Overestimated Diffusion Coefficients For The Prediction Of Worst Case Migration From Pet: Application To Recycled Pet And To Functional Barriers Assessment

This paper defines parameters that can be used to predict worst-case migration from recycled PET bottles, with & without functional barrier. Starting with a set of diffusion coefficients determined in well-defined experimental conditions (temperature, presence or not of a solvent, with & without swelling effect), empirical equations for the diffusion coefficient of a migrant or a pollutant in PET at 40 deg C are given as a function of molecular weight. An equation is also derived for migration from PET into water. Surrogates representative of worst-case migrants are identified & discussed in terms of molecular weight, structure & interaction with the PET matrix. In the second part of the paper, the empirical equations have been used to simulate the migration from monolayer bottles & from multilayer bottles with different geometries of functional barrier.