Hybrid Chemomechanical Plastics Recycling: Solvent-Free, High-Speed Reactive Extrusion of Low-Density Polyethylene

Shawn Martey, Bennett Addison, Nolan Wilson, Bin Tan, Jianger Yu, John Dorgan, Margaret Sobkowicz

Research output: Contribution to journalArticlepeer-review

15 Scopus Citations

Abstract

Low-density polyethylene (LDPE) is ubiquitous in the packaging industry owing to its flexibility, toughness, and low cost. However, it is typically contaminated with other materials, seriously limiting options for mechanical recycling. Interest in chemical recycling techniques such as pyrolysis and hydrothermal liquefaction is growing, but most of these processes face technoeconomic challenges that have limited commercial deployment. This study concerns a hybrid chemomechanical approach using reactive twin-screw extrusion (TSE) for tailoring the molecular weight and chain structure of reclaimed LDPE. Two types of zeolite catalysts at several loading levels are evaluated over a range of processing conditions. Structural, thermal, and rheological properties of the extruded samples are investigated and compared to virgin LDPE and LDPE extruded without the catalyst. NMR spectroscopy is used to investigate changes in the structure of the polymer. LDPE extruded with microporous Y zeolite shows lower degradation temperature and increased short chain branching. Mesoporous MCM-41 also induces increased branching but has no effect on the degradation temperature. The theoretical mechanical energy input for the chemical modification is calculated by using process modeling. The demonstrated hybrid reactive extrusion process provides a potential low-cost, simple approach for repurposing LDPE-based flexible packaging as coatings and adhesives.

Original languageAmerican English
Pages (from-to)4280-4290
Number of pages11
JournalChemSusChem
Volume14
Issue number19
DOIs
StatePublished - 2021

Bibliographical note

Publisher Copyright:
© 2021 Wiley-VCH GmbH

NREL Publication Number

  • NREL/JA-2800-80337

Keywords

  • heterogeneous catalysis
  • plastic recycling
  • polyethylene
  • twin-screw extrusion
  • zeolites

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