Permeation of gases, water vapor and volatile organic compounds

9 Permeation of gases, water vapor and volatile organic compounds 

The simplest interaction to describe physically and mathematically is steady state permeation. The same material constants required for describing this interaction are also used for the description of non-steady state permeation and migration processes. 

Given the numerous different substances found in packaging and products and the resulting large number of possible combinations of packaging materials with products, not all the necessary material constants required have been experimentally determined. This leads to the use of estimation methods for substance material constants based on their chemical structures. In addition to the simple estimation methods for 

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