| abstract |
The yield stress of rheologically plastic fluids such as coatings, sealants, and personal care lotions, determines their tendency to flow at low gravitational stress. Yield Stress is the apparent threshold stress above which flow is observed on an arbitrary time scale. An on-line technique to monitor yield stress during processing was developed, and can be used in controlling the slump or non-slump behavior of such products. A residual stress, after a flow excursion returns to zero shear rate, is related to yield stress. This residual stress can be used for process monitoring. It is measured from the residual pressure or torque after a controlled strain rheometer reaches zero strain rate. |