High gas barrier coating using non-toxic nanosheet dispersions for flexible food packaging film

Abstract

One of the major challenges in the circular economy relating to food packaging is the elimination of metallised film which is currently the industry standard approach to achieve the necessary gas barrier performance. Here, we report the synthesis of high aspect ratio 2D non-toxic layered double hydroxide (LDH) nanosheet dispersions using a non-toxic exfoliation method in aqueous amino acid solution. High O2 and water vapour barrier coating films can be prepared using food safe liquid dispersions through a bar coating process. The oxygen transmission rate (OTR) of 12\u2009μm PET coated film can be reduced from 133.5 cc·m−2·day−1 to below the instrument detection limit (<0.005 cc·m−2·day−1). The water vapour transmission rate (WVTR) of the PET film can be reduced from 8.99\u2009g·m−2·day−1 to 0.04\u2009g·m−2·day−1 after coating. Most importantly, these coated films are also transparent and mechanically robust, making them suitable for flexible food packing while also offering new recycling opportunities.Food packaging industry is in search of non-toxic, stable, and recyclable coatings acting as gas-barriers. Here the authors synthesise transparent films meeting these requirements, based on high aspect ratio layered double hydroxide nanosheets obtained by exfoliation in aqueous amino acid solution.