Dielectric Breakdown Properties of Polypropylene Blended with Various Copolymers

Polypropylene blends have recently been proposed to replace conventional cross-linked polyethylene in power cable insulation. This is mainly due to polypropylene's higher melting temperature, hence higher current-carrying capacity and higher voltage limit over cross-linked polyethylene. Although blending polypropylene with copolymers improves polypropylene's flexural modulus for the ease of power cable extrusion, this often comes with compromised dielectric breakdown strength of the final polypropylene blends. The current work therefore investigates the effect of blending polypropylene with different types of copolymers to determine their structure and breakdown property relationship. The results show that different types of copolymers have different effects on the breakdown strength of the final polypropylene blends. The mechanisms underlying the breakdown changes are discussed with the aid of microstructure interpretations. This paves the way for the development of next-generation power cable insulation.