Microstructure evolution effect on high-temperature thermal conductivity of LDPE/BNNS investigated by in-situ SAXS

The low-density polyethylene (LDPE) and its composites incorporated boron nitride nanosheets (BNNS) (<= 5 wt%) were fabricated and their thermal conductivities (K) as a function of temperature (20-80 degrees C) were measured. The K of the composite filled with 5 wt% BNNS increased 22% at room temperature and 48% at a high-temperature (below melting point) compared with pure LDPE. In order to reveal the enhancement mechanism for the high-temperature K of the composites, the microstructure evolution of the samples with temperature increasing was investigated by in-situ Small Angle X-ray Scattering (SAXS). The results show that the structural stability with temperature increasing and the lower interfacial thermal resistance are favorable for high-temperature K of the composites. This work provides a new recognition for the effect of microstructure evolution on high-temperature K of LDPE-based composites. It is hoped that the research will be instructive for enhancing K of LDPE-based composites by low-content doping and making them well-suited for the high-temperature practical applications. (C) 2018 Elsevier B.V. All rights reserved.