Effects of lactic acid and mixed acid aqueous solutions on the preparation, structure and properties of thermoplastic chitosan

Rheological and Film-Forming Properties of Chitosan Composites

Chitosan (Chit) and its composite films are widely used in biomedical, cosmetic, and packaging applications. In addition, their properties can be improved and modified using various techniques. In this study, the effect of the type of clay in Chit composites on the structure, morphology, and physical properties of Chit solution and films was tested. The liquid flow properties of Chit solution with and without clay were carried out using the steady shear test. Chit films containing clay were obtained using the solution-casting method. The morphology, structure, and physical properties of the films were characterized by scanning electron microscopy, atomic force microscopy, infrared spectroscopy, swelling behavior, and tensile tests. The results reveal that for the Chit solution with clay (C1) containing 35 wt.% dimethyl dialkyl (C14-C18) amine, the apparent viscosity is the highest, whereas Chit solutions with other clays show reduced apparent viscosity. Rheological parameters of Chit composites were determined by the power law and Cross models, indicating shear-thinning behavior. Analytical data were compared, and show that the addition of clay is favorable to the formation of intermolecular interactions between Chit and clay, which improves in the properties of the studied composites.

Microstructure and properties of thermomechanically processed chitosan citrate-based materials

The traditional solvent casting method for preparing chitosan-based materials has limited productivity relative to the productivity of thermomechanical processing. Consequently, the thermomechanical processing technique was evaluated as a way to increase chitosan production. The role of citric acid (CA) as a destructuring and crosslinking agent during such processing was examined. SEM images revealed robust fibers that were associated with a superior mechanical strength (145%), which were produced after thermomechanical processing of chitosan in the presence of CA. Based on articles reviewed, this is the first time that this structure has been closely observed in the microstructure of chitosan-based materials. FTIR and XRD characterization showed the occurrence of chemical crosslinking and the successful destructuring of chitosan powder by CA during processing. Compared to acetic acid, the use of CA led to the development of materials with a homogeneous morphology and good physicochemical and mechanical properties that are suitable for biomedical applications.

Laccase-Catalyzed Grafting of Lauryl Gallate on Chitosan To Improve Its Antioxidant and Hydrophobic Properties

Biografting is a promising and ecofriendly approach to meet various application requirements of products. Herein, a popular green enzyme, laccase, was adopted to graft a hydrophobic phenolic compound (lauryl gallate, LG) onto chitosan (CTS). The resultant chitosan derivate (Lac/LG-CTS) was systematically analyzed by Fourier transform infrared (FTIR), grafting efficiency, scanning probe microscopy (SPM), and X-ray diffraction (XRD). This grafting technique produced a multifunctional chitosan copolymer with remarkably enhanced antioxidant property, hydrophobicity, and moisture barrier property. Furthermore, the swelling capacity and acid solubility of the copolymer film decreased significantly, although the tensile strength and elongation were slightly weakened as compared to those of native chitosan. These results suggest that the Lac/LG-CTS holds great potential as a food-packaging material, preservative agent, or edible coating material.