Xanthan behavior above

Above 40°C the behavior is quite normal and controlled by the main helix-coil transition of the polysaccharide. This is not the case when the temperature is lower thus when the optical rotation of the acidic form of Xanthan is investigated, there is... 

It is possible that the zero-shear viscosity of polymer samples with very high molar mass and strong non-Newtonian flow behavior cannot be measured in a capillary viscosimeter. In case of a maximum shear rate in the capillary above the critical shear rate of the sample the calculated viscosity will be too low as one can see in Fig. 5.10 for different samples of high molar mass xanthan gum. 

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