High improvement in trap level density and direct current breakdown strength of block polypropylene by doping with a β-nucleating agent

Polypropylene is one kind of eco-friendly insulating material, which has attracted more attention for use in high voltage direct current (HVDC) insulation due to the long-distance transmission, low loss, and recyclability. In this work, the morphology and thermal and electrical properties of the block polypropylene with various beta-nucleating agent (beta-NA) contents were investigated. The relative fraction of the beta-crystal can reach 64.7% after adding 0.05 wt. % beta-NA. The beta-NA also greatly reduced the melting point and improved the crystallization temperature. The electrical property results showed that the alternating and direct current breakdown strength and conduction current were obviously improved. In addition, space charge accumulation was significantly suppressed by introducing the beta-NA. This work provides an attractive strategy of design and fabrication of polypropylene for HVDC application. Published by AIP Publishing.