Artigos de revistas: "From viscosimetry to rheometry"

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Figueroa-Ochoa, Edgar Benjamín, Lourdes Mónica Bravo-Anaya, Ricardo Vaca-López, Gabriel Landázuri-Gómez, Luis Carlos Rosales-Rivera, Tania Diaz-Vidal, Francisco Carvajal, Emma Rebeca Macías-Balleza, Yahya Rharbi e J. Félix Armando Soltero-Martínez. "Structural Behavior of Amphiphilic Triblock Copolymer P104/Water System". Polymers 15, n.º 11 (31 de maio de 2023): 2551. http://dx.doi.org/10.3390/polym15112551.

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A detailed study of the different structural transitions of the triblock copolymer PEO27–PPO61–PEO27 (P104) in water, in the dilute and semi-dilute regions, is addressed here as a function of temperature and P104 concentration (CP104) by mean of complimentary methods: viscosimetry, densimetry, dynamic light scattering, turbidimetry, polarized microscopy, and rheometry. The hydration profile was calculated through density and sound velocity measurements. It was possible to identify the regions where monomers exist, spherical micelle formation, elongated cylindrical micelles formation, clouding points, and liquid crystalline behavior. We report a partial phase diagram including information for P104 concentrations from 1 × 10−4 to 90 wt.% and temperatures from 20 to 75 °C that will be helpful for further interaction studies with hydrophobic molecules or active principles for drug delivery.

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WAGNER, Oliver, Herwig SCHÜLER, Peter HOFMANN, David LANGER, Peter DANCKER e Juergen BEREITER-HAHN. "Sound attenuation of polymerizing actin reflects supramolecular structures: viscoelastic properties of actin gels modified by cytochalasin D, profilin and α-actinin". Biochemical Journal 355, n.º 3 (24 de abril de 2001): 771–78. http://dx.doi.org/10.1042/bj3550771.

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Polymerization and depolymerization of cytoskeletal elements maintaining cytoplasmic stiffness are key factors in the control of cell crawling. Rheometry is a significant tool in determining the mechanical properties of the single elements in vitro. Viscoelasticity of gels formed by these polymers strongly depends on both the length and the associations of the filaments (e.g. entanglements, annealings and side-by-side associations). Ultrasound attenuation is related to viscosity, sound velocity and supramolecular structures in the sample. In combination with a small glass fibre (2mm×50µm), serving as a viscosity sensor, an acoustic microscope was used to measure the elasticity and acoustic attenuation of actin solutions. Changes in acoustic attenuation of polymerizing actin by far exceed the values expected from calculations based on changes in viscosity and sound velocity. During the lag-phase of actin polymerization, attenuation slightly decreases, depending on actin concentration. After the half-maximum viscosity is accomplished and elasticity turns into steady state, attenuation distinctly rises. Changes in ultrasound attenuation depend on actin concentration, and they are modulated by the addition of α-actinin, cytochalasin D and profilin. Thus absorption and scattering of sound on the polymerization of actin is related to the packing density of the actin net, entanglements and the length of the actin filaments. Shortening of actin filaments by cytochalasin D was also confirmed by electron micrographs and falling-ball viscosimetry. In addition to viscosity and elasticity, the attenuation of sound proved to be a valuable parameter in characterizing actin polymerization and the supramolecular associations of F-actin.

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Götz, Joachim, Hartmut Balzer e Ruth Hinrichs. "Characterisation of the Structure and Flow Behaviour of Model Chocolate Systems by Means of NMR and Rheology". Applied Rheology 15, n.º 2 (1 de abril de 2005): 98–111. http://dx.doi.org/10.1515/arh-2005-0005.

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Abstract In order to characterise the structure and flow behaviour of model chocolate systems Nuclear Magnetic Resonance (NMR) and rheometry were used to determine the T1 - and T2 - NMR relaxation times and their corresponding flow functions. T1 and T2 characterise the molecular mobility of fluids and correlate with both the zero-shear-rate and infinity viscosity of various chocolate model systems (determined with rotational rheometry and capillary rheometry). Based on this correlation, NMR provides the possibility to determine characteristic viscosities of chocolate masses by means of NMR-relaxation experiments. The viscosities of chocolate masses are important process parameters, as they are used for quality control of the production process. An online process viscosimetry via T2 relaxation would allow the installation of an efficient process control and, thus, a process automation. This NMR application with comparatively short measuring times is especially interesting for disperse systems where the use of conventional rheometric techniques may cause large errors. The only prerequisite for the measurement of the viscosities using NMR is a previous calibration. This was performed with the help of rotational and capillary rheometry. The NMR self-diffusion experiments are especially appropriate to characterise the influence of emulsifiers on the structure and the flow behaviour of chocolate masses.

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Strobelt, Jonas, Joerg Bauer, Marc Dreissigacker, Ole Hoelck, Tanja Braun, Karl-Friedrich Becker, Martin Schneider-Ramelow e Klaus-Dieter Lang. "COMBINING ADVANTAGES OF RHEOMETRY AND INLINE VISCOMETRY FOR IMPROVED VISCOSITY MODELING". International Symposium on Microelectronics 2019, n.º 1 (1 de outubro de 2019): 000568–72. http://dx.doi.org/10.4071/2380-4505-2019.1.000568.

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Abstract In microelectronic packaging, encapsulation by compression and transfer molding is a crucial process block to ensure device reliability. Material properties of encapsulants, highly filled systems of reactive epoxy molding compounds (EMC), strongly depend on process conditions in a complex manner and vary over time. Shear-thinning behavior, as well as time- and temperature-dependent conversion strongly impact the viscosity of the polymer melt. In all fields of application, such as automotive or IoT, demands towards miniaturization, lifetime and environmental conditions increase. Thus, detailed understanding of the complex material behavior is of vital importance. Typically, shear-thinning behavior of polymer melts is characterized using a conventional rheometer in oscillation mode under varying shear-rates and temperatures. Limitations of this approach are, that measurements at process temperature typically cannot be performed due to the high reactivity of the encapsulant at these temperatures (e.g. 175 °C for transfer molding). Therefore extrapolation to the correct temperature range is required. Furthermore, measurements in oscillation mode cannot necessarily be transferred to real process conditions, where a continuous flow is present. To overcome these limitations the inline viscometer can be used, a specially designed measurement tool for a transfer molding machine developed by Fico/Besi. The polymer melt is pressed through a narrow slit under known volumetric flow at process temperature. By measuring the pressure difference before and after the slit, the viscosity can be calculated. In order to better understand and also predict material behavior, inline viscosimetry is combined with rheometer measurements. This allows to maintain the advantages of conventional rheometry regarding material consumption and large shear-rate measuring range. At the same time, the inline approach provides relevant data under process conditions. The synthesis of both approaches yields a correction of the rheometer measurements, ultimately improving viscosity modeling and being an improved basis for process simulation.

