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

Multilayer films consisting of nanocellulose and nanochitinasoxygen barrier coatings and a conventional petroleum-based moisturebarrier plastic as the substrate have been widely studied for foodpackaging applications. A challenge with enabling recycling of suchhybrid multilayer materials is separating the coating from the substrate.In this work, we studied multilayer films consisting of poly(ethyleneterephthalate) (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 forcoating removal. PET coated with bilayers of recycled CNC and ChNWhad an oxygen permeability (OP) of 6.6 cm(3)& BULL;& mu;m/m(2)/day/kPa. It had a 27% increase compared to PET with the originalbilayer coatings (5.2 cm(3)& BULL;& mu;m/m(2)/day/kPa)while still provided a 62% reduction compared to uncoated PET (17.3cm(3)& BULL;& mu;m/m(2)/day/kPa). Additionally,single-layer coatings of CNC were recycled for up to three runs, andno significant difference was found in the OP values for the filmswith recycled CNC coatings. This study demonstrates a pathway forrecycling of the relatively expensive coating, which may provide amore sustainable solution for production of food packages. This work proposes a facile aqueous-basedmethod for theremoval of the bilayer barrier coatings from a plastic substrate,which enables the reuse of the coatings.