Large-area, highly thermally conductive, but electrically insulative industrial aramid papers with hierarchical multiscale compositing structures

The rapid development of emerging 5G electrical fields has put forward high requirements to the thermal dissipation performance of industrial aramid papers (IAPs), which are commonly used as the insulation layers of electrical equipment. Herein, we reported a facile method for preparing large-area (>7000 cm2), thermally conductive, but electrically insulative IAPs by compounding multiscale boron nitride nanosheets (BNNSs), industrial diamond microparticles (DMPs), and industrial aramid micropulps and microfibers (AMPs & AMFs) towards hierarchical compositing structures. Specifically, BNNSs can adhere to the surface of DMPs through electrostatic interaction and reduce the thermal resistance between neighboring DMPs, which ultimately ensures high in-plane thermal conductivity (11.66 W/(mK)) of IAPs, which is about 7 times that of pure aramid papers. Meanwhile, IAPs also exhibit high volume resistivity of 4.95 × 1015 Ω·cm. At last, the IAPs were successfully applied in a transformer for insulation and thermal conducting, demonstrating their high potential in industrial electrical equipment.