Colophony (+ Magnesium oxide)

It was requested to comminute smaller amounts of colophony (dried rosin). The sample was provided in form of flat fragments with a length about 10 mm maximum. The sample was lightly yellowish colored and minimal sticky to the touch.

With the requested planetary mill, we estimate that such a sample would only become compressed by the grinding balls. For such a type of sample, we would recommend using a Knife Mill PULVERISETTE 11.

Instead of standard equipment, we used the 40 ml single-use grinding vessels. Those are dedicated for a comminution of small amounts and no sticky residues have to be removed afterwards.

The 40 ml vessel was almost filled to its maximum when it was clicked into the adapter. We used a SOP which was programmed to comminute the sample in steps of 3 seconds with maximum speed (14.000 rpm); after each cycle, one second pausing time was programmed.

After 5 cycles (a total grinding time of 15 seconds), we checked the sample. As expected, the sample was ground very fine (see the following pictures). Already agglomerates were present which could be flattened easily with a spatula. Surely a majority of sample was already < 40 µm fine.

The sample was sticking lightly to the single-use vessel and could be brushed out without problems. Only on the knife of the lid, some residues of colophony remained.

For the second test, we used the colophony and MgO (bitte ausschreiben) mixture. Since it was requested to grind 400 ml of the composition, we used a 100 ml single-use grinding vessel which was refilled by us a total of 5 times and ground analogously to result 01.

Even with the double of amount of sample in the container, 15 seconds of grinding time were sufficient to grind it down to approximately < 40 µm.

Because of the additive of MgO powder, the sample was less sticky and we co brushed off all the ground sample after each batch was comminuted.