Effects of processing method on the structure and electrical performance of polypropylene containing intrinsic elastomers for cable insulation applications

With the increased worldwide awareness of sustainable development, the development of polypropylene (PP)-based insulation material is highly recommended. However, uncovering the processing-structure-property relationship of PP insulation materials for recyclable cables is still a long-standing issue. In this study, PP in-reactor alloys containing intrinsic elastomer were considered an important component to substitute crosslinked polyethylene. We studied the effects of processing methods on the phase morphology, crystalline structure, and electrical properties of PP in-reactor alloys. The lower cooling rate was conducive to constructing smaller rubber phase, and higher crystallinity with a small number of β crystals, which could form deep trap energy levels due to their reduced free volume in β crystals and boundaries among β crystals. The suitable thermal treatment temperature had a positive effect on eliminating defects in the interface and facilitating the perfection of PP crystals. As a result, PP films exhibited an enhanced breakdown strength. The exploration of the relationship between processing technology, microscopic structure, and macroscopic performance is expected to has significant guidance for the manufacture of PP-based recyclable cables.