Advanced Renewable Cellulose Nanocrystal and Chitin Nanofiber Barrier Packaging

Plastic waste is one of the most prominent materials impacting the environment and human health due to the inability to recycle or the difficulty of recycling and the release of toxins in the form of microplastics. To this end, there is a critical need to develop highly functional bioderived materials for applications such as food packaging, which is the most significant contributor to unrecyclable or difficult-to-recycle plastic waste. Cellulose nanocrystals (CNCs) and chitin nanofibers (ChNFs) are two biologically sourced materials that can be used to create biodegradable and sustainable oxygen and moisture barrier materials that are comparable to widely available barrier layers such as polyethylene terephthalate (PET). In this talk, we will discuss how the functionality of CNC and ChNF barrier thin films can be enhanced through material synthesis and manufacture. Attention will be paid to the process-structure-property relationships of the barrier thin film. Here, we demonstrate the viability of dual layer slot die coating of CNC/ChNF bilayers onto cellulose acetate (CA) substrates when compared to spray coating. It was observed that the dual layer slot die coating on a roll-to-roll system that applies the bilayer in a single pass enables a significantly lower oxygen permeability versus spray coating. It has been found that spray coated bilayer thin films were on average 25% thinner than the dual layer slot die coated bilayer film. However, the thickness-normalized oxygen permeability (OP) of the dual layer slot die coated ChNF/CNC bilayer thin film on CA was 20 times better than that of the spray coated bilayer thin films. OP values for the slot die coated bilayer thin films under optimized drying conditions were as low as 1.2 cm3 μm m(-2) d(-1) kPa, corresponding to an oxygen transmission rate of 0.32 cm3 m(-2) d(-1) at 23 °C and 50% relative humidity. It is also noted that the adhesive properties of the dual layer coating are also improved when the barrier thin film is air dried. Challenges to industrial implementation and approaches to overcome these will also be analyzed.