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.

Efficient recycling of polyethylene (PE) waste depends on optimized pretreatment and processing strategies. This study presents a systematic evaluation of how washing conditions (temperature, time, and NaOH concentration) and melt filtration affect the quality of recyclates from three industrially relevant PE waste streams: food‐grade stretch film (rPE LLD), post‐consumer PE low‐density (rPE‐LD), and mixed PE films (rPE mix). Unlike previous studies, this work combines laboratory‐scale washing and twin‐screw extrusion, including single and double melt filtration, with comprehensive material characterization. Results reveal that washing significantly influences melt mass‐flow rate (MFR), oxidation onset temperature (OOT), and tensile strength positively and negatively, while melt filtration primarily improves optical quality and reduces volatile organic compounds (VOCs). Puncture resistance was largely unaffected. The most substantial property differences stem from the heterogeneity of the input streams. These findings demonstrate that tailored washing, using cold water without NaOH for rPE‐LLD, NaOH‐assisted cold washing for rPE‐LD and rPE mix, can enhance quality while minimizing degradation. A second melt filtration step is recommended when optical clarity is critical, though its thermal impact must be considered. This study provides guidance for industrial recyclers seeking to optimize process settings based on input stream characteristics and application‐specific quality requirements.

Sorting is crucial for the recyclability of plastic packaging waste, yet flexible packaging poses challenges due to factors like low film mass, color variations, and multi-layer structures. This study assessed the impact of sorting quality on recyclate properties by analyzing four sorting grades. Grade 1 was compiled based on the composition of commercial wastes in Upper Austria. Composition analysis showed that Grades 2 and 3 had high polyethylene (PE) film content (87.1% and 84.0%, respectively), while Grade 4 had significantly less (59.6%) and higher contamination levels (23.2% vs. 7.0% in Grade 2). Mechanical recycling and characterization revealed that better sorting improved recyclate properties. Oxidation onset temperature (OOT) remained stable across Grades 1 to 4. Density decreased from Grade 1 to Grade 4. Transparency declined with increasing contamination, with Grade 4 exhibiting 3,510 inclusions/m ² compared to 250 inclusions/m ² in Grade 1. Mechanical properties, such as strain and stress, also decreased from Grade 1 to Grade 4, as larger inclusions (300–599 µm) in poorly sorted grades disrupted the polymer matrix and reduced tensile strength. Comparisons with three commercial recyclates highlighted the superior quality of well-sorted materials. This study demonstrates that improved sorting enhances recyclate quality, emphasizing the need for advancements in sorting technologies, optimized waste collection systems, and increased market demand for recyclates to support a circular economy. Graphical abstract

Due to the diversity of plastic film waste streams available on the market and the associated variety of contaminants’ size and number, the use of melt filtration is necessary. Currently, single and double filtration systems are state of the art in the plastic recycling industry, depending on the application of the produced post-consumer recyclate (PCR). Using PCR for thin films demands small contamination sizes, which are easier to reach using a second filtration step. In the case of relatively clean post-consumer input materials, it must be investigated whether the additional load from the second filter has a counterproductive effect on the material and whether single filtration would be sufficient. For this paper, polyethylene (PE) film waste stemming from a separate post-consumer collection in Austria was processed using an industrial-sized recycling machine with different combinations of filter sizes and systems. Melt flow rate (MFR), ash content, oxidation onset temperature (OOT), and optical contaminant detection were measured to investigate the influence of single and double filtration systems. The investigation showed that, even though the contamination amount and size were reduced, the second filter had a distinct effect on specific properties.

The production of plastic recyclates is becoming an increasingly feasible and common practice within the industry. Nevertheless, these materials are frequently downcycled for use in applications of reduced value. To bridge the gap between recyclate properties and end-use requirements in flexible packaging, this study investigates the systematic blending of three distinct post-consumer polyethylene (PE) flexible film packaging waste streams with virgin PE materials (low-density and linear low-density). A comprehensive characterization using melt mass-flow rate, oxidation onset temperature, transparency, tensile properties, and puncture properties was conducted on the modified recyclates. Additionally, three commercially available polyethylene-based recyclates and five commercial products containing these recyclates were investigated. The study employs a systematic approach to evaluate the properties of both lab-created and commercial recyclates, as well as those of commercially available flexible film packaging. In light of these findings, recommendations are put forth for the targeted applicability of the recyclates. Results show that key mechanical and optical properties improve with increasing virgin content, though in several cases, up to 80% recyclate content still met or exceeded property requirements for target applications. By enhancing the properties of the recyclate and enabling precise classification for specific applications, this research proposes optimized material formulations and targeted market applications, thereby facilitating the expansion of the scope and value of recycled plastics in the circular economy.