Retsch Mixer Mill MM 500 nano, Руководство пользователя

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Operating the Device
36
6.6 Special grinding methods
6.6.1 Cryogenic grinding
WARNING
W7.0000
Risk of injury caused by liquid nitrogen
Use of liquid nitrogen during cryogenic grinding
−
Liquid nitrogen has a boiling point of
– 196 °C and causes burn-like
injuries and frostbite if there is skin and eye contact.
•
Take note of the liquid nitrogen safety data sheets.
•
Always wear goggles and protective gloves when using liquid
nitrogen.
WARNING
W8.0000
Risk of injury caused by liquid nitrogen and dry ice
Use of liquid nitrogen and dry ice in closed grinding jars
- Liquid nitrogen and dry ice expand and generate high pressure in closed
receptacles. This high pressure bursts grinding jars and leads to serious
injuries.
•
Under no circumstances should you put liquid nitrogen or dry ice
into the grinding jar and then close the jar.
•
Only undertake indirect embrittlement for cryogenic grinding.
Materials that can only be ground with difficulty or not at all under normal temperatures must be
ground cold. Indirect embrittlement with liquid nitrogen ( - 196 °C) improves the fracture
behaviour of thermoplastics, rubber products, greasy foodstuffs, pharmaceuticals etc.

For cryogenic grinding, Retsch GmbH offers the Cryo Kit (Order Number: 22.354.0003) for
cooling the grinding jars with liquid nitrogen.
Carry out the embrittlement of elastic and tough sample material as follows:

The embrittlement of sample material for grinding must be performed indirectly.

Only use grinding balls and grinding jars made of stainless steel or hardened steel
for cryogenic grinding.
Grinding balls and grinding jars made of zirconium oxide or tungsten carbide are
not suitable for grinding at very low temperatures.

The sample material must be filled together with the grinding balls (steel) in a grinding jar
(steel), and the grinding jar (steel) firmly sealed.

Using the Cryo Kit tongs, the firmly sealed grinding jar (steel) is then dipped into a bath of
liquid nitrogen until this stops bubbling.

The sample material inside the grinding jar (steel) is then likewise cooled and ready for
grinding.

Under no circumstances should you fill liquid nitrogen or dry ice into the grinding jar and
then close it. The high pressure generated in the grinding jar would burst it.