Dielectric Spectrum of Random Copolymerization Polypropylene Nanocomposites Doped with Nano Silica at Different Temperatures

Random copolymerization polypropylene (PPR), a recyclable thermoplastic material with a melting temperature of over 150°C and excellent mechanical properties, has potential to become the insulation materials used in high voltage cables. To investigate dielectric properties of PPR and its nanocomposites at different temperatures, especially the dielectric spectrum at high temperatures, film samples of PPR and its nanocomposites doped with different content of nano silica were prepared. The microscopic morphologies were observed firstly for analyzing the dispersion of nanoparticles. Then the dielectric spectrums were measured at temperatures of 30, 50, 70, 90, 110 and 130°C. After this, the effects of nanoparticle content, temperature and frequency on the relative permittivity and dielectric dissipation factors are discussed and the mechanism is analyzed. It can be concluded that relative permittivity of PPR and its nanocomposites are almost unaffected by temperature in the range of 30 - 110°C and remains relatively low values. When the temperature is below 110°C, the relative permittivity of the PPR nanocomposites increases with the increase of temperature; And when the temperature is 110°C or above, the value is related to the applied voltage frequency and the content of nanoparticles. And with the temperature rising, the dielectric dissipation factor of PPR nanocomposites have an evident increase at lower frequency, which contributes to the DC conductivity.