Modification of vinyl ester and vinyl ester–urethane resin-based bulk molding compounds (BMC) with acrylated epoxidized soybean and linseed oils

Acrylated epoxidized soybean and linseed oils of different characteristics were incorporated in the absence and presence of polymeric methylene diphenyl isocyanate (PMDI) in a vinyl ester (VE) resin-based bulk molding compound (BMC) up to 15 wt% (with respect to VE resin). The thermal, thermo-mechanical, static fracture mechanical, dynamic impact (Charpy), and thermal degradation properties of the BMC compounds were determined. With increasing amount of functionalized plant oils the glass transition temperature (T g) of the matrix, the stiffness (E modulus) and Charpy impact strength of the BMCs decreased. The static fracture toughness was slightly increased and the fracture energy remained unaffected by the modification with increasing amount of oil. Additional crosslinking of VE, induced by PMDI, markedly enhanced the T g but yielded a large drop in the glassy modulus. This finding was traced to resin dilution and to unfavored PMDI/kaolin interactions triggered by the water content of the latter. The thermal degradation of the BMCs was less affected, however, their degradation started earlier for the modifications either with functionalized plant oil or PMDI. Dilution of VE-based BMCs with acrylated epoxidized plant oils requires reworking of the corresponding recipes to keep the property degradation limited.