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AUG 2018

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AUGUST 2018 36 CompositesWorld FEATURE / US Styrene Reduction Update exposure and often are not based on the weight of the entire body of scientific evidence. Additionally, the use of hazard assessments only sets precedents that other groups may follow." Thermoset technology changes ermoset resin suppliers and compounders who work with vinyl ester (VE) and unsaturated polyester (UP) have not waited for additional styrene regulations, but have instead prepared for them by introducing alternative diluents, changing compounding methods, or entirely reformulating resin systems as not only styrene-free but also low-VOC/low-odor. "We're doing a significant amount of work to address a variety of customer needs in different markets," notes Laura Gigas, senior product manager – transportation at Ashland LLC (Dublin, OH, US). "For example, we've developed styrene-free versions of our products for every market, using alternative monomers or even [styrene-] monomer-free versions of products. [Styrene-] monomer-free products for prepreggers or SMC compounders would entail switching from solvent-based compounding to hot-melt systems." She acknowledges that not everyone has the equipment necessary to use those types of products, so another approach Ashland has taken is to use a combination of proprietary technolo- gies to drive the conversion of styrene during resin crosslinking to higher levels (as measured by differential scanning calorimetry), leaving less unreacted styrene and hence reducing VOCs. "In SMC, we now have grades where we can drive cure from a typical 95% to a higher level of 99.7%," Gigas adds. "Interestingly, we see slightly better mechanicals with these alternative-monomer products vs. those using styrene, but they're still close to our conventional grades. And because styrene is cost-effective, and a very effective reactive diluent, a third approach we've taken is to develop lower- VOC, lower-odor versions that replace a portion of the styrene with alternative diluents of lower volatility. We've found we can retain 20-30% styrene but reduce volatiles from 3,000-5,000μg/bag to 10-50. at minimizes impact on the customer, and those products perform just as well as styrenated versions — regardless of whether you're using open-mold, pultrusion or compression molding." "Polynt-Reichhold has been a leader in reducing VOC and styrene content for over 20 years," explains Steve Voeks, North American R&D director, Polynt-Reichhold Group (Carpentersville, IL, US). He cites the low-styrene/low-VOC gel coats and UP resins the group commercialized in the 1990s prior to the activation of Maximum Achievable Control Technology (MACT) standards codified in Title III of the 1990 Clean Air Act Amendments. He also points to the group's work developing and promoting low-cost, closed-mold technologies with inherently lower emissions, plus development of numerous technologies to remove all styrene and, in some cases, most VOCs in advance of regulatory requirements. "We have a strong, market-facing strategy to address customer needs for the foreseeable future — even in the face of more strin- gent styrene regulation," Voeks adds. "Using a combination of strategies and working closely with trade associations and regula- tory officials, we've arrived at achievable goals for gel coats as well as resins and we continue to develop new chemistry and other technologies that will provide further reductions." Depending on the market and its requirements, the group has either reformu- lated existing resins by replacing some or all of the styrene with alternative reactive diluents, or has developed new diluent-free resins with low odor under the Polylite HS tradename. "Our early products with reduced styrene or alternative monomers were less user-friendly and offered lower performance vs. high-styrene formulations," he notes. "However, over the last Preparing for the worst case Anticipating more stringent styrene regulations, thermoset and thermoplastic resin suppliers and compounders have been developing low- and no-styrene/VOC polymer formulations. For example, resin supplier Polyscope Polymers BV (Geleen, The Netherlands) offers a portfolio of styrene maleic anhydride (SMA) copolymers and styrene maleic anhydride N-phenylmaleimide (SMANPMI) terpoly- mers designed to address the need for styrenic engineering plastic compounds with higher temperature resistance and lower VOCs. These neat resins are available under the brand names XIRAN SZ and XIRAN IZ and are used to boost thermal performance in styrenic thermo- plastic compounds such as ABS and ASA. Source | Polyscope Polymers BV

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