Characterization and analysis of powders

In the previous issue of [J 2 251], we described some of the fundamental physical properties of powders. In this dossier, we complete that description by focusing on methods for characterizing other properties, no less important and essential to understanding the interactions between powders and their surrounding environment, particularly in the presence of humidity, electric fields, electrostatic charges or even contact with a gas current that can lead to the emission of dust.

While physical properties, the subject of the first dossier [J 2 251], can be reliably and acceptably determined using the analytical means that have become "routine" today, the same cannot be said of the behavioral properties described in this dossier [J 2 252]. Moreover, the theory and practice of powder technology are such that it remains difficult to predict the collective properties of particles from their individual characteristics, especially as powders are rarely made up of just one type of particle. However, it is the collective properties of the particles that determine the behavior of a powder in a variety of circumstances, such as its ability to fluidize, to take on electrostatic charge, to emit dust, to compress, to attrition, to caking or to segregation.

Characterizing these behavioral properties therefore requires, first and foremost, the development of application tests to determine the behavior of powders during the various operations they undergo (mixing, drying, coating, compacting, storage, etc.). Some use these tests to attempt to explain and rationalize observed behavior, while others can predict the suitability of the powder under test for various manipulations in the process chain.