2.6. Rheological essays
Flow curves were obtained by a stress-controlled rheometer (Physica MCR301, Anton Paar, UK) at 25 °C. The shear rate varied in the range between 0 and 300 s−1 and the flow curves were obtained in sequential three steps: up-down-up. The second up curve was fitted to the Herschel–Bulkley model:
equation(4)
View the MathML source
in which σ is the shear stress (Pa), σ0 is the yield stress (Pa), View the MathML source is the shear rate (s−1), k is the consistency index (Pa sn) and n is the flow index.
2.7. Statistical analysis
The difference in the results of particle size distribution and rheological parameters was statistically analyzed through the Tukey test, using the software Statistica 7.0 (Statsoft Inc., USA).