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Characterization of chitosan in acetic acid: Rheological and thermal studies

This study examined the influence of temperature, concentration, shearing time, and storage time on the rheological properties, i.e. the dynamic viscosity and shear stress, as a function of shear rate of chitosan solubilized in weakly acid solutions. The results showed that shear thinning behavior (pseudoplastic non-Newtonian behavior) was pronounced at temperatures from 20 to 50 °C, but was more remarkable at lower temperature. In addition, the activation energy value derived from ln h vs. 1/T data was found to be 20.86 kJ mol-1. When the effect of concentration was studied, the shear thinning behavior was pronounced at all concentrations. The effect of shearing time on the dynamic viscosity and shear stress of chitosan solutions did not show any significant differences at all shearing times applied in this study. Furthermore, an increase in viscosity was obtained with extending the period of storage to 3 months, after which a drop in viscosity was recorded. Thermal properties of chitosan films were also investigated by employing thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) in this work. Results of TGA revealed that the decomposition of the chitosan film proceeds in 2 distinct stages, which was confirmed with DSC curves.