Closed-Loop mechanical recycling of post-consumer polystyrene for food-contact applications

This study evaluates an industrial-scale mechanical recycling process for post-consumer polystyrene (PS) waste, combining advanced pre-treatment with a specialized material conversion. Refined sorting and hot washing at 80 °C achieve a material purity of 98.8%, exceeding the 95% food-contact origin regulatory target. Subsequent conversion involves 80 µm melt filtration and a super-cleaning unit operating at < 2 mbar vacuum for 20 min. Although conversion induces rubber-phase cross-linking (∼47% reduction in polybutadiene double bonds), the resulting recycled PS (rPS) retains the mechanical and rheological characteristics required for 100% rPS cup production. Challenge tests with eight surrogates and subsequent product migration tests confirm that decontamination efficiencies exceed safety requirements for food-contact packaging. Life cycle assessment demonstrates significant environmental advantages over virgin PS, although producing 1 kg of food-grade rPS requires 3.63 kg of source material, with remaining fractions diverted to conventional PS recycling. This study provides a validated blueprint for polystyrene closed-loop recycling.