Hydroxyl-group decreased dielectric loss coupled with 3D-BN network enhanced high thermal conductivity epoxy composite for high voltage-high frequency conditions

The rapid development of electrical and electronics industry puts forward new requirements for high thermal conductivity and low dielectric loss of insulating materials. However, the traditional strategies to improve thermal conductivity of insulating materials with high thermal additives quantity usually accompany with the huge increase in dielectric loss, which will eventually lead to thermal breakdown and cannot meet the real demand under high voltage-high frequency conditions. Herein, in-situ bubble-induced self-assembled strategy was used to fabricate 3D boron nitride (BN) network/epoxy composites. The cellulose with rich hydroxyl groups could both crosslink with epoxy group and form hydrogen bonding with the hydroxyl groups on BN, which restricts the polymer chain movement and ensures the low dielectric loss. Improved thermal conductivity (1.62 W/(m·K), 8 times higher than that of EP) and decreased dielectric loss (0.00597, 18.1% lower than that of EP at 46.4 kHz, 20 °C) of the as-prepared composites contribute to the significant extension of the thermal breakdown time (411.4% higher than that of EP at 44 kHz). In addition, the partial discharge inception voltage of the composites is 8.9% higher than that of EP. These advantages make it attractive to high reliability of thermal management applications in the electrical and electronics industry.