Viscometers, different, reproducibility

Figure 10. Rheological measurements performed with a coaxial cylinder viscometer and different geometries. The fact that the curves are not superimposed implies that the measurements are affected by wall slip. (Reproduced with permission from reference 13. Copyright 1991 E.irF.N. Spon.)...

The effects of gel preparation and shear history could then be compared. The HPG-titanium gels were cross-linked at a shear rate of 675 s" in the two mixing devices. The viscosity measurements for samples with no additional shear conditioning are presented in Table I. Data are shown for the two rotational viscometers and two different reciprocating capillary viscometers. The viscosity values compare favorably between the instruments with a range from 89 to 109 mP s at 70 min. These data demonstrate that reproducible viscosity measurements (i.e., the same viscosity measured for the same gel composition) can be made, provided that the gel structure is formed under similar conditions. (For these experiments, the magnitude and time at shear, heat-up rate, etc., were matched as closely as possible.)... 

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