Structure and properties of glycerol-plasticized chitosan obtained by mechanical kneading

This paper reports the elaboration of plasticized chitosan by thermo-mechanical treatment, as a possible alternative route to solvent casting, and the corresponding material properties. Glycerol was used as plasticizer with a concentration fixed at 25 wt.%. The water uptake, crystallinity evolution, mechanical and dynamic-mechanical thermal properties were studied during the post-processing ageing at different relative humidities. The properties of plasticized chitosan were compared with those of glycerol-free samples. For instance, increased elongation at break (+40%) is observed with plasticized chitosan. Like most plasticized polysaccharides, the material properties are strongly impacted by water content. The water uptake measurements evidenced that the hydrophilic character of the material is enhanced by the addition of glycerol. Both tensile tests and DMTA results confirm the plasticizing effect of glycerol and water. The analyses evidenced that several weeks of controlled storage are required to reach stabilized properties. The best results are obtained for materials stabilized in a medium relative humidity atmosphere (57% RH).