Effect of branched alumina on thermal conductivity of epoxy resin

Composites prepared by using epoxy resin (EP) as matrix had limited practical applications owing to their poor thermal conductivity. The thermal conductivity of composites can be enhanced by doping inorganic fillers. However, it could not be significantly enhanced owing to the saturation of inorganic fillers. In this study, we prepared branched alumina (b-Al₂O₃) by using high-temperature sintering and doped it as a filler to obtain b-Al₂O₃/EP composites. The results shown that the thermal conductivity of the EP composites with 70 wt% b-Al₂O₃ was 1.13 W·m⁻¹·K⁻¹, which was seven times higher than that of pure EP. This could be attributed to the overlapping of b-Al₂O₃ for the formation of a continuous mesh structure that results in thermal conduction channels inside the EP, which reduced the interfacial thermal resistance and improved the thermal conductivity of the composite. The resistivity of b-Al₂O₃/EP was 9.64 × 10¹⁴ Ω·m and that of pure EP was 2.08 × 10¹⁴ Ω·m. The dielectric constant of the b-Al₂O₃/EP composites increased with the increase in b-Al₂O₃ content, while the dielectric loss factor decreases. This was significant for the application of EP composites in the field of electrical insulation.