Synergetic optimization of charge transport and breakdown strength of epoxy nanocomposites: Realizing sandwich topological structure through constructing a SiC@SiO2/EP surface layer and m-BNNS/EP insert layer

Polymeric materials doped with wide-bandgap semiconductors exhibit intriguing nonlinear conductivity and rapid charge dissipation characteristics. However, excessive doping to accelerate charge dissipation occurs at the expense of breakdown strength. In this work, a sandwich topological structure is proposed to realize synergetic optimization of charge transport and breakdown strength. SiC nanoparticles decorated with insulation shell SiO2 were prepared, which served as fillers in the two surface layers of sandwich structured epoxy composites with exfoliated and functionalized m-BNNS doped into epoxy as the insert layer. The significantly improved breakdown strength approaches 65.8 kV/mm (44% higher than pristine epoxy resin) for sandwich structured composites due to local electric field redistribution while maintaining excellent charge dissipation ability owing to surface charge dissipation and charge decay along the bulk. Moreover, the dielectric loss still retains a low value of 0.02. These novel sandwich structured composites present promising potential in electrical and electronic insulation systems.