X-RAY-INDUCED DEGRADATION OF POLY(VINYLIDENE FLUORIDE) FILMS

The X-ray induced degradation of poly(vinylidene fluoride) (PDVF) films has been investigated by IR, X-ray diffraction, UV/visible and differential scanning calorimetry (DSC) techniques. The IR spectra show a significant decrease in intensity of bands characteristic of crystalline regions, namely a moderate decrease in intensity of bands corresponding to the alpha-form and a small decrease in intensity of bands of the beta-form. The X-ray results show an increase in crystallinity after the first 3 h of irradiation; at longer exposure times, there is a decrease in crystallinity, the alpha-form being preferentially attacked relative to the beta-form, as shown by IR spectra. The loss of crystallinity under X-ray irradiation was demonstrated by DSC measurements. The appearance of a new IR band at 1714 cm-1, whose intensity increases with X-ray exposure time, is evidence of the formation of conjugated double bonds by dehydrofluorination. The UV/visible spectra show several absorption bands associated with diene, triene and tetraene, the diene band being dominant. The DSC thermograms show changes in the shape of the curve and the appearance of new melting peaks at lower temperatures with increasing exposure time. The reactions taking place in PVDF films irradiated in vacuum by X-rays are thus apparently similar to those in films irradiated by gamma-rays or electron beams and films subjected to high-energy ion implantation.