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Faria, Hugo, F. M. Andrade Pires e A. Torres Marques. "Modeling the rheology of SR1500 and LY556 epoxies under manufacturer's recommended cure cycles after viscosimetry and rheometry characterization". Polymer Engineering & Science 54, n.º 4 (24 de junho de 2013): 831–39. http://dx.doi.org/10.1002/pen.23607.

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Tan, Grace, Weizhong Zou, Mike Weaver e Ronald G. Larson. "Determining threadlike micelle lengths from rheometry". Journal of Rheology 65, n.º 1 (janeiro de 2021): 59–71. http://dx.doi.org/10.1122/8.0000152.

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Manzhai, V. N., S. G. Kulyshkina, L. V. Chekantseva e I. G. Yashchenko. "COMPOSITION AND STRUCTURE OF HIGH-VISCOSITY OILS FROM VARIOUS DEPOSITS". Oil and Gas Studies, n.º 1 (1 de março de 2018): 112–18. http://dx.doi.org/10.31660/0445-0108-2018-1-112-118.

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The article presents the results of investigations of oil samples from various deposits. The samples contain asphaltenes, resins and paraffins in different concentrations. It is established that all oil samples are non-Newtonian fluids and they have pseudoplastic properties. Due to the results of experiments, which were carried out by the method of rotational viscosimetry, size of complex structural units of oils at various sliding velocities was calculated.

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Postema, Michiel, Christine Gering, Nicole Anderton, Craig S. Carlson e Minna Kellomäki. "Monitoring the gelation of gellan gum with torsion rheometry and brightness-mode ultrasound". Current Directions in Biomedical Engineering 8, n.º 2 (1 de agosto de 2022): 33–36. http://dx.doi.org/10.1515/cdbme-2022-1010.

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Abstract Gellan gum is a hydrogel with several applications in ultrasonic imaging, novel drug delivery, and tissue regeneration. As hydrogels are dynamic entities, their viscocelastic and therefore their acoustic properties change over time, which is of interest to monitor. To determine the speed of sound from brightness-mode images, however, rather large quantities of hydrogel are needed. In this study, we investigated torsion rheometry as a means to determine acoustic properties. Perceived speeds of sound were derived and computed from torsion rheometry measurements of gelating gellan gum mixed with spermidine trihydrochloride crosslinker. For comparison, brightness-mode ultrasonic images were recorded of the same material inside a phantom well. The rheometry data converged to a speed of sound within a standard devitation of the speed of sound measured from the brightness-mode images.We have shown that dynamic acoustic properties of gelating gellan gum can be simulated and experimentally determined using torsion rheometry.

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Schindler, Ralf, Elke Weichselsdorfer, Oliver Wagner e Jürgen Bereiter-Hahn. "Aldolase-localization in cultured cells: Cell-type and substrate-specific regulation of cytoskeletal associations". Biochemistry and Cell Biology 79, n.º 6 (1 de dezembro de 2001): 719–28. http://dx.doi.org/10.1139/o01-137.

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The role of aldolase as a true F- and G-actin binding protein, including modulating actin polymerization, initiating bundling, and giving rise to supramolecular structures that emanate from actin fibrils, has been established using indirect immunofluorescence, permeabilization of XTH-2 cells and keratocytes, and microinjection of fluorescence-labeled aldolase. In addition, binding to intermediate filaments, vimentin, and cytokeratins has been demonstrated. In permeabilized cells in the presence of fructose-1,6-bisphosphate (202000 µM) aldolase shifts from association with actin fibres to intermediate filaments. Plenty of free binding sites on microtubules have been revealed by addition of fluorochromed aldolase derived from rabbit skeletal muscle. However, endogenous aldolase was never found associated with microtubules. Differences in actin polymerization in the presence of aldolase as revealed by pyrene-labeled actin fluorimetry and viscosimetry were explained by electron microscopy showing the formation of rod-like structures (10 nm wide, 2060 nm in length) by association of aldolase with G-actin, which prevents further polymerization. Upon the addition of fructose-1,6-bisphosphate, G-actinaldolase mixture polymerizes to a higher viscosity and forms stiffer filaments than pure actin of the same concentration.Key words: aldolase, cytoskeleton, electron microscopy, viscosimetry.

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Kavehpour, H. P., e G. H. McKinley. "Tribo-Rheometry: From Gap-Dependent Rheology to Tribology". Tribology Letters 17, n.º 2 (agosto de 2004): 327–35. http://dx.doi.org/10.1023/b:tril.0000032471.06795.ea.

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Nguyen, An Tien, Nguyen Thi Hoa, Do Truong Thien, Vu Thi Hue, Vu Thi Minh Thu e Lai Thi Thu Trang. "CHARACTERIZATION OF GLUCOMANNAN FROM AMORPHOPHALLUS PANOMENSIS IN VIETNAM". Vietnam Journal of Science and Technology 54, n.º 2 (12 de abril de 2016): 224. http://dx.doi.org/10.15625/0866-708x/54/2/6384.

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A glucomannan has been isolated from the tuber of amorphophallus panomensis by a simple method without using toxic chemicals. The weight content of the glucomannan was about 4% of original amorphophallus tuber. The structure of the glucomannan was investigated by infrared (IR) and nuclear magnetic resonance spectroscopy (NMR). The results showed that the structural component of the glucomannan was consisted of mannose and glucose units with the mannose/glucose ratio was about 1.00/0.13. The degree of crystalation and molecular weight of the glucomannan were also investigated by XRD diffraction and viscosimetry, respectively. The results indicated that the glucomannan was amorphous and molecular weight was Mv = 1.2´106Da.

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Zou, Weizhong, Grace Tan, Hanqiu Jiang, Karsten Vogtt, Michael Weaver, Peter Koenig, Gregory Beaucage e Ronald G. Larson. "From well-entangled to partially-entangled wormlike micelles". Soft Matter 15, n.º 4 (2019): 642–55. http://dx.doi.org/10.1039/c8sm02223b.

