Shear‐rate dependent viscosity of dilute polymer solutions

Abstract

SynopsisShear-thinning viscosities have been investigated for dilute solutions (c < c*) of high-molecular weight polymers, namely, poly(ethylene oxide) (PEO) and polyacrilamide in water and polyisobutylene in kerosene. Measurements have been performed using capillary viscometers and a Zimm-Crothers viscometer with rotors having angular velocities of different magnitude. Shear rate was varied within the range of 0.1-3000 s-I. This made it possible to obtain full curves of viscosity versus shear rate. Owing to a high measurement accuracy, significant data were obtained using concentrations as low as 5 ppm. For the PEO solutions, the shear-rate dependence of viscosity was investigated as a function of concentration and temperature of the solution as well as molecular weight of the dissolved polymer. The data were compared with theoretical predictions based on the idea of molecular dispersion of the polymer in the solution at low concentrations. Experimental results were found to deviate significantly from the theory and this is explained by supermolecular organization characteristics of the high-polymer solutions even at low concentrations. A parameter was introduced: the relative amplitude of the shear-thinning viscosity. This parameter is important for describing hydrodynamic behavior of the polymer solutions.

Iterated stretching, extensional rheology and formation of beads-on-a-string structures in polymer solutions

“…The measurements (described in detail below) give a fluid relaxation time of λ ≈ 0.23 ± 0.02 s for a concentration of 2000 ppm. We have performed additional rheological experiments with different polymer concentrations and find that the relaxation time and the polymeric contribution to the viscosity both exhibit a dependence on concentration that scales approximately as √ c in agreement with other measurements in dilute and semidilute aqueous solutions [42,43].A s the concentration is varied, the dimensionless parameters S,Oh and De -which are relevant to formation of beads-on-a-string structure -also vary. At higher polymer concentrations, the increase in the fluid viscosity (and the correspondingly larger value of Oh) results in an axially uniform and long-lived filament of the shape observed in capillary-thinning experiments with highly elastic Boger fluids [28,44] and no bead formation.…”

Rheological characterization of poly(ethylene oxide) solutions of different molecular weights

“…Steady shear viscosity, normal stress difference and linear viscoelastic material functions were found to collapse onto master curves independent of concentration and temperature. Shear-thinning viscosities of dilute solutions (concentrations as low as 5 ppm) of high molecular weight PEO have been investigated as a function of concentration and temperature of the solution and molecular weight of the polymer, by Kalashnikov [11]. Briscoe and co-workers reported the effects of pressure and temperature on the rheological behavior of PEO aqueous solutions, with and without added inorganic salts [12] and in water-based solvents, namely, ethanol-water mixtures and electrolyte solutions [12,13].…”

Influence du polyéthylène oxyde (PEO) de différentes masses moléculaires sur les propriétés rhéologiques des suspensions d’argile

“…Ces résultats (rhéogrammes des solutions de polyéthylène oxyde) concordent avec ceux obtenus antérieurement par d'autres chercheurs (Briscoe et al, 1998 ;Gauri et Koelling, 1997 ;Kalashnikov, 1994 ;Kang et al, 2005 ;Ortiz et al, 1994 ;Powell et Schwarz, 1975 ;Powell, 1979).…”