Effect of molecular chain mobility on the electrothermal stability of polyethylene/multi-walled carbon nanotube electrothermal composites

In this study, we pay close attention to the structure design of high-temperature electrothermal composites. Two kinds of high density polyethylene-based electrothermal composites filled with multi-walled carbon nanotubes (5960G1/MWCNTs and 5000 S/MWCNTs) prepared by melt compounding is employed as examples. The relationship between molecular weight of matrix and electrothermal properties of composites are studied through the investigation of the changes of microstructure and conductive network in the composites during heating-cooling cycles. Benefiting from the increased high-molecular-weight component and decrease of molecular chain mobility, 5960G1/MWCNTs composites shows excellent electrothermal stability with the surface temperature stabilized at about 120 °C within 10 h (applied voltage of 18 V). In addition, owing to the protection of internal conductive network from low molecular chain mobility of the 5960G1, a reduced disruption of conductive network from the thermal expansion of 5960G1/MWCNTs composite can be ensured by the low deformation of matrix with high molecular weight chains, in turn, 5960G1/MWCNTs composite exhibits good electrothermal repeatability at sequent heating-cool cycles. Thus, high molecular weight polyethylene as a matrix favors high temperature use of electrothermal materials and is expected to be applied in the field of commercial high-temperature electrical heating cables.