High-temperature dielectrics with ultrahigh electrical breakdown strength prepared by epoxy-benzoxazine copolymerization

Epoxy with high mechanical and insulation performance has promising applications for the crucial components of power equipment. However, with the rapid development of equipment that has ever higher voltage, power density, and a more compact size, achieving superior heat-resistant and insulation in epoxy remains a significant challenge. Here, we prepare a copolymerized resin using diphenylmethane diamine-type benzoxazine (BOZ-M) as a modifier and curing agent for epoxy. Attributed to the rigid conjugated groups of BOZ-M, the molecular chain rigidity and cross-linking density of the copolymerized resin are improved, resulting in remarkable mechanical strength (63.31 MPa) and glass transition temperature (T_g=215.81 ℃), respectively. The optimization of the molecular structure decreases the free volume of the copolymer resin, resulting in enhanced stability of high-temperature dielectric performance; at the same time, calculations based on the density functional theory (DFT) and experimental characterizations revealed that introducing a multitude of shallow traps to the epoxy can effectively enhance the migration of charge carriers, co-contributing to a substantial improvement of the electrical breakdown strength of the copolymer resin (139.65 kV/mm). In addition, a comparative study was conducted on ANFs/Epoxy composites, demonstrating that the current method is more effective in enhancing the same performance without a complex filler treatment process, thus making it suitable for industrial-scale applications.