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We combine mechanical rheometry, DWS, and SANS with a simulation model, the “pointer algorithm”, to obtain characteristic lengths and time constants for WLM solutions over a range of salt concentrations encompassing the transition from unentangled to entangled solutions.

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Costa, Sónia, Paulo Teixeira, José Covas e Loic Hilliou. "Assessment of Piezoelectric Sensors for the Acquisition of Steady Melt Pressures in Polymer Extrusion". Fluids 4, n.º 2 (3 de abril de 2019): 66. http://dx.doi.org/10.3390/fluids4020066.

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Piezoelectric sensors have made their way into polymer processing and rheometry applications, in particular when small pressure changes with very fast dynamics are to be measured. However, no validation of their use for steady shear rheometry is available in the literature. Here, a rheological slit die was designed and constructed to allow for the direct comparison of pressure data measured with conventional and piezoelectric transducers. The calibration of piezoelectric sensors is presented together with a methodology to correct the data from the inherent signal drift, which is shown to be temperature and pressure independent. Flow curves are measured for polymers showing different levels of viscoelasticity. Piezoelectric slit rheometry is validated and its advantage for the rheology of thermodegradable materials with viscosity below 100 Pa·s is highlighted.

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Masimov, E. A., B. G. Pashaev e G. Sh Hasanov. "Structure of aqueous solutions of sucrose, derived from viscosimetry data and IR spectroscopy". Russian Journal of Physical Chemistry A 91, n.º 4 (28 de março de 2017): 667–71. http://dx.doi.org/10.1134/s003602441704015x.

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Qiu, Zhi Ping, Ji Da Chen, Juan Bu e Rong De Shu. "Modified Hydroxyl Value Assay and Application in Analysis of Molecular Ingredient of Polylactic Acid Oligomers". Advanced Materials Research 306-307 (agosto de 2011): 692–95. http://dx.doi.org/10.4028/www.scientific.net/amr.306-307.692.

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A modification was proposed to overcome problems of inaccuracy while traditional end group analysis was applied for hydroxyl value assay of polylactic acid oligomer owing to hydrolyzation. The modified method possessed simplification and accuracy resulting from avoiding hydrolyzation of polylactic acid oligomers, and it could be used for characterising molecular ingredient of polylactic acid oligomers, while the other techniques, such as 1H-NMR, Fourier transform infrared spectroscopy and viscosimetry, were applied at the same time.

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Ravendran, Rathesan, Peter Jensen, Jesper de Claville Christiansen, Benny Endelt e Erik Appel Jensen. "Rheological behaviour of lubrication oils used in two-stroke marine engines". Industrial Lubrication and Tribology 69, n.º 5 (4 de setembro de 2017): 750–53. http://dx.doi.org/10.1108/ilt-03-2016-0075.

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Purpose The purpose of this study is to investigate the rheological behaviour of commercial lubrication oils used for cylinder lubrication in two-stroke marine diesel engines. Furthermore, it is of interest to investigate whether the viscosity of lubrication oils is affected by different levels of alkalinity. Design/methodology/approach Viscosity measurements are performed using both rotational and capillary rheometry. It was possible to measure oil viscosity in the shear rate from 0.1 to 3,000 s−1 using rotational rheometry, whereas capillary rheometry allowed measurements in higher shear rates from 5 × 105 to 1.3 × 106 s−1 at 50°C. Findings The viscosity measurements show that the studied lubrication oils behave as a Newtonian fluid and that the viscosities are insensitive to the level of alkalinity. Furthermore, the viscosity/temperature dependency for the lubrication oils was found to fit the Arrhenius model. Originality/value This study presents useful information about the rheological behaviour of lubrication oils, more precisely how the oil properties are affected by shear rate, temperature and level of alkalinity. The value of this research is considered to be important for designing two-stroke diesel engines and cylinder lubrication systems.

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De Hoog, F. R., e R. S. Anderssen. "Simple and Accurate Formulas for Flow-Curve Recovery from Couette Rheometer Data". Applied Rheology 16, n.º 6 (1 de dezembro de 2006): 321–28. http://dx.doi.org/10.1515/arh-2006-0022.

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Abstract In Couette rheometry, most of the current flow-curve recovery algorithms require the explicit numerical differentiation of the measured angular velocity data. The exceptions and popular choices, because it avoids the need for a numerical differentiation, are the parallel plate approximation (cf. Bird et al. [1], Table 10.2-1) and the simplest of the formulas given in Krieger and Elrod [2]. However, their applicability is limited to narrow gap rheometer data. In this paper, equally simple formulas are presented which are exact for Newtonian fluids, do not involve a numerical differentiation and are consistently more accurate than the simple formulas mentioned above. They are based on a generalization of the Euler-Maclaurin sum formula solution of the Couette viscometry equation given in Krieger and Elrod. As well as illustrating the improved accuracy for the recovery of flow-curves for fluids with and without a yield-stress, details about more general and accurate formulas for flow-curve recovery from Couette rheometry data are given. The situation for the recovery of flow-curves from wide gap rheometery measurements is also discussed.

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Shachneva, E. Yu, e V. Ya Khentov. "Investigation of the Molecular Structure of the “Polyacrylamide Flocculant–H2O” System from Viscosimetry Data". Journal of Engineering Physics and Thermophysics 91, n.º 3 (maio de 2018): 831–42. http://dx.doi.org/10.1007/s10891-018-1806-z.

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Janderka, Pavel, e Leoš Zábrš. "Electroreduction of a benzenediazonium salt in the presence of a radical acceptor". Collection of Czechoslovak Chemical Communications 56, n.º 10 (1991): 2067–72. http://dx.doi.org/10.1135/cccc19912067.

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Potentiostatic reduction of p-methoxybenzenediazoniumtetrafluoroborate was studied in acidic aqueous solutions and in dimethylformamide. The mean number of electrons transferred to a molecule of the depolarizer is influenced by the presence of a radical acceptor, acrylamide, and depends on its concentration. The course of electrolysis in the presence of acrylamide was investigated by measuring the relative viscosity of the electrolysed solution. A polymer was isolated from both aqueous and nonaqueous solutions, and its mean relative molecular mass was determined by viscosimetry in an aqueous solution.

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Byelyayeva, N. V. "Physicochemical properties of biological fluids in patients with chronic pancreatitis". Herald of Pancreatic Club 63, n.º 2 (30 de maio de 2024): 19–22. https://doi.org/10.33149/vkp.2024.02.03.

