Particle packing theory guided multiscale alumina filled epoxy resin with excellent thermal and dielectric performances

Polymers and composites with high thermal conductivity are promising yet challenging for the growing demand of thermal management in electrical and electronic equipment. Guided by the closest packing model, a multiscale filling Al₂O₃ strategy was designed and incorporated with epoxy resin (EP) to form high thermal conductive composites in this work. Epoxy composites with single filler loading were also prepared. The microstructures, thermal, rheological, and dielectric characteristics of the multiscale filling Al₂O₃/EP composites have been investigated. Compared with single-scale Al₂O₃ filled epoxy based composites, it is found that the multiscale filling Al₂O₃/EP composites exhibit higher thermal conductivity under the same filler loading of 50 vol %, which is attributed to the efficient heat conduction paths formed by appropriate multiscale fillers. Particularly, a remarkably improved thermal conductivity of 2.707 W m⁻¹ K⁻¹ was acquired in Al₂O₃/EP composites at filler loading of 50 vol% (5 μm Al₂O₃ (26.67 vol%), 30 μm Al₂O₃ (27.41 vol%) and 70 μm Al₂O₃ (45.92 vol%)), which is about 1300% higher than that of the pure epoxy resin. In addition, the dielectric constant of the Al₂O₃/EP composites were significantly improved while keeping the dielectric loss almost unchanged. The finite element simulation further verified the effectiveness of improving the thermal conductivity of materials in the heat dissipation of electrical equipment. Therefore, this research provides a simple strategy for manufacturing high thermal conductive composite materials with a wide range of potential applications as packaging materials.