Rheology capillary flow

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. 

There are numerous other GNF models, such as the Casson model (used in food rheology), the Ellis, the Powell-Eyring model, and the Reiner-Pillippoff model. These are reviewed in the literature. In Appendix A we list the parameters of the Power Law, the Carreau, and the Cross constitutive equations for common polymers evaluated using oscillatory and capillary flow viscometry. 

There is also a variety of wall-slip techniques used in rheological analysis (Gupta, 2000). The methods described here are flow visualization, capillary flow and torsional flow. 

The yield stress can be obtained by the rotational viscometry technique as shown in Chapter 4. Thus from two sets of rheological determinations, one the capillary flow technique and the other rotational viscometry, enough information can be obtained to treat the problems associated with the flow of grease in pipes. 

In practical applications, flow of the material through an orifice is perhaps the most frequently encountered rheological phenomenon. It is then natural to be used for the viscosity measurement of suspensions (53-55). However, the flow through an orifice is not precise in terms of shear measurement because the shear rate is not well defined under such circumstances. To meet this objection, the orifice is in most cases extended to a tube. This leads to the capillary flow type of viscometers, the simplest, and for Newtonian fluids, the most accurate type, comprising the familiar Ostwald und Ubbelohde viscometers. The fully developed axial velocity in the laminar regime is given by... 

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. 

Mooney viscosities of MNR-ADS blends were found to be much higher than those of MNR-STR 5L blends. Rheological measurements were carried out the same method as described above.The apparent values of shear stress, shear rate and shear viscosity were calculated using the derivation of the Poiseuille law for capillary flow as shown in Equations (18.1) to (18.3). Plots of the apparent shear stress versus apparent shear rate for various blend compositions of MNR-STR/STR 5L and MNR-ADS/ADS were shown in Figures 18.32 and 18.33, respectively. Straight lines of the flow curve were observed for all sets of the test. The results corresponded to the power law equation proposed by Ostwald as shown in Equation 18.4. 

Gerrard, J.E. and Philoppoff, W. Viscous Heating and Capillary Flow, 4th International Congress of Rheology, Paper 51, 1963. 

The behavior at later times may be explained by the shear-thinning rheology of the two liquids as predicted by (1.69), the velocity of the capillary flow decreases with the penetration distance, consequently the shear-rate decreases and the viscosity increases. Hence a coupling is estabHshed between viscosity and velocity, leading to the reduction of the velocity of the capillary motion. 

Alle, N. and Lyngaae-Jorgensen, J., Polypropylene-polyethylene blends, the relationship between rheology and morphology in capillary flow, Rheol Acta, 19, 104-110 (1980). 

Akay, G., Rheology of reinforced thermoplastics and its application to irijection molding IV. Transient injection capillary flow and injection rmflditig, Pofym. Eng. ScL, 22,1027 (1982). 

Rheology Measures flow characteristics of resin using a capillary rheometer D3835... 

J. Laven, Non-isothermal Capillary Flow of Plastics Related to Their Thermal and Rheological Properties Delft University Press 1985. 

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