Modifications of Gamma poly (vinylidene fluoride) (gamma-PVDF) films by high-energy electron beam irradiation

摘要

It is a challenge to intentionally prepare the pure PVDF film containing exclusive gamma-phase (gamma-PVDF film). In this study, the gamma-PVDF film containing extremely rare beta-phase was prepared by solution casting method. gamma-PVDF films were then irradiated with 2.5 MeV electron beam in vacuum at 92, 442 and 993 kGy, respectively. Modifications of gamma-PVDF films by the irradiation were detailedly investigated by FTIR, DSC, TGA and XPS measurements. FTIR results show that the irradiation does not induce the crystal phase transition and carbon carbon double bonds (C=C bonds) are obviously formed for gamma-PVDF films when irradiated at high dose of 442 and 993 kGy. In addition, the evolution process of chemical structures was proposed for gamma-PVDF films by the irradiation at different dose based on FTIR and XPS analyses. For thermal properties, the irradiation decreases the melting and crystallization temperatures, and thermal decomposition temperature for gamma-PVDF film due to the irradiation-induced damage effects. The sample irradiated at 92 kGy has the maximum melting and crystallization enthalpies. However, the irradiation increases the residual yield at high temperature ( 500 degrees C) of gamma-PVDF film due to the formation of crosslinked network structures in the irradiated samples.