Biopolymer (chitosan)

Usually, we recommend a pre grinding step (e.g. with 1mm sieve rings) if big particles use to be fed. By this, durability of small sieves like the used 80µm sieve ring will be much longer.

By grinding with Variable Speed Rotor Mill PULVERISETTE 14, usually ground particles will show a d50 smaller has half of the opening diameter of the used sieve ring. For the 80µm sieve ring, particles with d50 < 40µm might be found.

After 2 minutes, all sample use to be fed. Sieve ring and rotor use to be mainly free of residues,. Therefore, a grinding of higher amounts use to be possible.

After only 5 minutes of dry grinding, sample use to start sticking to grinding bowl and balls.

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

Within this kind of sample, even particles with 3mm and longer can be found. Therefore, a grinding in a planetary mill is not recommended for that kind of sample.