Radiation-Induced Changes in the Degree of Crystallinity of Powdered Polytetrafluoroethylene

Abstract

An analysis of the diffraction patterns of powdered polytetrafluoroethylene (PTFE) γ-irradiated at room temperature in a nitrogen atmosphere to doses of 10–500 kGy with a fluence of 1.50 ± 0.3 Gy/s has shown that the diffraction peak 100 of the crystalline phase at 2θ ∼ 18° and the halo at 2θ = 10°–25° are most sensitive to ionizing radiation. It is found that the intensity, FWHM, and position of the maximum of reflection 100 change with an increase in the absorbed dose; this fact is indicative of the doublet nature of the peak profile. It is established that the doublet components differently response to ionizing radiation. The interplanar spacings, amplitude and sign of arising stress, and the degree of crystallinity (DOC) of polymer are calculated as functions of the irradiation dose. The radiation-induced change in the DOC of PTFE should be considered as a complex process, which includes radiative destruction and topochemical reactions of different types in crystals.