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The solubility of C2H6 and C2F6 in two amorphous glassy fluoropolymers, Teflon® AF1600 and AF2400, has been modeled with the non equilibrium statistical associating fluid (NE-SAFT) and non equilibrium perturbed hard sphere chain (NE-PHSC) theories. Experimental swelling data during sorption are available to obtain a complete prediction of the solubility isotherms at 35°C. The solubility of C2F6 in both fluoropolymers is rather satisfactorily predicted by the models with no adjustable parameters, while that of C2H6 is overestimated, and a correction factor equal to about 0.90 must be applied on the binary energetic interactions estimated with the first approximation mixing rule. This result, combined with what previously obtained with the NE-lattice fluid (NE-LF) model, reveals inadequate representation of the hydrocarbon solubility in fluoropolymers by the geometric mean rule used to estimate the binary energetic interactions.

The solubility isotherms of C2H6 and C2F6 in Teflon AF1600 and 2400 at 35°C were calculated with the NE-PHSC and NE-PC-SAFT models and compared to experimental data. While the models are quite successful in predicting the solubility of C2F6 in the two fluoropolymers with no adjustable parameters, the solubility of C2H6 calculated from the first approximation mixing rule is underestimated, and a correction factor (1 – kij) equal to about 0.90 must be applied to estimate the binary interactions. The results confirm a general trend already observed for other gas–polymer solutions formed by hydrocarbon and fluorocarbon molecules. The correction factors to be applied on the geometric mean rule are similar to the ones obtained when modeling the same systems with the NE-LF model, indicating that the reason for the inaccurate estimation lies in the mixing rule used.