A new method for the prediction of diffusion coefficients in poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) is used in several packaging applications, especially for beverages. Due to the low concentration of potential chemical compounds like polymer additives or monomers leached out of the polymers and found in food or beverages, the compliance of a PET packaging material is shown often by use of migration modeling. Diffusion coefficients for migrants, however, are rare in the scientific literature. The aim of the study was to develop an equation for the prediction of diffusion coefficients in PET on the basis of activation energies of diffusion for possible migrants in PET. As a result, a correlation between experimentally determined activation energies of diffusion EA and the volume of the migrant V was established for PET. In addition, a correlation of the pre-exponential factor D0 with the activation energy EA was found. Combining both correlations lead to an equation where the diffusion coefficients DP are predictable from the molecular volume V of the migrant. The equation might be useful for migration prediction and consumer exposure estimations.