Simultaneous recycling and electrical insulation of epoxy resin enabled by dynamic boronic ester bonds

Epoxy resins are widely used as primary insulating materials in high voltage power equipment. However, the irreversible three-dimensional cross-linked networks formed by conventional epoxy resins pose significant challenges for recycling processing of retired equipment. In this paper, dynamic boronic ester bonds are introduced into epoxy resin to construct reversible dynamic covalent network, aiming to endow materials with recyclability while meeting the performance requirements of power equipment. Experimental results show that, comparing to the traditional anhydride-cured epoxy resin, dielectric loss is reduced by 37% and dielectric breakdown strength is increased by 17% of the developed epoxy Vitrimers, when the sulfhydryl-epoxy stoichiometric ratio is 1:1. This improvement is attributed to the introduction of flexible boronic ester chains, which shorten the relaxation time and modulate the relaxation peak range. Dynamic boronic ester bonds within the network enable topological rearrangement at elevated temperatures, thereby imparting good reprocessing capability. After multiple physical recycling and remolding, the retained breakdown strength remains over 80% of the original value. Additionally, the constructed dynamic covalent network allows epoxy resin to be fully degraded in ethylene glycol solution, demonstrating environmentally friendly end-of-life behavior. These properties highlight the potential of this epoxy system to serve as an internal insulating material in electrical engineering applications, particularly for insulation components in gas-insulated switchgear (GIS).