Effect of different nanoparticles on tuning electrical properties of polypropylene nanocomposites

Polypropylene (PP) has shown great potential as recyclable HVDC cable insulation material. This paper aims to investigate the effect of different nanoparticles on tuning the electrical properties of PP. Surface modified MgO, TiO₂, ZnO and Al₂O₃ nanoparticles with various contents were melt blended with PP. The microstructural morphology, dielectric properties, DC volume resistivity, space charge behavior and DC breakdown strength of the nanocomposites were investigated. It was found that the dielectric permittivity all increases with the increase of nanoparticle content, only the dielectric loss of TiO₂/PP nanocomposites increases. For MgO and TiO₂ nanocomposites, the DC volume resistivity increases with the increase of nanoparticle content and then decreases, while it continues to increase for Al₂O₃ nanocomposite. TiO₂/PP nanocomposite with 5 phr nano-TiO₂ shows lower volume resistivity than PP. Space charge suppression and DC electric breakdown strength show similar variation trend, both increase with the increase of nanoparticle content and then decrease. MgO and TiO₂ nanocomposites show the most obvious space charge suppression and TiO₂ nanocomposites exhibit the highest DC breakdown strength, which is 43% higher than that of pure PP. Considering the electrical properties investigated, the optimal content for MgO, TiO₂, ZnO and Al₂O₃ nanoparticles is about 3, 1, 1 and 1 phr, respectively. Among these four kinds of nanoparticles, MgO and TiO2 nanoparticles are more capable than ZnO and Al₂O₃ nanoparticles to modify the electrical properties of PP and more potential to be used as recyclable HVDC cable insulation material.