Enhanced thermal conductivity of epoxy composites by constructing thermal conduction networks via adding hybrid alumina filler

Abstract High thermal conductivity of polymer composites could be achieved through constructing 3D continuous thermally conductive networks into polymer composites. Herein, we demonstrate a simple, effective method to optimize the segregated alumina networks by using ternary mixture of alumina particles with different diameter ratios (5.8 μm + 2.6 μm + 0.5 μm) at the fixed total content of 60 wt% via conventional melt blending method. The thermal properties of epoxy composites were investigated as a function of the weight fraction and particle size of alumina particles. The thermal conductivity (TC) values of composites with coarse fillers (13.2 μm) are in agreement with Agari model at high filler loading (57 ~ 67 wt%). And the value of C 2 was ~0.949 (close to 1), indicating that the formation of heat conduction paths in the composites. The addition of 60 wt% smaller fillers (2.6 μm) facilitates a higher interaction degree between the polymer/fillers, consequently, leads to a higher T g of 147.8°C. A high TC of 1.109 W m −1 K −1 is achieved as the ratio of alumina filler with different particle sizes is 7/2/1, corresponding to a TC enhancement of 23%–32% compared to the composites with a single particle size filler. A suitable proportion of hybrid fillers is crucial for constructing three‐dimension continuous network, in which nano‐particles filled between the micro‐particles could increase the particle‐to‐particle connectivity.