Effect of an epoxy additive on the electrical aging of impregnated P/P films

The authors have compared the electrical aging of capacitor models with or without epoxy additive under the same experimental conditions. Electrical degradation was evaluated from the film breakdown voltage and from chemical degradation evaluated by Fourier-transform infrared mapping. Both techniques were found to be adapted to heterogeneous degradation studies. The authors have also determined the role of epoxides in thermal oxidation of the liquid and in electrode passivation caused by a possible electrochemical polymerization of the epoxide. It is concluded that the epoxy additive increases the oxidation of impregnant and of polypropylene. However, liquid oxidation does not cause the degradation of film, and the presence of oxidation groups in polypropylene macromolecules does not explain the decrease of its breakdown voltage