Facile method to prepared photoinitiated cationic curable plant oil and its enhancement on the impact strength of cycloaliphatic diepoxide

In this study, a modified soybean oil (SBO) with urethane branched chain terminated by epoxy group (SBO-URE) was prepared by highly efficient thiol-ene photo-click chemistry and isocyanate polyurethane reaction. The structure of modified plant oil was characterized by FT-IR and H-1-NMR. Then, the obtained bio-resin was blended with a petroleum-based cycloaliphatic epoxy 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (ECC) with different composition ratios. The photoinitiated cationic process and properties of curing formulation were investigated. The epoxy conversion was improved by adding chlorothioxanthone (CTX) through photosensitization process of onium salts. The DMA, TGA, and a series of tensile tests indicated that the addition of SBO-URE can increase the impact resistance with a modest decrease of tensile properties without sacrificing thermal stability. The formulation system exhibited a better performance than the formulation with its commercial counterpart epoxidized soybean oil (ESO), thereby revealing that the introduction of urethane branched structure terminated by epoxy group of soybean oil can react with epoxy matrix during curing process, and offered a certain improvement of impact strength without serious depletion of tensile properties.