Contaminant transfer during the coextrusion of tri-layer polymer films with a recycled layer. Effect of this transfer on the time of protection of the food.

Reusing old polymer packages as new food packages necessitates the coextrusion of tri-layer polymers, the old polymer being located between two virgin polymer layers. As it takes some time for the contaminant initially located in the old polymer, the virgin polymer layer acts upon the food pollution as a functional barrier. With the coextrusion process, the polymer layers are heated up to a high temperature and let cool down in air. During this coextrusion stage, the contaminant diffuses through the package at a fast rate over a short period of time. Then the time of protection of the functional barrier is significantly reduced. The process of the contaminant transfer is especially studied either during the coextrusion stage of the film or in the package-food system at room temperature.