The mechanism of degradation of polymer under electrical stress

The mechanism of polymer degradation was studied by means of an accelerated electrical aging test of polypropylene. The microchemical structure and physical structure of the sample before and after aging were investigated by small angle X-ray scattering, electron paramagnetic resonance, and infrared spectroscopy. The trap parameter was evaluated using the photoconductive current spectrum and surface potential. The macromolecules were scissored under high electrical stress. The free radicals initiated further decomposition, and micropores resulted from chain reactions involving macromolecules. Micropores, free radicals, short groups, and the terminals of scissored groups formed in aged samples and increased in number with aging time. The free radicals and micropores were the manifestations of the traps created by electrical stress. The relations among the chemical structure and the trap density and depth are discussed