The electrical treeing characteristics of pure Polypropylene (PP) and two different contents of styrene grafting PP were investigated in this study. The electrical tree inception time result indicates that styrene grafting modification stalls the treeing inception process in PP. The electrical growth statistics show that styrene grafting modification can also slow down the treeing growth rate and the morphology of trees in pure PP and styrene grafting PP is different. The difference of the tree characteristics in these three materials is attributed to the changes of trap level distribution and crystallinity properties. In styrene grating PP, the increases in the level of traps and the density of deep traps together restrict the mobility of electrons and the decrease in the size of spherulite narrows the amorphous region with lower insulation performance comparing to crystalline part, thus, leading to the improvement in the electrical treeing properties.

grafting modification, electrical tree, polypropylene