Synthesis and Characterization of Bismaleimide-modified, Soy-based Epoxy Matrices for Flame-retardant Applications

Abstract

Epoxidized soybean oil at various concentrations was cured with amine curing agent. The prepared matrices were chemically modified with three types of bismaleimides, namely N, N′ -bismaleimido4,4 ′ -diphenylmethane (BMI-1), 1,3-bis(maleimido)benzene (BMI-2) and 3,3′ -bis(maleimidophenyl) phenylphosphine oxide (BMI-3). The interpenetrating networks thus developed were characterized for glass transition temperature, thermal stability, dynamic mechanical analysis, heat distortion temperature, flame retardancy and water absorption behavior. The incorporation of bismaleimides in the soy-based epoxy matrices significantly enhanced thermal stability and flame retardancy. The excellent flame retardant properties of the BMI-3 incorporated system were also demonstrated by high char yield and high limiting oxygen index. Dynamic mechanical analysis studies showed that the storage modulus increased with the increase in the concentration of bismaleimides and a reduction in the tan δ value for the bismaleimide-modified, 30 wt.% soy-based epoxy system due to enhanced cross-linking density and rigidity.