Effect of functional barrier thickness for a food package with recycled polymer

Food packaging films can be made of bilayer polymers, one being a virgin polymer and the other the recycled polymer. The mathematical treatment of the diffusion of a contaminant with constant diffusivity when the two polymers are of the same nature is considered. Moreover it is considered that the contaminant does not pass through the external surfaces of the packaging. The effect of the relative thicknesses of the virgin and recycled polymers is presented using dimensionless numbers so as to establish general results. Master curves of the profiles of concentration of contaminant developed through the packaging are drawn as are the kinetics of contaminant transfer into the virgin polymer and the increase in its concentration at the external surface of the virgin polymer. From the master curves thus obtained it is possible to determine in any typical case the time necessary for a given transport of pollutant to occur.