The development of polymeric barrier materials requires a quantitatively accurate description for the diffusion of small organic penetrants in high polymer systems. The common experimental methods for studying this process are sorption and permeation. For sorption, one measures the mass of penetrant sorbed by a polymer sample following a step increase of the penetrant activity in the environment; for permeation one measures the mass throughput following a step increase in the activity on one side of a barrier. Such experiments show that the classical theory for diffusion embodied by Fick's laws cannot describe the process accurately in all cases. This paper advances a new theory of diffusion and presents mathematical equations which are derived for the process description. The discussion is presented under these headings: application to differential transport processes; and analytical solutions for the shear flow of second-order fluids.
|Original language||English (US)|
|Number of pages||11|
|Journal||Journal of polymer science. Polymer letters edition|
|State||Published - Jan 1 1985|
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