STRUCTURE OF POLYTETRAFLUOROETHYLENE FILM AFFECTED BY ELECTRON RADIATION AND TEMPERATURES

The thermal conductivity of the polytetrafluoroethylene film in the temperature range of 80–330 K and radiation doses from 5 to 30 kGy was investigated. Methodology. Thermal conductivity studies were carried out at the TAU–5 thermophysical facility. Results. The temperature dependence of the thermal conductivity of polytetrafluoroethylene at different irradiation doses was obtained, and the resulting thermal conductivity curves demonstrate phase transitions at temperatures T1 = 293 K and T2 = 303 K. The irradiation of polytetrafluoroethylene films with low doses resulted in a shift of phase transition temperatures to the low temperature region, with a decrease in peak amplitude. Irradiation with a dose of D = 30 kGy resulted in a 2 % decrease in thermal conductivity λ, a significant decrease in the intensity of the phase transition peak at T1 and a complete disappearance of the second peak at T2. As the temperature and irradiation dose increased, there was a notable rise in interplanar distances, degree of crystallinity, and unit cell volume. Conversely, there was a reduction in crystal size, a rearrangement of the crystal structure, and a smoothing of phase transitions. Conclusion. It was determined that the thermal conductivity of the polymer at low temperatures is attributed to skeletal vibrations of the main chain, while at high temperatures and irradiation doses, it can be attributed not only to the rearrangement of the crystal structure, but also to the disappearance of pores and the ordering of the crystalline phase of polytetrafluoroethylene.