Thermally stimulated currents in polyvinylidene fluoride. II. Effects of stretching

For pt.I see ibid., vol.14, p.1139 (1981). The effects of stretching and crystalline morphology upon the thermally stimulated currents (TSC) in polyvinylidene fluoride (PVDF) have been investigated. Uniaxially and biaxially stretched specimens showed only two TSC peaks, P 1 ' and P 4 ', while unstretched specimens had four TSC peaks, P 1 , P 2 , P 3 and P 4 . The P 1 and P 1 ' peaks corresponded to the alpha a relaxation. The P 2 peak, corresponding to the alpha c relaxation, was drastically reduced by stretching. There were some differences between peaks P 3 and P 4 ', corresponding to interfacial polarisations in the amorphous-crystalline boundaries. The P 3 peak shifted to a lower temperature with increase in poling field, while the peak temperature of P 4 ' remained unchanged. A saturation in TSC with increase in poling field appeared at a lower poling temperature for P 3 than for P 4 '. The activation energies for the P 3 and P 4 ' peaks were 0.85 eV and 1.1 eV respectively. It was concluded that stretching had a greater influence on TSC in PVDF through structural changes in the amorphous regions and/or in the amorphous-crystalline boundaries than through the change in the relative amounts of the alpha - and beta -form crystals.