How to Measure Powder Uniformity

Mankind has been breaking down solid materials into their particulate forms for millennia. The resultant powders have served as domestic ingredients for food goods and industrial feedstocks alike; each of which required a rudimentary understanding of powder uniformity.

Our earliest indication of mankind using rudimentary methods to achieve a precisely homogenized mixture of powdered materials is the mortar and pestle. Historians have also uncovered evidence to suggest that Ancient Egyptians exploited sieves to separate precious metal feedstocks into homogenous components, in what is believed to be the world’s first example of industrial beneficiation.

These precursors to modern homogenization and purification techniques operated on a purely qualitative approach to powder uniformity. Homogenous mixtures were assumed once a powder reached a certain consistency as determined by touch or successful sieving. There was no true solution to quantitative powder uniformity measurements until the onset of microscopy and modern materials science. Now, with a plethora of micro-scale optical observation technologies available, it is possible to determine powder uniformity with respect to several key parameters.

Outlining Powder Uniformity

Powder uniformity tends to refer to what is known as content uniformity, which is essentially a measure of consistency throughout a bulk powder. If a sample can be taken from any location within a mixture and display the same proportion of ingredients as those present in the bulk powder, it can be described as having a uniform composition. Achieving powder uniformity is the ideal outcome of blending processes in myriad market sectors, from pharmaceuticals to the food and beverage industry.

However, the dissimilar properties of powder ingredients can inhibit the formation of a truly homogenous mixture: concentration; density; moisture content; particle shape and size; etc. Successful mixing processes will consider correct dosing of ingredients and strict selection of distinct ingredient particle size distributions (PSDs) to encourage the formation of a homogenous powder mixture in the shortest time-frame possible. This goes for in-process powders and finished dosage units alike.

Measuring Powder Uniformity with Particulate Systems

Measuring powder uniformity requires a robust analytical solution capable of simultaneously assessing the distinct characteristics of multiple components in a bulk powder. This can be conducted using a dedicated segregation tester.

The SPECTester from Particulate Systems measures powder uniformity after a sample volume has been filled into the aperture of the hopper. From there, it feeds into the analyser via a material chute with precise variable speed control. The sample is measured by spectral reflectance and cross-referenced with the specific spectral fingerprints of the individual components in the bulk sample – as confirmed via independent, integrated analysis. Particulate Systems offers two SPECTester models operating with either visible light or near-infrared (NIR) detection.

This testing methodology provides a quantitative measure of component concentration and particle size distribution, which assists with uniformity indexing. It can reliably measure mixtures with up to six primary components and provide accurate data regarding concentration, size differences, and uniformity information to assist in the identification of mixing parameter issues.

Browse our full brochure for the SPECTester Innovative Segregation Tester for any more details, or contact a member of the Particulate Systems team of you have any specific queries about measuring powder uniformity for your application See our SPECTester Web Landing Page for further information.

[Source: Science Direct]

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