Pseudoplastic INDEX

This combination of long riser and relatively shallow hole probably favours a polymer with a high pseudoplastic index - high viscosity at the low shear rate in the slow-moving fluid in the riser - and rapid, clean breaking at the well bottom temperature. 

In the specific case of polymer melts these almost invariably are of the pseudoplastic type. In such cases the flow behaviour index n is less than 1 the greater the divergence from Newtonian behaviour the lower its value. 

The non-Newtonian index is plotted against the blend ratio in Fig. 2. There are three distinct stages of the change of value with %NBR in the preblend. First, a decrease of up to 40% of NBR, a rapid rise of up to 60% of NBR, and beyond this ratio a further decrease are observed. Heating of blends shows the only minimum at 50 50 ratio. It is obvious that 60-50% of Hypalon in the NBR-Hypalon blend is an optimum range where maximum extent of interchain crosslinking reaction is expected, and this blend is supposed to be more pseudoplastic. 

Decreases in concentration or increases in temperature usually decrease the consistency indexes K and K but leave the flow-behavior indexes n and n relatively unaltered. The latter appear to be determined primarily by the components of the non-Newtonian fluid and increase only slightly with increases in temperatures or decreases in concentration for pseudoplastic materials. 

Values of the consistency index K and the flow behavior index n for a non-Newtonian fluid can be determined experimentally. For pseudoplastic fluids, n < 1. 

The exponent, n, the power-law-index is n = 1 for Newtonian behaviour, and n < 1 for pseudoplasticity. The apparent viscosity is then given by ... 

For a Newtonian fluid, the power law index n = 1, and k is the fluid viscosity. Also, for shear-thinning (pseudoplastic) fluids, n < 1. 

Power Law Fluid or Emulsion A fluid or emulsion whose rheological behavior is reasonably well-described by the power law equation. Here shear stress is set proportional to the shear rate raised to an exponent n, where n is the power law index. The fluid is pseudoplastic for n < 1, Newtonian for n = 1, and dilatant for n > 1. 

Vemuri S. Flow and consistency index dependence of pseudoplastic guar gum solutions. Drug Dev Ind Pharm 1988 14 905-914. 

One can see that the index n of a power-law fluid substantially affects the velocity profile. With increasing pseudoplasticity the distribution of the velocity becomes more and more homogeneous, approaching a quasisolid distribution with profile V = (V) = const in the limit as n —> 0. On the contrary, dilatancy makes the flow field more and more nonuniform, and as n - oo the velocity profile approaches the triangular shape given by... 

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