Testing and evaluation of recycled plastics for food packaging use--possible migration through a functional barrier

A coextruded three-layered polypropylene (PP) cup with recycled PP material (R-PP) in the middle layer was investigated with respect to its possible use for a specific food packaging application. From the results of this investigation a general approach to testing and evaluating the use of recycled plastic materials in food packaging is presented. The method which focuses on the direct comparison of the R-PP containing cup with a food grade PP cup manufactured from virgin material involves essentially three investigation levels: 1, compositional analysis of the raw materials, i.e. PP and R-PP granules; 2, compositional analysis of the PP and R-PP cup materials and 3, migration testing of both types of cups applying practical as well as more severe test conditions. The aim of this approach is to test the PP food contact layer for its functional barrier behaviour. One key step is the estimation of migration under practice-like test conditions in concentrations below the analytical detection limits. This can only be achieved by selecting appropriate R-PP specific guide compounds whose migration can be monitored under more severe conditions than occur in practice. From the results of this investigation general conclusions on functional barrier testing are drawn.