Recycling of unsorted post-consumer polyethylene and polyethylene terephthalate via mechanochemical compatibilization for food packaging

Abstract

The rising accumulation of plastic waste from packaging materials poses a severe environmental threat, emphasizing the need for advanced recycling technologies to repurpose post-consumer (PC) polymers effectively. Conventional mechanical recycling methods for plastic waste treatment involve sorting, chopping, cleaning, and melt-reprocessing. However, packaging materials often consist of multiple tightly adhered polymer layers that are difficult to separate completely. As a result, incompletely sorted mixtures of PC polymers undergo meltreprocessing, typically producing recycled products with inferior material properties unsuitable for reuse. To address this limitation, an advanced recycling approach enabling in situ compatibilization of mixed polymers during melt-reprocessing is essential. In this study, we applied mechanochemistry (MC) and plasma-assisted mechanochemistry (PMC) to reprocess unsorted blends of low-density polyethylene (LDPE) and polyethylene terephthalate (PET). By applying high-energy mechanical forces-and plasma gas in the case of PMC-in a dry environment, these mechanochemical treatments generated covalent linkages between LDPE and PET, forming amphiphilic copolymers that acted as compatibilizers. This enhanced interfacial compatibility resulted in improved mechanical, barrier, and optical properties in the melt-reprocessed blend, making it suitable for reuse as food packaging material. By promoting in situ compatibilization through MC and PMC, our study offers a breakthrough in the mechanical recycling of unsorted, multicomponent PC plastic blends, potentially reducing dependence on virgin polymers and mitigating the environmental impact of plastic waste.