Understanding Yield Stress Measurements
The yield stress characteristic is a property associated with numerous types of complex fluids - whereby the material does not flow unless the applied stress exceeds a certain value. This is evident in everyday tasks such as squeezing toothpaste from a tube or dispensing ketchup from a bottle, but is important across a whole range of industries and applications. The determination of a yield stress as a true material constant can be difficult as the measured value can be very much dependent on the measurement technique employed and the conditions of the test, of which there are many. Consequently, there is no universal method for determining yield stress and there exist a number of approaches, which find favour across different industries and establishments. This White Paper discusses the various approaches available to measure yield stress, and aspects of the practical measurement set-up and test parameters that need to be considered to obtain relevant, robust and reliable yield stress data using a rotational rheometer.