Parallel-Disc Viscometer

Viscometers can be divided into rotational instruments and axial flow instruments. Rotational instruments include concentric cylinder (cup and bob), cone and plate and parallel disc viscometers, while axial flow instruments include capillary, slit and extrusion rheometers. 

The most common dynamic method is oscillatory testing, in which the sample is subjected to a sinusoidal oscillatory strain, and the resulting oscillatory stress measured. The more sophisticated rotational viscometers have the additional capability of dynamically testing liquid-like materials using small angle oscillatory shear. A parallel disc viscometer can be set up for testing solid-like materials (e.g., butter), in oscillatory shear. Some UTM-type solids rheometers, in which the moving crosshead can be made to reciprocate sinusoidally, can be used to test solid-like materials in oscillatory deformation in compression, tension or shear. 

Conventional rheometer geometries such as concentric cylinders, cone and plate and parallel discs are unsuitable, even when the rheometer is designed to allow measurement of normal forces. Many of the disadvantages of such geometries are overcome in the sliding-plate viscometer (Gunasekaran and Ak, 2002). In this instrument (Figure 22.9), the sample (the exact shape and size of which need not be known) is held between a... 

For filled polymer studies, rotational viscometers with either the cone-plate or parallel-disc configuration are used. 

The parallel-disc viscometer used for measuring the shear stress and normal stress difference of filled polymer systems is similar in principle... 

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

Oscillatory shear measurements can be done with the parallel-disc arrangement in a similar manner as in the case of the cone and plate viscometer and similarly the material functions, and others... 

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

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