Oxygen Permeation in PET Bottles with Passive and Active Walls

The aim of this paper is to provide a framework, whereby gas permeation rates through plastic packaging walls, and hence, food shelf life may be estimated. Although the approach is quite general, specific attention is given to the case of liquid-filled polyethylene terephthalate (PET) bottles with oxygen as the permeating gas. Two situations art, considered: when the walls simply provide a passive resistance to the flux (as is the case for standard PET or PET blended with some other low permeability material) and when an active gas scavenger is incorporated within the boundary material. For the passive wall, permeability data relative to oxygen have been collected from literature sources and also measured using specific oxygen transmission rate experiments. For the active walls, scavenger kinetic constants were estimated from data obtained using test bottles prepared with varying scavenger concentrations. Numerical predictions in both cases have been verified by comparison with data on gas concentration in water-filled bottles maintained tinder controlled conditions for periods of up to 6 months. Copyright (c) 2008 John Wiley & Sons, Ltd.