Space charge and dielectric breakdown in polypropylene

摘要

Direct space-charge probing, dielectric breakdown tests with prestressing and so on were carried out on PP, and the following conclusions were obtained, (ⅰ) Under high fields, electrons are injected even during a very short time (< 4μs) and seem to play an important role in the breakdown process, (ⅱ) Both at room temperature and 60℃ the effects of prestressing are qualitatively and quantitatively explained in terms of field distortion due to the space-charge formation, (ⅲ) At room temperature the breakdown is initiated in the region near the cathode during the preceding prestressing, whereas that at 60 ℃ is triggered in the region where the local field is highest (ⅳ) The above space-charge effect explains the reduction of FBdc above room temperature in PP.