Gap Effects in a Rheometrical Flow of a Hydrophobically Associating Polymer Solution: Apparent Slip or Material Instability?

Abstract

In this paper, we study gap effects and apparent slip phenomena in a torsional flow of a moderately concentrated hydrophobically modified associative polymer solution.Slip is investigated by varying the gap between concentric parallel disks, and the plate surface roughness.The onset of apparent slip is shown to occur when the associative network is destroyed, and the slip velocity to increase with increased shear stresses in the strong shear-thinning region of the flow curve.The apparent slip phenomenon is shown to be due to the associative character of the polymer solution; it has been attributed to the existence of clusters of associating polymers (microgels),which behave like soft particles in a low viscous dispersing medium once the associative network is destroyed.Apparent slip can be eliminated by using measuring plates with roughness of about 100µm, that is of the order of the characteristic size of the microgels.

Laponite Dispersions in the Presence of an Associative Polymer

“…The hydrophobic substituents are randomly distributed along the macromolecular backbone, and the average number of alkyl groups per chain is expected to lie between 0 and a few tens . The rheological properties of these polymers were thoroughly studied at different concentrations and under different experimental conditions. − …”

“…19 The rheological properties of these polymers were thoroughly studied at different concentrations and under different experimental conditions. [20][21][22][23] HPG and HMHPG/Laponite Dispersions. All samples tested in this work were prepared by following the same protocol: in a first step, a 6000 ppm polymer solution and a 4 × 10 -2 % Laponite suspension were prepared at room temperature and at a fixed ionic strength of 10 -3 M in NaCl.…”