Testing Powders
Hi Joelle,
Testing powders can be tricky. You are trying to set up a standard measurement to guide quality control for your process. There is no instant answer.
One practical approach is to try several alternative tests. Compare these with production results. Then you would be in a position to pick the one test which has proven to be the most consistent predictor of the quality parameter you are seeking to control.
Regards - John.rz ■
Test For Pressing Consistency
In principle, a tensile test would best reflect the ability of the powder to hold together after pressing but ,for a quicker and simpler test, I would suggest measuring the compacted strength with a small vertical shear tester. This method essentially compresses a sample in a cell under a standard load, trims the depth to a common value and measures the force required to punch a hole through the bed. See www.ajax.co.uk for an example. The size of test device we make and use is for hopper design, so a smaller version may be appropriate for the scale of application in your case. ■
Powder consistency characterisation
Dear Lyn,
In our company we make very cohesive cosmetic powder mixtures (with wet binder) for pressing on rotative press. We use common vessels for mixing, and hammer mills.
We seem to have problems of powder consitency because for each bulk the pressing parameters have to be changed.
I am trying to find a characteristic to check after each powder manufacturing, before the pressing process, to identify the differences between bulks. What kind of parameter would be the most adapted according to you? Time of flowing through a cavity (Degusa), angle of talus, flowability index (Carr, Hausner)?
Thank you very much for your help.
Regards. ■