Modeling gas transport in packaging applications

The barrier to gas transport provided by the container material is an important consideration in many packaging applications. This paper considers cases where a simple steady-state or pseudosteady-state analysis does not adequately represent the transport situation and, thus, the dynamics of the diffusion process must be considered. In these cases, a simple permeability coefficient is not sufficient to describe the barrier characteristics but detailed knowledge of the solubility and diffusion processes must be known. The adequacy of the phenomenological model used to represent these processes and various mathematical approximations in their application in modeling packaging problems have been considered. A specific example involving prediction of shelf-life of carbonated beverages in plastic bottles is given. In addition, the question of the approach to steadystate in transient permeation experiments is analyzed. The familiar rule of three time lags is seen to provide a conservative criterion for glassy polymers obeying the dual sorption, dual mobility model. © 1982.