GC–MS analysis of process-induced changes during mechanical recycling of PP and PS waste streams

The uncertain origin of post-consumer plastic waste often complicates effective recycling, especially for food-contact materials (FCMs). Given the extensive range of potential applications, the number and concentration of possible contaminations is similarly vast. For this study, FCM waste was hand sorted, first by polymer type (PP and PS) and then by color fraction. The sorted waste was reprocessed along the mechanical recycling path: washing, extrusion, and solid-state decontamination (SSD). Changes in the analyte profile were monitored during each step by two separate methods for gas chromatography coupled to mass spectrometric detection (GC–MS). The research findings indicate that PP and PS were affected in different ways throughout the same recycling process chain, resulting in varying cleaning efficiencies for the individual processing steps. The outcome of this study showed that by considering the entire recycling pathway, it is possible to identify which parameter adjustments have the greatest impact on higher cleaning efficiencies.