Recyclable Polypropylene-Based Insulation Materials for HVDC Cables: Progress and Perspective

Polypropylene (PP)-based recyclable materials have attracted tremendous interest for HVDC cable insulation applications due to their superior electrical properties, e.g., high thermal stability and superior recyclability. Compared with crosslinked polyethylene (XLPE), PP-based materials exhibit the advantages of not only higher working temperatures but also facile and efficient cable manufacturing with reduced costs, which are highly desirable in HVDC cable manufacturing. Considering their promising advantages, PP-based materials have received significant attention from both academia and industry in the field of HVDC cable insulation. In order to adopt PP as a cable insulation material, the mechanical flexibility of PP should be improved. However, regulations of the mechanical properties inevitably influences the electrical properties of PP. So extensive research has been conducted on the regulation of the mechanical and electrical properties of PP. This review summarizes the research progress on recyclable PP-based materials for HVDC cable insulation applications. Particular attention is placed on the electrical property regulations and material structure-property relationships. The challenges that remain to be addressed and the opportunities for future studies on PP-based recyclable HVDC cable insulation materials are also presented.