Viscometer cone-plate

Chaturani, P, and Narasimman, S., 1990. Flow of power-law fluids in cone-plate viscometer. Acta Mechanica 82, 197-211. 

Normal Stress (Weissenberg Effect). Many viscoelastic fluids flow in a direction normal (perpendicular) to the direction of shear stress in steady-state shear (21,90). Examples of the effect include flour dough climbing up a beater, polymer solutions climbing up the inner cylinder in a concentric cylinder viscometer, and paints forcing apart the cone and plate of a cone—plate viscometer. The normal stress effect has been put to practical use in certain screwless extmders designed in a cone—plate or plate—plate configuration, where the polymer enters at the periphery and exits at the axis. 

Cone—Plate Viscometer. In a cone—plate viscometer (Fig. 28), alow angle (<3°) cone rotates against a flat plate with the fluid sample between them. The cone—plate instmment is a simple, straightforward device that is easy to use and extremely easy to clean. It is well suited to routine work because measurements are rapid and no tedious calculations are necessary. With careful caUbration and good temperature control it can also be used for research. Heated instmments can be used for melt viscosity measurements. 

Fig. 28. Cone—plate viscometer. R is the radius of the cone, a is the angle between cone and plate, and Q is the relative angular velocity.

In most rotational viscometers the rate of shear varies with the distance from a wall or the axis of rotation. However, in a cone—plate viscometer the rate of shear across the conical gap is essentially constant because the linear velocity and the gap between the cone and the plate both increase with increasing distance from the axis. No tedious correction calculations are required for non-Newtonian fluids. The relevant equations for viscosity, shear stress, and shear rate at small angles a of Newtonian fluids are equations 29, 30, and 31, respectively, where M is the torque, R the radius of the cone, v the linear velocity, and rthe distance from the axis. 

Brookfield has introduced a new digital cone—plate viscometer in two versions. The CAP 1000 is a single speed instmment (12,000 or 3, 000 with 60 Hz current) that upgrades the ICl cone—plate design (ASTM D4287). The CAP 2000 is a multispeed viscometer with a viscosity range of 1 15, 000 mPa-s. This instmment covers a wide range of shear rates (166-26, 600 ) and complements the low shear WeUs-Brookfield viscometer. 

The Ferranti-Shidey viscometer was the first commercial general-purpose cone—plate viscometer many of the instmments stiU remain in use in the 1990s. Viscosities of 20 to 3 x 10 mPa-s can be measured over a shear rate range of 1.8-18, 000 and at up to 200°C with special ceramic cones. Its features include accurate temperature measurement and good temperature control (thermocouples are embedded in the water-jacketed plate), electrical sensing of cone—plate contact, and a means of adjusting and locking the position of the cone and the plate in such a way that these two just touch. Many of the instmments have been interfaced with computers or microprocessors. 

Two main types of viscometers are suitable for the determination of the viscosity of a polymer melt The rotation viscometer (Couette viscometer, cone-plate viscometer) and the capillary viscometer or capillary extrusiometer. The latter are especially suitable for laboratory use since they are relatively easy to handle and are also applicable in the case of high shear rates. With the capillary extrusiometer the measure of fluidity is not expressed in terms of the melt viscosity q but as the amount of material extruded in a given time (10 min). The amount of ex-trudate per unit of time is called the melt index or melt flow index i (MFI). It is also necessary to specify the temperature and the shearing stress or load. Thus MFI/2 (190 °C)=9.2 g/10 min means that at 190 °C and 2 kg load, 9.2 g of poly-... 

Prior to the removal of the film from the gel block, samples of liquid were rapidly removed at various temperature levels and their viscosities measured on a Ferranti-Shirley cone plate viscometer at 20°C. The amount of material required fcr each measurement was very small and enough could be obtained by making one pass with a small spoon spatula across the width of the plastisol. At a temperature... 

Melt Viscosity. Low shear melt viscosities were measured by Kepes cone-plate viscometer (7) at 150°, 170°, and 190°C. No stabilizer was added to the sample. The flow curves are shown in Figure 6. The viscosities of NMWD are in good agreement with those observed by others (8) the viscosities of BMWD by our measurements are somewhat lower. The Newtonian viscosities, y0, were observed with NMWD sample. With BMWD sample, vo was estimated by extrapolation shown in the figure. The extrapolated values are uncertain they may have been underestimated. The Newtonian viscosities are listed in Table III. 

The viscosity of emulsions obtained from two mutually incompatible polymers dissolved in a common solvent was studied by a falling ball viscometer, a cone-plate viscometer, and a capillary viscometer. The two polymers are polyacrylonitrile and polyurethane, and the solvent is N-methyl-pyrrolidone. The measurements are compared with theory, and a model is proposed for the development of a stationary pressure flow of an emulsion in a capillary. 

Viscosity measurements on emulsions were carried out with three types of viscometers. Figure 2 shows the flow curves of emulsions with different volume ratios of the two solutions, as measured with a Ferranti-Shirley cone-plate viscometer. The ratio between the viscosities of the two pure polymer solutions is about 3 at low shear rates but only 2 at the highest shear rates. 

Figure 2. Flow curves of emulsions of different compositions and the pure components as measured with a cone-plate viscometer...

Cone-Plate Viscometer. Measurements with the cone-plate viscometer were made between 500 and 30,000 dynes/cm2. Evidently, the PU droplets in the emulsions are deformed into long streaks during the experiments at these high stresses. To understand the measured results, the Taylor model for the emulsions must be replaced by another model. For... 

Figure 7. Measurements with a cone-plate viscometer reduced fluidity of the emulsions vs. their composition...

The authors thank J. E. van Laar for the elaborate preparatory experimental work and the measurements with the cone-plate viscometer. 

The viscosity measurements were carried out using a cone-plate viscometer (Model R-16 Weissenberg Rheogoniometer-Sangamo... 

The pressure varies only over about a ten psi range between the injector and producer, even with the higher viscosity foam present as compared to the viscosity of the other fluids. The higher viscosity of the foam was obtained by assigning a fictitiously high viscosity to the surfactant, such that the blend of v/ater and surfactant which was injected had a viscosity of 62 cp (kPa-s), which is the viscosity measured for foam in the laboratory experiments (with a Brookfield cone plate viscometer). 

Elemental Analysis and Physical Properties. Elemental analysis was accomplished by conventional microanalytical techniques in a commercial testing laboratory. Density, refractive index, average molecular weight (VPO), Conradson carbon residue, and ash content were determined by standard methods. Viscosity was determined by a cone-plate viscometer. Simulated distillation was accomplished using a y4" x 18" column of Anachrome Q, 3% Dexil 300, programmed from -30 to... 

Solution viscosities for 2 to 14% (w/w) concentrations of cellulose in TFA-CH2CI2 (70 30 v/v) at three different cone rotation speeds (or shear rates) in the cone/plate viscometer are shown in Table VI and Figure 1. 

A Ferranti-Shirley cone-plate viscometer was interfaced to a minicomputer system by means of a microcomputer. The microcomputer collects data from the instrument corresponding to shear rate, shear stress and temperature. Data are transmitted to the minicomputer for storage, analysis and the generation of reports and plots. Four types of analyses are performed ... 

ASTM D 4287. 2010. Standard test method for high-shear viscosity using a cone/plate viscometer. West Conshohocken, PA ASTM International. 

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