Recent Advances in the Curing of Epoxy Resins Using the Epoxy/Thiol-Ene Photopolymerization Technique

Abstract

Epoxy/thiol-ene photopolymerization is an innovative technique employed to photocure epoxy resins. In this method, a thiol-ene system is added to an epoxy resin at varying concentrations. The thiol-ene system comprises a basic curing agent of the ditertiary amine type functionalized with allyl groups, a multifunctional thiol and a radical photoinitiator. This technique enables the concurrent anionic ring opening polymerization of the epoxy resin and a thiol-ene photopolymerization resulting in a crosslinked polyether-polythioether network. The presence of polythioethers enhances the toughness of the polyether derived from the curing of the epoxy resin. This type of photopolymerization has found applications in the preparation of glass-fiber and natural-fiber composites, as well as in the development of smart materials such as shape-memory and self-healing polymers. It has also been utilized to produce foamed epoxy polymers and biobased thermoset materials. Recently, this technique has been employed in 3D printing by mixing with multifunctional acrylates.