Solubility gases in polymers

We have shown previously (10) that based on Geefs thermodynamic analysis of gas solubility in polymers (12) and the theory of corresponding states (14), the solubility coefficient, a, can be expressed as,... 

Zhong, C. and Masuoka, H., Modeling of gas solubilities in polymers with cubic equations of state. Fluid Phase Equilibria, 144, 49, 1998. 

Another quantity which is often encountered in discussions of gas solubility in polymers is Henry s law coefficient of sorption (ko). For rubbery and molten polymers, kD is defined very simply as the low-pressure limit (p—>0) of the solubility where C varies almost linearly with p. 

Simha, R., and Moulinie, R., Statistical thermodynamics of gas solubility in polymers, in Foam Extrusion Principles and Practice, Lee, T. S., Ed., Technomic, Lancaster, RA, 2000. 

Simha, R., and Xie, H., Applying lattice-hole theory to gas solubility in polymers, Polym. Bull., 40, 329-335 (1998). 

SOL Solms, N. von, Nielsen, J.K., Hassager, O., Rubin, A., Dandekar, A.Y., Andersen, S.I., and Stenby, E.H., Direct measurement of gas solubilities in polymers with a high-pressure microbalance, J. Appl. Polym. Sci., 91, 1476, 2004. 

The dependence of permeability, diffusion, and solubility coefficients on penetrant gas pressure (or concentration in polymers) is very different at temperatures above and below the glass transition temperature, Tg, of the polymers, i.e., for mbbery and glassy polymers, respectively. Thus, when the polymers are in the rubbery state the pressure dependence of these coefficients depends, in turn, on the gas solubility in polymers. For example, as mentioned in Section 61.2.4, if the penetrant gases are very sparsely soluble and do not significantly plasticize the polymers, the permeability coefficients as well as the diffusion and solubility coefficients are independent of penetrant pressure. This is the case for supercritical gases with very low critical temperatures (compared to ambient temperature), such as the helium-group gases, Ha, Oa, Na, CH4, etc., whose concentration in rubbery polymers is within the Heruy s law limit even at elevated pressures. 

Errors associated with models for predicting gas solubilities in polymers. 

Recently, Hilic et al. [18,19] designed an original technique to evaluate the gas solubility in polymers that permits simultaneous determination in situ of the amount of gas penetrating the polymer and the concomitant change in volume of the polymer due to gas sorption. This technique associates a VW force sensor, acting as gravimetric device, and a pressure decay installation to evaluate the amount of gas penetrating into the polymer. 

The gas solubility in polymers follows the same relationships as the gas solubility in organic liquids. Hie key factor is the condensability of the gas thus relationships between gas solubility and boiling temperature, critical temperature, and Lennard-lones temperature have been observed. As noted above, these relationships typically take the form... 

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