NMR measurements on 60Co γ-ray irradiated polytetrafluoroethylene with high radiation doses

The effects of 60 Co γ-irradiation and post-irradiation heat treatment on NMR line of PTFE are studied over the temperature range -50°C to 50°C for a total dose of 8.9×10 8 R. Lowering of transition temperature associated with crystalline regions of PTFE, narrowing of the line width of broad component, broadening of the line width of narrow component, and appearance of very sharp line component are observed in the NMR line shape of the irradiated PTFE. When the irradiated PTFE is annealed near the melting temperature, the very sharp line component disappears and the transition temperature shifts to higher temperature, differing from that of the unirradiated PTFE. This difference is considered to be associated with the decrease in the average molecular weight of the irradiated PTFE. Changes resulting from post-irradiation heat treatment can be attributed to the removal of defects and low molecular weight products trapped within PTFE. No charge is observed in the line width or narrow component by post-irradiation heat treatment.