Effect of Cooling Rate on the Dielectric Properties of Polypropylene for Cable Insulation

Polypropylene (PP) has attracted significant attention from scholars due to its exceptional thermal and electrical properties. And its environmentally friendly and recyclable nature is consistent with the development concept of green insulating materials. In this paper, PP samples were prepared using two distinct cooling methods: natural cooling and water cooling. The crystallization properties of the samples were characterized through X-ray diffraction experiments, while their dielectric properties were evaluated by DC conductivity and DC breakdown experiment. The results showed that a slower cooling rate facilitated a more complete crystallization process in the samples, leading to a higher degree of crystallinity. Specifically, the samples prepared by natural cooling exhibited a remarkable DC breakdown strength of 320.6 kV/mm and a conductivity of 1. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4\times 10^{-16}\mathrm{S}/\mathrm{m}$</tex>, outperforming the samples obtained by water cooling in terms of dielectric properties. This finding reveals that natural cooling has better performance in enhancing the electrical properties of PP compared with water cooling.