The present article describes the results of studies of the peculiarities of thermal behavior and degradation of low-molecular fractions obtained by sublimation of the powder ultradispersed polytetrafluoroethylene under isothermal conditions at 50 degrees C-100 degrees C. The peculiarities of fractions transition into the gas phase at heating were studied with IR spectroscopy method and interpreted based on the quantum-chemical calculations of the model fluorocarboned molecules. The calculation and spectroscopic data provide grounds to assume the presence of small molecules and radical structures in gas phase. The radical fragments formed in the gas phase as a result of the polymer chains thermal destruction provide the structure recovery during the subsequent condensation of the sample. A new averaged powder fraction is formed during condensation. (C) 2019 Society of Plastics Engineers.