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Human biological fluids (BF) contain a variety of low- and high-molecular-weight surfactants that can adsorb at liquid phase boundaries and alter surface tension (ST), thereby accelerating or delaying the processes of matter and energy transfer through biological membranes. Numerous proteins, lipids, electrolytes, and hormones that have surfactant properties and ability to change the ST of blood, urine, and pancreatic secretions are altered in chronic pancreatitis (CP). We examined 72 patients with CP in the acute stage, ranging in age from 20 to 63 (34 men and 38 women). Of them, 36 had biliary CP and 36 had alcohol-induced pancreatitis. 30 healthy people were examined. Interfacial tensiometry and rheometry techniques were used to study the physicochemical properties of blood, urine and duodenal contents. CP patients’ dynamic ST of BF was examined using the MPT-2 Lauda computer tensiometer (Germany). We assessed the rheological properties of the BF, which consist of elastic and viscous components, using an enhanced ADSA. There are substantial changes in the physicochemical properties of blood, urine, and duodenal contents in CP patients. Interfacial tensiometry and rheometry parameters of the BF in patients with CP vary according to the surfactant content, which includes enzymes and pancreatic hormones. Tensiometry and rheometry indices of the BF in CP correlate with changes in exocrine and endocrine pancreatic functions and the severity of sonographic CP manifestations. Interphase tensiometry and rheometry of blood, urine, and duodenal contents can be used as integral criteria for evaluating biochemical and functional changes in CP.

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Nasonov, F. A., V. M. Aleksashin, D. A. Melnikov e S. V. Bukharov. "Zinc-stearate modification of epoxy resins and carbon plastics based on them and its influence on the basic technological properties of the composition". Voprosy Materialovedeniya, n.º 3(95) (10 de janeiro de 2019): 146–56. http://dx.doi.org/10.22349/1994-6716-2018-95-3-146-156.

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The influence of the special modification of epoxy resins and polymer composites based on them on the basic technological properties of the composition is investigated. Modification is performed in order to reduce the opening damage. The most important technological properties of the initial epoxy composition and modified technological additives are studied and compared by standard methods (viscosimetry, thermoanalytical methods). A kinetic model of the curing process was created, the experimental production of samples from plastics filled with carbon long filler (impregnation under pressure, autoclave molding) and its non-destructive testing were carried out.

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Baravian, Christophe, Audrey Lalante e Alan Parker. "Vane Rheometry with a Large, Finite Gap". Applied Rheology 12, n.º 2 (1 de abril de 2002): 81–87. http://dx.doi.org/10.1515/arh-2002-0005.

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Abstract The vane geometry with a large gap is used to determine the Newtonian, non-Newtonian and viscoelastic properties of complex fluids. We show that when this geometry is carefully characterized, it can be used for precise rheometry. A novel effective cylinder approximation is used to obtain the shear rate and shear stress factors. The effective radius is found to be close to the height of the triangle formed by joining the tips of adjacent blades. This result differs significantly from that of previous work. Flow visualization has been used to confirm that the stream lines bend towards the centre between the blades. These factors can be used to determine the flow curves of non-Newtonian liquids, using Krieger’s power law expansion. The standard procedure for using the vane to determine the yield stress is also carefully investigated and alternative procedures are suggested.

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Balakrishna, Subramaniam, e William W. Schultz. "Improved capillary rheometry for viscous Newtonian filaments". Physics of Fluids 34, n.º 4 (abril de 2022): 042101. http://dx.doi.org/10.1063/5.0083973.

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The efficacy of the kinematic differential analysis of McCarroll et al. [“Differential analysis of capillary breakup rheometry for Newtonian liquids,” J. Fluid Mech. 804, 116 (2016)], expanding on McKinley and Tripathi [“How to extract the Newtonian viscosity from capillary breakup measurements in a filament rheometer,” J. Rheol. 44, 653 (2000)], to evaluate the surface tension to viscosity ratio for Newtonian filaments is examined. The analysis is valid during and after stretch, while the latter is traditionally applied after cessation of stretch as the midfilament radius approaches zero. Through numerical simulations, the evaluation of viscosity is investigated for two common stretch histories: (a) the ramp function and (b) the modified step strain. The challenges with stretch are twofold: rapid stretch (large capillary number) results in a nearly cylindrical filament with a rapid change near the plate that challenges the one-dimensional (1D) approximation, while slow stretch results in a nearly static solution with limited viscous information. We examine the capillary number-aspect ratio parameter space and find the ramp function with small stretching speeds optimal. Hence, the most accurate measurements are taken while the filament is being stretched.

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Zheng, R., N. Phan-Thien e V. Ilic. "Falling Needle Rheometry for General Viscoelastic Fluids". Journal of Fluids Engineering 116, n.º 3 (1 de setembro de 1994): 619–24. http://dx.doi.org/10.1115/1.2910322.

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This paper reports theoretical and numerical studies on a flow of a general viscoelastic fluid past a needle placed at the centerline of a cylindrical tube, supplemented by a comparative experimental study. It is shown that the drag per unit length on the needle, which is assumed to be infinitely long, depends on the fluid viscosity only, whatever the first and second normal stress differences may be. This general theory is then specified to obtain solutions for the power-law and the Phan-Thien-Tanner fluids. The power-law fluid results provide a general technique for obtaining flow curves of non-Newtonian fluids from the measured drag forces on falling needles. This is achieved by using KU/R as the effective shear rate, where U is the terminal velocity of the needle, R is the radius of the tube, and K is a function of the power-law index n and the system geometry a/R (where a is the radius of the needle). The effect of the aspect ratio of the needle on the drag force is investigated numerically using a boundary element method for the flow of Phan-Thien-Tanner fluid. Experimentally, a flow curve was obtained for a kerosene solution of PIB (3.39 percent by weight), using falling needles of aspect ratio greater than 40 in a circular cylinder. The result compared well with Carri-Med 50 CS rheometer data.

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Crosby, Bryan J., Tom McLeish e Harry Block. "TOWARDS UNDERSTANDING ER FLUIDS USING SALS/RHEOMETRY". International Journal of Modern Physics B 10, n.º 23n24 (30 de outubro de 1996): 3029–36. http://dx.doi.org/10.1142/s0217979296001471.

