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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, an empirical method to calibrate the measuring head of a torque-rheometer to obtain the power-law parameters of polymer melts was developed, where only one geometrical parameter, with well-defined physical limits, is needed for calibration, instead of the two arbitrary parameters proposed by the previous authors.
Abstract: In this work we develop an empirical method to calibrate the measuring head of a torque-rheometer to obtain the power-law parameters of polymer melts. This method is based on a similar analysis developed by Lee and Purdon. However, in this work, only one geometrical parameter, with well-defined physical limits, is needed for calibration, instead of the two arbitrary parameters proposed by the previous authors. Moreover, this parameter is closely related to the ordinate of the logarithmic relationship between the torque (M T ) and the angular velocity (S 1 ), obtained from the torque-rheometer data. This allows us to define a calibration function for this parameter, which is used to evaluate the consistency index (m) of the melt. On the other hand, experimental results confirm the equivalence between the slope of the logarithmic values of torque and angular velocity obtained from the torque-rheometer data and those of shear stress vs. shear rate obtained from capillary rheometry. This further highlights the feasibility of evaluating the melt flow index (n) and the consistency index (m) from the torque-rheometer data.

63 citations

Journal ArticleDOI
TL;DR: In this article, a novel technique for measuring viscosity at high shear rates is described, which is an extension of a well-established method, parallel disk viscometry, which has been limited traditionally to low shear rate ( 50,000 s−1) to be attained without disrupting the torsional flow field.
Abstract: A novel technique for measuring viscosity at high shear rates is described. The technique is an extension of a well‐established method, parallel‐disk viscometry, which has been limited traditionally to low shear rates ( 50,000 s−1) to be attained without disrupting the torsional flow field, and thus controlled measurements of viscosity could be made at those shear rates. The presence of flow disturbances such as shear heating, surface fracture, and radial migration, common impediments in high‐shear measurements, can be readily detected with a thixotropic loop program, and the effect of such disturbances can be separated from the actual rheological response of the fluid. Data are presented on some well‐defined fluids, both Newtonian and shear‐thinning, and the limitations of this technique are discussed.

63 citations

Journal ArticleDOI
Perviz Ahmedzade1
TL;DR: In this article, the effects of styrene butadiene-styrene (SBS) and SBS with new reactive terpolymer (Entira®Bond 8) modifications on the rheological properties of pure bitumen were investigated and compared to each other.

63 citations

Journal ArticleDOI
TL;DR: In this article, the authors measured the stress in the startup of uniaxial elongational flow until steady state, followed by stress relaxation, for a narrow molar mass distribution polystyrene melt with a molecular weight of 145kg∕mol.
Abstract: The stress in the startup of uniaxial elongational flow until steady state, followed by stress relaxation, has been measured for a narrow molar mass distribution polystyrene melt with a molecular weight of 145kg∕mol. The experiments are conducted on a filament stretching rheometer, where a closed loop control of the midfilament diameter ensures controlled uniaxial extension. The closed loop control algorithm is extended to apply to the stress relaxation part of the experiment. It ensures a constant midfilament diameter, by controlling the motion of the end plates. By dividing the measured stress with the theoretically predicted stress from the Doi and Edwards model during relaxation, the stretch factors corresponding to each imposed stretch rate are obtained. These stretch factors converge to a unique envelope and eventually converge to unity for long times for all measured elongational rates.

63 citations

Journal ArticleDOI
TL;DR: In this paper, the role of particle migration was found to be of prime importance in the formation of string-like structures in suspensions containing polystyrene spheres in viscoelastic suspending media.
Abstract: Flow-induced structures in suspensions containing spheres in viscoelastic suspending media were investigated by microscopy and rheo-optical methods. Suspensions of monodisperse polystyrene spheres with diameters ranging from 1.2 to 2.8 μm and dispersed in aqueous solutions of hydroxypropylcellulose were studied in simple shear flows. Optical microscopy observations as well as small-angle light-scattering (SALS) experiments were performed using a parallel plate geometry. In agreement with previous work, necklaces of particles aligned in the flow direction were observed when shearing faster then a critical shear rate, which was found to be independent of particle size. In contrast to earlier work, however, the role of particle migration was found to be of prime importance. Particles were shown to migrate toward the plates where the particles assembled and aligned in strings running in the flow direction. For the smallest particles (1 μm diameter), the formation of particle doublets or short strings along the vorticity direction was observed at low shear rates, which flipped to an orientation into the flow direction and grew into longer strings at higher shear rates. SALS experiments were used to quantify the degree of alignment and its dependence on particle size, shear rate, and gap. For the system under investigation, the degree of alignment was found to increase with increasing shear rate and particle size and with decreasing gap. The present results suggest that, depending on the details of the suspending medium and the size and nature of the suspended particles, the formation of aligned structures is affected by the relative magnitude of the colloidal and hydrodynamic forces and the kinetics of string formation versus the kinetics of migration.

63 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023240
2022487
2021164
2020196
2019201
2018162