Sustainable Delamination of Multilayer Plastic Films for Advanced Recycling

Abstract

A novel delamination process for multilayer plastic films using supercritical CO₂ is proposed as a sustainable alternative to facilitate their recycling. The method involves exposing the films to pure CO2 or CO2 modified with a small amount of cosolvent under mild conditions (40–80 ºC, up to 200 bar), followed by rapid depressurisation. As proof of concept, the delamination of three commercial films used in food packaging is presented. The starting material and the delaminated layers were analysed by ATR-FTIR, TGA, DSC and SEM microscopy. Multilayer polymer films formed by polyethylene (PE) and polyethylene terephthalate (PET) or PE and Machine Directed Oriented PE (MDO-PE) prepared with polyurethane adhesive (PU) were delaminated at the PET/PU and MDO-PE/PU interfaces. Furthermore, PolyAl from an aseptic beverage carton delaminated partially, releasing a thin PE layer and an aluminium-enriched PolyAl composite. DMSO and methanol showed the highest delamination efficiency among the cosolvents, while acetone and water were ineffective under the conditions studied. A multiple mechanism for the process is proposed: (1) mechanical stress due to CO₂-induced polymer swelling and rapid depressurisation; (2) selective adhesive debonding via cosolvents. Further studies are needed to corroborate the mechanism, validate the process across varied materials, and optimise its performance. This technology could contribute significantly to a more circular and sustainable economy.