X‐ray and NMR measurements on irradiated polytetrafluoroethylene and polychlorotrifluoroethylene

Abstract

AbstractThe effects of 60Co γ‐radiation on polytetrafluoroethylene (PTFE) and polychlorotri‐fluoroethylene (PCTFE) have been studied for radiation doses up to 940 Mrad. The dependence of per cent crystallinity upon irradiation level has been determined from x‐ray analysis. An initial increase in crystallinity in PTFE, attributable to chain scission in the amorphous phase of the material, was found, followed (above 300 Mrad) by a gradual decrease associated with a disordering of the crystallites. No initial increase was observed for annealed samples of PCTFE due to the large initial value of the per cent crystallinity. Above 200 Mrad the crystallinity was found to decrease with accumulated dose. Nuclear magnetic resonance measurements on PTFE have indicated a radiation‐induced broadening of the amorphous component of the NMR line appearing to maximize above 700 Mrad. Similar measurements of PCTFE have shown a narrowing of the crystalline component of the NMR line and subsequent appearance of the amorphous component at approximately 200 Mrad. The data indicate that the radiation‐induced behavior of PTFE and PCTFE is similar above 200 Mrad.