Defining quality by quantifying degradation in the mechanical recycling of polyethylene

• Published in: Nature communications 2024-10, Vol.15 (1), p.8733-8, Article 8733
• Main Authors: Patel, Arpan D., Schyns, Zoé O. G., Franklin, Thomas W., Shaver, Michael P.
• Format: Article
• Language: English
• Subjects: 639/301/923/1028; 639/301/923/1029; 639/638/298/923/1028; Chain branching; Chain scission; Circular economy; Construction industry; Control methods; Degradation; Environmental degradation; Extrusion; High density polyethylenes; Humanities and Social Sciences; Manufacturing; multidisciplinary; Packaging; Polyethylene; Polymerase chain reaction; Polymers; Polyolefins; Quality control; Raw materials; Recyclability; Recycled materials; Recycling; Reprocessing; Rheological properties; Rheology; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-52856-8

Polyolefins have a multitude of uses across packaging, automotive and construction sectors. Their resistance to degradation during reprocessing enables recyclability, but variability in recycled polymer feedstocks renders it difficult to assure their manufacturing suitability. The lack of quality control methods has disabled circular economy pathways; product failure is costly, wasteful and time-intensive. Using rheology-simulated and extrusion-based recycling experiments, we explore the degradation pathways of high-density polyethylene (HDPE). Chain scission dominates during the initial degradation of HDPE, and increasing exposure to O 2 shifts the dominant mechanism to long-chain branching. Importantly, extending this method to post-consumer recyclate (PCR), the results show potential as a methodology to assess recyclate quality to enable a circular plastics economy. In this study, we establish the validity of this rheology simulation to define a characteristic degradation parameter, relating it to the structural evolution under different environments defined for virgin HDPE and post-consumer recyclate (PCR). Polyolefins are used across packaging, automotive and construction but variability in recycled polymer feedstocks renders it difficult to assure a consistent manufacturing quality. Here, the authors use rheology-simulated and extrusion-based recycling experiments to explore the degradation pathways of high-density polyethylene and present a rheology-based method to assess the quality of the recycled material.