The flow behavior,thixotropy and dynamical viscoelasticity of N,O- carboxymethyl chitosan solutions

The flow behavior,thixotropy and dynamical viscoelasticity of N,O- carboxymethyl chitosan solutions were measured by steady- shear and small- amplitude oscillatory experiments,respectively.Power- law and Cross models were used to analyze the flow properties of the systems. The results showed that N,O- carboxymethyl chitosan solutions exhibited two different flow behaviors due to the variation of concentration. When the N,O-carboxymethyl chitosan solutions was in low concentrations( 0.01% ~ 1%),the systems exhibited obvious characteristics of Newton fluid.However,shear- thinning regions were observed and found to be well correlated to the Cross model for high concentrations of N,O- carboxymethyl chitosan solutions( 5% ~15%).The variation of the hysteresis loops area suggested a stronger thixotropic behavior as the polymer concentration increased.Dynamical viscoelastic properties showed a transition from fluid- like( G″ > G') to gel- like( G' > G″) structure with the increase of frequency,and the appearance of cross point was dependent on the concentrations of N,O- carboxymethyl chitosan solutions.