Thermo-compression molding of chitosan with a deep eutectic mixture for biofilms development

A eutectic mixture of choline chloride (ChCl) and citric acid (CA) was successfully used for the preparation of chitosan (Chit) bio-films by thermo-compression molding. Optimization of the film preparation conditions was carried out using response surface methodology and a Box-Behnken design based on the best mechanical properties and lowest energetic requirements (lower compression load and time). The optimum film, made with chitosan and ChCl-CA (eutectic mixture), was compared with films prepared using only CA in their formulation. Chit-ChCl-CA films presented higher elasticity, opacity and total color difference, and a lower tensile strength in relation to the Chit-CA films. Films prepared with the eutectic mixture presented higher water vapor permeability values. These results were associated with the films microstructures. FTIR analysis confirms the occurrence of chemical changes in the processed films. The thermo-compression process significantly affects the crystallinity of the pristine chitosan. The films thermal stability is depressed when compared to the stability of each component.