Comparisons of different polypropylene copolymers as potential recyclable HVDC cable insulation materials

The potential recyclable thermoplastic materials represent the future trend of the HVDC cable insulation material to replace crosslinked polyethylene (XLPE). Polypropylene block copolymer (PPB) and polypropylene random copolymer (PPR) with different weight-averaged molecular weight (Mw) were used to investigate the influence of different structure on their properties. The morphology, thermal, mechanical and electrical properties of the PP copolymers were comprehensively studied. The results show that PPB has good thermal properties, but its poor mechanical properties of low breaking elongation and low DC breakdown strength make it not suitable for recyclable HVDC cable insulation application. While PPR has relatively good thermal properties, high breaking elongation and high breakdown strength, which is significantly higher than XLPE and its space charge behavior is much better than PPB and XLPE. So PPR is more potentially suitable for recyclable cable insulation application.