Electrical Tree Resistance Enhancement of Polypropylene Based on Heterogeneous Structure Modulation

This paper focuses on the Electrical tree resistance enhancement of polypropylene based on heterogeneous structure modulation. The heterogeneous mesoscopic structure is modulated by $\alpha$ -nucleating agent $(\alpha-\text{NA})$ , and its effects on the partial discharge and electrical tree properties are investigated using a combination of experimental and simulation methods. The results show that the difference in the dielectric properties from the crystal to amorphous regions, triggered by the diversity in molecular chain arrangement and density, led to localized strong electric field distortion and further induced the growth of electric tree along the amorphous region at the boundary of the spherical crystals. The addition of a-NA refined the spherical crystal size and raised the spherical crystal density. The electric field distortion, induced by excessive size and loosely stacked spherical crystals, were suppressed to some extent, and the strength and frequency of partial discharges are thus weakened. The electrical tree resistance and breakdown strength of the material were consequently markedly enhanced.