Effect of Blend of Polystyrene on the Temperature Dependence of DC Breakdown Characteristics of Polyethylene

As one of environment-friendly high voltage direct current (HVDC) insulation materials show good application potential, polymer blends have aroused much attention. One of the central concerns for the application of these material systems lies in the high temperature performance of the materials, which becomes important for the insulation design considering working condition of HVDC cable. In this paper, we investigate DC breakdown strength of low density polyethylene (LDPE)-polystyrene (PS) blends at a series of temperature for 30°C, 50°C, 70°C and 90°C. The results show that at 70°C and 90°C, DC breakdown strengths of the blends are enhanced compared with pure LDPE, and they increase with the increase of PS content. Furthermore, the morphology of these blends was studied by optical microscope, and it is found that PS is dispersed into LDPE in nearly spherical shape with the dimension of several micron meter, and the improvement of high-temperature DC breakdown strength might be ascribed to such a structural modification of blending.