Rheology of concentrated microgel solutions

R. J. Ketz, R. K. Prud'homme, W. W. Graessley

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200 Scopus citations


Viscosity, modulus, and yield stress for 0-6 wt% aqueous solutions of Carbopol 941 were investigated using constant shear rate, constant shear stress, and dynamic oscillatory experiments. The microgel character of the polymer was evident from the solid-like behavior of the solutions above 1 wt%. Yield stress increased with concentration, but yield occurred at a critical shear strain of 40%, independent of concentration. The static stress-strain relationship became non-linear at ~ 25% strain, in fair agreement with the onset of non-linear response in the storage modulus at ~ 10% strain. Small strain moduli from static and low frequency measurements agreed rather well; modulus values obtained from the recoverable strain after yielding were 30-40% smaller. Solutions flowed at near-constant stress in the low shear rate regime; at higher rates the stress increases with shear rate more rapidly. The viscosity did not obey the Cox-Merz rule. Steady-state viscosity scaled with polymer concentration to the 3/4 power. Results were interpreted using a cellular, deformable sphere model for the polymer, in analogy to emulsions and foams.

Original languageEnglish (US)
Pages (from-to)531-539
Number of pages9
JournalRheologica Acta
Issue number5
StatePublished - Sep 1988

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Chemical Engineering (miscellaneous)
  • General Materials Science


  • Yield stress
  • dynamic modulus
  • microgel solution
  • strain modulus
  • yield strain


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