Effect of Copolymerization on the Conductivity and Breakdown Properties of Polypropylene for Recyclable Cable Insulation

Modified polypropylene (PP) is regarded as a potential eco-friendly insulating material. Blending modification, grafting modification and nanoparticle doping have been used to improve the performance of PP with the inevitable introduce of impurities. Copolymerization is a prospective way to reduce impurity in PP, which deserves further research. In this paper, isotatic polypropylene (iPP), PP copolymer based on iPP (PPC) and cross linked polyethylene (XLPE) were compared through differential scanning calorimetry (DSC), polarized optical microscopy (POM), conductivity and AC breakdown test. IPP and PPC show higher melting temperature and breakdown field than XLPE, indicating that PP cable can withstand higher temperatures. The results of conductivity show that the current density of PPC is smallest under same electric field and the transition field strength of PPC is highest, indicating that the deep trap level and density of PPC may be higher than those of iPP, which might be caused by the structure defects observed in the results of POM. Therefore, PPC shows better performance than iPP and XLPE, suggesting that copolymerization of PP is a feasible way for future eco-friendly cable insulation.