The effect of non-Newtonian viscosity

Many on-line instruments are calibrated with Newtonian liquids, so that the results are presented as equivalent Newtonian viscosity—this can be far from the truth Very few viscometers give the actual imambiguous (non-Newtonian) viscosity as a function of the 

If the particular product is not very non-Newtonian, a single-point measurement might be sufficient. Even then however we must be sure that the flow type is the same. For instance if our experience off-line is built up from steady-state, simple-shear flow curves, then a too-fast measurement might mean the measurement is not made under steady-state conditions. Equally if the on-hne flow has an appreciable extensional component, then problems can arise for some hquids, especially pol3nner solutions. Also if a vibrational mode is used, then it is probable that some non-hnear oscillatory function is being measured. Ah these facts could mean that we end up with no simple one-to-one correlation between on-hne and off-hne. Hence the safest way is to duphcate on-hne what is done off-hne. This is possible nowadays for most situations. 

we should mention one recruring problem with any kind of viscometry—wall shp. To be more correct, we should speak about the depletion of the dispersed phase of suspensions and emulsions that takes place at a smooth wah. This leads to a lubricating layer at the waU that can greatly interfere with the measurement. This can be overcome by roughening or profiling the surface of the measuring element [3]. 

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