Viscometer rotating-disk

Viscosity is a property sometimes difficult to assess, as figures can be measured on any one of several types of viscometer. One common type is the rotating disk viscometer, which must be used in a container big enough to eliminate wall effects. The main alternative is the cup-and-bob viscometer, where the viscous drag of the liquid between stationary and rotating concentric cylinders is indicated by a spring-loaded pointer moving over a dial. 

The measurement of the effects of mastication on the molecular weight of the rubber can be time-consuming even with sophisticated techniques such as size exclusion chromatography. The viscosity of natural rubber is usually measured by means of a Mooney rotating disk viscometer, an established method for following the effect of mill time and conditions. Adhesive formulators have successfully used this instrument to correlate Mooney viscosity to rubber end-use properties. 

OtherRota.tiona.1 Viscometers. Some rotational viscometers employ a disk as the inner member or bob, eg, the Brookfield and Mooney viscometers others use paddles (a geometry of the Stormer). These nonstandard geometries are difficult to analy2e, particularly for an infinite bath, as is usually employed with the Brookfield and the Stormer. The Brookfield disk has been analy2ed for Newtonian and non-Newtonian fluids and shear rate corrections have been developed (22). Other nonstandard geometries are best handled by determining iastmment constants by caUbration with standard fluids. 

In the Mooney shearing disk viscometer, a serrated disk is rotated ia a sample fixed ia a pressuri2ed cavity. The instmment was developed for mbber and other elastomeric materials and is a standard quaUty control iastmment ia the mbber iadustry (ASTM D1646). It is used to measure high viscosities givea ia arbitrary Mooaey units, but usually ca 7.5 x 10 mPa-s atlow(ca 1.5 ) shear rates. 

The Nametre Rotary B rotational viscometer measures torque in terms of the current needed to drive the d-c motor at a given speed while a material is under test. The standard sensors are coaxial cylinders or Brookfield disk-type spindles, but a cone—plate system is also available. The viscosity range for the coaxial cylinder sensors is 5 to 5 x 1(T mPa-s, and the maximum shear rate is 200. ... 

The unsuitable nature of many commercial instruments which are in common use clearly illustrates the confusion prevalent in the field of viscometric measurements. Many instruments measure some combination of properties which depend only partly on the fluid consistency since the flow is not laminar. In others the shear rates are indeterminate and the data cannot be interpreted completely. Examples of such units include rotational viscometers with inserted baffles, as in the modified Stormer instruments in which the fluid flows through an orifice, as in the Saybolt or Engler viscometers instruments in which a ball, disk, or cylinder falls through the fluid, as in the Gardiner mobilometer. Recently even the use of a vibrating reed has been claimed to be useful for measurement of non-Newtonian viscosities (M14, W10), although theoretical studies (R6, W10) show that true physical properties are obviously not obtainable in these instruments for such fluids. These various instru-... 

Mooney viscosity is used to measure the extent of mastication. Mooney viscosity is the torque required to rotate the disk in the shearing disk viscometer. When the disk or rotor as it is called, is rotating without any load, the Mooney viscosity reading is zero . When a torque of 100 Nm is applied on the rotor the viscosity scale is read as 100. This is the scale in the Mooney viscometer (ASTM D1646 [2]). 

For a parallel disk viscometer (i.e., cylindrical coordinates), the tangential velocity vg on the rotating plate is ftr. This reveals the radial dependence of vg at any axial position z between the rotating and stationary plates, because if one moves into the fluid in the z direction from the moving plate at constant r and a separation of variables solution to the 0-component of the equation of motion is valid, then the r... 

Parallel-plate viscometer n. (1) An instrument consisting of two circular parallel plates, the lower one stationary, the upper one rotatable, the disk-shaped specimen being confined between the plates. An example of this type of viscometer is the Mooney viscometer. 

Rotational Viscometers. These relatively complex instruments can be used in the steady state or in an oscillatory, dynamic mode. Some are useful up to the glassy state of the polymer. The working mechanism, in all cases, is one part that moves past another. Designs include concentric cylinders (cup and bob), cone-and-plate, parallel-plate, and disk, paddle, or rotor in a cylinder. 

Viscometer Also called a viscosimeter. This instrument is used for measuring the viscosity and flow properties of fluids such as plastic melts. Basically it is the property of the resistance of flow exhibited within a body of material. A commonly used type is the Brookfield that measures the force required to rotate a disk or hollow cup immersed in the specimen substance at a... 

The principal scheme of the torque pendulum is shown in Figure 5.21. A disk of radius R is placed at the surface of the liquid or at the interface between the two liquids (a polar aqueous surfactant solution phase and a nonpolar phase, that is, hydrocarbon or fluorocarbon). The disk is suspended on a thin wire that serves as a dynamometer. Turning this wire by an angle f produces a torque M, while the turn of a cuvette by an angle ( ) with respect to the disk leads to the total shear deformation of the adsorption film. The principle of operation of this instrument is similar to that of a rotation viscometer, with one principal difference in the torque pendulum it is not possible to utilize a thin gap between a disk and a cuvette. Because of this the stresses and the deformations in the film are not uniform. 

Many surface viscometers utilize torsional stress measurements upon a rotating ring, disk or knife edge (shown schematically in Fig. 5.16) within or near to the liquid/liquid interface [17]. This type of viscometer is moderately sensitive for a disk viscometer the interfacial shear viscosity can be measured in the range q > 10 Surface Pas. The disk is rotated within the plane of the interface with angular velocity w. A torque is exerted upon the disk of radius R by both the surfactant film with surface viscosity qg and the viscous liquid (with bulk viscosity q) that is given by the expression... 

The knife-edge viscometers are similar to the disk viscometers in most respects. A notable exception is the rotating-wall knife-edge viscometer, which entails the measurement of the velocity of a tracer particle within the fluid interface and is quite sensitive to interfacial shear viscosity measurements, irish 10 surface poises. Presently, this device is the most promising surface viscometer. For more details, see Refs. 58, 153, 154, 158, and 163-170. 

Figure 3.2 Schematic diagram showing the principal features of parallel eccentric disks rotational viscometer.

Another type of viscometer that finds occasional use is the disk-and-plate viscometer (Rgure 16.6). A disk of radius R rotates with an angular velocity of co relative to a parallel... 

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