The Solution and Diffusion of Gases in Elastic Polymers

The passage of a gas through a membrane is governed by the equation P = —D(dCjdx), where D is the diffusion constant, and dCjdx the concentration gradient. When the permeability P is known, and the solubility, the diffusion constant may be 

The predictions of all these expressions were verified by Daynes (3). The intercepts L were, for membranes about 1 mm. thick, suitably large for evaluating D, as Fig. 144(33) indicates. Most early measurements of solubility employed the static method (1), Wroblewski(29) found that Henry s law was obeyed Q = kp. The temperature dependence of the solu- 

COg-rubber systems, and also that the solubility of ethylene and carbon dioxide decreased with temperature (Fig. 145). The data plotted as log (solubility) against 1/5T give exothermal heats of solution of 3300 for COg and 2700 for ethylene. Venable and Fuwa also showed that adsorption was not important in determining the amount of gas taken up, since the observed uptake was not altered by increasing the total rubber surface. 

Tammann and Bochow(58) measured the solubility of hydrogen in a number of rubbers and at pressures as high as 1150 kgm./cm.2 Even at these pressures Henry s law was approximately valid, and the solubilities extrapolated to 

pressure were of the same order as the solubilities given in Tables 106 and 107. When the pressure on such a hydrogen-filled rubber was released, the rubber swelled to several times its original volume. 

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