Single effect of filler spatial distribution states on the thermal conductivity of epoxy composites and their heat conduction mechanisms

The characteristics of fillers (such as size, geometry, composition, and content) and their spatial distribution states have a significant impact on thermal conductivity (TC) of polymeric composites. However, as these factors are usually intertwined, their separate contributions to TC remain elusive. This work conducted systematic experiments and simulations to investigate the contributions of filler spatial distribution states to the TC performance, and further discussed the thermal conduction mechanisms. Firstly, silver nanowires (AgNWs) with high aspect ratio were prepared as fibrous-like fillers. Then, three different filler spatial distribution states were achieved in the corresponding composites, 1) individual randomly dispersion without interconnection; 2) a continuous filler network; and 3) continuous and aligned filler networks. Comparing to epoxy composites with randomly dispersed individual AgNWs, the formation of continuous AgNWs networks resulted in a 58.2% TC enhancement, increasing from 0.440 to 0.719 W/m·K with only 1 vol% loading of AgNWs. Additionally, the transition to vertically oriented silver network led to the highest directional TC of 1.227 W/m·K, without compromising the non-oriented directional TC properties.