Stable Micro Systems, one of the world’s leading texture analysis experts, has expanded its portfolio with a rig able to measure the flowability of unconfined powders
The Unconfined Yield Stress Rig offers manufacturers the ability to understand how powders and granular materials respond to pressure.
When stored, the weight of powder in a container puts pressure on particles on the bottom.
It is important that powder flows freely after being stored, rather than "caking," which is where understanding flowability is useful.
Unconfined yield stress is a simple technique that can be used to analyse the flow behaviour of many different types of powders and the changes in this behaviour with different consolidation stresses and times.
To conduct the test, the user fills a tube with powder and the rig compresses it. The load and container are then removed to leave behind a freestanding column, which is then compressed, or consolidated, by a probe until the powder yields.
Unconfined yield stress has little meaning as a measurement alone as it depends on the "consolidation stress" — a powder more firmly compressed is likely to flow less freely and have a higher yield stress.
Instead, flow functions of samples are compared, which are determined from the relationship between the consolidation stress and the resulting unconfined yield stress. The flow function curve of each sample shows how one factor is affected by the other; a steeper gradient highlighting a stronger dependence and, therefore, how flowability is influenced.
Applications Manager at Stable Micro Systems, Jo Smewing, commented: “For industries handling powders on a regular basis, understanding their flow behaviour is key for operational and quality purposes. Whether it’s the addition of flour in a bread recipe or testing the quality of an eyeshadow, the Unconfined Yield Stress Rig offers an accurate, objective measure of powder flow.”
The assessment of unconstrained powder characteristics is yet another measurement that the Texture Analyser can perform on powdered materials, complementing the functionality offered by the Powder Flow Analyser.