Theoretical Study on Reaction Mechanism of Curing Reaction of Epoxy-Imidazole Resin

Abstract

Epoxy resins are one of the functional materials used as paints, adhesives, and the like. The hardeners used in resin synthesis have a great impact on resins in terms of reactivity and physical properties, so the selection of hardener is very important. However, once curing reaction starts, it is difficult to experimentally analyze that reactivity and the like. In this study, we investigated the reaction mechanism of the curing reaction of epoxy-imidazole resin with imidazole as a hardener using density functional theory calculations. From the calculation results, it was clarified that the epoxy-imidazole curing reaction proceeds through a five-step reaction pathway with the reaction substrate and the imidazole formed during reaction the reaction serving as nucleophilic species. The active species in this reaction is the imidazole anion, and by generating that, the ring-opening reaction of the epoxide with low activation free energy proceeds repeatedly.