ABSTRACT
The membrane permeation process is particularly useful as a separation technique whenever conventional separation methods cannot be used economically to get reasonable separation. Several factors determine the ability of a molecule to permeate through a membrane — size, shape and chemical nature of the permeant, physical and chemical properties of the polymer, and interactions between the permeant and the polymer. The “permselective” behavior of polymeric membranes is of considerable interest for a large number of applications. In order to properly design and use membrane separation procedures it is necessary to understand the basic nature of permeation and the factors which govern the flux and permselectivity of polymer membrane systems. The local chain segmental mobility of a polymer is enhanced by the presence of an added plasticizer, resulting in a lowering of the glass transition temperature of the polymer. The permeation of solvents in a polymer is similar in that the sorbed and diffusing solvent acts to “plasticize” the polymeric system.
