Temperature resistivity behaviour in carbon nanotube/ultrahigh molecular weight polyethylene composites with segregated and double percolated structure

Abstract

A novel conductive polymer composite (CPC) based on carbon nanotube (CNT) and binary polymer blend of low density polyethylene (LDPE) and ultrahigh molecular weight polyethylene (UHMWPE) was successfully fabricated by high speed mechanical mixing and hot pressing. The conductive CNT/LDPE component was only dispersed on the surfaces of UHMWPE particles, manifesting combined segregated and double percolated structure. The temperature resistivity behaviour of the CPC was investigated in this paper. A typical double positive temperature coefficient (PTC) of resistivity was observed near the melting points of LDPE and UHMWPE followed by a negative temperature coefficient (NTC) of resistivity. The resistivity began to rise at the maximum crystallisation temperature during cooling, indicating that the conducting nanoparticles were expelled from the crystalline phase. This CPC also exhibited a relatively low PTC and NTC effect, which was determined by the combined segregated and double percolated conductive network as well as high viscosity of UHMWPE matrix. Moreover, with the assistance of in situ optical micrograph and transmission electron microscopy, we found that the subtle microstructural evolution of the conductive network via Brownian motion and crystallisation induced flow was responsible for the higher room temperature resistivity.