FRITSCH PULVERISETTE 9 - Manual (Page 25)

6.1.3 Dry grinding
Below a particle size of approx. 20 µm, the surface forces prevail and the
material to be ground starts to "stick".
Additional dry comminution can be achieved by adding surface-active
substances to the material to be ground.
Examples (maximum amount to be added in mass%)
n Stearic acid 2-3%
n Aerosil (fine-particle silicic acid) 0.5-2%
n Quartz sand ~ 2%
n Glass powder ~ 2%
6.1.4 Wet grinding (grinding in a suspension)
During the transition to grinding in suspension, you can add a liquid aux-
iliary agent with high boiling point (>80°C) and low vapour pressure.
DANGER!
Explosion hazard! Ignition hazard!
The device is not explosion-protected. If flammable liquids
are used, make sure that the heat developing in the
grinding bowl does not reach the solvent's boiling point.
Program appropriate cooling phases. If the vapour pressure
is too high, vapours may escape and ignite. If it can be
avoided, we recommend using non-flammable liquids or
liquids with a high boiling point. The boiling point should be
above 80 °C and above 100 °C for a long grinding duration.
During wet grinding, a higher final fineness can be achieved. During wet
grinding though, the pressures and temperatures in the grinding vessel
may get very high. Be careful when releasing the clamping device (3); hot
steam may escape at high pressure. Open the level slowly; allow the set
to cool down in the device.
CAUTION!
Risk of splashing!
During wet grinding, the high temperature may have cre-
ated overpressure.
Wear protective goggles!
Using the device
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