DIFFUSION AND SORPTION OF ORGANIC LIQUIDS THROUGH POLYMER MEMBRANES .5. NEOPRENE, STYRENE BUTADIENE RUBBER, ETHYLENE PROPYLENE DIENE TERPOLYMER, AND NATURAL-RUBBER VERSUS HYDROCARBONS (C8-C16)

Diffusion and sorption of four long-chain hydrocarbons, namely, 2,2,4-trimethylpentane, dodecane, tetradecane, and hexadecane, through four commercial polymer membranes has been studied in the temperature interval of 25-60-degrees-C by conventional weight gain experiments. The diffusion results have been analyzed in terms of the simple Fickian model. The slightly anomalous transport behavior of the polymer-solvent systems has been attributed to a slow leaching out of the indigenous elastomer compounds and/or additives during solvent immersion. The dependence of diffusion coefficient and other related parameters on the size and shape of the penetrant molecule has been discussed. It was found that the transport parameters decreased with an increase in penetrant molecular size. A temperature dependence of transport parameters was used to estimated the Arrhenius activation energies for the process of sorption, diffusion, and permeation. The estimated activation energies of diffusion and permeation in the temperature interval of 25-60-degrees-C showed an increase with increasing penetrant size. Furthermore, the sorption results have been interpreted in terms of the semiquantitative estimates of the kinetic rate constants and enthalpy of sorption. Experimental results and the predicted quantities have been used to study the nature of polymer-solvent interactions in terms of polymer structure and solvent power.