NELF model solubility calculations

It is also interesting to observe that the solubility coefficient of a penetrant in a glassy polymer, in the limit of low pressure, is independent of the partial molar volume of the penetrant component in the mixture and can be reliably calculated from the NELF model using only the pure polymer density (14). Thus, also in the absence of volume dilation data the NELF mcidel can be reliably used, albeit in a limited pressure range often in the order of few bars at least (14). 

Solubility of Gaseous Mixtures Comparison with Experimental Data. The experimental determination of the solubility of gas mixture components in a solid polymer is a very complicated task relative to the measurement of solubility of a pure gas or vapour. Indeed, very few mixed gas sorption data are available in the technical literature. To compare with predictions of the NELF model, only the experimental data for the solubility of GO2/C2H4 mixtures in PMMA at 35°C (4, 75, 76) will be considered in this article. Since the volume dilation produced by the gas mixture is not available, the analysis of the data is confined to the low pressure range, where the swelling of the glassy polymer may be neglected. Indeed, in the calculation which follows the non-equilibrium solubility is estimated from the NELF model assuming... 

For the calculations, different EoS have been used the lattice fluid (LF) model developed by Sanchez and Lacombet , as well as two recently developed equations of state - the statistical-associating-fluid theory (SAFT)f l and the perturbed-hard-spheres-chain (PHSC) theoryt ° . Such models have been considered due to their solid physical background and to their ability to represent the equilibrium properties of pure substances and fluid mixfures. As will be shown, fhey are also able to describe, if not to predict completely, the solubility isotherms of gases and vapors in polymeric phases, by using their original equilibrium version for rubbery mixtures, and their respective extensions to non-equilibrium phases (NELF, NE-SAFT, NE-PHSC) for glassy polymers. 

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