The effect of filler concentration on slow polarization in LDPE/SiO2 mocro- and nanocomposites

Nano-SiO₂/ low density polyethylene composite and micro-SiO₂/ LDPE composite were prepared via a method of double-solution mixture. The discharging current of all samples after being prestressed at a DC electric field were recorded via Keithley 6517A. Currents of the both composites are less than those of pure LDPE. In addition, the curve shape of the nanocomposite is different from that of pure LDPE and or the microcomposite, which suggests the slow polarization mechanism of the nanocomposite containing nano-SiOx differs from that of pure LDPE and or the microcomposite. The slow polarization characteristics of all samples were analyzed via a method of Fast Fourier Transfer (FFT) in a frequency domain and parameters of epsiv\´ - epsiv_infin and epsiv" of all samples were obtained by converting the discharging currents. The polarization intensity of pure LDPE is the highest among all of the samples, while the polarization peak locates at lowest frequency. At the same time, the polarization intensity of microcomposite was higher than that of nanocomposite, and the polarization peak location of microcomposite was lower frequency than that of nanocomposite. The polarization peak of the nanocomposite increases with the loading level whereas that of the microcomposite does not vary with loading level at all.