Rheometry capillary flow

CALENDER, 144 194 CALIBRATION, 94 377 CAPILLARY DIE, 172 CAPILLARY FLOW, 443 CAPILLARY RHEOMETRY, 252 CAR MAT, 451 CARBON, 316... 

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. 

Capillary Flow Rheometry Next we examine the experimentally obtained results with the capillary flow rheometer shown in Fig. 3.1, which are directly relevant to polymer processing flows, since the attainable shear rate values are in the range encountered in polymer processing. The required pressure drop AP does not increase linearly with increases in the volumetric flow rate Q, as is the case with Newtonian fluids. Rather, increasingly smaller increments of AP are needed for the same increases in Q. The Newtonian Poiseuille equation, relating flow rate to pressure drop in a tube, is linear and given by... 

Rheometry (capillary/dynamic/melt-flow index) Filler dispersion... 

FIGURE 8.14 Comparison of Cross model prediction with experimental viscosity data for a high-molecular-weight poly(dimethylsiloxane) using parallel plate, cone-and-plate, and capillary flow rheometry at 23°C. The fitted parameters are A, = 34.5 s, = 0.604, and t (, = 98.0 kPa s. 

Yiscometry (using coaxial cylinder, cone and plate and vane rotational viscometers, and controlled stress capillary viscometers) can be used for soft cheeses. Lubricated squeezing flow rheometry is particularly useful for measuring cheese meltability. 

It was determined that the shear rate in PVC passing through a copper wire coating die was in excess of 4000000 Is. This resulted in volatilisation of the dioctyl phthalate plasticiser and changes in the polymer molecular structure, as determined by infrared spectroscopy. The flow was studied using capillary rheometry with a die of a 0.15 mm diameter. It was concluded that the change in... 

Funatsu K. and Sato M., "Measurement of slip velocity and normal stress difference of polyvinylchloride, Adv. in Rheol., 4 (Mexico 1984) 465-472. Knappe W. and E. Krumbock, "Evaluation of slip flow of PVC compounds by capillary rheometry," Adv. in Rheol., 3 (Mexico 1984) 417-424. de Smedt C., Nam S., "The processing benefits of fluoroelastomer appUcation in LLDPE," Plast. Rubber Process. Appl. 8,11 (1987). 

The relationships (17.10), (17.14), and (17.16) are very important for the generation of flow curves for hot melts using capillary rheometry. 

In normal capillary rheometry for polymer melts, the flowing stream exits into the atmosphere, and the driving static pressure in the reservoir is taken to he AP. In such cases, end effects involving viscous and elastic deformations at the entrance and exit of the capillary should be taken into account when calculating the true shear stress at the capillary wall, particularly if the ratio of capillary length to radius L/R) is small. 

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. 

The most commoidy-used laboratory process to determine the flow characteristics of ceramic bodies is that of capillary rheometry, for which various instruments are available, in the form of either single-bore capillary or twin-bore capillary rheometers. Using a pressure piston, the ceramic body is forced through a nozzle of a defined geometry at different feed rates. The resistance of the ceramic body against the deformation in the nozzle causes a pressure drop within the capillary, which corresponds to a certain... 

As with all thermoplastics it is important to characterise the molecular weight distribution of PAEK. In practice simple measurements such as melt flow index (MFI) and capillary rheometry are used to give an indication of molecular weight. The lower shear rate of MFI is... 

Chapter 3 deals with rheometry which is the method of measurement of the various rheological parameters described in Chapter 2. The rheometers may be of Ae rotational type or the capillary type for shear flows and the shear free t)rpe for extensional flows. 

If melt distortion limits shear stress for highly viscous (and elastic) materials, turbulent flow potentially puts an upper limit on capillary rheometry of low viscosity fluids. The classical Reynolds number criteria for the onset of turbulence in tube flow gives... 

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