Mechanical relaxation process at 208 K for highly irradiated polytetrafluoroethylene



The internal friction of highly irradiated samples of polytetrafluoroethylene(PTEF) was measured over the temperature range below the room temperature transition; the results indicated the appearance at 208 K of a mechanical relaxation between the γ and the β processes.

The relaxation at 208 K was sensitive to effects of thermal treatments; when the relaxation weakened in intensity, the α and the β processes were emphasized. The apparent activation energy estimated was consistent with that of the relaxation which had appeared at the same temperature for as-polymerized PTFE. The 208 K relaxation seems to be attributed to local mode motion in the intermediate phase, in which molecules arranged in parallel but with random chain separation.