2.3.1. Rheological measurements
Rheological measurements at 20.0 ± 0.5 C were done by
duplicate using a stress controlled rheometer (RheoStress 80,
Haake Inc. Instruments, Germany) with a cone and plate sensor
geometry (cone angle ¼ 2 ; diameter ¼ 35 mm). Before measurements,
each sample rested during 180 s allowing relaxation. A thin
film of silicone oil (100 cP) was applied to the exposed sample
edges to prevent water vaporization during measurements.
Rotational rheometry was performed in the shear rate range of
0.5e100 s1. Values of steady shear viscosity (hðg_ Þ) as function of
shear rate (g_ ) were determined.
Creep tests were performed applying a range of shear stress
from 1 to 300 Pa during 5 min. Values of strain (g) as function of
shear stress (t) were obtained.
Dynamical rheometry was carried out performing frequency
sweeps (1e10 rad s1) in the linear viscoelastic region (LVR) at
constant stress amplitude (5 Pa). Prior to each frequency sweep, a
stress sweep (1e300 Pa) was done at the maximum frequency