Electric Field‐Induced Orientation of Boron Nitride/Alumina Fillers for Enhanced Thermal Conductivity of Epoxy at Low Loading

Epoxy resin (EP) serves as a standard potting adhesive in dry‐type transformers, yet its relatively low thermal conductivity, about 0.18 W/(m K), hampers the effectiveness of heat dissipation. This study proposes an alternating current (AC) electric field‐induced orientation strategy to construct continuous planar thermal conduction pathways. The strategy applies AC electric fields of varying frequencies and induction durations to hexagonal boron nitride and spherical alumina particles added at 10% by mass to EP. Under optimal conditions (5 Hz, 40 min), the composite reaches a thermal conductivity of 0.514 W/(m K), an improvement of 185.6% over pure EP and 44.3% over randomly filled systems. At the same time, the composite shows a 24.1% enhancement in flexural strength and an approximately 20% improvement in breakdown strength. This scalable and process‐compatible approach simultaneously enhances thermal, mechanical, and electrical properties, offering a highly promising solution for insulation systems in dry‐type transformers.