Effect of morphology and structure of polyethylene fibers on thermal conductivity of PDMS composites

Abstract

Polyethylene fibers (PEFs) with high inherent thermal conductivity have been proved to be able to prepare fully organic thermally conductive composites. Herein, the effect of macroscopic fiber orientation and microscopic molecular chain orientation on the thermal conductivity of PEF composites was investigated. Specifically, four kinds of PEFs (PENT, PESF, U1PEF, U2PEF), were selected to prepare fully organic thermally conductive composites. The morphology results show that PENT distributed randomly and loosely in the composite, while the other three PEFs showed high orientation stacking arrangement. As a result, PENT composite shows a low thermal conductivity of 0.132 W/mK due to the absence of effective heat transfer channels and the serious phonon scattering at matrix-to-fiber interfaces. By comparison, the parallel arrangement of continuous fiber provides an ideal channel for phonon transport, so that PESF composite has substantial increase in thermal conductivity (6.543 W/mK). Furthermore, U1PEF and U2PEF composites with higher chain orientation and crystallinity in the inner of fibers, thus reveal the higher thermal conductivities of 11.07 and 15.48 W/mK. Therefore, it can be concluded that not only the fiber orientation distribution, but also the chain orientation structure of fibers both have an important influence on the thermal conductivity of PEF composites.