Please use this identifier to cite or link to this item: http://hdl.handle.net/2445/24848
Title: Shear thinning and thixotropy of HMHEC and HEC water solutions
Author: Maestro Garriga, Alicia
González García, Ma. Concepción
Gutiérrez González, José María, 1953-
Keywords: Reologia
Viscositat
Revestiments
Tixotropia
Rheology
Viscosity
Coatings
Thixotropy
Issue Date: 2002
Publisher: The Society of Rheology
Abstract: Steady state viscosity and thixotropy of hydrophobically modified hydroxyethyl cellulose HMHEC and nonassociative cellulose water solutions are studied. Although all the samples are shear thinning, only the HMHEC is thixotropic, since the migration of hydrophobes to micelles is controlled by diffusion. The Cross model fits steady state curves. The Mewis model, a phenomenological model that proposes that the rate of change of viscosity when the shear rate is suddenly changed is related to the difference between the steady state and current values of viscosity raised to an exponent, fits structure construction experiments when the exponent, n, is estimated to be around 2. The Newtonian assumption used by Mewis cannot be used here, however. This seems to be related to the fact that the thickening is due to bridged micelle formation, which is a slow process, and also to topological constraints and entanglements, which are rapid processes. The kinetic parameter was redefined to kn in order to make it independent of initial conditions. So, kn depends only on how the shear affects the structure. kn reaches a plateau at shear rates too low to produce structure destruction and decreases at higher shear rates.
Note: Reproducció del document publicat a: http://dx.doi.org/10.1122/1.1516789
It is part of: Journal of Rheology, 2002, vol. 46, p. 1445-1457
Related resource: http://dx.doi.org/10.1122/1.1516789
URI: http://hdl.handle.net/2445/24848
ISSN: 0148-6055
Appears in Collections:Articles publicats en revistes (Enginyeria Química i Química Analítica)

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