A UV-responsive mechanically robust insulating polymer that achieves intrinsic self-healing of electrical tree damage based on reversible anthracene photodimerization

Abstract

Microscale damage, including cracks and electrical trees, is inevitably generated in the polymer insulation materials used in the packaging of power equipment and power electronic devices during long-term operation, which leads to premature insulation failure or even widespread power outages. Self-healing insulation materials are the most promising way to solve this problem. However, the mechanical/electrical strength or the dimensional stability of the materials could be sacrificed during the repair process, which has limited their application as insulation materials. In this study, we report an intrinsic self-healing epoxy resin based on reversible anthracene photodimerization (ISEP-RAP) that remains mechanically robust while ensuring efficient healing via a reversible reaction. The damaged area is decrosslinked by 254 nm UV and thermal excitation, which accelerates the molecular chain diffusion to the damaged area to fill and repair the damaged channels. The ISEP-RAP is recrosslinked by 365 nm UV to restore the mechanical and electrical properties after self-healing. Due to the combined action of the epoxy-amine permanent crosslinking sites and the anthracene reversible crosslinking sites, high crosslinked ISEP-RAP possesses excellent tensile and dielectric strength similar to that of standard epoxy resin and a lower permittivity constant. Importantly, the decrosslinked ISEP-RAP still possesses sufficiently high strength to keep the macrostructure unchanged. ISEP-RAP achieves high-efficiency, repeatable, non-contact intrinsic self-healing of scratches and electrical trees with whole-process dimensional stability. This work provides a new method for intrinsic self-healing in mechanically robust insulation materials to eliminate microdamage with repeatability, high reliability, and high efficiency.