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 paper, a filament stretching rheometer has been constructed to measure the elongational viscosity of polymer melts at high temperatures, and a constant elongational rate has been obtained by an iterative application of the Orr-Sridhar method for specification of the endplate movement.
Abstract: A new filament stretching rheometer has been constructed to measure the elongational viscosity of polymer melts at high temperatures. Two polymer melts, a LDPE and a LLDPE, were investigated with this rheometer. A constant elongational rate has been obtained by an iterative application of the Orr–Sridhar method for specification of the end-plate movement. Agreement has been found with linear viscoelastic measurements performed in shear. Hencky strains up to about 6 have been reached. Steady values of the viscosity have been sustained in some cases for about two Hencky strain units.
167 citations
TL;DR: In this paper, the dynamic and steady state behavior of metallocene linear low density polyethylene (m-LLDPE) blended with high-density polyethylen and with low-dense polyethylenes (LDPE), was measured in parallel plate rheometer at 160, 180, and 200 degrees C. The results were consistent with the rheological properties of these two series of blends.
166 citations
TL;DR: This study probes the bulk and the interfacial viscoelasticity of surfactant-free bovine serum albumin (BSA) solutions using a stress-controlled torsional rheometer, augmented by microfluidic rheometry and interfacial rheometric measurements.
Abstract: Globular proteins influence the flow, microstructure, phase behavior and transport of biofluids and biomolecules in the mammalian body. These proteins are essential constituents of food, drugs and cosmetics, and their dynamics determine the physical properties and application of these multicomponent materials. In conventional rheological studies conducted using typical geometries on torsional rheometers, solutions of globular proteins are commonly reported to have a solid-like response at concentrations as low as 0.03% by weight. Typical explanations invoke the presence of long-range repulsions that are stronger than electrostatic interactions. In this study, we probe the bulk and the interfacial viscoelasticity of surfactant-free bovine serum albumin (BSA) solutions using a stress-controlled torsional rheometer, augmented by microfluidic rheometry and interfacial rheometric measurements. We demonstrate that the origin of this yield-like behavior, which is manifested as a highly shear-thinning bulk rheological response, lies in the formation of a film of adsorbed protein, formed spontaneously at the solution/gas interface. We provide direct interfacial rheometric measurements to study the concentration-dependent viscoelasticity of the adsorbed protein and we describe a simple, but quantitative, additive model useful for extracting the interfacial viscosity contribution from bulk viscosity measurements over a wide range of shear rates.
163 citations
TL;DR: In this paper, a model with an elastic-limit yield stress, a static yield stress and a dynamic yield stress was introduced to describe the yielding process of statically cooled waxy crude oil.
Abstract: The yielding process of statically cooled waxy crude oil was examined in detail. Three direct measurementsa controlled stress test, a creep−recovery test, and an oscillatory testwere employed using a controlled stress rheometer to investigate the yielding of two distinctly different statically cooled waxy crude oils. The results showed that yielding of waxy crude oil occurs by an initial elastic response, followed by viscoelastic creep and a final fracture. A model with an elastic-limit yield stress, a static yield stress, and a dynamic yield stress was introduced to describe the yielding process. The three yield stresses were determined by means of different techniques. The effect of the time scale in different measurements on the three yield stresses was studied. It was shown from both the creep−recovery and oscillatory tests that the elastic-limit yield stress was independent of the time scale. The static yield stress was found to be dependent on the time scale in the three tests. The dynamic yield str...
161 citations
TL;DR: In this article, the effect of an external homogeneous magnetic field on the viscoelastic properties of these materials is studied by dynamic experiments (shear oscillations on a rheometer).
Abstract: Novel magnetorheological elastomers (MRE) based on a highly elastic silicone rubber filled with carbonyl iron magnetic particles of 3―5 and 3―50 μm are synthesized. The effect of an external homogeneous magnetic field on the viscoelastic properties of these materials is studied by dynamic experiments (shear oscillations on a rheometer). It is shown that the magnetic response of the MRE increases with a decrease of the strain. At 1% deformation both the storage and loss moduli of the new MRE demonstrate a giant response to the magnetic field, namely, an increase of more than two orders of magnitude in both moduli in a field of 300 mT is observed. In addition, these new MREs show a twofold increase of the damping ratio, which is important for their application as tunable vibration absorbers.
161 citations