Threshold effect of residual catalyst on volume resistivity of polypropylene polymers

Polypropylene (PP) has become the focus of research and development of recyclable polymer dielectric materials because of its excellent electrical and thermal properties. The residual catalyst after PP polymerisation is the main part of ash. It was found that ash particles are uniformly dispersed in the PP matrix. The increase in ash content leads to a gradual decrease in their spacing, and leads to a significant decrease in electrical properties, with a difference of more than one order of magnitude for volume resistivity. The decrease in the ion migration potential barrier caused by the increase of ash content is the key factor in deteriorating the electrical properties of PP. The effect of ash on the electrical properties of PP mainly lies in enhancing the migration of ion carriers. The PP volume resistivity corresponds to an ash threshold of 292 ppm, above which the concentration leads to an increase in ion carriers. The accumulation of carriers leads to internal electric field distortion enhancing the transition ability of carriers and leading to a rapid decrease in the electrical properties of PP. This study provides a feasible reference for the development of high‐performance PP insulation materials for power cables and other applications.