With high melting temperature, excellent insulation performance and recyclability, polypropylene (PP) is considered as a potential HVDC cable insulation material. It is classified as homo-polypropylene (PPH), blocked copolymerized polypropylene (PPB) and random copolymerization polypropylene (PPR) by difference in polymerization modes. Nevertheless, the traditional PP is not capable as cable insulation because of its stiffness and brittleness at room temperature. Blending with polyolefin elastomers (POE) can improve the mechanical properties of polymers. Space charge accumulation is a key problem affecting the electrical performance of HVDC cables, which may be reduced by doping with nanoparticles to some extent. The current research on PP mainly focuses on the modification of PPH. The mechanical properties of PPB and PPR are better than that of PPH, but there are few studies on the properties of modified PPB-based or PPR-based nanocomposite, especially its electrical properties. PPB/POE/SiO₂ and PPR/POE/SiO₂ nanocomposites were prepared by melt blending. Morphology, space charge, volume resistivity and breakdown strength of two types of PP nanocomposites were studied.It was found that PPR/POE/SiO₂ nanocomposites have less space charge injection, because the structure of PPR with less amorphous region is more orderly than PPB. In addition, PPR nanocomposites show higher volume resistivity and breakdown strength than PPB nanocomposites, too. Nanosilica can suppress the effect of the interface between PPR and POE on the PPR nanocomposites and improves the electrical properties of PPR blending with POE. PPR nanocomposite is more suitable for recyclable cable insulation application than PPB nanocomposites.



 

polypropylene copolymer,polyolefin elastomer,insulation materials,HVDC cable,electrical properties