Applications of chitin and cellulose based materials as sustainable plastics
Satam, Chinmay C.
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Plastics waste is a land management and logistical problem, with difficulties in recycling packaging being of particular concern. A composite barrier material was developed by spray coating chitin nanofibers (ChNFs) and cellulose nanocrystals (CNCs) onto poly(lactic acid) (PLA). The resulting renewable flexible film had similar barrier properties to poly(ethylene terephthalate), with oxygen permeability of 19.6 cm3-µm/m2/day/kPa, resulting from structures driven by synergistic interactions of ChNFs and CNCs. Films formed from blended ChNF and CNC aqueous suspensions were investigated in order to determine whether synergy between the components leads to optimal mechanical and barrier properties. Solution cast films from CNCs were found to have higher oxygen permeability (OP) than deacetylated ChNF films. Addition of 25 wt. % ChNFs to CNCs resulted in an OP reduction by 87 % to a value of 1.7 cm3-µm/m2/day/kPa similar to that of pure deacetylated ChNF films. These developments allow lowering the amount of ChNFs used in the ChNF-CNC formulations without significant impact to barrier properties if deacetylated ChNFs were used. Additionally, the homogenization process for the ChNF manufacture was optimized through controlled deacetylation. The resulting surface cationization allowed ChNFs to be homogenized in 8 passes as opposed to 30 passes at a lower pressure of 551 bar. Deacetylated material had similar barrier properties, higher light transmission (up to 85 %T) and showed 164 % and 162 % improvement in tensile strength and strain at break, respectively. Finally, a hybrid film was produced using chitosan, cellulose derived poly(glucuronic) acid and polyethylene glycol, which exhibited high oxygen barrier (0.2 cm3-µm/m2/day/kPa) and polymer-like water vapor permeation (8.2 g-mm/m2/day). This material takes advantage of reactions between chitosan and carboxylic acid groups on poly(glucuronic acid) that could form the basis for a new class of biodegradable materials. In summary, these developments contribute to optimization of renewable bio-based nanomaterial blends to produce alternative barrier packaging that could be produced in a circular manner at a lowered cost.