Effect of X-ray beam on the molecular–topological structure of the surface of kynar® polyvinylidene fluoride resin

Abstract

Thermomechanical analysis of poly(vinylidene fluoride) (PVDF) film shows that, unlike the completely amorphous structure of the native polymer, after irradiation with X-rays, the weight fraction of the crystalline modification in the polymer is 0.5. The initial PVDF film had a linear thermal expansion coefficient of α1 = 11.33х105 K−1 and a glass transition temperature of Tg =256 K. An efficient conversion of the amorphous structures of the polymer pseudo-network into crystalline networks occurs under X-ray irradiation. The irradiated polymer exhibits amorphous (Tg =239 K) and crystalline topological blocks (Tm =385 K). The presence of polyenyl and alkyl radicals is found in the electron paramagnetic resonance (EPR) spectra of the irradiated polymer. Lines with a splitting of 3.3 m T can be observed at the edges of the EPR spectra, consistent with radical centers like -CF2-C•H-CF2-. At high doses of radiolysis, polyenyl radicals are the main observed radicals. The macromolecular chains contain all three (α, β, γ) morphologies of the polymer. The Raman spectra show that X-ray irradiation can lead to carbonization and the formation of unsaturated bonds. Electronic structure calculations were used to aid in the analysis of the observed spectra.