Characterization of electron-irradiated biaxially-oriented polypropylene films

Post-radiation changes in the electrical and mechanical properties of capacitor-grade isotactic polypropylene films exposed to electron radiation were previously reported by the authors (ibid., vol.NS-34, no.6, p.1822-6, Dec. 1987). Based on the data obtained, it was suggested that crosslinking, chain scission and oxidative degradation were responsible for the radiation-induced changes in the film. In the present investigations, additional electrical characterizations that included the DC breakdown voltage and AC conductivity measurements were performed. Effects of the electron radiation on the physical and chemical properties were also evaluated to identify the actual degradation mechanisms. These studies included scanning electron microscopy, X-ray diffraction, infrared spectroscopy and sol-gel measurements. The results obtained confirm that crosslinking and chain scission of the polymer are responsible for the changes in the lower dose range, whereas oxidative degradation becomes predominant at higher dose levels.<
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