Effect of application time of <scp>DC</scp> electric field on properties of h‐<scp>BN</scp>/<scp>EP</scp> composites

Abstract By applying an electric field, the thermal conductivity( λ ) of composites can be enhanced through the induced orientation of high λ fillers within the matrix. As far as the DC electric field is concerned, the pattern of the electric field application time on the λ of the composites is not clear. In this work, a 400 V/mm DC electric field was selected to prompt the alignment of boron nitride (h‐BN) within the epoxy resin (EP) matrix, with an in‐depth analysis of how the timing of the electric field application influences the λ of the composites. Results demonstrate that the λ of h‐BN/EP composites exhibits a pattern of increasing, decreasing, then increasing and finally stabilizing when the electric field application time is 0–480 min. When the electric field was applied for 20 min, the composites exhibited a maximum λ of 0.544 W/(m K), a value that is 3.88 times of pure EP, and 2.32 times of that of the composites without electric field under the same filling content. In addition, the composite exhibits an AC breakdown field strength ( E b ) that is slightly elevated compared to the pure EP. Highlights Boron nitride (h‐BN) was successfully oriented in epoxy resin (EP) matrix by electric field induction. λ of the composite is proportional to orientation Angle of h‐BN in the matrix. λ of composite can be increased by electric field induced fillers orientation. Electric field induction does not damage the insulation properties of composite. The excellent in‐plane λ and insulation properties of h‐BN are fully utilized.