The diffusion time lag in polymer membranes containing adsorptive fillers

Immobilizing adsorption of diffusing penetrants is known to occur in a number of polymer membrane systems. It will cause very large increases in the diffusion time lag but will have only minor effects on the steady-state permeation. This effect may be troublesome in that considerable errors may be incurred when the time lag method is used to analyze quantitatively the sorption and diffusion behavior in such systems. On the other hand, this effect can be utilized in a beneficial way to design very effective protective coatings, packaging materials, timed release mechanisms, etc. for special situations. The time lag in this case can be predicted very accurately from a theoretical result reported previously. This point is demonstrated here by comparing theoretical predictions with experimental time lag data obtained for various gases in a model membrane synthesized by dispersing highly adsorptive molecular sieves into silicone rubber. The agreement is excellent.