New measurements of the flow-curves for Carbopol dispersions without slip artefacts

Abstract

The thickening properties of many commercial thickeners are difficult to measure because of wall slip artefacts. Here we report a series of experiments on a typical thickener where these artefacts have been successfully eliminated. As a result, complete, steady-state flow-curves of aqueous Carbopol 980 (the toxicologically preferred version of the older and more well-known Carbopol 940) dispersions are reported for a range of concentrations of 0.045–1.0 wt%. The vane-and-basket flow geometry was used to avoid slip problems at low shear stress, with the geometry housed in a TA AR1000-N controlled-stress rheometer, whilst a Haake RV2 viscometer with an SV2P and MV2P concentric-cylinder geometries were used at higher shear rates. The flow-curves obtained show a smooth but steep transition from a very high Newtonian viscosity at low shear stress to a much lower viscosity at high shear stress. No real yield stresses were detected, but the higher shear rate results can be fitted to the Herschel-Bulkley model, which assumes an apparent yield stress. The various model parameters are displayed as a function of Carbopol concentration.

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Received: 29 November 2000/Accepted: 26 February 2001

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Roberts, G., Barnes, H. New measurements of the flow-curves for Carbopol dispersions without slip artefacts. Rheol. Acta 40, 499–503 (2001). https://doi.org/10.1007/s003970100178

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  • Key words Wall slip
  • Carbopol
  • Dispersion
  • Herschel-Bulkley
  • Vane
  • Controlled-stress rheometer