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This paper details work in Cranfield and Leeds Universities of making a stock of transparent ER fluids, which could later be utilised in a new optical electro rheometer (OER) to be assembled at Leeds University. Two basic routes were attempted. One was to use glass microspheres and the other was to use polymer spheres. In order to increase the strength of the ER effect, it was necessary to increase the volume loading while still maintaining sufficient transmission (about 75% over 2 mm). It was found to be possible to increase the ER effect quite substantially in some instances, and in others it was possible to get a near perfect refractive index match. It was not possible to combine both requirements in one fluid such that a high static yield stress was apparent in a transparent ER fluid. However one fluid was made which gave acceptable diffraction losses at high volume fractions, remained in suspension for extended periods and provide about 700 Pa yield stress at 4kV/mm and about 30% volume fraction viz: untreated poly(ethylene vinyl acetate) microspheres in Cereclor/bromonaphthalene/polystyrene solution. The OER being assembled at Leeds University is intended to record small angle light scattering (SALS) profiles, electrical and mechanical properties of ER fluids simultaneously. The OER is based around a DSR 500 machine purchased from Rheometric Scientific with quartz tools coated with transparent indium tin oxide(ITO), which is capable of measuring both steady state (DC) and oscillatory (AC) material parameters.

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Leblanc, Jean L., e Christophe de la Chapelle. "Characterizing Gum Elastomers by Fourier Transform Rheometry". Rubber Chemistry and Technology 76, n.º 4 (1 de setembro de 2003): 979–1000. http://dx.doi.org/10.5254/1.3547786.

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Abstract Fourier transform (FT) rheometry is an emerging new technique that allows the linear and non-linear viscoelastic behavior of polymer materials to be accurately investigated. Basically samples are submitted to torsional harmonic strain at fixed frequency and temperature in order to capture strain and torque signals. A commercial instrument, i.e. the Rubber Process Analyzer RPA 2000® (Alpha Technologies), was suitably modified, essentially in using a fast electronic analogic-digital conversion card to record and treat torque and strain signals using purposely written software. Details of such modifications were previously published and the work presented is a sequel of this development. The quality of the applied strain is first precisely documented through FT and found excellent, particularly in the high strain range. Three gum EPDM with different macromolecular characteristics (MWD and long chain branching) were analyzed either using standard dynamic testing, i.e. essentially in the linear viscoelastic range, or using the Fourier transform rheometry approach, by considering data gathered in the far non-linear viscoelastic range. Data obtained are considered with respect to know features of the samples. A series of SBR 1500 samples, collected from various manufacturers, were first analyzed using standard methods; as expected very small differences were seen. Then FT was used to consider torque signals at very high strain (up to 400% at 1 Hz). Using a simple 4-parameter model to treat the variation upon increasing strain of the relative third harmonic component of the torque signal, differences are clearly detected that are discussed with respect to available polymer manufacturing information.

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Lai, V. M. F., e C. Y. Lii. "Gelation Kinetics of Agars from Pterocladia capillacea Examined by Dynamic Rheometry". Journal of Food Science 67, n.º 2 (março de 2002): 672–81. http://dx.doi.org/10.1111/j.1365-2621.2002.tb10658.x.

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Vernáez, Oscar, e Alejandro J. Müller. "Relaxation time spectra from short frequency range small-angle dynamic rheometry". Rheologica Acta 53, n.º 5-6 (11 de abril de 2014): 385–99. http://dx.doi.org/10.1007/s00397-014-0766-2.

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Vingaard, Mathias, e Jesper de Claville Christiansen. "Activation energy of poly(methyl methacrylate) from rheometry and polymer welding". Journal of Materials Science 46, n.º 13 (julho de 2011): 4660–66. http://dx.doi.org/10.1007/s10853-011-5372-4.

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Blanco, P., C. Sieiro, A. Diaz e T. G. Villa. "Production and partial characterization of an endopolygalacturonase from Saccharomyces cerevisiae". Canadian Journal of Microbiology 40, n.º 11 (1 de novembro de 1994): 974–77. http://dx.doi.org/10.1139/m94-155.

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Saccharomyces cerevisiae CECT1389 secreted an extracellular endopolygalacturonase (EC 3.2.1.15) when grown in shake flasks in medium containing galactose alone, or either galactose and polygalacturonic acid or galactose and galacturonic acid as the carbon sources. The synthesis of the enzyme was repressed by glucose and by high oxygen tensions. The enzyme was partially purified by gel exclusion chromatography over Sephacryl S-200, where it showed an apparent molecular mass of 39 kDa; the value determined by high-performance liquid chromatography (HPLC) was 65 kDa. The optimal temperature and pH for enzyme activity were45 °C and 5.5, respectively. The Km and Vmax values for polygalacturonic acid were 4.7 mg∙mL−1 and 6.4 nmol∙mL−1∙min−1. The Ki for HgCl2 was 6.8 × 10−5 M. The enzyme exhibited an endo-splitting mechanism as deduced from viscosimetry experiments as well as from an HPLC study of the end products.Key words: characterization, endopolygalacturonase, Saccharomyces cerevisiae.

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ROMANO, R. C. O., M. A. CINCOTTO e R. G. PILEGGI. "Hardening phenomenon of Portland cement suspensions monitored by Vicat test, isothermal calorimetry and oscillatory rheometry". Revista IBRACON de Estruturas e Materiais 11, n.º 5 (outubro de 2018): 949–59. http://dx.doi.org/10.1590/s1983-41952018000500003.

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Abstract This work was conducted to evaluate the hardening phenomenon of pastes formulated with Portland cements blended with limestone filler (CPIIF), ground blast furnace slag (CPIIE) or pozzolan (CPIIZ). Vicat test, isothermal conduction calorimetry and oscillatory rheometry were the methods used to monitor this transition. The results of Vicat test indicates the faster setting time of pozzolan cement, but no information before this time was obtained. Using isothermal calorimetry was possible to monitor the related changes to the chemical reactions since the first contact with water, and using rheometry, the rate and force of cement particles agglomeration. The main purpose of this work was not extensively explain the results of these three methods, but show that they are complementary to better explain the transition from fluid-to-solid behavior in function of different kind of mineral addition.

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Nichetti, Dario. "Oscillating shear capillary rheometry (OSCAR) for polymer melts". Journal of Polymer Engineering 40, n.º 9 (25 de outubro de 2020): 737–42. http://dx.doi.org/10.1515/polyeng-2019-0231.

