How to characterise an unknown powder sample

Most powder testing hands you a full menu of tests and leaves you to work out which one to run first, what the numbers mean, and what to do about them. That rewards experience. It does much less for the formulation scientist meeting a new ingredient, or the process engineer trying to work out why a hopper bridges on a Tuesday afternoon and not on a Monday.

So, we have built a different route through the Powder Flow Analyser: one fixed starting sequence, software that reads your results and tells you what they mean, and a clear next step every time. You do not need to know which test to reach for. You need to know what your powder is going to do.

Watch how it works within Exponent Connect software:

Step 1: Run the Three PFA Tests in One project

Cohesion, PFSD and Caking, run back-to-back on a single sample in around 18 minutes of walk-away time. The order is deliberate: the least destructive test runs first and the most destructive last, so every stage of the sequence is still working with a representative sample.

Nine parameters come out of it. Cohesion Index, Bridging Factor, Bulk Density, Speed Sensitivity Ratio, Flow Stability, Cake Height Ratio, Mean Cake Strength, Cake Strength and Column Height Ratio.

Step 2: Let the results come to you

A macro inside Exponent Connect reads your finished results spreadsheet and opens the Results Interpreter with your data already in place. Nothing to type, nothing to transcribe, and nothing to mistype at four o’clock on a Friday.

Step 3: Read an answer, not a spreadsheet

The Interpreter leads with the single most significant risk your data points to, in plain language, before anything else. Then it shows you the working:

• Every measurement in its band, colour coded by severity, with the numeric limits of that band alongside it
• How the powder behaves, described separately for cohesion, dynamic behaviour and caking
• Where problems are most likely to show up, ranking filling, hopper discharge and storage from most likely to least likely for your powder, with the parameters behind each one on show
• Which test to run next, and why, tied to the pattern in your own results

Every band boundary and every severity colour is explained in the tool itself, so nothing is asked of you on trust.

Step 4: Put the result in context

A number on its own is hard to judge. The Sample Comparator sets two samples side by side: two batches, two suppliers, or the same material before and after a process change. Or compare your sample against a reference powder from our training library of well-known samples, to see how far you sit from behaviour that is already understood.

Where this fits in the wider test range

Three tests are a starting point rather than the whole picture, and the Interpreter says so: every result comes with the next test to run. Some of those are further Powder Flow Analyser tests, such as Compressibility, Consolidation and Caking, or Cohesion at 4 Speeds.

Others move the same powder onto the TA.XTplusC Texture Analyser, where a family of complementary tests takes it further: unconfined yield stress, which relates to hopper discharge, arching and ratholing risk; vertical shear strength, which supports hopper and bin design; granule compaction, for the strength of a granule before tabletting; and powder compaction, where the powder ends up as a tablet, pellet or compact. One instrument platform, one powder, from how it flows through to how it performs as a finished product.

See the complementary powder tests

Why this matters

A result on its own is a number. A result with an interpretation is an answer. A result compared against something you already understand is a decision you can act on. That holds whether you are commissioning your first Powder Flow Analyser test or you have been running them for twenty years.

Available in Exponent Connect from version 8,1,17,0. Get the latest software.