PRESENTATION AND EXPERIMENTAL-VERIFICATION OF A PHYSICOMATHEMATICAL MODEL DESCRIBING THE MIGRATION ACROSS FUNCTIONAL BARRIER LAYERS INTO FOODSTUFFS

For several years there has been an ongoing controversial scientific d iscussion about the so-called functional barrier concept which, althou gh mostly connected with the re-use of recycled plastics for food pack aging, has general relevance and is principally applicable to any type of multilayer structure. Concerning the definition of the efficiency of a functional barrier there exists different understandings, ranging from the absolute physical barrier requirement over the acceptance of toxicologically insignificant migration to a completely lag time-rela ted definition. The starting point of this work was the fact that func tional barriers are in most cases already in-situ-contaminated due to the thermally extreme coextrusion conditions of the manufacturing proc ess. As a consequence, middle layer contaminants may already have pene trated the functional barrier of a food package and may provide direct contact with the foodstuff at the time when the package is filled. Ne vertheless, depending on the individual food package parameters, the r emaining functional barrier efficiency can still prevent inadmissible migration. To meet this real-life situation and to describe the underl ying migration process a theoretical migration model was developed and experimentally verified in this work using artificially-contaminated multilayer HIPS sheets with different functional barrier thicknesses. An important result of this study was the finding that compared with t he interdiffusion between the package's layers in situ during their fo rmation in the coextrusion process, the interdiffusion at ambient temp erature until the filling time point of the package is able to be negl ected.