The authors have compared the electrical aging of capacitor modelswith or without epoxy additive under the same experimental conditions.Electrical degradation was evaluated from the film breakdown voltage andfrom chemical degradation evaluated by Fourier-transform infraredmapping. Both techniques were found to be adapted to heterogeneousdegradation studies. The authors have also determined the role ofepoxides in thermal oxidation of the liquid and in electrode passivationcaused by a possible electrochemical polymerization of the epoxide. Itis concluded that the epoxy additive increases the oxidation ofimpregnant and of polypropylene. However, liquid oxidation does notcause the degradation of film, and the presence of oxidation groups inpolypropylene macromolecules does not explain the decrease of itsbreakdown voltage
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