(673h) Synergistic Interactions of Chitin Nanofibers and Cellulose Nanocrystals in Blended Films with Enhanced Barrier Properties
Petroleum derived plastics are a huge environmental concern today due to their low biodegradability combined with the increased environmental impact associated with the use of petroleum. Of particular concern is the accumulation of waste plastics in oceans and landfills, which causes environmental, land management and logistical problems. In 2018, we developed a 100% bio-based composite barrier material by spray coating chitin nanofibers (ChNFs) and cellulose nanocrystals (CNCs) onto poly(lactic acid) (PLA). The resulting flexible film had similar barrier properties to poly(ethylene terephthalate), but with the added benefit of renewability and compostability. To investigate the synergistic interactions between ChNFs and CNCs we explored free standing films formed by solution casting ChNFs and CNC blends from aqueous suspension. The unique aspect of this study is that two different kinds of ChNFs with high and low degrees of deacetylation were studied. Another unique aspect of this study is that blends over the range of compositions from 0 to 100 wt% of chitin and cellulose were investigated. The solution-cast films were analyzed for their light transmission, oxygen barrier properties and mechanical properties, which have not been previously reported in literature for these particular systems. We found that solution cast films from CNCs had higher oxygen permeability than deacetylated ChNF films. On addition of 25 wt % ChNFs to CNCs the oxygen permeability of the resultant films was reduced by 87 % and was similar to that of pure deacetylated ChNF films. Furthermore, undeacetylated ChNF films were found to have 4 times the oxygen permeability as compared to deacetylated ChNF films but the oxygen permeability was still lower than CNC films. Addition of 50 wt % undeacetylated ChNFs to CNCs was found to lower the oxygen permeability of the films by 90 % and was similar to blended films of CNCs with 25 wt % deacetylated ChNFs. The blended films of undeacetylated ChNFs and CNCs were found to have lower oxygen permeability than their pure solution cased ChNF counterpart. In addition, the tensile strength and strain at break of blended ChNF-CNC films was better than their pure CNC film counterparts and the improvement was seen with the use of both deacetylated and undeacetylated ChNFs. These developments indicate that the amount of ChNFs used in the spray coated multilayer ChNF-CNC-PLA composite films can be lowered without significant impact to barrier properties if deacetylated ChNFs are used. This brings ChNF-CNC multilayer films closer to commercialization and towards replacing some plastics in food packaging with more renewable materials that are compostable and can be produced in a circular manner.