Relation between concentration and shear-extensional rheology properties of xanthan and guar gum solutions (original) (raw)
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Rheological studies of concentrated guar gum
Rheologica Acta, 2003
Polymers and surfactants are essential ingredients of the printing paste. Polysaccharides are used commercially to thicken, suspend or stabilise aqueous systems. Also they are used to produce gels and to act as flocculates, binders, lubricants, to serve as modifiers of film properties, and have a function as adjusters of rheological parameters. Surfactants, on the other hand, perform numerous functions acting as dispersants, wetting agents, emulsifiers and antifoaming agents. The rheological properties of polysaccharide thickeners (guar gums with different substitution levels and different producers) at different concentrations and temperatures and, second, the effects produced by the addition of nonionic surfactants (polyoxyethylene stearyl alcohols with different numbers of EO groups) have been studied under linear and nonlinear shear conditions. Experimental data have been correlated with the different models: flow curves with the Cross, Carreau and Meter-Bird model, and mechanical spectra with the generalized Maxwell model and Friedrich-Braun model. The surface tensions of aqueous systems containing polysaccharide and/or surfactants have been determined over extended concentration ranges in order to detect the CMC conditions and to provide a better understanding about the polysaccharide-surfactant interactions.
Rheological Characterization and Modeling of Aqueous Guar Gum Solutions
2003
The rheological properties of aqueous guar gum solutions have been investigated for different concentrations and temperatures in a cone-and-plate rheometer in the linear and in the non-linear viscoelastic regime. In the linear viscoelastic regime we performed low amplitude oscillato- ry shear experiments to measure the complex modulus. We adopted the time-temperature and the time-concentra- tion superposition principle to increase the
Rheologica Acta, 2009
Mixtures of xanthan and guar gum in aqueous solution were studied in two flow situations: simple shear and porous media. In addition, solids transport in vertical annular flow of sand suspensions was explored. The zero shear rate viscosity of the solutions displayed a pronounced synergy: the viscosity of the mixture is higher than that of the polymer solutions in a wide range of relative concentrations of the two polymers, in agreement with previous literature. However, at relatively high shear rates, the viscosity approaches the value of the more viscous xanthan gum solutions at mass fractions of xanthan gum between 0.1 and 0.15, and the degree of synergy substantially decreases. Stress relaxation experiments in simple shear indicate that the polymer mixtures exhibit a well-defined yield stress after relaxation that is absent in solutions of pure polymers. In porous media flow experiments, a synergistic behavior mimicking the shear flow results was obtained for the polymer mixtures at low shear rates. However, at a critical shear rate, the apparent viscosity in porous media flows exceeds the shear viscosity due to the elongational nature of flow in the pores. The solids transport capacity in annular flows is well-represented by trends in shear viscosity and stress relaxation behavior. However, the lack of viscosity synergy at high shear rates limits the applicability of the mixtures as a way to improve solids suspension capacity in annular flows.
Studies in rheological behaviour of guar gum solution
Macromolecules: An Indian Journal, 2014
Guar gumis one of the largely available polysaccharide which is completely biodegradable, with high water absortion capacity. It is used in large many industrial, cosmetic, food and medical applications. 1 % guar gum solution in water is largely used for making any potential product from guar gum. Guar gum is processed by making a solution of it in dissolved water and subsequently blended or cross-linked or directly asked to prepare a required type of product. Thus, itÂÂs very important to understand the rheology of the guar gum to know its flow behavior during processing. This paper deals with the various rheological characteristics of 1 % guar gum solution in water.
Journal of Texture Studies, 2010
Rheological studies of tragacanth and guar gums dispersions were carried out by means of steady shear (3 to 1000/s) and small amplitude oscillatory shear experiments (0.1 to 10 rad/s) for concentrations up to 8.9 g/L for tragacanth and 7.6 g/L for guar gum at 25C using stress controlled rheometer. The dispersions exhibited shear‐thinning characteristics. A simplified Cross model was adequate to fit the shear‐dependent viscosity behavior for both gums. Model parameters for guar gum were correlated with concentration employing power functions (with flow index constant) and for tragacanth gum the dependence was linear for flow index, power for time constant and exponential for zero‐shear rate viscosity. Mechanical spectra revealed that dispersions behave as dilute systems of coil polymers with trend to entangled systems at the highest concentrations. Loss and storage moduli were correlated with frequency and the resulting parameters were correlated with concentration. Cox–Merz rule hol...