Electrical properties of polypropylene/styrene-ethylene-butylene-styrene block copolymer/MgO nanocomposites

With the development of the long-distance DC electrical power transmission, high voltage direct current (HVDC) cables have attracted more attention as an important transmission medium. HVDC transmission systems offer the best technical and economical solutions for long distance transmission. Polypropylene (PP) has better prospect than cross-linked polyethylene (XLPE), which is attributed to its excellent performance as an eco-friendly material in HVDC cables. However, the main problem in restricting the development of HVDC cables is the space charge injection and accumulation which can cause the breakdown and aging of materials. In this paper, we prepared the nanocomposites with the modified MgO, PP and Styrene-Ethylene-Butylene-Styrene Block Copolymer (SEBS) through melt blending method. The space charge, breakdown strength and dielectric properties of the nanocomposites were also investigated. Results showed that the nanocomposites with 0.5 phr surface-treated MgO dispersed well in the matrix. The addition of MgO effectively suppressed the space charge accumulation compared to PP/SEBS blends and improved its breakdown strength. At last, we explained the mechanism of space charge suppression using the trap theory. This work could provide theoretical basis for PP used as an eco-friendly insulating material in HVDC cables.