Characterization and Physical Properties of New Isobutylene-Based Graft Copolymers

1998 ◽  
Vol 71 (4) ◽  
pp. 803-819 ◽  
Author(s):  
Mun F. Tse ◽  
A. J. Dias ◽  
H-C. Wang
Keyword(s):  
Rheological Behavior ◽  
Triblock Copolymers ◽  
Graft Copolymers ◽  
High Shear ◽  
Shear Dependent Viscosity ◽  
Viscosity Effects ◽  
Lower Viscosity ◽  
Dependent Viscosity ◽  
Hot Melt ◽  
Low Shear

Abstract A number of isobutylene-based graft copolymers with different compositions are compared to several commercial thermoplastic block copolymers, such as SIS, SBS and SEBS, in terms of morphology and viscoelasticity. The backbone of these graft copolymers is a terpolymer (BIMS) of isobutylene, p-methylstyrene and p-bromomethylstyrene, and the side chains are either polystyrene or poly(2,6-dimethyl-1,4-phenylene ether). Graft copolymer synthesis, statistics of graft formation, and stress-strain properties are described. Overall, these graft copolymers exhibit unique shear dependent viscosity effects, such as rapid thickening (quick setting) at low shear and lower viscosity (better processability) at high shear, compared to linear triblock copolymers. The rheological behavior of these graft copolymers could be a key advantage for high-shear calendering, extrusion, hot-melt spraying, and injection molding.

The Rheology of Saliva

1987 ◽  
Vol 66 (1_suppl) ◽  
pp. 660-666 ◽  
Author(s):  
W. H. Schwarz
Keyword(s):  
Salivary Gland ◽  
Rheological Properties ◽  
Medical Management ◽  
Artificial Saliva ◽  
Salivary Gland Dysfunction ◽  
Shear Dependent Viscosity ◽  
Saliva Analysis ◽  
Whole Saliva ◽  
Saliva Substitutes ◽  
Dependent Viscosity

The rheology of saliva affects the coating and lubrication of oral surfaces and the consistency of ingested foods. Salivary gland dysfunction can cause tissue damage and dysphagia. Therefore, we have considered the problem of designing a synthetic saliva for medical management. Also, we have measured certain rheological properties [shear-dependent viscosity η (k)] and the frequency-dependent moduli [G′(f) and η′(f)] of normal stimulated whole saliva. Analysis of the rheological data and consideration of requirements for using artificial saliva have resulted in a better understanding of the rheological functions of natural saliva and the desirable characteristics of synthetic saliva. In addition, we have measured rheological properties of two commercial saliva substitutes for comparison.

Stability of Shear-Thickening Liquids Between Rotating Cylinders

2010 ◽  
Author(s):  
Nariman Ashrafi ◽  
Habib Karimi Haghighi
Keyword(s):  
Couette Flow ◽  
Dynamical Behavior ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Taylor Vortex ◽  
Shear Dependent Viscosity ◽  
Shear Thinning Fluids ◽  
Shear Thickening Fluids ◽  
The Stability ◽  
Dependent Viscosity

The effects of nonlinearities on the stability are explored for shear thickening fluids in the narrow-gap limit of the Taylor-Couette flow. It is assumed that shear-thickening fluids behave exactly as opposite of shear thinning ones. A dynamical system is obtained from the conservation of mass and momentum equations which include nonlinear terms in velocity components due to the shear-dependent viscosity. It is found that the critical Taylor number, corresponding to the loss of stability of Couette flow becomes higher as the shear-thickening effects increases. Similar to the shear thinning case, the Taylor vortex structure emerges in the shear thickening flow, however they quickly disappear thus bringing the flow back to the purely azimuthal flow. Naturally, one expects shear thickening fluids to result in inverse dynamical behavior of shear thinning fluids. This study proves that this is not the case for every point on the bifurcation diagram.

