emission during this stage by 50% (Figure 2).
STANDARD IS0
LOW vex
FIGURE2: Total volatile loss during spray application. II
/I
’“* 5
60 60 40
STANDARD IS0
LOWVOC
FIGURE3: Total volatile loss during the curing stage
I
Please note the already low result of standard Cray Valley Iso spray gel-coat. This is for total VOC loss not just for styrene and is made even more impressive when we consider that some standard resin systems have a VOC loss whilst curing in excess of 100 g/m’. If this figure of 100 g/m* was related to loss in relation to a gel-coat film then it would related to a 20% loss of VOC! Reducing the emission of VOC during the cure stage still further is not an option at the moment as far as Cray Valley is concerned. Further reductions, we believe, will be at the expense of gel-coat to laminate bond strength.
The consideration of weathering properties is something that Cray Valley has taken very seriously with the STANDARD LOW voc introduction of ArmorIS0 tote IMC in the UK. FIGURE4: Volatile loss as a percentage of gel-coat applied (500 g/m’). The approval by Ford The loss of monomer for this product has been during the cure stage is especially important. additives as used in LSE resin related to the amount of monomer The weathering properties of our systems. left in the gel-coat, the surface new low VOC gel-coat were therearea/film thickness and the air flow Cray Valley’s new low VOC gelfore an important consideration and across the part. The loss of monocoat benefits from lower styrene one on which we placed particular mer during the cure stage can be levels in the product and low levels emphasis. reduced by either decreasing the of film forming additives. Figure 3 The reduction in styrene is a shows the differences between the amount of monomer in the gel-coat further improvement to weatherstandard product and the low VOC or by incorporating film forming
Reitiorced
Plastics October
1996
Cray Valley cuts VOCs from gel-coat
ing properties providing that the reduction is not below the minimum required for adequate cure. The excess styrene in formulations can cause a premature yellowing of the gel-coat. The balance in the new low VOC gel-coat is controlled to enable full cure of the product after application.
increased whilst maintaining the other physical properties compared with the Iso System. Figure 8 shows the increased elongation at break of our standard white Iso gel-coat compared with the white low VOC gel-coat.
FIGURE 5: Colour change after 1000 hours exposure to QUVA
The results of lengthy development work are of a new gel-coat, including the base resin, to give the weathering properties shown in Figure 5.
80 .E! -
The formulation of the low VOC gel-coat is different from that of the standard material because the styrene content is much lower and therefore the resin solids and pigment solids are higher. The increase in solids means that the shrinkage caused by the cross-linking process is lower. This decrease in shrinkage means that the chance of prerelease is once again decreased and the cured film thickness is greater. Figure 6 shows the main differences in formulation between the standard Iso system and the low VOC gel-coat. Figure 7 gives an indication of the reduced shrinkage of the new low VOC gel-coat at application rates of 500, 650 and 750 microns. The new high performance resins used to manufacture the low VOC gel-coats mean that elongation at break is
Reinforced Plastics October
The reduced styrene level means that there is noticeably less odour using the low VOC gel-coat and because we have chosen not to use any new acrylate systems to replace styrene, the spray operators notice only reduced styrene levels not any new chemicals. The back surface sprayed gel-coat films normally, with good atomization, have an orange peel type surface but with low VOC gel-coat the orange peel effect is very much reduced. This can have the advantage of improved appearance for the finished part.
GEL COAT
FIGURE 6: Gel-coat composition
by weight.
FIGURE 7: Curedfilm thickness ofgel-coat at an application 500, 650 and 750 micron.
STANDARD
SO
FIGURE 8: Elongation at break.
1996
LOW voc
rate of
I
One of the most important things to consider when formulating a new gel-coat is the ease of product application. This involves how easy it is to atomize and the resultant spray pattern achieved, the amount of porosity in the finished film, whether the system is prone to prerelease and of equal importance whether pigment separation is likely. After four years of sales and experience in the USA we can confirm that the new low VOC gel-coat does benefit from the same ease of use characteristics our customers have come to expect of the standard Is0 systems. n
Reinforced Plastics October 1996
q ‘*
Europe and so we are presently scaling up production of the low VOC gel-coat. The product has been well researched, tried and tested since 1992 in both the sanitary and marine market. CCP saw an opportunity for a low VOC gel-coat and after lengthy development work trying out several replacement/ semi-replacements for styrene it introduced its present low VOC gel-coat. The choices we had were to either replace the styrene or reduce it. After considering the alternatives it was decided that the best option was to reduce the styrene content rather than replace one monomer
0034-3617/96/$15.00 Copyright01996, Published by Elsevier Science Ltd. Au rights reserved.
