Synthesis and characterization of N,N′-bismaleimido-4,4′-diphenyl methane -: Vinyl ester oligomer modified unsaturated polyester interpenetrating matrices for advanced composites

An intercrosslinked network of hybrid bismaleimide-modified vinyl ester oligomer-unsaturated polyester matrix systems were developed. Vinyl ester oligomer was used as a toughening agent for unsaturated polyester resin and was added in 10, 20 and 30% (by weight). Benzoyl peroxide was used as curing agent. The vinyl ester oligomer-toughened unsaturated polyester matrix systems were further modified with 5, 10 and 15% (by weight) of bismaleimide. Bismaleimide-modified vinyl ester-unsaturated polyester matrices were characterized by mechanical (tensile strength, flexural strength, tensile modulus, flexural modulus and impact strength), thermal [differential scanning calorimetry (DSC) thermogravimetic analysis (TGA) and heat deflection temperature analysis (HDT)] and morphological studies [scanning electron microscope (SEM)] and water absorption. Data obtained from mechanical and thermal studies indicated that the introduction of vinyl ester oligomer into unsaturated polyester resin improved the fracture toughness with marginal reduction in the values of heat deflection temperature and glass transition temperature. The introduction of bismaleimide into vinyl ester oligomer-incorporated unsaturated polyester resin enhanced both thermal and mechanical behavior. The SEM micrographs of fractured surfaces of vinyl ester oligomer modified unsaturated polyester systems and BMI modified vinyl ester-unsaturated polyester matrices illustrate the presence of heterogeneous morphology.