Sandra Czaker

Mechanically recycled plastic dominates the recycled plastics market, yet its suitability for food-contact applications depends on effective decontamination. This study provides industrial-scale data on decontamination throughout the mechanical recycling of post-consumer polypropylene from mixed waste and separate collection. Samples were collected throughout the recycling process, standardized into film sheets, and analyzed to track decontamination and identify food-contact-relevant contaminants. Volatile organic compounds (VOC) decreased by 74–80%, with the largest reduction during sample cup production. Elevated washing temperatures promoted VOC release but induced degradation when combined with sodium hydroxide and deinking agent. Linear alkylbenzenes remained high in the separately collected stream and were not fully removed by processing alone. These substances likely originate from offset printing ink or soap packaging. Overall, this recycling process requires further improvement to meet food-contact requirements, and VOC analysis is a suitable tool to guide decontamination optimization and assess the application potential of the resulting recycled material.

About 10% of plastic products are recycled worldwide, highlighting the need for technology improvements based on deeper material understanding. In packaging, which holds the highest market share in plastics demand, odor and potential hazards remain critical barriers to high-quality recycling. Conventional characterization relies on chromatography with extensive sample preparation. A gas chromatography system equipped with thermal desorption and dual flame ionization and mass spectrometric detection (ATD-GC/FID-MS) was established to analyze recyclates directly, thereby accelerating technology adaptation and guiding follow-up analyses. For calibration and validation, liquid standards were introduced into TenaxTA-filled tubes via a packed column injector and compared to a loading rig. The injector exhibited losses for higher-molar-mass compounds and solvent-dependent signal shifts. A storage study on compounded recycled polypropylene stored under various conditions showed that samples not frozen in sealed containers should be analyzed within 30 days. Experiments with varying sample geometries demonstrated that higher surface-to-volume ratios increase volatile release and variability in results, highlighting the need for uniform shapes. Applying the method to recycled yogurt cups enables the identification and quantification of contaminants, facilitating optimization of the washing process. Overall, ATD-GC/FID-MS provides a rapid screening tool for recyclate quality control and supports the improvement of recycling technologies.

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.

Mechanical recycling is an essential tool in transitioning the plastics industry to a circular economy. The traditional route requires pelletizing after extrusi Mechanical recycling is an essential tool in transitioning the plastics industry to a circular economy. The traditional route requires pelletizing after extrusi