Cellulose

For a daily grinding of smaller amounts of sample, a standard rotor made of tool steel might be usable as well. With hardmetal tungsten carbide, the durability of the knives will be immensely enlarged. For this, we would recommend using a rotor with tungsten carbide knives.

By standard, sieve cassettes down to 0,25 mm trapezoidal perforation are available for a cutting mill. 0,1 mm openings are available on special request, but in general, sample should be very brittle to get a proper grinding result with such fine openings. For example, those sieve cassettes can be used for a grinding of dry coal or coke samples.

Because the start size of the original paper sheets uses to be way too big, the sheets need to be ripped into pieces before feeding. To prevent hand injuries (when the rotor will pull the paper), we recommend just ripping of smaller pieces of ~ 10 cm and folding them to feed the machine.

As expected, only a bit of sample has been fed before the airflow will interrupt. Sample is lying in front of the sieve cassettes openings without been ground any further. Even switching on and off of the cyclone separator is not improving the grinding result. We recommend to use the next bigger sieve cassette of 0,25 mm trapezoidal perforation (see result 2 & 3).

With a 0,25 mm sieve cassette, sample can be ground as expected. With this trial, we used 2 sheets of paper and ripped them into smaller pieces with a length of ~ 10 cm. The pieces have been rolled and folded once for a feeding to the standard funnel.

It took about 3:30 minutes for the first sheet to be fed. With the second sample, a few folded pieces did not get grabbed by the rotor and a second piece has been used with the sample pusher to move both pieces into the grinding chamber. The second sheet of paper took about 4:30 minutes to be ground.

The fluffed up and ground sample got removed out of the grinding chamber and can be found in the 5 liter collecting glass of the cyclone separator.

After grinding, only a few particles use to be found lying loose on the sieve cassette. Most openings of the sieve cassette are free, a grinding of higher amounts of sample use to be possible. A cleaning can be done rapidly by vacuuming with a soft brush.

The rotor temperature rose to 47 °C and might rise a little higher when more samples will get ground.

Also the sample B can be ground analogue result 2. Because the material uses to be a little thicker, we ripped the pieces a little fine before folding and feeding to the machine.

With sample B, it took about 10 minutes instead of 8 minutes for a grinding of two sheets of paper.

Just like result, only a few particles are left after grinding, cleaning can be performed rapidly by vacuuming with a soft brush. The rotor temperature rose to 48 °C.

The optional cyclone separator will produce a high airflow which will chill sample and grinding equipment, for this, we are guessing that the temperature of the rotor will not rise immensely.

We like to mention that a continuous grinding is not possible for a laboratory mill, security switches will cut down the power supply when the motor of the machine will become too hot. We are guessing a grinding for up to 1 hour might be possible (so about 15 sheets can be ground before a chilling will be required).

It is also possible to precut the sample, using a Power Cutting Mill PULVERISETTE 25. With the small opening of the lid of the funnel for long and bulk solids, a feeding is problematic; still a pre cutting can be required.

It might be beneficial using the protected funnel with sample pusher for pre cutting the sample. When the pusher will be removed, sample can be fed into its channel and the pusher can be used to press the complete paper sheet into the grinding chamber for comminution.

Then a grinding in < 2 min per sheet can be realized.

All ground particles have a size which is suitable for a direct feeding into a Universal Cutting Mill PULVERISETTE 19 with funnel for long and bulk samples.