Abstract

Transmission electron microscopy and low-temperature nitrogen sorption, X-ray phase analysis and differential scanning calorimetry have been used to study the effect of γ-radiation of the 60Co isotope on the sorption properties, degree of crystallinity and surface morphology of powdered polytetrafluoroethylene depending on the absorbed dose (10-1000kGy). It was found that the degree of crystallinity of polytetrafluoroethylene increases from 35 to 80% upon irradiation with doses up to 50kGy, and then practically does not change. Specific surface area of the polymer powder decreases upon irradiation up to dose of 10kGy, and then increases by 21% upon further γ-irradiation up to 50kGy. There is a tendency towards a gradual decrease in the specific surface area in the region of absorbed doses of 100-1000kGy. Also, in the range of 10-50kGy, an intensive formation and growth of screw dislocations was found. A conclusion is made about the dislocation mechanism of the radiation crystallization process, as well as about the correlation between the change in sorption properties, the degree of crystallinity and the surface morphology of polytetrafluoroethylene particles.

Keywords: Polytetrafluoroethylene; Radiolysis; Ionizing radiation; Crystallization; Specific surface area; Screw dislocation