Cray Valley
with another compound.
cuts VOCs from gel-coat
product in terms of styrene loss during this stage. Figure 4 shows how data in Figure 3 relate to the actual VOC loss as a percentage of the overall formulation.
organic
Figure 1 shows the reduction in the level of styrene, comparing the standard Iso system with the new low VOC gelcoat. This reduction in styrene content has not been to the detriment of other properties. In fact the advantages of the low VOC gel-coat over the standard gel-coats include: reduced monomer loss; superior weathering properties; increased cured film thickness (less shrinkage); less odour; increased elongation; and maintained ease of use. The reduction in monomer loss is achieved in two stages. Firstly we have to consider the loss during application i.e. spraying, and secondly the loss during the curing stage. The loss of monomer during application is linked to the styrene content in the gel-coat formulation, degree of atomization, air flow, overspray and type of spray equipment, etc. Our tests indicate that the low VOC gel-coat can reduce the styrene emission during this stage by 50% (Figure 2).
STANDARD IS0
LOW vex
FIGURE2: Total volatile loss during spray application. II
/I
’“* 5
60 60 40
STANDARD IS0
LOWVOC
FIGURE3: Total volatile loss during the curing stage
I
Please note the already low result of standard Cray Valley Iso spray gel-coat. This is for total VOC loss not just for styrene and is made even more impressive when we consider that some standard resin systems have a VOC loss whilst curing in excess of 100 g/m’. If this figure of 100 g/m* was related to loss in relation to a gel-coat film then it would related to a 20% loss of VOC! Reducing the emission of VOC during the cure stage still further is not an option at the moment as far as Cray Valley is concerned. Further reductions, we believe, will be at the expense of gel-coat to laminate bond strength.
The consideration of weathering properties is something that Cray Valley has taken very seriously with the STANDARD LOW voc introduction of ArmorIS0 tote IMC in the UK. FIGURE4: Volatile loss as a percentage of gel-coat applied (500 g/m’). The approval by Ford The loss of monomer for this product has been during the cure stage is especially important. additives as used in LSE resin related to the amount of monomer The weathering properties of our systems. left in the gel-coat, the surface new low VOC gel-coat were therearea/film thickness and the air flow Cray Valley’s new low VOC gelfore an important consideration and across the part. The loss of monocoat benefits from lower styrene one on which we placed particular mer during the cure stage can be levels in the product and low levels emphasis. reduced by either decreasing the of film forming additives. Figure 3 The reduction in styrene is a shows the differences between the amount of monomer in the gel-coat further improvement to weatherstandard product and the low VOC or by incorporating film forming
Reitiorced
Plastics October
1996
Cray Valley cuts VOCs from gel-coat
ing properties providing that the reduction is not below the minimum required for adequate cure. The excess styrene in formulations can cause a premature yellowing of the gel-coat. The balance in the new low VOC gel-coat is controlled to enable full cure of the product after application.
increased whilst maintaining the other physical properties compared with the Iso System. Figure 8 shows the increased elongation at break of our standard white Iso gel-coat compared with the white low VOC gel-coat.
FIGURE 5: Colour change after 1000 hours exposure to QUVA
The results of lengthy development work are of a new gel-coat, including the base resin, to give the weathering properties shown in Figure 5.
80 .E! -
The formulation of the low VOC gel-coat is different from that of the standard material because the styrene content is much lower and therefore the resin solids and pigment solids are higher. The increase in solids means that the shrinkage caused by the cross-linking process is lower. This decrease in shrinkage means that the chance of prerelease is once again decreased and the cured film thickness is greater. Figure 6 shows the main differences in formulation between the standard Iso system and the low VOC gel-coat. Figure 7 gives an indication of the reduced shrinkage of the new low VOC gel-coat at application rates of 500, 650 and 750 microns. The new high performance resins used to manufacture the low VOC gel-coats mean that elongation at break is
Reinforced Plastics October
The reduced styrene level means that there is noticeably less odour using the low VOC gel-coat and because we have chosen not to use any new acrylate systems to replace styrene, the spray operators notice only reduced styrene levels not any new chemicals. The back surface sprayed gel-coat films normally, with good atomization, have an orange peel type surface but with low VOC gel-coat the orange peel effect is very much reduced. This can have the advantage of improved appearance for the finished part.
GEL COAT
FIGURE 6: Gel-coat composition
by weight.
FIGURE 7: Curedfilm thickness ofgel-coat at an application 500, 650 and 750 micron.
STANDARD
SO
FIGURE 8: Elongation at break.
1996
LOW voc
rate of
I
One of the most important things to consider when formulating a new gel-coat is the ease of product application. This involves how easy it is to atomize and the resultant spray pattern achieved, the amount of porosity in the finished film, whether the system is prone to prerelease and of equal importance whether pigment separation is likely. After four years of sales and experience in the USA we can confirm that the new low VOC gel-coat does benefit from the same ease of use characteristics our customers have come to expect of the standard Is0 systems. n