Electrical properties enhancement of dually grafting modification for polypropylene cable insulation

Polypropylene (PP) is believed to be a rather promising cable insulating material for high-capacity electric power system with low carbon emission due to its decent thermo-resistance and recyclable nature. In this paper, a new dually chemical grafting modification strategy by methyl acrylate (MA) and acrylic acid (AA) is put forward to tailor the charge transportation behavior in PP, thus further enhancing the electrical properties. Experimental results indicate that the dually grafted PP with 2.3 weight percent (wt%) MA and 1.9 wt% AA shows enhanced volume resistivity and electrical breakdown strength than pure PP, and the space charge injection is significantly suppressed. This work further adopts thermally stimulated depolarization current (TSDC) test and computational analysis based on density functional theory (DFT) to reveal the mechanism of enhancement. The analysis shows that grafted chemical groups can introduce quantities of deep traps and electrostatic potential wells which are strongly correlated with the carbonyl group and would hinder the charge transportation thus improving the electrical insulating performances of PP. This work would provide a new route of PP-based dually grafting modification for the development of high-voltage cable insulation.