Lifetime characteristics of electrically and thermally preaged polypropylene films

Constant stress voltage aging studies were conducted on electrically and thermally preaged 25-μm-thick capacitor-grade polypropylene (PP) films, and lifetime characteristics were determined at room temperature. The electrical preaging level was 70% of the breakdown voltage applied for one and two hour durations. For thermal preaging, the film was heated at 90°C for five hours and ten hours, respectively. It is noted that both modes of prestressing seem to affect the lower end of the test field region, where nonlinear failure mechanisms predominate. The results are presented and analyzed on the basis of available theoretical aging models, and possible new interpretations are discussed. A thermodynamically favorable breakdown, is indicated for electrically preaged data, while no such consistent relation was obtained for the thermally preaged data