Preparation and characterization of chitosan/SiO2 composite films

Composite films made from chitosan, plasticizer, and incorporated silica nanoparticles were evaluated for their mechanical properties, thermal stability, water permeability, and surface characteristics. The influence of the chitosan amino group protonation upon the observed silica effects was also analyzed. Only slight differences between most of the properties of composite films and those of the biopolymer alone were observed. The lack of complete and uniform dispersion of the silica particles within the biopolymer matrix and the absence of relevant polymer-filler interactions in such composite membranes lead to a low level of interaction between the filler and the polymer, and only a reduced effect of the filler on the film properties. The silica effects worthy to mention are the decrease in Young's modulus and the increase in film elongation, and the slight influence on surface hydrophobicity and water vapour permeability, which were dependent on the neutralization pos-treatment process.