Signatures of physical aging and thixotropy in aqueous dispersion of Carbopol

In this work, we investigate signatures of physical aging in an aqueous dispersion of Carbopol that shows yield stress and weak enhancement in elastic modulus as a function of time. We observe that the creep curves, as well as strain recovery, show a significant dependence on waiting time elapsed si...

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Bibliographic Details
Published in:Physics of fluids (1994) 2019-06, Vol.31 (6)
Main Authors: Agarwal, Mayank, Joshi, Yogesh M.
Format: Article
Language:English
Subjects:
Aging
Creep (materials)
Dispersion
Fluid dynamics
Modulus of elasticity
Physics
Power law
Relaxation time
Signatures
Strain
Superposition (mathematics)
Thixotropy
Time dependence
Yield strength
Yield stress
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Summary:In this work, we investigate signatures of physical aging in an aqueous dispersion of Carbopol that shows yield stress and weak enhancement in elastic modulus as a function of time. We observe that the creep curves, as well as strain recovery, show a significant dependence on waiting time elapsed since shear melting. The corrected strain, which is the strain in excess of the recovered strain, has been observed to show time–waiting time superposition in the effective time domain, wherein time is normalized by time dependent relaxation time that shows a power-law dependence. The corresponding power law exponent, which is close to unity in a limit of small stresses, decreases with stress and tends to zero as stress approaches the yield stress. For a range of stresses, the material shows time–stress superposition suggesting the shape of the evolving relaxation time spectrum to be independent of the time as well as the stress. This work, therefore, suggests the presence of physical aging in an aqueous dispersion of Carbopol even though the elastic modulus shows only a weak enhancement. We also discuss the Andrade type of creep behavior in aqueous Carbopol dispersion.
ISSN:1070-6631
1089-7666
DOI:10.1063/1.5097779