Structure disorder observation of fluoropolymers composed of vinylidene fluoride and tetrafluoroethylene in supercritical CO2 using time-resolved small- and wide-angle X-ray scattering

Abstract

Fluoropolymers have a growing range of applications in many industries. Neat fluoropolymers and fluorinated copolymers were prepared via the suspension polymerization method with entire mass ratio of vinylidene fluoride (VdF) and tetrafluoroethylene (TFE). Supercritical CO2 was applied as a fluid stimulus to the fluoropolymers. An increase in structural disorder was investigated using time-resolved small-angle X-ray scattering (SAXS). The SAXS change induced by the stimulus proceeded more slowly with increasing VdF ratio of the copolymer, suggesting that the higher VdF content contributes to the tolerance of microvoid formation and the corresponding onset of breakdown in the polymer material. The degree of crystallinity of the fluoropolymers was evaluated using wide-angle X-ray scattering, showing the degree of crystallinity was similar before and after the stimulus. Time-resolved and in-situ SAXS/WAXS measurements were carried out on the copolymer with a ratio of VdF:TFE = 8:2 as the copolymer having the highest VdF content studied here.