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Author index ►Y. Peysson, T. Aubry, M. Moan

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Phenomenological Approach of the Effective Viscosity of Hard Sphere Suspensions in Shear-Thinning Media

Appl. Rheol.16:3 (2006) 145-151 ►

In this work we investigate the rheological behaviour of macroscopic buoyant hard spheres dispersed in a shearthinning suspending fluid. We focus on the phenomenological study of the influence of the shear-thinning behaviour of the suspending medium on the effective apparent suspension viscosity at different volume fractions. In the oil industry, the effective viscosity concept is widely used and very useful to quickly characterize a change of viscosity due to an increase of the solid content. Viscosity measurements are compared to the effective viscosity of a suspension of hard spheres in an Ostwald fluid. The power law index of the suspending fluid is shown, both experimentally and theoretically, to influence strongly the volume fraction dependence of the suspension effective viscosity. All experimental results are shown to be quite correctly plotted on a master curve, with only one adjustable parameter, the maximum packing fraction φ_m. The best fit is obtained for φ_m = 0.57, corresponding to the theoretical maximum random packing volume fraction.► Cite this publication as follows:

Peysson Y, Aubry T, Moan M: Phenomenological Approach of the Effective Viscosity of Hard Sphere Suspensions in Shear-Thinning Media, Appl. Rheol. 16 (2006) 145.

The effects of composition and resulting morphology on the rheology of thermoplastics filled with different talc platelets were studied in the 0-22% range of volume fraction, F. The sufficiently filled polymer composites exhibit a rheological behavior which significantly differs from the pure polymers used in this work, a linear low density polyethylene, a low density polyethylene and a polyamide 12. The changes in the rheological behavior are influenced by the size, the concentration and the surface treatment of plate-like talc particles. They also depend on the chemical nature and viscous and elastic characteristics of the polymer matrix. In particular, the effect of platelet orientation on the viscoelastic properties of reinforced composites was pointed out. For sufficiently filled systems, a low frequency response indicative of a pseudo solid-like behavior is obtained only during the first frequency sweep. In fact, the low frequency storage modulus, G., is constant. With repeated frequency sweeps, more platelets were aligned in the flow direction, thus the low frequency storage modulus gradually decreases.► Cite this publication as follows:

Mederic P, Moan M, Klopffer M-H, Saint-Gerard Y: Talc filled thermoplastic composites: Melt rheological properties, Appl. Rheol. 13 (2003) 297.

► Cite this publication as follows:

Aubry T, Blonce L, Moan M: Gap Effects in a Rheometrical Flow of a hydrophobically associating polymer solution: apparent slip or material instability?, Appl. Rheol. 10 (2000) 31.

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