Viscometer parallel-disk

A. Yoshimura and R.K. Prud homme, Wall Slip Corrections for Couette and Parallel Disk Viscometers, J. Rheol., 32 53-67 (1988). 

Yoshimura, A. and Prud homme, R. K. 1988a. Wall slip corrections for Couette and parallel disk viscometers. J. Rheol. 32 53-61. 

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... 

Kalyon, D.M., Yaras. E, Aral, B. and Yilmazer, U. (1992), "Rheological Behavior of a Concentrated Suspension. A Solid Rocket Fuel Simulant," Submitted to J.Rheol. Yoshimura, A. and Prud homme, R.K. (1988), "Wall Slip Corrections for Couette and Parallel Disk Viscometers", J.Rheol., 32,53-61. 

The parallel-disk viscometer used for measuring the shear stress and normal stress difference of molten thermoplastics is similar in principle to the cone-n-plate viscometer except that the lower cone is replaced by a smooth circular disk. This type of viscometer was initially developed for measuring the rheological properties of rubber [29-33] and therefore made use of serrated disks placed in a pressurized cavity to prevent rubber slippage. When it was adapted for thermoplastic melts [1534,35], measurements were performed using smooth disks and without pressure. 

The rheological properties in the parallel-disk viscometer are based on the shear rate at the outer radius of the disk. Thus,... 

The shearing disk viscometer introduced in 1934 by Mooney [M40] has played a very important role in the rubber industry because of its utilization for monitoring and control of rubber samples (Fig. 14). It is related to the parallel disk type shear flow instrument that has been widely used for polymer solutions and melts. 

FIGURE 14 Shear disk viscometers (a) parallel disk, (b) Mooney. 

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. 

Oscillating-disk viscometers consist of an axially symmetric disk placed between two fixed parallel plates and suspended fi om a torsion wire, so that it performs oscillations in the fluid about its axis of symmetry. Such a viscometer has been used by several researchers as an instrument for viscosity measmements (see, for example, DiPippo et al, 1966 Kestin et al, 1977, 1978a,b, 1980 Correia et al., 1979 Correia and Kestin, 1980 Kestin and Shankland, 1981b, 1984b and Krall et al, 1987, 1992). The theoretical and experimental problems of this technique have been... 

Here aj = M/IttR L is the stress at the inner cylinder and N is the slope of a log-log graph of O vs. M. The corresponding correction for the parallel-disk rheometer is known as the Burgers correction, and is similar to the Weissenberg-Rabinowitsch correction described above for the capillary viscometer ... 

Oscillatory shear measurements can be done with the parallel-disk arrangement in a manner similar to the case of the cone-n-plate viscometer and, similarly, the material fimcdons i), G, C, and others can be generated. However, a slightly different tedinique [36] is at times used wherein the polymer melt sample is deformed between two oscillating parallel eccentric disks as shown in Fig. 3.2. In this case, too, it has been shown that the fluid elements undergo a periodic sinusoidal deformation and the forces exerted on the disk are thus interpreted in terms of G and G" [4]. 

Somewhat higher viscosities, up to 10 poise or so, are measured using a parallel plate viscometer (see ASTM C1351M-96). In the parallel plate viscometer, a suitably sized disk (about 8 mm in diameter by 3 to 6 mm thick) of glass is sandwiched between two parallel plates (inconel plates covered with platinum foil or thin alumina substrates). The top plate is loaded with known weights. Viscosity can be calculated by measuring the rate of decrease in the thickness of the specimen with a linear variable differential transformer (LVDT) device. 

For thermoplastic melt studies, rotational viscometers with either the cone-n-plate or parallel-disk configuration are used. 

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. 

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... 

Another type of viscometer which finds occasional use is the disk-plate viscometer (Fig. 16.8). A disk of radius R rotates with an angular velocity of CO relative to a parallel plate. The disk and plate are separated by a distance d(d R with the test fluid in between. The torque M on either the disk or plate is measured. This is known as torsional (twisting) flow, and is another example of a viscometric flow. 

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