SHEAR DEPENDENCE IN THE VISCOMETRY OF HIGH POLYMER SOLUTIONS: A NEW VARIABLE-SHEAR CAPILLARY VISCOMETER

1961 ◽  
Vol 39 (1) ◽  
pp. 203-215 ◽  
Author(s):  
L. H. Cragg ◽  
H. Van Oene
Keyword(s):  
Polymer Solutions ◽  
Relative Viscosity ◽  
Free Fall ◽  
External Pressure ◽  
Capillary Viscometer ◽  
Shear Stresses ◽  
High Polymer ◽  
Variable Shear ◽  
Newtonian Liquids ◽  
Low Shear

The principles of capillary viscometry are reviewed, and design criteria for capillary viscometers to be used with non-Newtonian liquids are discussed. A description is given of a new type of variable-shear capillary viscometer—a modification of the Ubbelohde suspended-level viscometer—designed for measurements in the low-shear range. The instrument is rugged, convenient, and precise, and makes possible measurements at free fall over a 10-fold range of shear stress (or shear rate), a range that can easily be extended by use of two or more suitably modified instruments or by the application of external pressure. Experimental evidence is presented to show that proper choice of the dimensions of the instrument eliminates or minimizes most of the "effects" that limit the precision of measurements of relative viscosity (and related functions) of high polymer solutions in the range of low shear stresses.

Susceptibility of density-fractionated erythrocytes to subhaemolytic mechanical shear stress

2018 ◽  
Vol 42 (3) ◽  
pp. 151-157 ◽  
Author(s):  
Antony P McNamee ◽  
Kieran Richardson ◽  
Jarod Horobin ◽  
Lennart Kuck ◽  
Michael J Simmonds
Keyword(s):  
Blood Cell ◽  
Red Blood Cells ◽  
Red Blood Cell ◽  
Blood Cells ◽  
Shear Stresses ◽  
Mechanical Stimuli ◽  
Cell Deformability ◽  
Red Blood Cell Deformability ◽  
Cell Age ◽  
Low Shear

Introduction: Accumulating evidence demonstrates that subhaemolytic mechanical stresses, typical of circulatory support, induce physical and biochemical changes to red blood cells. It remains unclear, however, whether cell age affects susceptibility to these mechanical forces. This study thus examined the sensitivity of density-fractionated red blood cells to sublethal mechanical stresses. Methods: Red blood cells were isolated and washed twice, with the least and most dense fractions being obtained following centrifugation (1500 g × 5 min). Red blood cell deformability was determined across an osmotic gradient and a range of shear stresses (0.3–50 Pa). Cell deformability was also quantified before and after 300 s exposure to shear stresses known to decrease (64 Pa) or increase (10 Pa) red blood cell deformability. The time course of accumulated sublethal damage that occurred during exposure to 64 Pa was also examined. Results: Dense red blood cells exhibited decreased capacity to deform when compared with less dense cells. Cellular response to mechanical stimuli was similar in trend for all red blood cells, independent of density; however, the magnitude of impairment in cell deformability was exacerbated in dense cells. Moreover, the rate of impairment in cellular deformability, induced by 64 Pa, was more rapid for dense cells. Relative improvement in red blood cell deformability, due to low-shear conditioning (10 Pa), was consistent for both cell populations. Conclusion: Red blood cell populations respond differently to mechanical stimuli: older (more dense) cells are highly susceptible to sublethal mechanical trauma, while cell age (density) does not appear to alter the magnitude of improved cell deformability following low-shear conditioning.

Surface-tension-driven breakup of viscoelastic liquid threads

1982 ◽  
Vol 120 ◽  
pp. 245-266 ◽  
Author(s):  
Simon L. Goren ◽  
Moshe Gottlieb
Keyword(s):  
Relaxation Time ◽  
Stress Relaxation ◽  
Polymer Solutions ◽  
Small Diameter ◽  
Shear Thinning ◽  
Prior History ◽  
Axial Tension ◽  
Dilute Polymer Solutions ◽  
Linearized Stability ◽  
Newtonian Liquids

A linearized stability analysis is carried out for the breakup of small-diameter liquid filaments of dilute polymer solutions into droplets. Oldroyd's 8-constant model expressed in a corotational reference frame is used as the rheological equation of state. The crucial idea in this theory is the recognition that the liquid may be subject to an unrelaxed axial tension due to its prior history. If the tension is zero, the present analysis predicts that jets of shear-thinning liquids are less stable than comparable jets of Newtonian liquids; this is in agreement with previous analyses. However, when the axial tension is not zero, and provided the stress relaxation time constant is sufficiently large, the new theory predicts that the axial elastic tension can be a significant stabilizing influence. With reasonable values for the tension and stress relaxation time the theory explains the great stability observed for jets of some shear- thinning, dilute polymer solutions. The theory explains why drops produced from jets of such liquids are larger than drops from corresponding Newtonian liquids. The theory also appears capable of explaining the sudden appearance of irregularly spaced bulges on jets after long distances of t,ravel with little amplification of disturbances.

