Influence of additives on the ageing of PP films caused by partial discharges

IR spectroscopy, microscopic observations, and breakdown voltage measurements were used to study the influence of additives on physicochemical changes of polypropylene (PP) produced by a corona discharge treatment in air. The untreated film contained a high-temperature antioxidant. The film was treated to remove the antioxidant and then impregnated with an epoxide solution, DGEBA (diglycidylether ether of biphenol A) in cyclohexane. As previously reported, it appears that the changes in the characteristics of corona-treated films occur not only in a surface layer but also at appreciable depths in the polymer. Unsaturation and cross-linking were found together in treated films. The effect of the DGEBA additive is attributed to an increase in the PP reticulation