Effect of an interface layer on thermal conductivity of polymer composites studied by the design of double-layered and triple-layered composites

The interfacial thermal resistance of polymer composites is a key factor affecting their thermal conductivity. But the interfacial thermal resistance might be influenced by many interface factors, such as defects, interface bonding strength, compatibility and the interface layer, which are difficult to be distinguished individually. The thickness of interfaces between fillers and polymers is in nanometer scale, leading to the research of effect of interface layer on thermal conductivity is very difficult. Herein, inspired by the differential calculus in mathematics, the effect of interface layer on thermal conductivity was studied through a design of double-layered and triple-layered alumina/silicone rubber composites and reflected by the through-plane thermal conductivity of the composites at the same filler loading. The top and bottom layers in the composites were used to represent a matrix and a filler, respectively. The middle layer in the triple-layered composites was assumed as an interface layer. The results showed that the presence of the interface layer could increase thermal conductivity when the thermal conductivity difference between the top and the bottom layers was high. A series model was used to simulate the dependence of thermal conductivity on the interface layer at triple-layered composites and real filler/polymer interface, respectively. This work could provide a new method to study the interface thermal resistance and promote the development of polymer composites with high thermal conductivity. (C) 2019 Elsevier Ltd. All rights reserved.