Viscosity measurements dynamic

FIGURE 12.32 Shear moduli and dynamic viscosities measured for silica spheres at = 0.46, a = 28 2nm, O + a = 76 2nm(Mellemaetal. [68]). The broken lines correspond to the infinite shear viscosities (de Kruif et al. [43]) and the solid curves to the frequency dependence predicted by the visco-elastic fluid model of Table 12.4 with the measured values of 170,171 , and Gi. Redrawn from Russel et al. [31]. Reprinted with the permission of Cambridge University Press. 

Generally large yield stress effects were dominant in the nematic melts, but they were strongly pre-history dependent. A three region flow curve for 15 mol % modified poly(pheny1-1,4-phenylene terephthalate) was probably due to a not completely molten system. Dynamic viscosity measurements showed strong pseudoplastic behaviour. Strain and time dependence phenomena were not observed. 

A complementary use of polymer viscometry is the indirect evaluation of the MWD of a polymer from dynamic viscosity measurements [28-30]. The methods used to correlate the MWD of polymers to rheological data are based on the previous determination of the polymer relaxation spectrum from linear oscillatory shear experiments [31, 32]. MWDs obtained from viscometric data analysis can help in the determination of the MWD curve from online measurements, or in cases where this curve cannot be easily determined from size exclusion chromatography (SEC) [30, 31]. 

The compatibility of the polymers in solutions was determined by dynamic viscosity measurements using a rotational viscometer at 293 K and shear rate 1312 s. The morphology of the film cast from a solution was examined with a polarization-interference microscope by differential method, at magnification of 250x. Dynamic mechanical measurements were made using direct reading visco-elastometer, the Rheovibron. The temperature was scanned... 

According to the International System of Units (SI), the dynamic viscosity measurement unit is the Pascal-second (Pa-s). This unit is the fundamental measurement unit of viscosity. Respectively, in the CGS system, the viscosity measurement unit is in dyne-s/cm (=1 g-s/cm). This unit is known as poise (P). The relation between Pa s and poise is as follows 1 Pa-s = 10 P. Sometimes, centipoise (cP) is also used, where 1 cP = 0.01 P. Centipoise may have been adopted due to the fact that water s viscosity at 30°C is 1 cP. 

Dynamic viscosity measurements have been reported (Fernandez-Martin and Montes, 1976) for the saturated fatty acids C12-C18 between 70 and 90 °C. A Newtonian behaviour was obtained at all shear rates with the values of rj (cP) at 70 and 90 °C... 

A study using confocal Raman spectrometry was carried out to determine the concentration profile within the extrudate of rubbery particles in a polyethylene matrix during capillary flow (Chartier et al. 2010). Chartier et al. reported that the effect of the concentration of particles on the apparent viscosity of polymer melts measured using capillary flow was the opposite of that based on observations made using linear dynamic viscosity measurements (Fig. 7.41). Shear-induced migration can be detected from the concentration profile of the components of the... 

Fig. 10. Temperature dependence of the optical transmission at 600 nm (d=l cm) and of the dynamic viscosity (measuring conditions parallel plates of 25-mm diameter, frequency 1 rad/s) of LiCl containing aqueous polyether samples with a fixed polyether/water mixing ratio of 4 1 and various LiCl contents ranging from 0 to 6 wt%.

To confirm the presence of mesophases, dynamic viscosity measurements were made and microscopic photographs in polarized light were taken for aqueous solutions of SML/ESMIS mixtures at the concentrations of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90 wt%. 

Dynamic viscosity measurements generally are easier to perform over a wide range of frequencies than are steady shear measurements over a wide range of shear rates, while steady shear viscosity is of more value in the analysis of polymer processing. Thus, the Cox-Merz rule is frequently assumed and t data are used in place of steady shear viscosity data. 

Viscosity is a key lube oil property and is a measure of the fluidity of the oil. There are two measures of viscosity commonly used kinematic and dynamic. The kinematic viscosity is flow due to gravity and ranges from approximately 3 to 20 cSt (centistokes) for solvent neutrals and about 30-34 cSt at 100°C for Bright stock. The dynamic viscosity is flow due to applied mechanical stress and is used to measure low temperature fluidity. Brookfield viscosity for automobile transmission fluids (ATF s) at -40°C and cold cranking simulator (CCS) viscosity for engine oils at -25°C are examples of dynamic viscosity measurements. 

The complex balance of Coulomb, van der Waals, and hydrogen bond interactions is reflected in the viscosity of a medium. The temperature-dependent dynamic viscosity measurements showed no linear correlation. However, although the dynamic viscosity is a non-molar quantity (as it is a measure of the inner friction between neighboring liquid layers moving with different velocities), it depends linearly on the molar composition of the mixture. The only exception in our current work (Fig. 11) is the mixture [C2mim][0Ac]/[C2mim][CF3C02]. 

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