Читать книгу The Rheology Handbook - Thomas Mezger - Страница 114

Flow curve model function according to W. Ostwald jun. (of 1925 [3.2]) and A. de Waele (of 1923 [3.39]) with “flow coefficient” c [Pas] and exponent p. Sometimes, c is referred to as “consistency”, and p to as “flow index” or “power-law index”. It counts: p = 1 for ideal-viscous flow behavior, p < 1 for shear-thinning, p > 1 for shear-thickening.

A disadvantage of this model function is that for flow curves of most polymer solutions and melts it cannot be fitted as well in the low-shear range (since it was developed for linear scaled diagrams) as well as in the high-shear range. These are the ranges of zero-shear viscosity and infinite-shear viscosity. Despite this, the model function is often used in the polymer industry to be fitted in the medium shear rate range (see Figures 3.6 and 3.7, 3.15 and 3.16, and the curve overview of Chapter 3.3.5).

For “Mr. and Ms. Cleverly”