Molecular Regulation of Thermal Conductivity and Dielectric Properties of Boron Nitride–Alumina Complex-Filled Epoxy Resin Composites

The development of energy vehicle drive motors toward high specific power and high voltage has put forward greater demands on the electrical and thermal properties of insulating materials. Epoxy resin (EP), as a potting material, can enhance insulation properties and improve the heat dissipation ability of the winding. However, the thermal conductivity (TC) of traditional EP is less than 0.2 W/(m·K), which cannot meet the needs of potting insulating materials. In this paper, EP composites are developed through filling modification and molecular regulation by filling high TC inorganic fillers (h-BN and Al₂O₃) and blending with the insulating dielectric PAA. The effects of different contents of h-BN, Al₂O₃, and PAA on the thermal, electrical, and mechanical properties of EP composites are systematically investigated. The results show that when 4 wt % PAA is added to 30 wt % h-BN–50 wt % Al₂O₃/EP composites, the TC is 1.881 W/(m·K), which is 10.69 times greater than that of pure EP (0.176 W/(m·K)), the breakdown field strength is 196.4 kV/mm, the volume resistivity is 3.57E16 Ω·m, the tensile strength is 25.4 MPa, and the elongation at break is 1.65%, possessing excellent comprehensive properties. This paper provides a reliable preparation program for EP potting compounds with high TC and dielectric properties for drive motors.