Effects of Matrix Viscosity on Nonlinear Conductivity of Electric-Field-Assisted SiC/LDPE Composites

Electric field assist is helpful for the improvement of the filler distribution in the polymer matrix and for the enhancement of the nonlinear conductivity characteristics of nonlinear resistive field grading composites. However, the effect of matrix viscosity on the nonlinear conductivity characteristics of electric-field-assisted composite is rarely reported. In this study, the silicon carbide (SiC)/low-density polyethylene (LDPE) composites are prepared with a series of hot-pressing temperature of 110 °C, 125 °C, 140 °C, and 155 °C, respectively, under the assisted electric field of 0.8 kV/mm. The viscosity of LDPE matrix is tested at different temperatures. Moreover, the composite’s microstructure, dielectric spectra, nonlinear conductivity, and surface potential decay (SPD) characteristics are also measured. The results illustrate that the viscosity of LDPE matrix decreases with the increasing temperature, but it has little effect on the electrical properties of the untreated SiC/LDPE composites. In comparison, the viscosity of LDPE matrix has great effect on the electric-field-assisted composites. At the lowest viscosity presenting at 155 °C, the nonlinear coefficient of the electric-field-assisted composite increases by nearly three times, and the SPD speed increases by about 80%. These are attributed to the formation of large amount of particle chains under the electric field assist since the viscous drag force acting on the particle decreases with the matrix viscosity. This work is of great significance for the development of high-performance nonlinear resistive field grading composites.