Performance Evaluation of Compression‐Molded Recycled Mixed Plastic Fractions From Light Packaging

ABSTRACT

Post‐consumer plastic bottle caps represent a relevant but highly heterogeneous polyolefin waste stream, mainly composed of polyethylene (PE) and polypropylene (PP), whose mixed nature hinders conventional recycling routes. In this study, the composition variability, mechanical performance, and recyclability of mixed bottle‐cap fractions from light packaging waste were investigated. Three batches collected at different times were characterized in terms of polymer composition, melt flow index, and mechanical behavior, and compared with corresponding virgin blends. Subsequently, a closed‐loop mechanical recycling study up to 10 cycles was performed on selected materials using compression molding to evaluate the evolution of mechanical, thermal, and rheological properties. The results reveal significant batch‐to‐batch variability in PE/PP ratio and melt flow behavior, which directly affects mechanical performance. Despite these variations, tensile and flexural properties of recycled materials remain within functional ranges, while impact strength is identified as the most sensitive parameter to degradation and heterogeneity. Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) further confirm good thermal stability, with stable melting and degradation temperatures throughout recycling cycles. In parallel, melt flow rate (MFR) measurements show controlled changes in processability, indicating moderate chain scission without abrupt loss of recyclability. Overall, this work demonstrates that mixed bottle‐cap waste can be mechanically recycled in a closed loop via compression molding without severe deterioration of key properties. The proposed experimental framework provides a practical and transferable approach for evaluating the recyclability of heterogeneous polyolefin fractions from light packaging waste, particularly in regions with limited sorting capabilities.