Rheometry capillary viscometer

Yiscometry (using coaxial cylinder, cone and plate and vane rotational viscometers, and controlled stress capillary viscometers) can be used for soft cheeses. Lubricated squeezing flow rheometry is particularly useful for measuring cheese meltability. 

Oscillatory shear measurements provide more precise data than capillary rheometry and require smaller samples. In addition, capillary viscometers are hmited to use at moderate to high shear rates and do not provide accurate results at shear rates below 10 s for most materials. It would thus be useful to be able to estimate the viscosity curve using data from oscillatory shear measurements. Based on their data for two polystyrenes, Cox and Merz [133] reported that the curve of apparent viscosity versus shear rate, as determined using a capillary viscometer, lay very close to the curve of complex viscosity versus frequency. While the apparent viscosity measured in a capillary viscometer is usually defined as the apparent wall shear stress divided by the apparent wall shear rate, it is likely that the entrance pressure drop was nearly negligible for the polystyrenes studied by Cox and Merz. Therefore, what they observed can be expressed as follows ... 

The complex rheology of polyblends, alloys, and filled plastics can be better understood when both capillary viscometer and stress controlled rotational rheometer are utilized. The capillary viscometer can provide more information about the effects of process history on the macrorheology of these kinds of plastics. This information is complimented with stress controlled rotational rheometry which is more suited for studying the microstructure. Very usefid is the yield stress data which relates to the interfacial bond strength between the clustered particles and the continuous matrix. 

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