Effect of non-uniformly distributed talc fillers in polypropylene under high voltage

The evolution of the space charge distribution in polypropylene including non-uniform distribution of talc fillers is studied. In the process of fabrication, a lack of fillers is clearly localized in the middle of the material which introduces a macroscopic heterogeneity. Under voltage, it acts as a macroscopic trap that imposes an alternating charge buildup, leading therefore to a limited electric field enhancement. Measurements have been carried out at 45°C with the pressure-wave-propagation method. The signal is carefully analyzed as to take into account only space charge distribution data.