Characterising powder flow properties - the need for a multivariate approach

 
Powders are challenging materials, as evidenced by frequent problems during storage, processing and final product quality. Powders are assemblies of solids, liquids and gases which results in complex behaviour that provides their industrial value - they can aerate to behave like a fluid or can compact into a tablet - but also makes characterisation difficult. Powder processing equipment present various stress and flow regimes making it possible for a powder to behave a certain way in one operation but differently in another. It is critical that powders are compatible with the process environment and the final application. Many powder testers don´t deliver relevant information as the tests don´t represent the process. Powder rheometers generate relevant data by measuring dynamic, bulk and shear properties enabling a powder´s response to different stress and flow regimes to be quantified.