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AbstractKnowing the flow parameters of a polymer melt under steady state condition is required to assess the performance of the material in die and mold design. Often, however, this is not sufficient for a full understanding of the polymer processing behavior, and information on the linear and non-linear viscoelastic behavior is needed. In this paper, the non-linear viscoelastic behavior of a polymer under shear flow has been investigated by measuring the stress response when a cyclic oscillating shear rate in a capillary rheometer is applied. The time-dependent wall shear stress has been decomposed into in-phase viscous and elastic components. A model to interpret the experimental results is presented and applied to a well-characterized polystyrene and two polyethylenes with similar rheology but different molecular structure (HDPE and LLDPE). The relevant characteristics resulting from the model, such as the generalized elastic and viscous modulus under shear, are compared and discussed.

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Jarfors, Anders E. W., Mahdi Jafari, Muhammed Aqeel, Patrik Liljeqvist e Per Jansson. "In-Production Rheometry of Semi-Solid Metal Slurries". Metals 12, n.º 7 (19 de julho de 2022): 1221. http://dx.doi.org/10.3390/met12071221.

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Semi-solid aluminium alloy processing (SSM) has advanced into a more mature process with many applications. The current paper aims to investigate the in-process behaviour of a production slurry using an engineering approach to estimate the properties. A method to assess the rheological properties of a semi-solid metal slurry was tested and found capable of producing meaningful measurements. The foundations of this were to use a Rushton turbine setup for the assessment through a model to optimize the factors included in the slurry rheology. In the analysis of the static and dynamic part of the viscosity, it was concluded that the slurry turns increasingly into a solid with increasing solid fractions where the static shear strength dominates the rheology more and more compared to the dynamic components. The static yield strength was also found significantly more dominant with increasing solid fraction, suggesting that the industrial-scale analysis using models based on Ostwald–de Waale and Carreau modelling is far from sufficient for a process, such as the RheoMetal process, with a very rapid slurry generation.

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Colby, Ralph H. "Fiber spinning from polymer solutions". Journal of Rheology 67, n.º 6 (1 de novembro de 2023): 1251–55. http://dx.doi.org/10.1122/8.0000726.

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The thinning of a cylinder of a polymer solution in a volatile solvent is argued to be controlled by solvent diffusion through a dense polymer layer at the cylinder surface. This naturally leads to the exponential time dependence of cylinder radius that is observed in experiments using a fast camera, such as capillary breakup extensional rheometry (CaBER). The relaxation time is controlled by the thickness of the dense (and often glassy) polymer layer and the diffusion coefficient of solvent through that layer. If correct, this means that while CaBER is very useful for understanding fiber spinning, the relaxation time does not yield a measure of the extensional viscosity of polymer solutions in volatile solvents.

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Fisher, Daniel T., David V. Boger e Peter J. Scales. "Measurement Errors in Yield Stress Rheometry that Arise from Torque Auto Zero". Applied Rheology 16, n.º 4 (1 de agosto de 2006): 206–9. http://dx.doi.org/10.1515/arh-2006-0015.

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Abstract The measurement of the shear rheology of concentrated particulate suspensions is important to a range of mixing, pumping and flow operations. The use of a four or six bladed vane attached to a rheometer in an open cup is a popular technique to achieve a rheological characterisation. A problem occurs in the use of automated software with a number of rheological devices for yield stress materials. A torque auto zero default causes the torque at the start of a test to be ignored, and can result in significant errors and underestimation of the yield stress or rheological response of the suspension. The potential effect of using a torque auto zero default is demonstrated for a concentrated particulate suspension of nickel laterite.

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Qiu, Hua, e Mosto Bousmina. "Determination of Mutual Diffusion Coefficients at Nonsymmetric Polymer/Polymer Interfaces from Rheometry". Macromolecules 33, n.º 17 (agosto de 2000): 6588–94. http://dx.doi.org/10.1021/ma991948k.

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Pfleiderer, Patrick, Seung Jae Baik, Zhenkun Zhang, Giovanni Vleminckx, Minne Paul Lettinga, Eric Grelet, Jan Vermant e Christian Clasen. "X-ray scattering in the vorticity direction and rheometry from confined fluids". Review of Scientific Instruments 85, n.º 6 (junho de 2014): 065108. http://dx.doi.org/10.1063/1.4881796.

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Sakr, Walid F., Mohamed A. Ibrahim, Fars K. Alanazi e Adel A. Sakr. "Upgrading wet granulation monitoring from hand squeeze test to mixing torque rheometry". Saudi Pharmaceutical Journal 20, n.º 1 (janeiro de 2012): 9–19. http://dx.doi.org/10.1016/j.jsps.2011.04.007.

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Siginer, D. A. "Multiple Integral Constitutive Equations in Unsteady Motions and Rheometry". Applied Mechanics Reviews 44, n.º 11S (1 de novembro de 1991): S232—S245. http://dx.doi.org/10.1115/1.3121360.

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The use of the integral fluid of order three to predict some simple nearly viscometric unsteady flows of viscoelastic liquids, driven by periodic forcing, is discussed. Flow enhancement effects, due to the parallel and orthogonal superposition of oscillatory and simple shear fields, are predicted. It is shown that it is feasible to determine the constitutive constants involved from a series of experiments of rheometry.

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Costanzo, Salvatore, Daniele Parisi, Thomas Schweizer e Dimitris Vlassopoulos. "REVIEW: Nonlinear shear rheometry: Brief history, recent progress, and challengesa)This manuscript was handled by Editorial Board Member R. H. Colby." Journal of Rheology 68, n.º 6 (17 de outubro de 2024): 1013–36. http://dx.doi.org/10.1122/8.0000897.

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High-shear rate rotational rheometry provides access to the fast nonlinear dynamics of soft materials and, particularly, their shear stress (exhibiting shear thinning and/or thickening) as well as the first and second normal stress differences, along with their time-dependent behavior. These material functions are valuable for understanding a material's processing performance and constitutive behavior and, hence, for designing new materials with desired rheology. However, their accurate measurement has been one of the most formidable challenges in rheometry. Here, we provide an overview of the different approaches used, along with their merits and drawbacks, while we discuss practical guidelines for the implementation of measurement protocols. We focus on the development and use of cone-partitioned plate fixtures, which have been shown to provide reliable data over a wide range of Weissenberg numbers, when properly used. Furthermore, this review presents selected applications and results from recent developments, identifies operating measurement windows, discusses new capabilities and open problems, and, finally, it provides perspectives for further developments.

