Approaches to reduced styrene emission in vinyl ester resin formulations

The increasing use of composite designs for advanced applications is not without environmental impacts. Recently, the Federal Environmental Protection Agency increased legislation to address hazardous emissions from composite manufacturing and repair by enacting new emission standards through the "National Emission Standards for Hazardous Air Pollutants: Reinforced Plastic Composites Production," which specifically targets styrene, methyl methacrylate, and methylene chloride as regulated hazardous air pollutants. A program is currently investigating methods of reducing emissions by modification of existing commercial formulations. A three-pronged approach is taken, which includes 1) substitution of styrene with low-volatile or highly reactive organic alternatives, 2) reduction of styrene concentrations by controlling molecular weight distributions of the vinyl ester monomers, and 3) sequestering of volatile organic compound (VOC) emissions by trapping with in situ vapor barrier formation. Additionally, formulations will address methods to reduced in-service VOC emissions, allowing for decreased life-cycle pollution. In order to characterize impacts of changes in chemistry on emission rates and total emission volumes, a method was developed that allows accurate and reproducible emission rates to be determined. The method and results for characterizing emissions of styrene from vinyl ester resins is presented. Successful alternative resin formulations will provide effective means to reduce or eliminate VOC release during manufacture or repair of composite structures and result in environmentally preferred composite-based military systems.