Calculation and Experimental Investigations of Mass Loss of Polymeric Material under the Influence of Ultraviolet Radiation in Vacuum

The effect of ultraviolet radiation on the mass loss kinetics of a sample of model polymer composite material in a vacuum chamber at a pressure of $10^{-5}$ Pa was studied. The source of ultraviolet radiation was a deuterium lamp DDS-30. A mass loss sensor based on quartz microbalance was used to measure the mass loss kinetics. A comparative analysis of the experimental time dependences of mass loss of the model material samples heated to ($70\pm 1$)~\textdegree C and samples when exposed to ultraviolet radiation, whose temperature is also kept equal to ($70\pm 1$)~\textdegree C, was conducted. The results of the analysis showed that simultaneous action on the model material in a vacuum of heat and ultraviolet radiation leads to an increase in the rate of mass loss of the sample, especially in the initial period of exposure --- during the first 10 hours after turning on the radiation source. The latter is explained by the composition of the model material. For qualitative interpretation of the experimental results, mathematical models describing the kinetics of mass loss under both thermal exposure and combined exposure of the sample material to heat and ultraviolet radiation, as well as a model of condensation of gas release products on the sensitive element of the mass loss sensor were proposed.