Mircorheology and jamming in a yield-stress fluid

Oppong, Felix K.; Bruyn, John R. de

doi:10.1007/s00397-010-0519-9

Cited by 46 publications

(43 citation statements)

References 31 publications

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“…8. Our picture is also similar to that proposed by Piau (2007) based on measurements of the yield stress of Carbopol 940 and is consistent with the results of studies of the diffusion of tracer particles in ETD 2050 (Oppong and de Bruyn 2011), which showed the presence of two distinct microrheological regimes at intermediate concentrations-one viscous and the other predominantly elastic-and a single elastic regime at high concentration.…”

Section: Discussionsupporting

confidence: 90%

“…The initial increase of the pH causes the acrylic acid groups within the polymer to dissociate. The presence of mobile counter ions results in an increase in the internal osmotic pressure, causing the microgel particles to swell by at least a factor of 1,000 in volume (Lee et al 2011;Oppong and de Bruyn 2011). Once the acid becomes fully dissociated, however, further addition of base simply adds ions that screen the fixed charges, decreasing the osmotic pressure and easing the compression of the polymer network.…”

Section: Discussionmentioning

confidence: 98%

“…In the case of Carbopol, the relationship between cand ϕ is not known in detail, since we have no direct way of measuring the degree of expansion of the microgel particles except at the lowest pH (Lee et al 2011) and the lowest concentrations (Oppong and de Bruyn 2011). However, it is clear that the volume fraction ϕ occupied by Carbopol microgels of a given concentration c increases with increasing pH as the microgel particles expand until the particles are fully space-filling, so we will discuss the behavior in these terms.…”

Section: Discussionmentioning

confidence: 98%

“…Oppong and de Bruyn (2011) analyzed the diffusion of tracer particles in Carbopol ETD 2050 at pH 6 over a concentration range 0.01 ≤ c ≤ 1.0 wt.%. At low concentrations, the tracer particles diffused freely in a purely viscous rheological environment.…”

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confidence: 99%

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Scaling and mesostructure of Carbopol dispersions

et al. 2012

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Rheological measurements were performed on aqueous dispersions of two commercial crosslinked polymer microgels, Carbopol Ultrez 10 and Carbopol ETD 2050, prepared over a wide range of concentration and pH. For all concentrations studied, both the yield stress and the elastic modulus initially increased dramatically with pH and displayed broad peaks at intermediate pH. This is consistent with the onset of jamming of the Carbopol particles due to a rapid increase in particle size caused by osmotic swelling in the presence of NaOH. Scaling of both yield stress and elasticity with concentration was observed only at higher concentrations, which we believe indicates a change from a percolated structure at low volume fractions to a space filling network of compressed particles at high volume fractions. This model is supported by confocal microscopy of fluorescently dyed Carbopol dispersions.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 98%

mentioning

confidence: 99%

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Scaling and mesostructure of Carbopol dispersions

et al. 2012

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“…We used Carbopol as a homogeneous transparent viscoplastic material. Carbopol has already been used as model viscoplastic material in various studies [Robert and Barnes, 2001;Coussot et al, 2009;Piau, 2007;Oppong and De Bruyn, 2011;Ovarlez et al, 2012]. Its rheological properties were determined independently using a rotational parallel plate rheometer.…”

Section: Introductionmentioning

confidence: 99%

Internal Dynamics of a Free-Surface Viscoplastic Flow Down an Inclined Channel

Freydier

Chambon

Naaïm

2016

IJECE

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This paper presents preliminary experimental results concerning the internal dynamics of a free surface viscoplastic flow down an inclined channel. Experiments are conducted in an inclined channel whose bottom is constituted of an upward-moving conveyor belt with controlled velocity. Carbopol microgel was used as a homogeneous transparent viscoplastic fluid. This experimental setup allows generating and observing stationary gravity-driven surges in the laboratory frame. We used PIV technique (Particle Image Velocimetry) to obtain velocity fields both in the uniform zone and within the front zone where flow thickness is variable and where recirculation takes place. Experimental velocity profiles and determination of plug position are presented and compared to theoretical predictions based on the lubrication approximation.

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Fat Plumes May Reflect the Complex Rheology of the Lower Mantle

Davaille

Carrez

2018

Geophysical Research Letters

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Recent tomographic imaging of the mantle below major hot spots shows slow seismic velocities extending down to the core‐mantle boundary, confirming the existence of mantle plumes. However, these plumes are much thicker than previously thought. Using new laboratory experiments and scaling laws, we show that thermal plumes developing in a visco‐plastic fluid present much larger diameters than plumes developing in a Newtonian fluid. Such a rheology requiring a yield stress is consistent with a lower mantle predominantly deforming by pure dislocation climb. Yield stress values between 1 and 10 MPa, implying dislocation densities between 10 8 and 10 10 m −2 , would be sufficient to reproduce the plumes morphology observed in tomographic images.

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Mircorheology and jamming in a yield-stress fluid

Cited by 46 publications

References 31 publications

Scaling and mesostructure of Carbopol dispersions

Scaling and mesostructure of Carbopol dispersions

Internal Dynamics of a Free-Surface Viscoplastic Flow Down an Inclined Channel

Fat Plumes May Reflect the Complex Rheology of the Lower Mantle

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