CONTAMINANT TRANSFER DURING THE PROCESSING OF THICK 3-LAYER FOOD PACKAGES WITH A RECYCLED POLYMER BETWEEN 2 VIRGIN POLYMER LAYERS

Studies are made on food three-layer packages, where a contaminated re cycled polymer layer is located between two virgin polymer layers. As the thick food packages are made by pressing the polymer layers ina mo uld kept at around the melting temperature of the polymer, the process is thus rather complex with heat transfer and contaminant transfer. H eat transfer is controlled by conduction through the package with a hi gh coefficient of heat transfer in the mould, and conduction through t he package and free convection at the surface during the cooling perio d in motionless air. The contaminant transfer is controlled by diffusi on through the polymer with a temperature-dependent diffusivity. A num erical model taking into account both the heat and mass transfer is bu ilt in order to resolve the problem. Various parameters appear of inte rest, such as the conditions of the processing with the temperature of the mould and time in the mould, the thicknesses of the polymer layer s. Two types of sandwich are considered with different thicknesses for each layer. The profiles of concentration of the contaminant are obta ined through the polymer packages.