Article

By Tim Freeman, Freeman Technology

In this series, I've been looking at traditional powder testing techniques, such as tapped density methods and shear analysis, to see how they fit with today's powder processing needs. Greater efficiency is the goal now dominating pretty much every area of production, so I really do feel it's appropriate to question whether we have the right powder characterization tools for modern applications.

We all know that powders exhibit complex behavior and are not as easily characterized as gases and liquids, for example. Over the years, many powder testing techniques have been devised, and each offers some insight into powder behavior. Where improved manufacturing efficiency is concerned, it is becoming clear that methods offering precision, sensitivity, and reproducibility — and which deliver process-relevant data — have most value.

Developments in powder testing instrumentation have not only introduced new methods, but have also improved the reproducibility and relevance of more established types of analysis. Dynamic testing, for example, which measures the flow energy of a powder, is a newer technique enjoying considerable industrial uptake. Shear testing, a well-established method, rightly remains popular, but its implementation in more modern instrumentation is improving both precision and reproducibility. In contrast, tapped density methods and other traditional tests such as angle of repose, despite their widespread use, are increasingly seen as having limited value for detailed process-related investigation.

Today's powder testers combine the best techniques available: shear, dynamic, and bulk property testing. They are automated and reproducibly deliver reliable data that correlates with process performance. Thanks to work over the last decade or so, it is reasonable to argue that the goal of reliable powder characterization has been realized. The more interesting question perhaps is: What's next?

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