Yield stress fluids and ageing

Joshi, Yogesh M.; Petekidis, George

doi:10.1007/s00397-018-1096-6

Cited by 79 publications

(77 citation statements)

References 213 publications

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“…43 Although this yield stress does not follow the conventional definition of yield stress that forbids viscous flow below it. 89 Very interestingly, the point at which Laponite dispersion yields has also been observed to be dependent not just on applied stress but also on the time of application of stress.…”

Section: Soft Glassy Dynamicsmentioning

confidence: 99%

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Microstructure and Soft Glassy Dynamics of an Aqueous Laponite Dispersion

2018

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Synthetic hectorite clay Laponite RD/XLG is composed of disk-shaped nanoparticles that acquire dissimilar charges when suspended in an aqueous medium. Owing to their property to spontaneously self-assemble, Laponite is used as a rheology modifier in a variety of commercial water-based products. In particular, an aqueous dispersion of Laponite undergoes a liquid-to-solid transition at about 1 vol % concentration. The evolution of the physical properties as the dispersion transforms to the solid state is reminiscent of physical aging in molecular as well as colloidal glasses. The corresponding soft glassy dynamics of an aqueous Laponite dispersion, including the rheological behavior, has been extensively studied in the literature. In this feature article, we take an overview of recent advances in understanding soft glassy dynamics and various efforts taken to understand the peculiar rheological behavior. Furthermore, the continuously developing microstructure that is responsible for the eventual formation of a soft solid state that supports its own weight against gravity has also been a topic of intense debate and discussion. In particularly, extensive experimental and theoretical studies lead to two types of microstructures for this system: an attractive gel-like or a repulsive glass-like structure. We carefully examine and critically analyze the literature and propose a state (phase) diagram that suggests an aqueous Laponite dispersion to be present in an attractive gel state.

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Section: Soft Glassy Dynamicsmentioning

confidence: 99%

“…The increase in G ¢ during aging is usually observed in the systems with strong enthalpic contributions. 88,89 Figure 5 also shows the effect of temperature ( ) T on the evolution of G ¢ and G ¢¢ . It can be seen that evolution gets accelerated at higher T and shifts to lower times without changing its shape.…”

Section: Soft Glassy Dynamicsmentioning

confidence: 99%

Microstructure and Soft Glassy Dynamics of an Aqueous Laponite Dispersion

2018

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“…5). The ability to measure the effect of time can also be useful to investigate the complex coupling between viscoplastic deformation, aging, and rejuvenation (Agarwal and Joshi 2019;Coussot 2018;Joshi and Petekidis 2018). Moreover, the methodology used appears competitive compared to some others (Kashani et al 2015) for its simplicity.…”

Section: Conclusive Remarksmentioning

confidence: 99%

An alternative approach for measuring yield stress and its application in Carbopol microgel

et al. 2021

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An innovative experimental apparatus for the direct measurement of yield stress was conceived and realized. It is based on a torsion pendulum equipped with a magnetic dipole and a rotating cylinder immersed in the material to be investigated. The pendulum equilibrium state depends on the mechanical torque applied due to an external magnetic induction field, elastic reaction of the suspension wire, and shear yield stress. Experimental results are reported showing that the behavior of the pendulum rotation angle, in different equilibrium conditions, provides evidence of the yield stress presence and enables its evaluation by equilibrium equations. The dependence on time of the equilibrium approach was also studied, contributing to shed light on the relaxation effect in the transition from a fluid-like to solid-like behavior, as well as on the eventual thixotropic effects in non-Newtonian fluids. The validity of the proposed technique and related experimental apparatus was tested in aqueous Carbopol solutions, with different weight percentages. The linear procedure, combined with the effectiveness and reliability of the proposed experimental method, candidates it to be used for the study of peculiar behaviors of other yield stress complex fluid such as blood, crude waxy oils, ice slurries, and coating layer used in the food industry and also for fault sliding in geodynamics.

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“…These two types of behavior allow to us to distinguish between colloidal gels that experience an irreversible yielding transition [16][17][18][19], and colloidal gels that can be rejuvenated due to the shear-reversible nature of the interparticle attractive interactions such as van der Waals or depletion interactions [20][21][22][23]. The re- * Corresponding author: ajhart@mit.edu covery step of the latter category of gels has been termed "rheological aging" and the kinetics of such phenomena are a complex function of the volume fraction, the nature of the interparticle interactions and the shear history [24][25][26][27][28][29]. Being able to tailor the yielding, flow and recovery of colloidal gels is crucial to achieving the desired shape, mechanical integrity and microstructure in direct-write 3D printing and molding.…”

Section: Introductionmentioning

confidence: 99%

Shear melting and recovery of crosslinkable cellulose nanocrystal–polymer gels

et al. 2019

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Cellulose nanocrystals (CNC) are naturally-derived nanostructures of growing importance for the production of composites having attractive mechanical properties, and offer improved sustainability over purely petroleum-based alternatives. Fabrication of CNC composites typically involves extrusion of CNC suspensions and gels in a variety of solvents, in the presence of additives such as polymers and curing agents. However, most studies so far have focused on aqueous CNC gels, yet the behavior of CNC-polymer gels in organic solvents is important to their wider processability. Here, we study the rheological behavior of composite polymer-CNC gels in dimethylformamide, which include additives for both UV and thermal crosslinking. Using rheometry coupled with in-situ infrared spectroscopy, we show that under external shear, CNC-polymer gels display progressive and irreversible failure of the hydrogen bond network that is responsible for their pronounced elastic properties. In the absence of cross-linking additives, the polymer-CNC gels show negligible recovery upon cessation of flow, while the presence of additives allows the gels to recover via van der Waals interactions. By exploring a broad range of shear history and CNC concentrations, we construct master curves for the temporal evolution of the viscoelastic properties of the polymer-CNC gels, illustrating universality of the observed dynamics with respect to gel composition and flow conditions. We therefore find that polymer-CNC composite gels display a number of the distinctive features of colloidal glasses and, strikingly, that their response to the flow conditions encountered during processing can be tuned by chemical additives. These findings have implications for processing of dense CNC-polymer composites in solvent casting, 3D printing, and other manufacturing techniques. arXiv:1901.04373v1 [cond-mat.soft]

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Yield stress fluids and ageing

Cited by 79 publications

References 213 publications

Microstructure and Soft Glassy Dynamics of an Aqueous Laponite Dispersion

Microstructure and Soft Glassy Dynamics of an Aqueous Laponite Dispersion

An alternative approach for measuring yield stress and its application in Carbopol microgel

Shear melting and recovery of crosslinkable cellulose nanocrystal–polymer gels

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