TRANSFER OF CONTAMINANT DURING THE PROCESSING OF THICK BILAYER FOOD PACKAGES MADE OF RECYCLED AND VIRGIN POLYMER LAYERS

A new route of recycling old polymers consists of using them as new fo od packages. Because of the potential contamination of the old polymer resulting from its previous use, the new packages are made of the old polymer layer bound to a virgin polymer layer.: As it takes some time for the contaminant to diffuse through the bi-layer packaging, the fo od is protected over a period of time. The process of binding the two polymer layers is studied, hen the two layers are heated at around the melted temperature and then cooled down at room temperature. Heat tra nsfer hy conduction through the polymer and the would during the heati ng stage is considered as well as the cooling period in ail During thi s heating and cooling period, the process of contaminant diffusion thr ough the two polymer layers is evaluated by considering a temperature- dependent diffusivity. The results a re expressed ill terms of profile s of temperature and of profiles of concentration of contaminant devel oped through the polymer layers. The kinetics of contaminant transfer from the recycled layer to the virgin polymer layer are also determine d, for various thicknesses of the package. Dimensionless numbers are u sed, as well as various thicknesses of the package. (C) 1998 Elsevier Science Ltd. All rights reserved.