Effect of crystalline morphology of polypropylene on breakdown field strength

Polypropylene (PP) is studied as an environmentally friendly insulating material in high voltage direct current (HVDC) transmission such as the wind power grid connection, island power supply and long-distance transmission across the sea because of its excellent insulating properties. As a semi-crystalline polymer, PP's crystal structure determines the insulating properties. In this paper, pure isotactic PP samples with different crystalline morphology were prepared to investigate the effect of crystalline morphology on the breakdown field strength. According to the microstructure and DSC(differential scanning calorimetry) curve, the breakdown field strength of isotactic PP samples was discussed. The breakdown mechanism was analyzed. Due to the different crystalline morphology forming in samples, the electron transportation path changes, leading to the breakdown field strength change.