Theoretical and experimental exploration of rules for combining transport parameters in laminar membranes

Permeabilities, time lags, and mean first passage times were measured in silastic (Sil) and ethylene vinyl acetate copolymer (EVAc) membranes and in the series composites Sil/EVAc and EVAc/Sil. These measurements were used to test phenomenological rules derived previously [R. A. Siegel, J. Phys. Chem. 95, 2556 (1991)] relating the parameters of the constituent membranes to the same parameters for the membrane composites. Reasonable agreement was found between experimental results and these rules. As predicted, permeability and time lag are the same in either direction of transport through the series composite, while mean first passage time is direction dependent. In addition to the experimental results, the combination rules are rederived using the partition/diffusion model of membrane transport, and certain new theoretical connections are noted.