Natural Deep Eutectic Solvent (NADES) as Plasticizer for Bioplastic Film Fabrication. A Comparative Study

Incorporation of chitosan into the bioplastic film could improve its mechanical properties. However, aqueous acidic solution is required to dissolve the chitosan. The aim of the present work was to explore the potential use of acidic NADES as the plasticizer as well as a solvent for chitosan without the addition of aqueous acidic solution. The film-forming solution consisted of sago starch as the matrix and chitosan as the filler was prepared by solution casting and evaporation method in the presence of acidic NADES. Acidic NADES was obtained by mixing choline chloride (ChCl) and lactic acid (LA) as the hydrogen bond acceptor and hydrogen bond donor, respectively. The mechanical properties and water uptake ability of chitosan-reinforced starch-based bioplastic films plasticized with acidic NADES were compared with the bioplastic films plasticized with conventional plasticizer, glycerol in the absence and presence of acetic acid solution. The results revealed that acidic NADES was capable of plasticizing the starch and dissolve the chitosan. Bioplastic film plasticized with acidic NADES achieved higher tensile strength and lower water uptake than the bioplastic film plasticized with glycerol in the presence of acetic acid solution. The interaction between chitosan and acidic NADES was confirmed by Fourier-transform infrared spectroscopy (FTIR). FTIR results exhibited that the amide II band of chitosan in the ChCl/LA film had shifted, and its intensity had decreased to almost undetectable.