Measurement and prediction of solubilities of hydrocarbon vapors in molten polymers

The solubilities of m-xylene and nonane vapors in polystyrene and of ethylbenzene and nonane vapors in polybutadiene were measured with a sorption apparatus in the temperature range from 130 to 175°C and 80 to 130°C, respectively. A new expression for the free-volume term derived previously was coupled with UNIFAC to predict activities of hydrocarbons in polymer solutions. In this study, the UNIFAC-FV model has been reexamined and the parameters in the free volume term have been revised. The parameters in the UNIFAC-FV model can be calculated by the group contribution. The model was applied to predict solubilities, activities, or mass-fraction Henry constants for the systems studied here and published in the literature. From comparison of experiment with calculation it is found that the present UNIFAC-FV model can give fairly good predictions of such equilibrium properties of organic vapors in polymers on the basis of a knowledge of molecular structure alone.