Applications of the Permeability Equation

Equation 14.13 is a simple but powerful equation that can be used to estimate the solution to several types of packaging problems. The equation relates many variables of a packaging system product characteristics q, p, and t package parameters P, A, and f and environmental conditions Pj and temperature. 

Select package materials. Together with mechanical properties, permeability values for Oj, COj, Nj, HjO and organic vapors, as applicable, should be used to determine the best performance/cost ratio for specific package materials. Tables and charts of permeability values can help the packaging professional in the selection. A word of caution most values of P are approximate values and there is no substitute for the experimentally determined value of P. 

Calculate the amount of gas or vapor taken up or eliminated by the packaged product, for specific conditions of temperature T, partial pressure differential Ap, and time, t, using 

If Ap changes through the shelf life period. Equation 14.33 has to be expressed as 

The above equations (Equations 14.33 and 14.34) give the value of the shelf life in terms of the length of time a packaged product remains in an acceptable or saleable condition under specific conditions of storage. The validity of the above equations is subject to the following conditions  

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