Effect of magnesium oxide nanoparticles on tailoring the properties of polypropylene

Recently, polypropylene (PP) is considered as the potential recyclable HVDC cable insulation material. MgO nanoparticles were introduced into PP to tailor the properties of PP so as to make it more capable for HVDC cable insulation application. We focused on the micro morphology and structure, thermal properties, space charge accumulation and DC electric breakdown strength of the MgO/PP nanocomposites as well as the effect of MgO nanoparticles on these properties of PP. The mechanism of space charge suppression and breakdown strength enhancement in MgO/PP nanocomposites was explained by measuring the depth and density of the charge traps. The results indicate that the introduction of MgO nanoparticles has little effect on the crystallinity, crystal structure and melting temperature of PP and the good thermal properties of PP remain in MgO/PP nanocomposites. Inclusion of MgO nanoparticles obviously suppresses homocharge injection and reduces space charge accumulation. MgO/PP nanocomposite with 3 phr MgO nanoparticles exhibits the highest DC breakdown strength, which is 29.3 % higher than that of pure PP. The results of thermally stimulated current show that deep traps increase in MgO/PP nanocomposites, which would suppress charge injection and decrease charge carrier mobility. The effect of MgO nanoparticles on the properties of PP is established, which provides a reference for the design and development of recyclable HVDC cable insulation material.