Effect of sample preparation methods on space charge behavior and dielectric properties of polypropylene nanocomposites

The accumulation of space charge in high-voltage DC cable insulation is the key problem leading to the insulation fault. Nano-silica (SiO
2
) and nano-alumina (Al
2
O
3
) doping methods are commonly used to improve the space charge performance of polypropylene (PP). In this paper, the dielectric spectra and space charge distribution of nano-SiO
2
/PP composites and nano-Al
2
O
3
/PP composites prepared by solution method and blending method were tested. Relative dielectric constant of the composites prepared by the solution method is higher than that of pure PP, which of composites prepared by the blending method is similar to that of pure PP. As the frequency increases, the dielectric loss factor shows a downward trend. After the addition of nanoparticles, the cathodic homopolar charge is obviously suppressed, and the inhibition effect of solution method is more obvious than that of blending method, which is related to the dispersion degree of nanoparticles in the samples prepared by the two methods. It is proved that the addition of nanoparticles can reduce the space charge in the composites and can achieve the effect of restraining the space charge. the better the dispersion of nanoparticles in the matrix, the better the inhibition effect.