Surface charge dynamic characteristics of EVA/CB nanocomposite under mechanical stretching

Ethylene-vinyl acetate (EVA) composite has been widely used in cable accessory insulation to uniform electric field and prevent partial discharge. However, local electric field distortion will cause charges accumulation and flashover, which is susceptible to the tensile strain upon the materials. Carbon Black (CB) nanoparticles can be applied to adjust the electrical properties of polymer composite. The effects of the CB contents on the surface charge characteristics of EVA/CB nanocomposite under various tensile strains need further investigation. In this paper, samples were prepared by incorporating CB nanoparticles into EVA matrix with fraction of 0, 1, and 5 wt% respectively. Tensile strains of 0, 5, 10 and 15 % were applied to provide four deformations. The dependence of the permittivity and surface charge decay on the CB contents under various tensile strains were measured. The trap distribution and carrier mobility were calculated to analyze the tensile strain effects. Obtained results show that the surface charges decay more quickly with the increasing tensile strains for all the samples. Moreover, the decay rate of the samples doping with 1 wt% CB nanoparticles is lower than the other samples. The combination effects of trap distribution and carrier mobility are responsible for the above results.