Hydrated salts as both solvent and plasticizer for chitosan

Some hydrated salts were determined to act as both solvent and plasticizer for chitosan. Chitosan was dissolved in aqueous salt solutions of high-valent cations (aluminium(III), iron(III) and chromium(III)) and dissolved almost completely in aqueous salts containing 3.10 mmol salts/g chitosan. Hydrated salts plasticized chitosan and aqueous aluminium(III) chloride/chitosan solution yielded plasticized films with the highest maximal tensile stress and elongation at break point, 71.9 MPa and 275%, respectively. The humidity dependence of dynamic viscoelastic properties and water content suggests that water plays an important role in the plasticization of chitosan and the water content required for such is approximately 20 wt.%. The addition of hydrated salts accelerates plasticization of chitosan, because sufficient water is available due to the presence of the salts.