Rheological Measurements with the Rotational Viscometer

Abstract

The rotating cylinder viscometer in various forms has found wide use for the measurement of viscosity and the study of so-called anomalous flow. Starch pastes, pigment dispersions, printing pastes, and coatings are examples of materials used in the textile industry which exhibit complex flow properties. Identification of the different kinds of flow and measurement in terms of valid physical units are necessary before the properties of these materials can be correctly described. It can be expected that with adequate specification of flow properties more effective control in mill processes will become possible. This article is concerned with essential features of instrumentation, definition, and computation. THE ADVANTAGES of the cylindrical rotational viscometer are so numerous that it deserves wider use for industrial measurements. It may be used on suspensions as well as on clear liquids and it is suitable for -determination of viscosities over a wide range at variable rates of shear. Different types of flow properties may be identified, and the data may be expressed in dimensionally consistent units. As it is commonly used, however, the data cannot be expressed in rational units, and, as a consequence, the literature is cluttered with meaningless measurements.The unsatisfactory state of instrumentation in this field is in part responsible, since commercially available instruments of moderate cost need modification before they can be used to best advantage. , This paper presents details on the modification of one of these instruments, the well-known Stormer viscometer. The mechanical changes required are comparatively simple and can be made at small cost. The modified instrument makes possible a measurement of viscosities which is based on accepted physical principles and yields data of moderate precision which are easily reproducible. Because the operation of rotational viscometer has not been systematized, a preliminary discussion on terminology and an analysis of the basic factors for this measurement have been included here. Experimental results,

Elastic properties of natural rubber tubes produced by dip‐coating

“…Then, the viscosity was also measured for a decreasing shear gradient, as indicated by the arrows. The experiment was performed with the latex bath inserted between the two cylinders of a rotational viscosimeter, and it consists of a measure of the resistance imposed by the material to the spinning of the internal cylinder 18, 19. As can be seen in Figure 3(i) the viscosity decreases nonlinearly with increasing shear gradient, and (ii) there is a hysteretic behavior (as guided by the arrows), which might be an intrinsic property of the liquid or might be also evidencing a tixotropic behavior of the samples (in other words, the viscosity varies with time ref.…”

“…A mixture of 4% sulfur and 2% polyvinyl methyl ether resin is also added to the latex, leading to a viscous and consistent material. The latex samples used to fabricate the tubes were characterized by a rheological test18, 19 (viscosity as function of the shear gradient) using a rotational viscometer Rheotest 2.…”

Influence of fabrication process on the final properties of natural-rubber latex tubes for vascular prosthesis

“…This work is based on two different starting latex samples, with different viscosities, which will be called Latex-1 (higher viscosity) and Latex-2 (lower viscosity). They were subjected to a rheologic test [14,15] (viscosity as function of the shear gradient) using a rotational viscometer Rheotest 2.…”

“…The viscosity was also measured for a decreasing shear gradient. The experiment was performed with the latex bath inserted between the two cylinders of the Rheotest 2, and consists of a measure of the resistance imposed by the material to the spinning of the internal cylinder [14,15]. The rheologic experiment shows that latex is a fluid with a pseudo-plastic behavior, since its viscosity decreases with a growing shear gradient [15].…”