Testing Powder and Granular Material Behavior
Powders and granular materials are deceptively complex. Unlike liquids and solid materials, their behaviour can change significantly depending on how they are stored, handled, transported and processed. A powder that flows freely during one stage of a process may become cohesive, compacted, aerated or difficult to discharge under different conditions. Understanding these changes is therefore essential for maintaining consistent processing, product quality and reliable powder performance.
Powder flowability is governed by the interactions between individual particles, groups of particles and the surrounding gas. Particle size, shape, surface properties and density can all influence behaviour, while external factors such as pressure, humidity, temperature, shear and impact can alter the powder structure. Importantly, powders can also exhibit a ‘memory’ of their previous handling and storage conditions, resulting in changes such as caking, agglomeration, de-agglomeration, attrition and changes in effective particle size.
For this reason, a single measurement of powder flowability may not provide a complete picture of how a material will behave in a real process. Evaluating powders under different states and conditions can reveal how their properties change as they move between consolidated, unconsolidated and fluidised states. Dynamic testing can provide insight into the micro-structure and flow behaviour of a powder, while static testing can assess the strength and stability of its macro-structure.
This application note explores the principles behind powder and granular material flow behaviour and the range of testing approaches available using Mercury Scientific instrumentation. It examines how powder properties can be characterised under realistic conditions, including the effects of consolidation, storage, shear, vibration and fluidisation. The aim is to provide a more complete understanding of powder behaviour and help identify changes that could affect handling, processing and final product performance.
