Dielectric Properties Improvement of Grafting-Modified Polypropylene by Silane for HVDC Cable Insulation
Shixun Hu, Xinhua Dong, Wei Wang, Shangshi Huang, Jun Hu, Qi Li, Jinliang He, Qing Shao, Hao Yuan, Hongwei Shi, Wenbo Song
Abstract
Polypropylene (PP)-based grafting modification is a promising and more applicable method to enhance dielectric properties instead of nanocomposites. In this paper, vinyltriethoxysilane (VTES)-grafted PP with different grafting monomer contents are prepared. The micro-morphology, thermal properties and dielectric properties of VTES-grafted PP are characterized and analyzed. The results show that the melting temperature and crystallinity slightly decrease after grafting VTES. Sphere-shaped dispersed phases are observed in micro-morphology characterization, which may be related to the self-polymerization of grafting monomer. The homo-charge injection near cathode is suppressed in grafting-modified PP, presenting low electric field distortion. The DC breakdown strength and DC volume resistivity of grafting-modified PP are significantly raised, exhibiting the improvement of 18.8% and an order of magnitude, respectively. Thermally stimulated current (TSC) results show a large number of deep traps introduced after grafting modification. Numerous deep traps might be beneficial to these improved dielectric properties of VTES-grafted PP as above. PP-based grafting modification shows enhanced dielectric properties and simplified modification process. This work would provide a strategy and reference for the research and development of grafting modified PP-based insulation material for HVDC cable.