Mike Bradley, Rob Berry and Richard Farnish – The Wolfson Centre, University of Greenwich

Powder flow properties can now be measured in ways that give a good indication of the likely behaviour of the powder in a given process, or conversely allow us to design a process so that it will work reliably with a given powder. The next logical step in powders research, is to understand ways to modify the flow properties of the powder so it will behave more favourably in the process we want to use.

Industrial practice in powder flowability modification is well established, usually to reduce a powder’s resistance to flow, through altering the moisture content, the size distribution, applying surface coatings and/or adding so-called “flow aids” or “glidants” to the powder. There are also some relatively new options on the scene, including for example “mechano-fusion”. However, many of these are used on a “trial-and-error” basis, chosen according to company tradition and with relatively little understanding of how to optimise their use or which might be a better option for a given application. “Improved flowability” can also have unwanted side-effects, for example increasing segregation tendencies and dustiness of a blend, so occasionally it is necessary to make powders less free flowing.

This paper will give a quick review of what “powder flowability” is and how it can be measured, then will concentrate on an overview of the different methods of powder flowability modification, how they work, their success in different applications, various side-effects and how to measure and control them. It will conclude with a review of some latest research going on in the area.e.