Effects of hydrogen bonds on soybean oil-based thermosets and their bamboo fibers composites

Abstract

Biocomposites were fabricated from bamboo fibers (BFs) and acrylated epoxidized soybean oil (AESO) resins. Two reactive diluents (RDs), i.e., butyl methacrylate (BMA) and hydroxyethyl methacrylate (HEA), were used as comonomers for AESO, respectively. The effects of type and usage of RDs on the curing behavior, rheological and mechanical properties of AESO resins, the interfacial bonding between BFs and AESO matrix, and properties of the resulting BF/AESO composites were investigated. The formation of multimer induced by hydrogen bonds (H-bonds) in HEA-AESO resin greatly increased the free-radical polymerization rate of C=C bonds, hence reducing the curing temperature and activation energy. The H-bonds provide physical cross-linking points for the cured HEA-AESO network, which significantly increased the tensile strength, tensile modulus, storage modulus, and glass transition temperature of the thermoset. The polar groups of the resins form H-bonds with the hydroxyl groups of BFs, resulting in a good interfacial adhesion between fibers and matrix. The HEA-containing composites demonstrated significantly higher mechanical properties, storage modulus, and water resistance than BMA composites.