Shear rate viscosity

Power consumption for impellers in pseudoplastic, Bingham plastic, and dilatant nonnewtonian fluids may be calculated by using the correlating lines of Fig. 18-17 if viscosity is obtained from viscosity-shear rate cuiwes as described here. For a pseudoplastic fluid, viscosity decreases as shear rate increases. A Bingham plastic is similar to a pseudoplastic fluid but requires that a minimum shear stress be exceeded for any flow to occur. For a dilatant fluid, viscosity increases as shear rate increases. 

Figure 8.5. Apparent viscosity-shear rate curves for dilatant fluid, a Newtonian fluid and pseudoplastic fluid which have the same apparent viscosity at zero shear rate...

Figure 3.27. Plot of apparent viscosity-shear rate relation using logarithmic axes...

Dynamic viscosity Kinematic viscosity Density Surface tension Shear stress Vapor quality Contact angle Shear viscosity Shear rate... 

The probability that a chain will break at its midpoint increases with increasing viscosity, shear rate, and the square of the molecular weight of the chain under consideration. 

Fig. 4.7.9 MRI apparent viscosity-shear rate data in comparison with a conventional rotational viscometer shear viscosity-shear rate data. (Permission granted to reprint Figure 4 on page 517 in Ref. [49].)...

Figure 3 Viscosity - shear rate curves at three different temperatures...

A similar variety of samples was tested for thermal stability by capillary rheometry and TGA. Figure 6.3 shows the viscosity-shear rate dependence for PCTFE homopolymers and one copolymer (Alcon 3000). All materials, save one, showed virtually identical viscosity relationships despite large changes in inherent viscosity. Only the polymers from runs initiated by fluorochemical peroxides (FCP) showed a dependence of molecular weight (as measured by inherent viscosity) upon melt viscosity. 

Viscometer Price Viscosity Shear rate capability, Temperature M anufacturer... 

Fig. 8.10. Viscosity-shear rate master curve for concentrated polystyrene-n-butyl benzene solutions. The data were obtained for molecular weights ranging from 160000 to 2400000 concentrations from 0.255 to 0.55 gm/ml, and temperatures from 30° C to 60° C (155)...

Judged by the superposability of viscosity-shear rate data on the same master curve for a variety of polymers [polystyrene (155) (Fig. 8.10), poly(a-methyl... 

Experimental viscosity-shear rate curves at high concentrations turns out to be rather similar to an expression for non-Newtonian viscosity derived from the Eyring s activated complex theory for the transport properties of liquids (341) ... 

See Table 3.2). One additional remark should be made with respect to Fig. 3.2. In this figure parameter p is calculated with the aid of the experimental viscosity-shear rate relation. As a consequence, the deviation from the quadratic relationship is less pronounced than in Fig. 3.1. 

Viscometer type Lowest viscosity Highest viscosity Shear rate range (s 1)... 

Material or process stream Approximate viscosity Shear rate Temperature... 

Newtonian and non-Newtonian calibration fluids were used to determine the necessary calibration constants for the impeller method. It has been previously determined that the impeller method is only valid for a Reynolds number (Re) <10. Impeller rotational speed and torque data from Newtonian calibration fluids of known viscosity were employed to determine the Newtonian calibration constant, c. Cone-and plate-viscometer data from non-Newtonian calibration fluids were used to determine a viscosity vs shear rate relationship. Impeller rotational speed and torque data of the non-Newtonian calibration fluids combined with a determined viscosity vs shear rate correlation were utilized to calculate the shear rate constant, k. The impeller method calibration constants allow the calculation of viscosity, shear rate, and shear stress data of non-Newtonian suspensions. Metz et al. (2) have thoroughly discussed the equations utilized in the impeller method. 

The so-called shear-thinning exponent describes the steepness of the viscosity-shear rate curve... 

Many of the comments in the previous chapter about the selection of grade, additives and mixing before moulding apply equally in preparation for extrusion. It is important of course that the material should be appropriate for the purpose, uniform, dry, and free from contamination. It should be tested for flow and while many tests have been devised for this it is convenient to classify them as either for low or high rates of shear. The main terms used in such testing ( viscosity , shear rate , shear strain , etc.) are defined in words and expressed as formulae in ISO 472, and it is not necessary to repeat them here. Viscosity may be regarded as the resistance to flow or the internal friction in a polymer melt and often will be measured by means of a capillary rheometer, in which shear flow occurs with flow of this type—one of the most important with polymer melts—when shearing force is applied one layer of melt flows over another in a sense that could be described as the relationship between two variables—shear rate and shear stress.1 In the capillary rheometer the relationship between the measurements is true only if certain assumptions are made, the most important of which are ... 

Newtonian viscosity shear rate on the wall apparent shear rate shear stress... 

APPARENT VISCOSITY—SHEAR RATE RELATIONSHIPS OF SHEAR-THINNING FOODS... 

Rheological Models for Apparent Viscosity-Shear Rate Data... 

Apparent viscosity-shear rate data of food polymer dispersions have been reviewed by Launay et al. (1986), Lopes da Silva and Rao (1992) and others. The general log versus log y curve, discussed in Chapter 2, has been used to characterize food polymer dispersions. For example, Lopes da Silva et al. (1992) found that both the modified Carreau and the Cross models, wherein the infinite shear viscosity was considered to be negligible, described the apparent viscosity-shear rate data of locustbean (LB)... 

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