Dynamic viscosity capillary-flow technique

Polypropylene compositions containing magnesium hydroxide, with and without magnesium stearate surface treatment, were characterised at low and high shear rates using dynamic and capillary measurement techniques [36]. A significant reduction in viscosity was observed when surface treatment was present, particularly at low shear rates. In addition, with this system, the yield stress for the onset of flow was markedly reduced (Compare magnesium hydroxide variants A and E in Fig. 9). 

A commercial instrument for extensional viscosity measurements is currently offered by the Thermo Electron Corporation [40], The device uses capillary breakup techniques and is called the Haake CaBER . Vilastic Scientific, Inc. also offers an orifice attachment to their oscillatory rheometer for extensional viscosity determinations [41,42], The principle of operation of the rheometer is oscillatory tube flow [43,44], Dynamic mechanical properties can be determined... 

With the Miesowicz technique one can measure three combinations of the Leslie viscosity coefficients from Eqs. (9.25) to (9.27). On account of the Parodi relationship, to find all five coefficients, one needs, at least, two additional measurements. In particular, the ratio of coefficients a3/a2 can be measured by observation of the director field distortion due to capillary flow of a nematic. The last combination yi = as — as can be found from the dynamics of director relaxation. 

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