Endowing Thermally Conductive and Electrically Insulating Epoxy Composites with a Well-Structured Nanofiller Network via Dynamic Transesterification-Participated Interfacial Welding

It is urgently required to achieve good thermal conductivity and electrical insulation performance in polymer-based composites with the minimum incorporation of functional fillers. In this work, the selective distribution of multiwalled carbon nanotubes (MWCNTs) in the segregated network of hexagonal boron nitride (h-BN) in the epoxy vitrimer matrix was achieved by compression molding, in which interfacial welding was enabled by small-molecule-participated dynamic transesterification at elevated temperatures. Due to the synergistic contribution of the well-structured nanofiller network, the epoxy vitrimer composites demonstrate enhanced thermal conductivity and electrical insulation at low filler content. The composite containing 1 wt % of MWCNTs and 8 wt % of h-BN shows thermal conductivity and electrical resistivity of 0.83 W/(m·K) and 1.92 × 1011 Ω·cm, respectively. The electrical resistivity can be further improved by increasing the segregated h-BN content. This method provides a novel way to prepare cost-effective polymer composites with excellent thermal conductivity and electrical insulation.