Shear Rate on Viscosity

For use in ophthalmic surgery, knowing the viscosity at three different shear rates 

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A number of empirical equations have been proposed to describe the influence of shear rate on viscosity. The most popular equation represents the so-called power law formulated by Ostwald (1925) and De Waele (1923) ... 

Figure 5. Influence of molecular weight and shear rate on viscosity of solutions of Natrosol.

Figure 9. Effect of shear rate on viscosity of 0.75 mol% RAM as a function of polymer concentration.

The effect of shear rate on viscosity has been discussed in some detail in the previous sections. However, there are some other variables that also affect the viscosity. Two important variables that influence the viscosity are temperature and pressure. The effect of these variables is generally not as strong as the effect of shear rate however, in many cases, the effect of temperature and/or pressure on viscosity cannot be neglected. 

FIGURE 6.1 Effect of shear rate on viscosity at different TLCP/PEN compositions (a) and the effect of TLCP/PEN compositions on the melt flow index (b). (Adapted from Kim Yun Seong et al. Composites Part A., 40, no. 5, 607-612, 2009.)... 

A unique aspect of this development is the use of a computer simulation to predict the pressure drop as a function of flow rate for laminar flow in a capillary under conditions where viscous heating and the influence of pressure and shear rate on viscosity are important. As discussed in the next section, this computer simulation is used in the analysis of the data and to check the consistency of the experimental results. 

The effect of shear rate on viscosity in this equation is very strong, and demonstrates the typical situation with flocculated systems where severe shear thickening is seen, giving what looks like a yield stress. 

Fig. 4.22. The effect of shear rate on viscosity of aqueous tragacanth solutions, a Flake form tragacanth, 1% b tragacanth, ribbon form, 0.5% (according to Whistler, 1973)...

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