On September 30, 2020, researchers from the University of Manchester in the United Kingdom published a review article in the peer-reviewed journal Macromolecular Rapid Communications. The study “covers the current methods and challenges for the mechanical recycling of the five main packaging plastics: poly(ethylene terephthalate), polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) through the lens of a circular economy.” It provides an overview of the fractions of packaging processed through recycling, energy recovery, and landfilling, as well as collection rates by polymer type. It further introduces some of the key mechanics and chemistry involved in mechanical recycling for each of the polymer types, and it provides an insight into the range of chemical additives used in recycling processes, such as stabilizers, chain extenders, compatibilizers, fillers, and plasticizers.
Concerning chemical recycling, the study suggests that “although both chemical and biological recycling are regarded as ‘green’ recycling methods, full and objective life‐cycle assessments are needed to evaluate their sustainability.” It further comments that its “analysis suggests that mechanical recycling will remain the most effective method to recycle plastics – in terms of time, economic cost, carbon footprint and environmental impact.”
Looking ahead, the review identifies a set of current limitations facing mechanical recycling including “material property deterioration, costs and sorting issues.” It also recognizes issues faced through the chemical additives used in the recycling processes where there is a lack of standards for different polymer grades and insufficient understanding of the role these additives play in affecting the recyclate quality. The authors write that “if we are to justify the continued use of plastics – which we should – we must have better control over their material life cycle and pursue solutions that can maintain their value over repeated uses and reprocessing.”
Schyns, Z. et al. (September 30, 2020). “Mechanical Recycling of Packaging Plastics: A Review.” Macromolecular Rapid Communications