The influence of impregnants on the breakdown behavior of polypropylene films

Experimental results are presented concerning the effects of impregnant type, immersion time, and temperature on the dielectric strength of polypropylene (PP) films. Two biaxially stretched PP films, one smoothed on both sides and one roughened on one side, were used with two synthetic oils (dimethylsilicone and phenyl xylene ethane) employed as impregnant. The infrared spectra of the smoothed PP films before and after immersion in silicone oil are shown. The effect of impregnation times and temperatures on the breakdown characteristics of the roughened PP films immersed in oils is shown to be complex. >