Low profile additives (LPA) are thermoplastics particles incorporated into unsaturated polyester (UP) resin in order to improve the surface finish of fiber glass/UP composites by shrinkage compensation. They are widely used in automotive applications where high-quality surface finish is required. In this article, the effect of low-profile additives on the thermo-mechanical properties of resin transfer molded fiber glass/UP panels is investigated. A combination of poly vinyl-acetate and poly methyl-methacrylate additives was tested with three concentrations (0%, 10%, and 40%). The flexural and shear properties were measured by three-point bending and short-beam tests. Thermo-mechanical and dynamic mechanical analyses were performed to measure the coefficient of thermal expansion and the glass transition temperature. The mechanical properties as well as the coefficient of thermal expansion were reduced upon addition of low-profile additives, whereas the glass transition temperature was improved with the content of low profile additives due to a better compatibility of the LPA/UP system.
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