Preparation, characterization, mechanical and barrier properties investigation of chitosan–clay nanocomposites

• Chitosan/clay nanocomposites with the novel “reflux-solution” method was obtained.
• Clay induces significant reinforcing and barrier effects in the chitosan systems.
• Dilution of chitosan solution improves chitosan's crystallinity in prepared samples.
• Reflux treatment improves mechanical and water barrier properties.

In the current study the effect of dilution of chitosan acetate solution and of the use of a reflux-solution method on the morphology, the mechanical and water barrier properties of chitosan based nanocomposites is being investigated. Two series of nanocomposite films from two chitosan acetate solutions with 2 w/v% and 1 w/v% in chitosan were prepared, with 3, 5 and 10 wt% Na-montmorillonite (NaMMT) and/or 30 wt% glycerol. Intercalation of NaMMT was more effective in films based on 2 w/v% solutions which presented decreased hydrated crystallinity. Upon NaMMT addition an enhancement was found in stiffness and strength (up to 100%) and a remarkable decrease in the elongation at break (up to 75%) and water vapor permeability (WVP) (up to 65%). This enhancement was less pronounced in 1 w/v% systems. Addition of glycerol had a negative effect on the stiffness, strength and WVP, and a positive effect on the elongation at break and the absorbed water. Compared with the conventional solution cast method, the reflux treatment led to a significant improvement of the tested properties of nanocomposite films.