gypsum

Disk Mill PULVERISETTE 13 classic line

gap setting: 0,1 mm (smallest possible gap setting)

grinding disks made of hardened steel cast

The complete sample amount has been ground within 3 minutes. A bit of sample use to stick lightly to the outside of the disks, we are guessing that even higher amounts should be grindable.

To determine the present fineness, a small aliquot of sample has been sieved with our Vibratory Sieve Shaker ANALYSETTE 3 Pro and a test sieve of 100 µm mesh. Almost 98% of sample passed the test sieve.

Planetary Mill PULVERISETTE 5 classic line with 4 grinding bowl fasteners

main disk speed: 360 rpm

500 ml grinding bowl made of zirconium oxide (ZrO2)

+ 25x 20 mm Ø ZrO2 grinding balls

After 2 minutes of dry grinding, sample starts to stick to the grinding balls.

This uses to happen after the majority of particles reached a fineness of < 20-30 µm. Interacting forces between fine ground particles will become bigger as their own g-force. Therefore, particles will stick to each other and become compressed by the used grinding balls. These clusters of particles also contain bigger particles which will not be ground any further. Longer dry grinding times are not recommended.

We determined a fineness of 73 % < 0,1 mm as desired.

To achieve a better grinding result, anti-sticking agents will delay a sticking of sample. Probably a drying of sample will be able to improve the result (moisture will lead to earlier sticking of sample).

A grinding in suspension is possible to achieve 100 % < 100 µm.