CAPILLARY VISCOMETRY

The concentration at which a steep rise in this curve begins has been termed as the critical or threshold concentration (2,3). Figure 6 shows such typical curves for PTF and BTF in n-hexane. Despite the fact that different shear rates are involved in capillary viscometry, it can be qualitatively said that at a given concentration, PTF viscosified n-hexane better than BTF. It is clear from Figure 6 that the critical concentration for these two compounds is above 0.7%, while analogous tri-n-alkyltin fluorides showed a critical concentration of less than 0.4% (3). This may be due to the presence of bulky Me3Si-groups nearer to the Sn-F bond, which causes some steric hindrance to auto-association. 

GPC/SEC, MALDI-MS, membrane osmometry, vapour pressure osmometry, viscometry, light scattering, TDFRS, SAXS, SANS, SEC-HPLC, SEC-MS, SEC-IR, FFF, ultracentrifugation, MALDI-TOF-MS, NMR, capillary electrophoresis... 

Shrinking of the polymer chains as a function of temperature was observed by capillary viscometry. The reduced viscosity, r]Sp/c, of polymer solutions approaches zero when the polymers are in their fully collapsed compact state and flow freely through the capillary. Above the cloud point, rjSp/c increases, which is indicative of aggregate formation. At low temperatures the... 

In addition, data on the size, shape and solvation of the polymer particles in aqueous solutions at temperatures below and above the transition phenomena registered by HS-DSC have been obtained [42]. Table 2 shows the results of capillary viscometry and light scattering experiments for the fractions p and s of poly(NVCl-co-NVIAz) synthesized at 65 °C from the feed with the initial molar comonomer ratio equal to 85 15. Since fraction p precipitates from the aqueous solution at temperatures > 34 °C, its intrinsic viscosity can be determined only at 20 °C, whereas for the fraction s such measurements were possible above and below the temperatures of the HS-DSC-registered conformational transition. 

Thickness of the Adsorbed PVA Layer. The thickness of the adsorbed PVA layer (6) was measured using two independent methods capillary viscometry and photon correlation spectroscopy. 

For Molecular weight determination by viscometry we do not need absolute h value, viscosity measurements may be carried out in simple Ostwald Viscometer. Because of (the non-Newtonian behaviour of most macromolecular solutions at high velocity gradients in the capillary, the viscometer dimensions are chosen in such a manner that the viscosity gradient is the smallest possible. 

Set up a constant temperature bath for capillary viscometry at a temperature of 25°C. 

In capillary viscometry, the fluid being measured flows through a capillary tube. How is this helpful in measuring viscosity ... 

Capillary viscometry measures the time it takes for the test fluid to flow through a capillary tube. The viscosity is calculated from this time and the calibration constant of the tube. 

The experimental techniques for the study of conformational branched properties in solution are the same as used for linear chains. These are, in particular, static and dynamic light scattering, small angle X-ray (SAXS) and small angle neutron (SANS) scattering methods, and common capillary viscometry. These methods are supported by osmotic pressure measurements and, nowadays extensively applied, size exclusion chromatography (SEC) in on-line combination with several detectors. These measurements result in a list of molecular parameters which are given in Table 1. 

Viscometry. Intrinsic viscosity. Kinematic viscosities (v=rj/p, where tj is the viscosity) were measured in a Cannon-Ubbelohde capillary viscometer. At least four concentrations, covering the relative viscosity range where the subscript s denotes the solvent) from about 1.8 to 1.2 were used to construct Schul -Blaschke plots. These plots of versus where... 

HI. 3 Viscosity Determination of Pure Liquids, Solutions and Serums Using Capillary Viscometry... 

Basic Protocol Using Capillary Viscometry to Determine the Viscosity of Pure... 

BASIC USING CAPILLARY VISCOMETRY TO DETERMINE THE VISCOSITY OF PROTOCOL PURE LIQUIDS AND SOLUTIONS... 

This protocol describes a method for measuring the viscosity of pure liquids and solutions by capillary viscometry. The sample is loaded into a Cannon-Fenske viscometer. The time required for the sample to flow between two time points on the viscometer is used to calculate the kinematic viscosity or viscosity. 

Finally, because the results obtained in capillary viscometry, especially for capillaries of small UR, are influenced by both extensional and shear flow phenomena associated with the fluid spatial accelerations at the capillary entrance, it is necessary to correct the values of tw given in Eq. E3.1-3. Chapter 13 covers the nature, magnitude, and significance of these, commonly known as Bagley corrections. 

The Rabinowitsch equation has been used in the long capillary viscometry data found in Appendix A. Figure E3.1 shows long capillary tw vs. TH. and rw vs. yw results with and without the Rabinowitsch correction. 

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. 

Figure 12.4 depicts schematically the experimental setup used in capillary flow studies. The primary application of the discussion that follows is in capillary viscometry, which is useful to die design. The ratio Rr/R should be greater than 10, so that the pressure drop due to the flow in the reservoir can be neglected.1 The reservoir radius cannot be too large, though, because the time required for uniform heating of the solid polymer load would be too long (see Fig. 5.6). Long heating cannot be used for sensitive polymers such as polyvinyl chloride (PVC), which readily degrade thermally.

The pressure drop calculated assuming the relationship Nu = 1.75 (Gz)1 3 for estimating h is smaller than the calculated AP, assuming isothermal flow. For the conditions depicted in Fig. 12.11, at T = 103 s 1 the isothermal pressure drop is about 30 % higher than the measured value. This fact must be taken into account in the design of extrusion dies, so that gross die overdesign can be avoided, as well as in capillary viscometry. 

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