Advancing Renewable Barrier Packaging with Lignocellulosic and Chitinous Biomaterials

There is strong interest in the introduction of renewable sources of packaging into global society. In particular, flexible barrier packaging and coatings are of interest due to their prevalence in the supply chain, e.g., at least 40% of all packaging is nonrenewable/nonrecycled flexible plastic. Forest-derived cellulose nanocrystals (CNCs) are a promising renewable source, and have been shown to be coatable as films with high oxygen barrier properties. Generally, CNCs are derived by acid hydrolysis processing that leaves pendant sulfate groups, imparting negative charge in aqueous media. Recent work in our group has shown that combining anionic CNCs with renewably sourced cationic nanofibers is a promising approach to developing manufacturable barrier films. Notably, chitin nanofibers (ChNFs) and nanowhiskers (ChNWs), which can be derived from renewable sources including crustacean food waste and fungi, are cationic and form complexes with CNCs that lead to dense barrier films. This talk describes recent innovations in optimizing the synergy between ChNWs and CNCs through careful tuning of the ChNW density and length. We find that optimal deacetylation of the ChNWs leads to formation of layered ChNW/CNC structures with oxygen permeability lower than poly(ethylene terephthalate) (PET), and blended ChNW/CNC structures that have permeability near poly(ethylene-co-vinyl alcohol) (EVOH). We also explore the use of thermal treatment and deposition temperature to further improve the film structures. These bilayers and blends have been applied to a variety of renewable and biodegradable substrates, such as poly(lactic acid) (PLA) and cellulose acetate (CA), as well as recyclable films like poly(ethylene terephthalate) (PET). We will discuss methods to improve the water vapor transport rates of these materials that include thermal and chemical treatments, as well as substrate pairing. Finally, we will discuss data that illustrate the biodegradability of these structures and the potential for recycling and upcycling.