Procedure for testing of a functional barrier.

A coextruded three-layered polypropylene (PP) cup with recycling PP material (R-PP) in the middle layer was investigated with respect to its possible use for a specific food packaging application. The applied test procedure focused on the direct comparison between the virgin (food grade) PP and the R-PP materials (pellets and cups) to identify recycling-related compounds for monitoring their migration behaviour into food simulants under practice as well as more severe test conditions. The migration data measured under more severe test conditions were used to estimate highest possible migration values of recycling-related compounds occurring under the practice-like conditions. In this way, migration values below of the detection limits of state-of-the-art analytical techniques could be made accessible. The results obtained allowed the evaluation of the R-PP material for the intended food packaging use. Furthermore, from the results of this specific investigation a general approach for t esting of functional barrier behaviour of a virgin polymer layer against unauthorised substances from the layers behind was derived.