Multiscale Structural Design of Epoxy Vitrimer for Stabilizing High-temperature Dielectric Insulation

Abstract

Epoxy vitrimers, featuring dynamic covalent bonds, are promising candidates for recyclable dielectric, yet their practical application in high-power systems is hindered by their dynamic networks at elevated temperatures, which leads to premature dielectric failure under the inevitable Joule heating. This work confirms the significant decline in insulation performance of epoxy vitrimer at elevated temperatures and proposes a multiscale filler-engineered strategy to develop thermally stable epoxy vitrimer dielectrics. The theoretical calculations of the filler-resin interface energy levels were used to guide the optimization of the engineered microstructure, and leveraging the 3D printing process to control the orientation of BN micro-platelets. The structured composites exhibit a superior overall performance, including a high thermal conductivity of 1.911 W·m⁻¹·K⁻¹, a glass transition temperature (Tg) of 122 °C, and a dielectric breakdown strength of 71.2 kV/mm at room temperature, which remains as high as 45 kV/mm at 180 °C, 67% higher than that of the pure resin. Variable-temperature infrared and UV–Vis spectra confirm the structural stability of the epoxy vitrimer composites under heating. Mechanistically, the excellent room-temperature dielectric performance of the composites arises from the deep trap energy level and the wide bandgap nature of the composites, while the high-temperature stability is attributed to suppressed chain mobility and the barrier effect of multiscale fillers against hot carrier transport. These findings highlight a scalable pathway toward recyclable, high-performance polymer dielectrics for demanding high-power applications.