Electrical ageing of polypropylene film

Accelerated tests of electrical aging for polypropylene film in vacuum and under uniform stress are reported. The results of the test show that the relation of electrical breakdown strength of the samples to the aging time can be expressed as t=KU^-n. During the aging, infrared spectrometry, thermogravimetry, photoconductive spectrometry, and surface potential measurement are used to analyze the chemical structure, pyrolytic temperature, and deep trap density of the sample. The short groups and the terminals of scissored groups of the specimen and the trap density increase with the aging time. It is suggested that trap density may act as a new parameter which stands for the characteristic of the electrical aging of the material. The present study is significant for developing a new theory of electrical aging tests and replacing the destructive tests of electrical aging with nondestructive ones