Rheological flows capillary

Many ceramic products are made by extruding materials which are not ex-trudable in their original state and must be made so by appropriate treatment and by incorporating various additives which adjust Iheir rheology or flow properties. The properties that are of importance for extrusion can, in fact, be characterized and quantified by means of rheological measurements. Capillary rheometry especially enables many different extrudability tests to be carried out, ranging from simple suitability tests to complex determinations of properties in order to achieve optimum processes and products. 

Figure 3.9 Plots of log rj versus log co (O) and log G versus log co (A) in oscillatory shear flow, and plots of log jj versus log y ( ) and log IVj versus log y (A) in steady-state shear flow for a commercial polystyrene at 200 °C. The data for jj and at low shear rates were obtained using the cone-and-plate fixture of a rotational-type rheometer, the data for jj and at high shear rates were obtained using a continuous-flow capillary rheometer, and the data for r and G were obtained using the paraUel-plate fixture of a rotational-type rheometer. Refer to Chapter 5 for details of the experimental methods employed to obtain the data. (Reprinted from Han, Rheology in Polymer Processing, Chapter 3. Copyright 1976, with permission from Elsevier.)...

In a series of experiments on the flow of flocculated kaolin suspensions in laboratory and industrial scale pipelines(26-27-2Sl, measurements of pressure drop were made as a function of flowrate. Results were obtained using a laboratory capillary-tube viscometer, and pipelines of 42 mm and 205 mm diameter arranged in a recirculating loop. The rheology of all of the suspensions was described by the power-law model with a power law index less than unity, that is they were all shear-thinning. The behaviour in the laminar region can be described by the equation ... 

Understanding the melt rheology of rubber nanocomposites is crucial from the processing perspective. Bandyopadhyay et al. [37] have studied the melt flow behavior of rubber-silica hybrid nanocomposites in a capillary rheometer. 

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. 

VISCOSITY. The internal resistance to flow exhibited by a fluid the ratio of shearing stress to rate of shear. A liquid has a viscosity of one poise if a force of 1 dyne/sqnare centimeter causes two parallel liquid surfaces one square centimeter in area and one centimeter apart to move past one another at a velocity of 1 cm/second. One poise equals 100 centipoises divided by the liquid density at the same temperature gives kinematic viscosity in centistokes (cs). One hundred centistokes equal on e stoke. To determine kinematic viscosity, the time is measured tor an exact quantity of liquid to flow by gravity ilirough a standard capillary. See also Rheology. 

J.L. Kokini and T.K. Chou, The Phenomenon of Slip in the Steady Shear Capillary Flow of Four Semi-solid Foods, presented at the Winter Meeting of the Society of Rheology, Santa Monica, California, January 18-21,1987. 

Instron Capillary Rheometry. Melt flow rheology was measured according to procedures first proposed by Merz and Colwell (10) and supplied by the Instron Engineering Corp. 

Melt flow rheology measurements were obtained on the MBAS polymer using an Instron capillary rheometer. The data reported were obtained using an 0.056-inch capillary, 90° included angle, with an L/D of 36. In Figure 5 the maximum shear stress (lb/in2) is plotted vs. the apparent shear rate (sec 1). The apparent viscosity (lb-sec/in2) vs. tem-... 

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