Rheological Characterization of Emulsions

The emulsions’ rheological properties were studied using an MCR 92 modular compact rheometer (Anton Paar, Graz, Austria), equipped with a PP50/S parallel plate geometry (diameter 50 mm) and a P-PTD 200/AIR Peltier plate to keep the measurement temperature constant at 25 °C. A steady-state flow ramp was used to determine flow curves for shear rates between 0.01 and 1000 s⁻¹. The flow curves were fitted to the Cross model [16 (link),26 (link)]: $$\eta =\frac{{\eta }_0}{1+{\left(\tau \left.\dot{\gamma }\right)\right.}^m}$$
where η is the apparent viscosity (Pa.s), η₀ is the viscosity at zero shear rate (Pa.s), τ (s) is the relaxation time (s), and m is a dimensionless constant, related to the exponent of pow-er law (n) by m = 1 − n [13 (link),16 (link)]. Frequency sweep tests were performed with frequencies ranging from 0.01 to 16 Hz for a constant strain of 0.5% that was well within the linear viscoelastic limit (LVE) evaluated through preliminary amplitude sweep tests.