Relaxation Process of Polypropylene and Polyolefin Elastomer Composites with Al 2 O 3 @SiO 2 Nanoparticles

In order to obtain polypropylene-based cable insulation materials with excellent dielectric properties, polypropylene composites with different Al2O3@SiO2contents and elastomers with fixed mass fractions are prepared. The change of the complex permittivity of polypropylene composites with frequency and temperature by the addition of core-shell nanoparticles is studied by frequency domain dielectric spectroscopy at multiple temperatures. To characterize the α and β relaxation processes, the triple Havriliak-Negami (HN) function model based on conductivity contribution is used to fit the dielectric spectrum curve, and the characteristic parameters such as dielectric relaxation intensity and relaxation time constant are obtained. Then, the Kirkwood–Fröhlich equation and Arrhenius' temperature-dependent law are used to analyze the dipole relaxation and activation energies reflected in the β relaxation process. The results show that the addition of Al2O3@SiO2has an inhibitory effect on the local segment movement of polypropylene at high temperature, and increases the activation energy of β relaxation. The higher the content of nanoparticles, the more obvious the inhibitory effect. The activation energy of of 1wt% Al2O3@SiO2is 0.219 eV, while that of the non-addition is only polypropylene composites 0.184 eV. However, filling a small amount of Al2O3@SiO2in polypropylene composites hardly has any effect on a relaxation.