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Dominique Dupuis, Karim Bekkour, Kaouther Ben Azouz
On the modeling of the rheological behaviour of bentonite dispersions in polymer solutions

Appl. Rheol. 24:2 (2014) 24283 (9 pages)

Bentonite dispersions in polymer solutions may behave as gel like materials. Under stress, the structure formed at rest is progressively destroyed and a solid-liquid transition occurs. The rheological characterization of such kind of systems is often done by applying stress ramps of the sample. A simple Herschel-Bulkley equation is not convenient to fit the answer of the material to the ramp since it does not take in account the effect of time. The models for yield stress fluids involving two viscosity levels are not convenient too since they don.t take in account the elastic behavior at low stresses. We propose in this paper two equations in order to determine some parameters characterizing the rheological behavior of such systems. The results obtained both in oscillatory and permanent shear are compared according to Winter.s representation and a rescaling of the complex modulus is proposed to superimposed the data in the solid/liquid transition region.

Cite this publication as follows:
Dupuis D, Bekkour K, BenAzouz K: On the modeling of the rheological behaviour of bentonite dispersions in polymer solutions, Appl. Rheol. 24 (2014) 24283.

Abdelhakim Benslimane, Karim Bekkour, Pierre Francois
Effect of addition of Carboxymethylcellulose (CMC) on the rheology and flow properties of bentonite suspensions

Appl. Rheol. 23:1 (2013) 13475 (10 pages)

In this work, bentonite suspension and mixtures containing 5 wt% of bentonite and 0.1 and 0.5 wt% of carboxymethyl cellulose (CMC) were investigated in terms of their rheology and hydrodynamic behaviour in pipe flow. All fluids exhibited non- Newtonian rheological behaviour that can be well described by the three parameters Herschel-Bulkley model. The axial velocity distribution was determined using ultrasonic pulsed Doppler velocimetry technique. In the laminar regime the flow parameters were predicted by integration of the constitutive rheological model used. In the turbulent flow, the Dodge and Metzner model was applied to fit the experimental data. The measurements of the friction factor showed a small amount of drag reduction for the pure bentonite suspension, whereas for the polymer.clay blend the drag reduction was more important.

Cite this publication as follows:
Benslimane A, Bekkour K, Francois P: Effect of addition of Carboxymethylcellulose (CMC) on the rheology and flow properties of bentonite suspensions, Appl. Rheol. 23 (2013) 13475.

Mohamed Ilies Bahlouli, Karim Bekkour, Adel Benchabane, Yacine Hemar, Ali Nemdili
The effect of temperature on the rheological behavior of polyethylene oxide (PEO) solutions

Appl. Rheol. 23:1 (2013) 13435 (15 pages)

The rheological properties of polyethylene oxide (PEO) solutions were investigated, at different temperatures, using small and large deformation rheological methods. Steady-state flow measurements showed that the flow behavior of the PEO solutions is well described by the Cross model, which yields the critical concentrations c* (from the dilute regime to semidilute regime) and c** (from the semi-dilute regime to the concentrated regime). In the range of the temperatures investigated here, the apparent viscosity is found to obey the Arrhenius equation below a critical temperature we believe corresponds to the cloud point temperature. Above the cloud point temperature, the viscosity increased with temperature. Similarly below the cloud point, both transient and dynamic tests showed that PEO solutions exhibit viscoelastic behavior, where both the elastic G' and viscous G'' modules increased with the increase in concentration and with the decrease in temperature. The Cox-Merz rule was found to apply to the PEO solutions at temperatures lower than the cloud point temperature, whilst divergence was reported after phase separation. The frequencies at which G' = G'', i.e. the reciprocal of the relaxation times of the temporary polymer network, was found to increase (the relaxation times decline) with decreasing polymer concentration, in agreement with the relaxation times, derived from the Cross model. In essence, this study demonstrates that it is possible to monitor accurately the cloud point temperature of PEO solutions by viscometric analysis.

Cite this publication as follows:
Bahlouli MI, Bekkour K, Benchabane A, Hemar Y, Nemdili A: The effect of temperature on the rheological behavior of polyethylene oxide (PEO) solutions, Appl. Rheol. 23 (2013) 13435.

Kaouther Ben Azouz, Dominique Dupuis, Karim Bekkour
Rheological characterizations of dispersions of clay particles

Appl. Rheol. 20:1 (2010) 13041 (9 pages)

In this work,we consider model fluids which are dispersions of clay particles in aqueous solutions of carboxymethyl cellulose. Their rheological properties are measured in both steady and oscillatory shear flows.We present the experimental results obtained for different polymer concentrations and for three different molecular weights of the polymer. The clay is a bentonite sample and the particle concentration is fixed to a value of 5 %. The mechanical properties of these materials is the result of a competition between different mechanisms: association-dissociation of aggregates of particles, adsorption of polymer on the particles and desorption of solvent molecules from the particles, bridging of the particles by long polymer chains.

Cite this publication as follows:
BenAzouz K, Dupuis D, Bekkour K: Rheological characterizations of dispersions of clay particles , Appl. Rheol. 20 (2010) 13041.

Karim Bekkour, Nadja Kherfellah
Linear Viscoelastic Behavior of Bentonite-Water Suspensions

Appl. Rheol. 12:5 (2002) 234-240

Bentonite are extensively used materials in a wide range of applications. Creep and oscillatory shear experiments in the linear viscoelastic domain were carried out on bentonite-water suspensions at different solid fractions. It was found that bentonite dispersions exhibit important viscoelastic behavior which could be represented by the generalized Kelvin-Voigt mechanical model. It is well known that an exhaustive study of colloidal dispersions may require the determination of its viscoelastic properties over a wide frequency scale. Unfortunately, due to microstructure changes, the experiments are limited in time. In order to avoid such limitation, oscillatory data were deduced from creep curves - without actually vibrating the clay dispersions - because a periodic experiment at frequency w is qualitatively equivalent to a creep test at time 1/w. That is, it was possible to complete the dynamic response in the low-frequency range using data obtained from the transient response in creep.

Cite this publication as follows:
Bekkour K, Kherfellah N: Linear Viscoelastic Behavior of Bentonite-Water Suspensions, Appl. Rheol. 12 (2002) 234.

K. Bekkour, H. Ern, O. Scrivener
Rheological Characterization of Bentonite Suspensions and Oil-In-Water Emulsions Loaded with Bentonite

Appl. Rheol. 11:4 (2001) 178-187

With stress controlled rheometer we investigate the behavior for different concentrations, of paraffin oil-inwater emulsions, bentonite suspensions as well as charged bentonite emulsions. We were particularly interested in how aging affects the rheological properties. Using a structural model, we correlate the macroscopic experimental results to the fluid microstructure characteristic parameters and we calculate the emulsions and suspensions mean characteristic unit size. The comparison of these mean particle diameters with those obtained by microscopy and light-scattering measurements confirms the soundness of such procedure to estimate the structural characteristics, the effective concentrations and the effective mean particle diameter of oil-in-water emulsions and bentonite suspensions.

Cite this publication as follows:
Bekkour K, Ern H, Scrivener O: Rheological Characterization of Bentonite Suspensions and Oil-In-Water Emulsions Loaded with Bentonite, Appl. Rheol. 11 (2001) 178.

Karim Bekkour
Evaluation of Slip Effects in the Capillary Flow of Foams

Appl. Rheol. 9:1 (1999) 10-16

Cite this publication as follows:
Bekkour K: Evaluation of Slip Effects in the Capillary Flow of Foams, Appl. Rheol. 9 (1999) 10.


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