SORPTION OF GASES IN GLASSY-POLYMERS - A PROBABILISTIC MODEL

The description of the sorption mechanism of gases in glassy polymers is of importance for membrane-based gas separation processes as well as for packaging applications. Dual mode theory, postulating a Henry and Langmuir process to occur and leading to an equation with three adjustable parameters, is usually proposed in order to describe the isotherms. A simple mechanistic model, based on an unequal affinity between the gas molecules and the matrix regions occupied either by polymer or a previously sorbed gas molecule, is presented in this paper; in contrast to dual mode theory, this approach does not postulate the existence of microvoids in the glassy matrix. Integration leads to an equation with two adjustable parameters, which is shown to describe precisely already reported isotherms.