Characterization of chitosan in acetic acid: Rheological and thermal studies

摘要

This study examined the influence of temperature,concentration, shearing time, and storage time on the rheologicalproperties, i.e. the dynamic viscosity and shear stress, as a functionof shear rate of chitosan solubilized in weakly acid solutions. Theresults showed that shear thinning behavior (pseudoplasticnon-Newtonian behavior) was pronounced at temperatures from 20 to 50°C, but was more remarkable at lower temperature. In addition, theactivation energy value derived from ln eta vs. 1/T data was foundto be 20.86 kJ mol^{-1}. When the effect of concentration wasstudied, the shear thinning behavior was pronounced at allconcentrations. The effect of shearing time on the dynamic viscosityand shear stress of chitosan solutions did not show any significantdifferences at all shearing times applied in this study. Furthermore,an increase in viscosity was obtained with extending the period ofstorage to 3 months, after which a drop in viscosity was recorded.Thermal properties of chitosan films were also investigated byemploying thermogravimetric analyses (TGA) and differential scanningcalorimetry (DSC) in this work. Results of TGA revealed that thedecomposition of the chitosan film proceeds in 2 distinct stages,which was confirmed with DSC curves.