Effect of high-relative-molecular-mass fractions on the self-regulating electrothermal effect of high-density polyethylene/ chain-like nickel composites

Polymer-based composite materials exhibiting positive temperature coefficient (PTC) effects can be utilized as self-regulating heating materials and the equilibrium temperature is primarily maintained near the PTC switching temperature range. Consequently, adjusting the switching temperature and stabilizing the equilibrium temperature are the most important issues for the application of polymer-based PTC composites as self-regulating heaters. In this study, HDPE of high molecular weight, low molecular weight and their blends were employed as matrix and the effects of high-relative-molecular-mass fraction on the PTC behavior and the temperature self-regulating stability of HDPE/chain-like nickel (c-Ni) composites were examined. By increasing the content of high-relative-molecular-mass fractions of the matrix, the volumetric expansion rate of the composites below the melting temperature was enhanced. The sensitivity of the c-Ni conductive network to changes in the matrix volume enabled the switching temperature of the PTC transition for the composites with increasing high-relative-molecular-mass fractions to decreased from 117.6 °C to 74 °C. Under a voltage of 30 V, the self-regulating equilibrium temperature can be adjusted within a wide range from 113 °C to 69 °C, and the highest equilibrium temperature, 110 °C, can be maintained in 12000s. Thus, this work provides insights into the regulation and stability of equilibrium temperature in self-regulating heating materials.