Rheological studies
Rheological measurements were carried out using a controlled strain rheometer (TA Instruments, Ares, New Castle, Del., U.S.A.)operating with a cone and plate geometry (cone dia, 50 mm; coneangle, 0.04 radian).
Samples were equilibrated at 30 °C, gentlymixed, and then portions (about 1.5 mL) were transferred to theinstrument.
The instrument had previously been equilibrated at 30 °C and the test was runimmediately.
The shear rate was increased from 0/s to 100/s over 7 min and the required stress used
to calculate the apparent viscosity.