Polarization and structural properties of high-energy electron irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer films

The effect of high-energy electron irradiation on structural and polarizati on properties of 50/50 mol % copolymer of poly(vinylidene fluoride-trifluor oethylene) was investigated for both mechanically stretched and unstretched films. Although stretching can significantly enhance the polarization and dielectric responses in unirradiated films, it was observed that this enhan cement was not significant in irradiated films. In addition, the polarizati on in both types of films after irradiation can be described quite well by a logarithmic mixing law of composites, which consist of crystallites embed ded in an amorphous matrix with nearly the same fitting parameters. On the other hand, the enhancement of the mechanical properties from stretching pe rsists after the irradiation, and the elastic modulus along the stretching direction remains high after irradiation in comparison with unstretched fil ms. It was found that the dielectric dispersion in both types of films afte r irradiation fits well to the Vogel-Fulcher law. It was also observed that the crystallinity decreases and the crosslinking coefficient increases con tinuously with dose. However, there was no direct one to one type relations hip between the crystallinity and the crosslinking coefficient. Although st retching can reduce the rate of crosslinking, the reduction of crystallinit y with dose for stretched and unstretched films does not show a marked diff erence. (C) 2000 American Institute of Physics. [S0021-8979(00)08501-7].