In a circular economy, polymeric materials are used in multiple loops to manufacture products. Therefore, closed-loops are also envisaged for the mechanical recycling of plastics, in which plastic is used for products that are in turn collected and reprocessed again and again to make further products. However, this reprocessing involves degradation processes within the plastics, which become apparent through changes in the property profile of the material. In the present paper, the influence of multiple recycling loops on the material properties of four different polyolefins was analyzed. Two different closed-loop cycles with industrially sized processing machines were defined, and each polyolefin was processed and reprocessed within the predefined cycles. For the investigation of the effect of the respective loops, samples were taken after each loop. The samples were characterized by high-pressure liquid chromatography coupled to a quadru-pole time-of-flight MS, high-temperature gel permeation chromatography, melt flow rate measurements, infrared spectroscopy, differential thermal analysis, and tensile tests. With increasing number of processing loops, the tested polyolefins showed continuous material degradation, which resulted in significant changes in the property profiles.

Meeting the recycled content targets of the Packaging and Packaging Waste Regulation requires significant improvements in recyclate quality for high‐performance rigid polypropylene (PP) packaging. However, the post‐consumer rigid PP stream is highly heterogeneous, resulting in intermediate recyclate properties when processed as a single stream. This study provides a comprehensive characterization of 20 representative rigid PP packaging products from an Austrian sorting facility, combining rheological, mechanical, thermal, molecular, and chemical analyses to derive a product‐property matrix and sorting implications. The results reveal substantial variability in melt flow rate, stiffness, impact strength, crystallinity, and molecular weight distribution, driven by polymer design and degradation during primary processing. Additional heterogeneity arises from chemical loads, particularly between food and non‐food products, as well as inconsistent stabilizer packages and barrier layers. These findings highlight inherent limitations of object‐based sorting, which cannot reliably infer material properties from external product attributes. Conversely, correlations between spectral‐relevant properties underscore the potential of property‐based flake sorting to classify materials by intrinsic characteristics. A systemic combination of both strategies is proposed: isolating food‐contact materials at the object stage and generating application‐specific recyclate fractions through flake sorting. Developing robust spectral‐property prediction models for PP remains a critical step towards substituting virgin grades.

Thermoforming of polypropylene (PP) requires low flowability and high stiffness, which are relevant to the processing and the application, respectively. A selec Thermoforming of polypropylene (PP) requires low flowability and high stiffness, which are relevant to the processing and the application, respectively. A selec

The transition toward a circular economy for food-contact plastics requires overcoming technical and regulatory hurdles regarding material stability and safety. This study evaluates an industrial-scale mechanical recycling process for post-consumer polystyrene (PS) waste, combining advanced pre-treatment with a specialized material conversion technology. Refined pre-treatment achieves high material purity by effectively removing foreign polymers and non-food-grade articles. Although the conversion step induces measurable polymer-chemical changes, specifically rubber-phase cross-linking, the resulting post-consumer PS recyclate retains robust mechanical and rheological characteristics. This technical integrity is proven by effective decontamination of various contaminations, achieving high material purity. Furthermore, the results of challenge tests confirm that the process meets established safety requirements for contact-sensitive food packaging applications. Life cycle assessment underscores the environmental advantages of this pathway compared to virgin production. This research provides a validated blueprint for closing the loop on polystyrene through high-performance mechanical recycling.