Topic
Rheometer
About: Rheometer is a research topic. Over the lifetime, 5759 publications have been published within this topic receiving 125849 citations.
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TL;DR: In this article, the correlation between interfacial interparticle forces, microstructure, and rheology of particle laden interfaces is characterized for a system of polystyrene particles at an air/water interface by using both aqueous salt concentration and particle surface concentration as control parameters.
Abstract: The correlation between interfacial interparticle forces, microstructure, and rheology of particle laden interfaces is characterized for a system of polystyrene particles at an air/water interface by using both aqueous salt concentration and particle surface concentration as control parameters. Characterizing linear, interfacial shear viscoelastic moduli and microstructure simultaneously using a custom imaging system attached to a double wall ring interfacial rheometer allows the relationship between these properties to be evaluated. Interfacial viscoelastic moduli magnitude is found to be determined locally by the degree of restricted particle motion, which is dictated to both by interparticle attraction due to capillarity and severity of caging caused by local microstructure. However, macroscale rheological behaviors, such as elasticity and yield, are tied to the mesostructural organization of local microstructure. Large domains of aligned hexagonal packed particles create elastic interfaces; when these...
45 citations
TL;DR: Exponential shear flows of polymer melts are investigated in this paper, which share some properties of both planar extension and simple, constant-rate, shear, yet the flow direction and velocity gradient are perpendicular, as for all shear deformations.
Abstract: Exponential shear flows of polymer melts are investigated. These flows are of interest because they share some properties of both planar extension and simple, constant-rate, shear. In particular, embedded points separate exponentially in time, like extensional flows, yet the flow direction and velocity gradient are perpendicular, as for all shear deformations. A comparison between the predictions of the “pom-pom” molecular model of McLeish and Larson [J. Rheol. 42, 81–110 (1998)] in exponential shear and experimental data is presented. The solutions in exponential shear are used to contrast this flow with simple shear and extensional flows and the physical processes driving the solutions are analyzed in each of the three geometries. Accurate quantitative predictions are made using the multimode approach, and the possibility of using exponential shear to obtain the multimode nonlinear spectrum of a melt is explored. It is concluded that although exponential shear is less effective than extensional flows at exposing the influence of the nonlinear parameters of a melt, there are still situations where it is a useful flow for obtaining these parameters.
45 citations
TL;DR: In this article, a modified Langmuir trough with double-wall ring rheometer is used to simultaneously visualize the microstructure of asphaltene interface and measure the rheological responses at air-water interfaces.
Abstract: Asphaltenes are surface-active polyaromatic molecules in crude oil that are known to deposit in pipelines or stabilize water droplets by flocculating at interfaces resulting highly viscous emulsions, leading to significant flow assurance problems. Commercial dispersants have been developed to disturb asphaltene aggregation to mitigate deposition, but their role on the interfacial properties of asphaltene films is unclear. In this study, we elucidate asphaltene interfacial rheology at air-water and oil-water interfaces at high and low asphaltene surface coverage and in the presence of dispersants. A modified Langmuir trough with double-wall ring rheometer is used to simultaneously visualize the microstructure of asphaltene interface and measure the rheological responses. Two surface coverages, 0.5 and 4 μg cm−2, show widely different rheological responses at air-water interfaces. Strong yielding behavior was observed for higher coverage while a less yielding behavior and wider linear viscoelastic regime we...
45 citations
TL;DR: In this paper, the rheology of non-shear thinning elastic fluids is re-examined to clarify some of the misconceptions that exist in regard to their behavior, demonstrating that these fluids are no more than dilute solutions, constructed by dissolving a high molecular weight polymer solute in a highly viscous Newtonian solvent.
Abstract: The rheology of non‐shear thinning elastic fluids is re‐examined to clarify some of the misconceptions that exist in regard to their behavior. It is demonstrated that these fluids are no more than dilute solutions, constructed by dissolving a high molecular weight polymer solute in a highly viscous Newtonian solvent. Organic and inorganic systems can be constructed and there is no magic recipe. The highly elastic non‐shear thinning fluid systems represent a class of real fluid behavior entirely consistent with molecular theory for dilute solutions and with the Oldroyd B constitutive equation. It is shown that the Oldroyd B constitutive equation is far superior to the convected Maxwell model for predicting the dynamic and steady shear properties of these materials. However the Oldroyd B model fails at higher shear rates and may be completely inadequate for representing the extensional properties of such materials. The paper concludes with some squeeze film flow experimental data for constant viscosity elas...
45 citations
TL;DR: The development of a miniaturized capillary rheometer that meets the needs of the biopharamaceutical industry and is potentially scalable to a multiwell format is reported.
45 citations