Rheological Characterization of Aqueous Polysaccharide Mixtures Undergoing Shear

U. Florjancic, A. Zupancic and M. Žumer

Abstract
We studied the rheological properties of aqueous polysaccharide mixtures, prepared by blending two compatible biopolymers, i.e. sodium carboxymethylcellulose and xanthan, under destructive and non-destructive shear conditions, in order to evaluate synergistic/ non-synergistic effects of mixed polysaccharide systems. The rheological experiments were carried out with the controlled stress rotational rheometer to detect the response of structured samples at low shear stresses. The flow behavior and the viscoelastic properties of polysaccharide systems under shear conditions were examined by applying continuous shear and oscillatory tests at ambient temperature. The empirical analysis of the flow behavior enabled us to evaluate the deviations in the zero shear viscosity, and the intensity of the shear-thinning behavior as determined for investigated binarym mixtures, when compared to the flow behavior of pure component solutions. The mechanical properties of polysaccharide mixtures in the range of the linear viscoelastic response were analyzed with the generalized Maxwell model and the relaxation spectra were determined. The examined mixtures exhibited complex rheological behavior under the shear conditions, regarding the flow characteristics as well as the viscoelastic properties in the linear viscoelastic regime.

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Keywords
Aqueous polysaccharide mixtures, sodium carboxymethylcellulose, xanthan, rheology, shear flow, viscoelasticity