Epoxy-based high-k composite vitrimer: With low dielectric loss, high breakdown strength and surface electrical damage repairability

High dielectric constant/permittivity (high-k) polymer-matrix composites (PMCs) are widely used in the electronics and electrical industries since their high energy density, ease of processing and light weight. However, the high dielectric permittivity (ε_r) usually leads to a significant increase in dielectric loss (tanδ) and an obvious decrease in breakdown strength (E_b), which is still a major problem that restricts the development of high-k PMCs. In addition, to extend the service life, the next generation electrical/electronic components also demand materials have electrical damage repairability. In this study, a new epoxy-based high-k composite vitrimer was constructed. The dynamic disulfide bonds were introduced into the cross-linked network to provide the high-k composite vitrimer with excellent repairability, while the nanoparticle (NPs) fillers surfaces were modified by grafting disulfides to improve the dynamic rearrangement ability of the composite network and enhance the electrical properties of the high-k composite vitrimer. The results show that this high-k composite vitrimer has low tanδ and high E_b, which is about 0.025 (at 0.1 Hz and room temperature) and 26.0 kV/mm (under 50 Hz AC voltage of 1 mm samples), respectively. Moreover, it has excellent mechanical damages and electrical damages repairability. For mechanical damages, it can repair mechanical scratches by heating at 180 °C for 10 min. For surface electrical damages, it can also eliminate the residual carbons, regain the surface organic structure, and restore more than 94% insulation strength by thoil treatment under 80 °C for 60 min. This study provides a new reference method for the preparation of low tanδ, high E_b and repairable high-k PMCs.