Surface flashover performance of phenolphthalein modified LDPE in vacuum

Abstract

Since surface flashover of insulators in vacuum restricts the operation of the power equipment, improvement of surface flashover performance is of considerable importance in various fields. Previous studies show that surface flashover performance is closely related to the trap parameters of materials. In this paper, the crystallization behavior of low density polyethylene (LDPE) is modified by phenolphthalein. It results in the change of the trap parameters, leading to the enhancements in surface flashover performance. Results of differential scanning calorimeter (DSC) and scanning electron microscope (SEM) show that the crystallization behavior of LDPE is greatly changed by phenolphthalein. The crystallinity increases initially and then decreases with the increase of phenolphthalein concentration, and its maximum value occurs at 0.4 wt%. The spherulite size of LDPE composites decreases obviously with the increasing phenolphthalein concentration. The results of thermally stimulated current (TSC) show that both the shallow trap (γ peak) and the deep trap (α peak) become deeper with the increase of phenolphthalein concentration. Furthermore, the impulse and dc surface flashover voltages present the optimum values at 1 wt% phenolphthalein concentration, which can be enhanced by 30.8% and 48.4%, respectively. It is concluded that LDPE with the smaller spherulite size indicates the deeper trap and the better surface flashover performance. This paper reveals the relationship between surface flashover performance and crystallization behavior of LDPE, and proposes a new method to enhance the surface flashover performance of semi-crystalline polymers in vacuum.