Powder Properties Characterisation

All the desirable properties of a powder are dependent on the powders physical characteristics so it is of huge importance to understand the link between these two. It is imperative to be able to analyse a powders properties to ensure that it will behave correctly within the process and not deviate or affect production in a negative way.

Within the PMTC we have a full suite of analysis equipment for the characterisation of powders physical properties, how it flows and how it compacts under force.

In parallel with sizing, a powders Morphology -the physical structure and shape of a powder - can also affect its flow and compaction characteristics within a manufacturing process. Both optical and Scanning Electron microscopes are used to investigate a powders morphology. Typically, spherical type powders that are not very fine flow well whereas acicular – needle shaped – powders do not flow well. In addition, powders exhibiting a porous structure generally compact well.

A powder or compacts Density is another important property to measure. The measurements generally undertaken are True density Bulk (aka apparent / volumetric) density and Tap density. The true density is measured using a Helium Pycnometer. This apparatus uses helium gas to infiltrate porosity within the powder so the volume measured is only that of the actual powder. This gives a real measurement of the powders density which can be used in calculations. Bulk, or volumetric, density along with Tap density are more in-process measurements rather than physical properties of the powder.

The density calculated when powder is gently poured into a known volume – without Tapping! - and that powder weighed is the Bulk density. If this weight is then tapped to force the powder to settle, reducing the volume, the resulting calculated density is called the Tap density. All these measurements are important for setting up and controlling a production process.

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