Recycling characteristics and dielectric/mechanical properties of epoxy resin based on disulfide-imine bond synergy

Abstract

Epoxy resin, as a critical thermosetting polymer, is widely used in electronic encapsulation and various applications due to its excellent mechanical and electrical insulating properties. However, the permanent three-dimensional cross-linked network formed upon curing renders the material diffulting in resource waste and posing challenges to sustainable development. To address this limitation, the present study employs a curing agent containing dynamic disulfide bonds—2-aminophenyl disulfide (2-AFD)—to cure bisphenol A diglycidyl ether (DGEBA), thereby establishing a cross-linked network embedded with dynamic disulfide bonds. Given the limited density of dynamic bonds achievable solely through curing agents, which results in suboptimal property retention after thermal reprocessing, this study further developed a vanillin-based epoxy resin (VOEP) incorporating dynamic imine bonds, with vanillin (VAN) employed as the primary precursor. By progressively replacing DGEBA with VOEP, the concentration of dynamic bonds within the cross-linked network is increased, significantly improving the property retention after hot-press recycling. Experimental results show that when the VOEP mass fraction reaches 60 wt%, the resulting epoxy resin exhibits outstanding overall performance: the power frequency breakdown strength reaches 61.64 kV/mm, the tensile strength is 58.25 MPa, and high thermal stability is maintained. Moreover, the material demonstrates remarkable reprocessability, with power frequency breakdown strength and tensile strength retention rates reaching 89.01% and 86.54%, respectively, after physical hot-press recycling. This exceptional recyclability provides a novel strategy and valuable reference for the green and sustainable advancement of epoxy resins in the field of electrical engineering.