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Vocht, Marc P., Ronald Beyer, Patricija Thomasic, Alexandra Müller, Antje Ota, Frank Hermanutz e Michael R. Buchmeiser. "High-performance cellulosic filament fibers prepared via dry-jet wet spinning from ionic liquids". Cellulose 28, n.º 5 (1 de fevereiro de 2021): 3055–67. http://dx.doi.org/10.1007/s10570-021-03697-x.

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AbstractWe report on a new process for the spinning of high-performance cellulosic fibers. For the first time, cellulose has been dissolved in the ionic liquid (IL) 1-ethyl-3-methylimidazolium octanoate ([C2C1im][Oc]) via a thin film evaporator in a continuous process. Compared to other ILs, [C2C1im][Oc] shows no signs of hydrolysis with water. For dope preparation the degree of polymerization of the pulp was adjusted by electron beam irradiation and determined by viscosimetry. In addition, the quality of the pulp was evaluated by means of alkali resistance. Endless filament fibers have been spun using dry-jet wet spinning and an extruder instead of a spinning pump, which significantly increases productivity. By this approach, more than 1000 m of continuous multifilament fibers have been spun. The novel approach allows for preparing cellulose fibers with high Young's modulus (33 GPa) and unprecedented high tensile strengths up to 45 cN/tex. The high performance of the obtained fibers provides a promising outlook for their application as replacement material for rayon-based tire cord fibers.

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McCarroll, Louise L., Michael J. Solomon e William W. Schultz. "Differential analysis of capillary breakup rheometry for Newtonian liquids". Journal of Fluid Mechanics 804 (8 de setembro de 2016): 116–29. http://dx.doi.org/10.1017/jfm.2016.531.

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We present a Newtonian, one-dimensional, differential analysis for capillary breakup rheometry (CBR) to determine the surface tension to viscosity ratio $\unicode[STIX]{x1D6FC}$. Our local differential analysis does not require specific assumptions for the axial force to preclude its measurement. Our analysis indicates that measuring gradients in filament curvature is necessary to accurately determine $\unicode[STIX]{x1D6FC}$ when axial force is not measured. CBR experiments were performed on five silicone oils ($0.35~\text{Pa}~\text{s}<\unicode[STIX]{x1D707}<10~\text{ Pa}~\text{s}$), three sample volumes, and three strains to evaluate the operating range of the differential analysis and compare its performance to that of a standard integral method from literature. We investigate the role of filament asymmetry, caused mainly by gravity, on the performance of the differential method for the range of conditions studied. Experimental and analytical details for resolving gradients of curvature are also given.

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Goubert, Alain, Jan Vermant, Paula Moldenaers, Axel Göttfert e Benoît Ernst. "Comparison of Measurement Techniques for Evaluating the Pressure Dependence of the Viscosity". Applied Rheology 11, n.º 1 (1 de fevereiro de 2001): 26–37. http://dx.doi.org/10.1515/arh-2001-0003.

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Abstract The different methods that can be used for measuring the effect of a hydrostatic pressure on the viscosity of polymer melts are evaluated. A linear low-density polyethylene is chosen as test material, as it can be expected to have a small pressure dependency. Special attention is given to methods employing capillary rheometry, as these methods yield a range of shear rates and pressures that are typically encountered under polymer processing conditions. The accuracy of the different techniques is evaluated considering also the complexity of the experimental devices. First it is investigated to which extent standard capillary rheometry can be used to extract information about the pressure dependency of the viscosity. Secondly, it is shown how the accuracy can be greatly increased by the simple addition of a pressure chamber below the exit of the capillary, with a needle valve to regulate the back pressure. The results from this device are compared with those from a more robust method using a pressurized double piston rheometer and with literature data. The experimental values for the pressure coefficient of the viscosity will also be compared with those predicted from PVT data using Utracki's method.

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Porges, K. G. A., S. A. Cox, C. Herzenberg e C. Kampschoer. "Flow Speed Measurement and Rheometry by Pulsed Neutron Activation". Journal of Fluids Engineering 111, n.º 3 (1 de setembro de 1989): 337–41. http://dx.doi.org/10.1115/1.3243649.

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Pulsed Neutron Activation (PNA) is a means of noninvasive flow velocity measurement based on tagging the flowing medium with a short-lived radioactivity. Previous work with salt or dye-tagging showed poor accuracy in turbulent and failed in laminar flow when conventional data processing was used. However, use of a data acquisition and processing scheme that is based on tag dispersion modelling can produce absolute values over a wide range of flow speeds and regimes with high accuracy. For non-Newtonian/laminar flow, rheological information can also be obtained. The inherently non-intrusive nature of PNA tagging makes this scheme available for slurry measurements. The performance of PNA in slurry flow at up to 60 percent solid content was compared to full-flow diversion and weighing. Errors ranged from less than 0.2 percent at high Reynolds’ numbers to about 2 percent for paste flow. Rheological parameters (yield shear stress or flow behavior index) could be determined with an accuracy that compared to that of a spindle viscometer with grab-samples. The PNA scheme thus offers a unique means of studying slurry flow in a dedicated laboratory facility, or of providing calibration for other flowmeters in an industrial plant through temporary installation by a team of expert consultants.

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WILLENBACHER, N., e C. OELSCHLAEGER. "Dynamics and structure of complex fluids from high frequency mechanical and optical rheometry". Current Opinion in Colloid & Interface Science 12, n.º 1 (fevereiro de 2007): 43–49. http://dx.doi.org/10.1016/j.cocis.2007.03.004.

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Swallow, Frank E. "Viscosity of polydimethylsiloxane gum: Shear and temperature dependence from dynamic and capillary rheometry". Journal of Applied Polymer Science 84, n.º 13 (16 de abril de 2002): 2533–40. http://dx.doi.org/10.1002/app.10563.

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Terkel, Matthew, Robert Wright e Juan de Vicente. "Magnetorheology in unsteady fields: From uniaxial DC to rotating AC fields". Journal of Rheology 67, n.º 4 (26 de maio de 2023): 833. http://dx.doi.org/10.1122/8.0000646.

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Magnetorheological fluids structured under precession fields are thoroughly investigated. Having complete dynamic triaxial magnetic field control, we are able to study both the structural and magnetorheological response via videomicroscopy and rheometry integration for a wide range of magnetic field configurations, once previously limited to traditional uniaxial fields. Optimal precession fields for driving the formation of more robust particle structures enhancing yield stress response are identified. It is believed that structural reinforcement comes from chain coarsening through lateral chain coalescence and particle compactness within the structures such that a lower energy configuration is found for certain field configurations. Particle level simulations supplement our understanding of lateral chain coalescence and structure strengthening.