GRAFT COPOLYMERS OF STYRENE AND METHYL METHACRYLATE: PART II: VISCOSITY BEHAVIOR

1956 ◽  
Vol 34 (8) ◽  
pp. 1027-1036 ◽  
Author(s):  
M. H. Jones
Keyword(s):  
Shear Rate ◽  
Methyl Methacrylate ◽  
Graft Copolymers ◽  
Free Fall ◽  
Capillary Viscometer ◽  
Linear Polymers ◽  
Viscosity Behavior ◽  
Shear Gradient ◽  
Constant Shear Rate ◽  
Made In

A study of the viscosity behavior of the graft copolymers described in Part I has been made with dilute solutions in benzene at 25 °C. Although the slope constants of the Huggins equation increase with the frequency of branching when measurements are made in a capillary viscometer under 'free fall' conditions, this is shown to be attributable to the dependence of viscosity on shear gradient. At a constant shear rate, the Huggins k′ values approximate to those of linear polymers. It is suggested that the marked increase in viscosity observed with decreasing shear rate for the graft copolymers is due to molecular entanglement.

scholarly journals Light Scattering of High Polymer Solutions

1946 ◽  
Vol 14 (1) ◽  
pp. 43-45 ◽  
Author(s):  
Jurg Waser ◽  
Richard M. Badger ◽  
Verner Schomaker
Keyword(s):  
Light Scattering ◽  
Polymer Solutions ◽  
High Polymer

scholarly journals Hydrous oceanic crust hosts megathrust creep at low shear stresses

2020 ◽  
Vol 6 (22) ◽  
pp. eaba1529
Author(s):  
Christopher J. Tulley ◽  
Åke Fagereng ◽  
Kohtaro Ujiie
Keyword(s):  
Oceanic Crust ◽  
Shear Zones ◽  
Interface Strength ◽  
Shear Stresses ◽  
Plate Interface ◽  
Strength And Deformation ◽  
Transition Field ◽  
Flow Laws ◽  
Sw Japan ◽  
Low Shear

The rheology of the metamorphosed oceanic crust may be a critical control on megathrust strength and deformation style. However, little is known about the strength and deformation style of metamorphosed basalt. Exhumed megathrust shear zones exposed on Kyushu, SW Japan, contain hydrous metabasalts deformed at temperatures between ~300° and ~500°C, spanning the inferred temperature-controlled seismic-aseismic transition. Field and microstructural observations of these shear zones, combined with quartz grain-size piezometry, indicate that metabasalts creep at shear stresses <100 MPa at ~370°C and at shear stresses <30 MPa at ~500°C. These values are much lower than those suggested by viscous flow laws for basalt. The implication is that relatively weak, hydrous, metamorphosed oceanic crust can creep at low viscosities over a wide shear zone and have a critical influence on plate interface strength and deformation style around the seismic-aseismic transition.

Rheology of Fluoride Gels

1976 ◽  
Vol 55 (3) ◽  
pp. 353-356 ◽  
Author(s):  
M. Braden ◽  
Ratna Perera
Keyword(s):  
Infrared Spectroscopy ◽  
Shear Rate ◽  
Elastic Behavior ◽  
Shear Stresses ◽  
High Shear ◽  
Shear Rates ◽  
Extreme Stress ◽  
Thickening Agents ◽  
Shear Rate Dependence ◽  
Low Shear

Six commercial fluoride gels have been studied, using a cone and plate viscometer. Also, the thickening agents have been analyzed using infrared spectroscopy. All gels showed stress thinning, which is the decrease of viscosity with shear rate. Such shear rate dependence is clinically convenient in that the gel will flow readily at the high shear stresses present when the gel is applied but will not flow readily under its own weight when on the tooth. Five materials containing hydroxyalkyl celluloses showed similar degrees of shear thinning. One material with a non-cellulosic thickener showed much more extreme stress thinning together with elastic behavior at low shear rates; such behavior may be clinically advantageous. All of the gels showed only slight temperature dependence of rheological properties.

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