Diffusivity and Solubility of Simple Gases

Simple gases interact weakly with polymers with a consequence that their diffusion behavior is Fickian. This means that the diffusion coefficient G does not depend on concentration and time but only on temperature. The dependence on temperature is expressed by an Arrhenius type equation as 

TABLE 4.8 Boiling (Tb, K), Critical (T , K), and Lennard-Jones (e/k, K) Temperatures and Collision Diameter (a, nm) of Various Gases 

The other important parameter is the constant E o. This was found to correlate with E rather well (Van Krevelen, 1990). For elastomers and glassy amorphous materials the 

Solution. The collision diameter of oxygen is 34.67 nm (from Table 4.8) and the Tg of polycarbonate (PC) is 150 °C = 423 K (glassy amorphous polymer). From Eq. 4.55 we estimate the activation energy as 

Solubility, S, is the amount of gas dissolved in a polymer matrix at equilibrium with a partial pressure, P, and it is defined as 

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