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Hoh, N. J., e R. N. Zia. "Hydrodynamic diffusion in active microrheology of non-colloidal suspensions: the role of interparticle forces". Journal of Fluid Mechanics 785 (16 de novembro de 2015): 189–218. http://dx.doi.org/10.1017/jfm.2015.602.

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Hydrodynamic diffusion in the absence of Brownian motion is studied via active microrheology in the ‘pure-hydrodynamic’ limit, with a view towards elucidating the transition from colloidal microrheology to the non-colloidal limit, falling-ball rheometry. The phenomenon of non-Brownian force-induced diffusion in falling-ball rheometry is strictly hydrodynamic in nature; in contrast, analogous force-induced diffusion in colloids is deeply connected to the presence of a diffusive boundary layer even when Brownian motion is very weak compared with the external force driving the ‘probe’ particle. To connect these two limits, we derive an expression for the force-induced diffusion in active microrheology of hydrodynamically interacting particles via the Smoluchowski equation, where thermal fluctuations play no role. While it is well known that the microstructure is spherically symmetric about the probe in this limit, fluctuations in the microstructure need not be – and indeed lead to a diffusive spread of the probe trajectory. The force-induced diffusion is anisotropic, with components along and transverse to the line of external force. The latter is identically zero owing to the fore–aft symmetry of pair trajectories in Stokes flow. In a naïve first approach, the vanishing relative hydrodynamic mobility at contact between the probe and an interacting bath particle was assumed to eliminate all physical contribution from interparticle forces, whereby advection alone drove structural evolution in pair density and microstructural fluctuations. With such an approach, longitudinal force-induced diffusion vanishes in the absence of Brownian motion, a result that contradicts well-known experimental measurements of such diffusion in falling-ball rheometry. To resolve this contradiction, the probe–bath-particle interaction at contact was carefully modelled via an excluded annulus. We find that interparticle forces play a crucial role in encounters between particles in the hydrodynamic limit – as they must, to balance the advective flux. Accounting for this force results in a longitudinal force-induced diffusion $D_{\Vert }=1.26aU_{S}{\it\phi}$, where $a$ is the probe size, $U_{S}$ is the Stokes velocity and ${\it\phi}$ is the volume fraction of bath particles, in excellent qualitative and quantitative agreement with experimental measurements in, and theoretical predictions for, macroscopic falling-ball rheometry. This new model thus provides a continuous connection between micro- and macroscale rheology, as well as providing important insight into the role of interparticle forces for diffusion and rheology even in the limit of pure hydrodynamics: interparticle forces give rise to non-Newtonian rheology in strongly forced suspensions. A connection is made between the flow-induced diffusivity and the intrinsic hydrodynamic microviscosity which recovers a precise balance between fluctuation and dissipation in far from equilibrium suspensions; that is, diffusion and drag arise from a common microstructural origin even far from equilibrium.

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Rodd, Lucy E., Timothy P. Scott, Justin J. Cooper-White e Gareth H. McKinley. "Capillary Break-up Rheometry of Low-Viscosity Elastic Fluids". Applied Rheology 15, n.º 1 (1 de fevereiro de 2005): 12–27. http://dx.doi.org/10.1515/arh-2005-0001.

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Abstract We investigate the dynamics of the capillary thinning and break-up process for low viscosity elastic fluids such as dilute polymer solutions. Standard measurements of the evolution of the midpoint diameter of the necking fluid filament are augmented by high speed digital video images of the break up dynamics. We show that the successful operation of a capillary thinning device is governed by three important time scales (which characterize the relative importance of inertial, viscous and elastic processes), and also by two important length scales (which specify the initial sample size and the total stretch imposed on the sample). By optimizing the ranges of these geometric parameters, we are able to measure characteristic time scales for tensile stress growth as small as 1 millisecond for a number of model dilute and semi-dilute solutions of polyethylene oxide (PEO) in water and glycerol. If the final aspect ratio of the sample is too small, or the total axial stretch is too great, measurements are limited, respectively, by inertial oscillations of the liquid bridge or by the development of the well-known beads-on-a-string morphology which disrupt the formation of a uniform necking filament. By considering the magnitudes of the natural time scales associated with viscous flow, elastic stress growth and inertial oscillations it is possible to construct an “operability diagram” characterizing successful operation of a capillary breakup extensional rheometer. For Newtonian fluids, viscosities greater than approximately 70 mPas are required; however for dilute solutions of high molecular weight polymer, the minimum viscosity is substantially lower due to the additional elastic stresses arising from molecular extension. For PEO of molecular weight 2 · 106 g/mol, it is possible to measure relaxation times of order 1 ms in dilute polymer solutions with zero-shear-rate viscosities on the order of 2 – 10 mPas.

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Feng, R., K. T. Ramesh e A. S. Douglas. "An Analytical and Computational Investigation of High-Rate Rheometry". Journal of Tribology 118, n.º 3 (1 de julho de 1996): 601–7. http://dx.doi.org/10.1115/1.2831579.

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This paper examines a class of experimental techniques used to develop constitutive models for lubricants, by simulating the shearing of a thin lubricant layer while accounting for transient phenomena. The complete transient thermal problem with fully nonlinear constitutive relations is solved, and heat conduction is accounted for both in the lubricant layer and into the walls. Numerical simulations are used to examine the shear stress history, the velocity profile, and the temperature profile as functions of time. As a particular example, the high-rate torsional Kolsky bar rheometer (Feng and Ramesh, 1993) is simulated. The computations indicate that the Kolsky bar experiments, which are able to examine the time-histories of the stresses and of the motion, can he used to obtain material properties for lubricants at high shear rates. A full numerical analysis may be required to properly interpret some of the data available from the Kolsky bar experiments, since at longer times (greater than that associated with the peak shear stress) the thermal softening may dominate the response and the velocity field may become strongly inhomogeneous. The numerical simulations are performed using both rate-dependent and limiting stress constitutive laws, and the effects of the layer thickness and the rise time of the relative velocities are examined. The simulations show that the film thickness and the rise time of the relative velocities can have strong effects on the character of the solution when the transient phenomena are included in the analysis. The computations also demonstrate that highly inhomogeneous and even localized flows may occur within rheometers as a result of transient effects. The development of these flows depends on the layer thickness, the rise-time of the boundary velocity, the thermal boundary conditions, and the constitutive behavior of the lubricant.

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