The effects of multiple‐sized compound fillers on the thermal, electrical, and processing properties of epoxy composites

Abstract The efficient filling of the multiple‐sized compound fillers can effectively increase the thermal conductivity of the polymer composite. However, determining the specific proportion of the compound fillers with different sizes is hard. This article proposes a random distribution model and the closest packing model to calculate the proportion of the compound fillers and prepare the epoxy composites with different compound fillers. By elaborately designing epoxy composites containing 75 wt% (48 vol%) ternary compound Al 2 O 3 fillers, its thermal conductivity reached 1.640 W/(m·K). In addition, the volume resistivity for all prepared Al 2 O 3 /epoxy composites was higher than 10 16 Ω cm. Besides, the electrical and dielectric properties of the epoxy composite with multiple‐sized compound fillers were comparable or superior to the composite with single‐sized fillers. Last but not least, the viscosity of the ternary compound Al 2 O 3 /epoxy mixture was significantly lower than the single‐sized Al 2 O 3 /epoxy mixture, which is beneficial for improving the processability of the epoxy composite. The results of this article will guide the development and utilization of epoxy composites with high thermal conductivities. Highlights A random distribution model and the closest packing model were proposed. The thermal conductivity of the designed epoxy composites reached 1.640 W/(m·K). The compound filler can effectively improve the processability of the composite.