Foam rheology: a model of viscous phenomena

Kraynik, Andrew M.; Hansen, M. G.

doi:10.1122/1.549940

Cited by 84 publications

(37 citation statements)

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“…In three dimensions the strain should be less; also partial interpenetration and polydispersity will reduce the yield strain. Similarly, the cellular model predicts strain dependence for the oscillatory data [11][12][13]. At small strains the particles do not move from their relative positions during an oscillation; the stress is linear in strain, leading to a constant storage modulus.…”

Section: Discussionmentioning

confidence: 97%

“…The structure of the microgel solution at higher concentrations is assumed to resemble the structure of concentrated foams and emulsions. At small strains such materials behave like purely elastic solids [11][12][13]. Microgel solutions also resemble concentrated solutions of highly branched polymers (many-armed stars) or small spheres with long grafted polymer chains for which equilibrium properties have recently been predicted [14,15].…”

Section: Discussionmentioning

confidence: 97%

“…Full recovery from applied stresses below the yield stress is predicted from the dense foam and emulsion analogies [11,13]. The yield stress is identified as the stress required to move the particles past one another in the "cellular lattice".…”

Section: Discussionmentioning

confidence: 99%

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Rheology of concentrated microgel solutions

1988

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Viscosity, modulus, and yield stress for 0-6wt% aqueous solutions of Carbopo1941 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.

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Section: Discussionmentioning

confidence: 97%