Rotational rheology

Olympic Stadium 482 Rotational rheology 154 Rubber, see Elastomers... 

Bird, R. B., Hassager, O., and Abdel-Khalik, S. I., Co-rotational rheological models and the Goddard expansion, AIChEJ., 20, 1041-1066 (1974). 

Rheology. Flow properties of latices are important during processing and in many latex appHcations such as dipped goods, paint, inks (qv), and fabric coatings. For dilute, nonionic latices, the relative latex viscosity is a power—law expansion of the particle volume fraction. The terms in the expansion account for flow around the particles and particle—particle interactions. For ionic latices, electrostatic contributions to the flow around the diffuse double layer and enhanced particle—particle interactions must be considered (92). A relative viscosity relationship for concentrated latices was first presented in 1972 (93). A review of empirical relative viscosity models is available (92). In practice, latex viscosity measurements are carried out with rotational viscometers (see Rpleologicalmeasurement). 

The study of flow and elasticity dates to antiquity. Practical rheology existed for centuries before Hooke and Newton proposed the basic laws of elastic response and simple viscous flow, respectively, in the seventeenth century. Further advances in understanding came in the mid-nineteenth century with models for viscous flow in round tubes. The introduction of the first practical rotational viscometer by Couette in 1890 (1,2) was another milestone. 

Specialized training is an absolute requirement for technical service personnel. A typical example is a person involved in supporting a polymer for which the use is the manufacture of rotationaHy molded consumer products. The technical service person is expected to be reasonably familiar with topics such as polymer rheology evaluations, gel-permeation chromatography, rotational mol ding, color science, regulatory requirements for use, mechanical and photochemical behavior of the pigmented polymer, optics, and so forth. Expertise of this variety caimot be expected to be obtained without careful... 

The mud rheological properties t, n and K are typically calculated based upon tbe data from two (or more)-spee(l rotational viscometer experiments. For these experiments, the following equations are applicable ... 

The effects of different surfactants on the rheological behavior of cement-water dispersions were studied by a rotational-type viscometer. The type of... 

In shear studies, the most commonly used type of device for the generation of well-defined flow fields is the rotational viscometer. The use of these devices for the rheological characterization of liquids is well established [137]. Compared with the capillary and jet devices (Sects. 5.1 and 5.2), rotational viscometers allow the investigation of the effects of continuous rather than intermittent shearing. 

A computer-controlled rheology laboratory has been constructed to study and optimize fluids used in hydraulic fracturing applications. Instruments consist of both pressurized capillary viscometers and concentric cylinder rotational viscometers. Computer control, data acquisition and analysis are accomplished by two Hewlett Packard 1000 computers. Custom software provides menu-driven programs for Instrument control, data retrieval and data analysis. 

This behavior can be explained with the help of the classical rheological theory of suspension of conventional filler reinforced systems. According to this theory [32], rotation of the filler is possible when the volume fraction of clay 4>fflier < 4 critical — (aspect ratiop1. All PBSNCs studied here follow this relation except PBSNC4 (MMT = 3.6 wt%), in which 4)mier (aspect ratio) 1. For this reason, in... 

As with spherical particles the Peclet number is of great importance in describing the transitions in rheological behaviour. In order for the applied flow field to overcome the diffusive motion and shear thinning to be observed a Peclet number exceeding unity is required. However, we can define both rotational and translational Peclet numbers, depending upon which of the diffusive modes we consider most important to the flow we initiate. The most rapid diffusion is the rotational component and it is this that must be overcome in order to initiate flow. We can define this in terms of a diffusive timescale relative to the applied shear rate. The characteristic Maxwell time for rotary diffusion is... 

Fig. 1.3 Relaxation map of polyisoprene results from dielectric spectroscopy (inverse of maximum loss frequency/w// symbols), rheological shift factors (solid line) [7], and neutron scattering pair correlation ((r(Q=1.44 A )) empty square) [8] and self correlation ((t(Q=0.88 A" )) empty circle) [9],methyl group rotation (empty triangle) [10]. The shadowed area indicates the time scales corresponding to the so-called fast dynamics [11]...

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