Permeation through polymer matrices and structures constructed from polymers determines the efficacy of both barrier packaging and membrane separation devices. Of course, membranes and barrier packaging materials typically are at opposite ends of the transport spectrum. The packaging engineer generally seeks to suppress permeation, while the membrane engineer seeks to promote it selectively. Nevertheless, barrier applications involving the concepts of "modified atmosphere packaging" begin to look a great deal like permselective membranes. In this presentation, emphasis will be placed on a physical understanding of the wide spectrum of issues that impact diffusion processes in and through glassy and rubbery polymers. The capabilities and limitations of molecular structure tailoring to achieve desired properties as compared to combination of multiple material types into higher order structures will be considered. Effects of temperature and penetrant-induced swelling and plasticization are also summarized.
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