Brookfield YR-1 Rheometer - Manual (Page 39)

Brookfield Engineering Labs., Inc. Page 39 Manual No. M02-215-B0412
IV. EXAMPLES
IV.1 Example Application: Body Wash Gel with Bath Beads
The test method and data shown in Figure IV-1 show an analysis of yield from a typical body
wash gel product. It is usually desirable to measure yield on products without transferring
them from their containers because doing so would “pre-shear” the material. This body wash
was a weak gel with suspended beads in it. The V-73 vane spindle was selected because it was
small enough to fit in the container’s neck with the cap removed. A 1/4 RVYR-1 Rheometer
was used for the test.
The spindle was immersed to the primary immersion mark and pre-shear was turned off. Zero
was turned on and a nominal “zero” speed of 0.1 rpm was chosen. This allows the motor to reset
the torque to zero prior to running the test. Occasionally, the spindle rotates a bit while being
lowered into the sample. This moves the torque sensor away from zero. It is usually desirable
to reset it to zero before starting the measurement. Run speed was set to 2.0 rpm. Often, 1.0
rpm is selected and is a good starting point when establishing test parameters. Low and high
yield limits (for Q.C.) were ignored.
This test resulted in a good mid-range torque of 77.0% at the yield stress, which was reported
as 19.3 Pa.
Figure IV-1: Body Wash Gel Sample