Degradation of perfluoroalkylpolyether Oils by γ-ray irradiation under vacuum conditions

Four kinds of fluorine group lubricating oil having different molecular structures were irradiated with Co-60 gamma ray in vacuum, and their behavior of deterioration was compared and examined by ESR, mass spectrometer, IR, liquid chromatograph and so on. FZ oil has acetal bond, and is apt to form radicals already at the initial stage of decomposition due to the absorption of gamma ray. It was found that accompanying the decomposition, the gas with low molecular weight like fluorine compounds was generated, and particularly in FZ oil, by the depolymerization from the end of acetal bond, a large quantity of carbonyl fluoride was generated. Except D oil, the viscosity lowered by gamma ray irradiation. In the case of D oil, since the radical is stable, cross linking and polymerization occurred, and the viscosity seemed to increase. Besides, it was found that since the distribution of molecular weight became wide, the deterioration of PFPE oil occurs under the competition among decomposition, cross linking and polymerization. Moreover, by gamma ray irradiation, -CFO radical was formed at the end of molecules, and the total acid value was heightened. The deterioration of PFPE oil by gamma ray irradiation depends on the molecular structures in this way. (K.I.)