Annular Frictional Pressure Losses During Drilling—Predicting the Effect of Drillstring Rotation

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Arild Saasen
Keyword(s):  
Rheological Properties ◽  
Pressure Loss ◽  
Drilling Fluid ◽  
Axial Flow ◽  
Drilling Fluids ◽  
Unstable Flow ◽  
Pressure Losses ◽  
Shear Dependent Viscosity ◽  
Water Based ◽  
Dependent Viscosity

Controlling the annular frictional pressure losses is important in order to drill safely with overpressure without fracturing the formation. To predict these pressure losses, however, is not straightforward. First of all, the pressure losses depend on the annulus eccentricity. Moving the drillstring to the wall generates a wider flow channel in part of the annulus which reduces the frictional pressure losses significantly. The drillstring motion itself also affects the pressure loss significantly. The drillstring rotation, even for fairly small rotation rates, creates unstable flow and sometimes turbulence in the annulus even without axial flow. Transversal motion of the drillstring creates vortices that destabilize the flow. Consequently, the annular frictional pressure loss is increased even though the drilling fluid becomes thinner because of added shear rate. Naturally, the rheological properties of the drilling fluid play an important role. These rheological properties include more properties than the viscosity as measured by API procedures. It is impossible to use the same frictional pressure loss model for water based and oil based drilling fluids even if their viscosity profile is equal because of the different ways these fluids build viscosity. Water based drilling fluids are normally constructed as a polymer solution while the oil based are combinations of emulsions and dispersions. Furthermore, within both water based and oil based drilling fluids there are functional differences. These differences may be sufficiently large to require different models for two water based drilling fluids built with different types of polymers. In addition to these phenomena washouts and tool joints will create localised pressure losses. These localised pressure losses will again be coupled with the rheological properties of the drilling fluids. In this paper, all the above mentioned phenomena and their consequences for annular pressure losses will be discussed in detail. North Sea field data is used as an example. It is not straightforward to build general annular pressure loss models. This argument is based on flow stability analysis and the consequences of using drilling fluids with different rheological properties. These different rheological properties include shear dependent viscosity, elongational viscosity and other viscoelastic properties.

An existence result for fluids with shear dependent viscosity — Steady flows

1997 ◽  
Vol 30 (5) ◽  
pp. 3041-3049 ◽  
Author(s):  
Jens Frehse ◽  
Josef Málek ◽  
Mark Steinhauer
Keyword(s):  
Existence Result ◽  
Steady Flows ◽  
Shear Dependent Viscosity ◽  
Dependent Viscosity

Rheological behavior of SAN/PC blends under extremely high shear rate

1989 ◽  
Vol 37 (7) ◽  
pp. 1837-1853 ◽  
Author(s):  
Hideroh Takahashi ◽  
Takaaki Matsuoka ◽  
Takashi Ohta ◽  
Kenzo Fukumori ◽  
Toshio Kurauchi ◽  
...  
Keyword(s):  
Shear Rate ◽  
Rheological Behavior ◽  
High Shear Rate ◽  
High Shear

Whole blood viscosity in the evaluation of thrombogenic milieu in mitral stenosis

2021 ◽  
Vol 15 (3) ◽  
pp. 181-190
Author(s):  
Elif H Ozcan Cetin ◽  
Mehmet S Cetin ◽  
Mustafa B Ozbay ◽  
Hasan C Könte ◽  
Nezaket M Yaman ◽  
...  
Keyword(s):  
Shear Rate ◽  
Blood Viscosity ◽  
Whole Blood ◽  
Mitral Stenosis ◽  
High Shear Rate ◽  
High Shear ◽  
Whole Blood Viscosity ◽  
Spontaneous Echo Contrast ◽  
Shear Rates ◽  
Low Shear

Aim: We aimed to assess the association of whole blood with thromboembolic milieu in significant mitral stenosis patients. Methodology & results: We included 122 patients and classified patients into two groups as having thrombogenic milieu, thrombogenic milieu (+), otherwise patients without thrombogenic milieu, thrombogenic milieu (-). Whole blood viscosity (WBV) in both shear rates were higher in thrombogenic milieu (+) group comparing with thrombogenic milieu (-). WBV at high shear rate and WBV at low shear rate parameters were moderately correlated with grade of spontaneous echo contrast. Adjusted with other parameters, WBV parameters at both shear rates were associated with presence of thrombogenic milieu. Discussion & conclusion: We found that extrapolated WBV at both shear rates was significantly associated with the thrombogenic milieu in mitral stenosis. This easily available parameter may provide additional perspective about thrombogenic diathesis.

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