Aqueous-Based Recycling of Cellulose Nanocrystal/Chitin Nanowhisker Barrier Coatings

Abstract

Multilayer films consisting of nanocellulose and nanochitin as oxygen barrier coatings and a conventional petroleum-based moisture barrier plastic as the substrate have been widely studied for food packaging applications. A challenge with enabling recycling of such hybrid multilayer materials is separating the coating from the substrate. In this work, we studied multilayer films consisting of poly(ethylene terephthalate) (PET) as a model substrate with chitin nanowhiskers (ChNWs) and cellulose nanocrystals (CNCs) as bilayer barrier coatings. Dissolution in aqueous media at different pH values was utilized for coating removal. PET coated with bilayers of recycled CNC and ChNW had an oxygen permeability (OP) of 6.6 cm 3 •μm/m 2 /day/kPa. It had a 27% increase compared to PET with the original bilayer coatings (5.2 cm 3 •μm/m 2 /day/kPa) while still provided a 62% reduction compared to uncoated PET (17.3 cm 3 •μm/m 2 /day/ kPa). Additionally, single-layer coatings of CNC were recycled for up to three runs, and no significant difference was found in the OP values for the films with recycled CNC coatings. This study demonstrates a pathway for recycling of the relatively expensive coating, which may provide a more sustainable solution for production of food packages.

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