The effects of the hexagonal boron nitride nanoflake properties on the thermal conductivity of hexagonal boron nitride nanoflake/silicone rubber composites

Hexagonal boron nitride nanoflakes (h-BNNFs) are usually selected as fillers to improve the thermal conductivity of polymer materials. However, previous research mainly focused on the influence of h-BNNF content and orientation. In this report, the effects of the content, geometry, thickness, modification and orientation of h-BNNFs on the thermal conductivity of h-BNNF/polymer composites were systematically investigated based on the h-BNNF/silicone rubber (h-BNNF/SR) composites. The thermal conductivity of h-BNNF/SR composites increased tremendously with the increase of h-BNNF content. Meanwhile, the h-BNNF contents also show great effects on the viscosity, hardness and thermal stability of the composites, and the h-BNNF content of 20% is more advantageous for processing and application of the composites. Besides, modified, flake-like and thinner h-BNNFs can result in better reinforcement in thermal conductivity than unmodified, agglomerated and thicker ones. h-BNNF/SR composites with shear force induced oriented h-BNNFs showed further enhanced thermal conductivity, and the composite with 40 wt% oriented h-BNNFs exhibits the best thermal conductivity of 0.901 W/(m K).