Seminars
Predictive Thermodynamic Models for the Solubility of Gases and Vapors in Glassy Polymers
Professor Giulio C. Sarti
Department of Chemical Engineering
Università di Bologna
When: Thursday, September 28, 2006
Time: 2:30 PM to 3:30 PM
Where: 1070 Duncall Hall
Abstract:
Solubility isotherms for gases and vapors in glassy polymers represent a relevant information for the development of barrier materials and membranes for gas separations. On the other hand, the calculation, possibly predictive, of solubility isotherms of gases and vapors in glassy polymers is a challenge since the solid phase is not under equilibrium conditions and the traditional equilibrium Thermodynamics does not apply.
The problem has been analyzed through the use of a macroscopic thermodynamic procedure, Non Equilibrium Thermodynamics of Glassy Polymers, which enables to properly extend to non-equilibrium glassy phases the equilibrium equations of state available for polymeric systems.
The possible use of the model as a predictive tool for gas solubility in glassy polymers is discussed first for the cases in which the polymer density is known from direct experimental measurements, for non swelling gases as well as for swelling penetrants. It is then shown how the thermodynamic procedure developed can be used in the common cases in which the polymer density due to dilation is not known from direct experimental measurements over the pressure range of interest.
The solubility isotherms calculated by the model are compared with several experimental data, obtaining a rather satisfactory representation of the sorption isotherms.
The extension of the model to the calculation of the solubility in glassy polymer blends and in mixed gases is straightforward and equally satisfactory.
The thermodynamic procedure proposed can be applied equally well to different equations of state as Sanchez-Lacombe lattice fluid, SAFT and PHSC as it is confirmed by different examples.
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