Thermal and mechanical properties of tetrafunctional epoxy resin toughened with epoxidized soybean oil

A potential epoxy resin, i.e. epoxidized soybean oil (ESO), was synthesized to toughen the tetrafunctional epoxy resins. The ESO was blended with the epoxy resins to obtain the modified network having ESO content from 0 to 20 wt.%. The neat epoxy resins and modified networks were characterized by the thermal and mechanical properties. As a result, thermal stability and glass transition temperature of the blends were slightly decreased with increasing the ESO content. This might be caused by the reduction of cross-linking density of the epoxy network, which could be attributed to the incomplete curing reaction in the blend systems. The critical stress intensity factor and flexural strength were increased up to 10 wt.% ESO content. This could be interpreted in terms of the addition of larger ESO molecule weight into the epoxy resins, resulting in increasing the flexible properties of the epoxy resins, or the final toughness of the blend systems.