High-field conductivity of non-oriented hazy polypropylene films

The conduction of nonoriented, hazy polypropylene films has been investigated between 8 and 123 degrees C at electrical stresses of up to 2*10/sup 6/ V/cm DC using a ramping speed of 200 V/s. The film thickness ranged from 70 to 80 mu m. The recorded current traces indicate some unusual behavior in the vicinity of 113 degrees C. Infrared absorption spectra suggest an increase in crystallinity, and high-resolution differential scanning calorimetry suggests a departure from linear behavior at this temperature. An attempt is made to explain this behavior in terms of structural changes that lead to the development of a negative resistance.<
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