Polypropylene Granulates

For this trial, we used our Variable Speed Rotor Mill PULVERISETTE 14 premium line which was converted into a cutting mill. The mill was equipped with a sieve shell set with 500µm and our high-performance cyclone separator with sample exhauster. The high-performance cyclone provides a constant air flow to chill sample and grinding parts and removes ground sample out of the grinding chamber.

We started our trial with a first batch of 50 grams to check, if the sample is grindable this way and if thermal problems or other difficulties might occur. The sample was ground without problems (and a lower feed rate) within 3:20 minutes. Only a few openings of the trapezoidal perforated sieve shells were clogged with sample. No smearing of sample was observed on the knifes or rotor body. Higher amounts of sample can be ground.

We proceeded grinding and checked the grinding chamber after a total amount of 200 grams and 500 grams as well. Still a majority of trapezoidal perforations remained free and we ground the last 500 grams batch without a cleaning step in between.

A Vibratory Feeder LABORETTE 24 could be used to automatize the feeding of sample into the PULVERISETTE 14. For the last batch of 500 grams, only 11:50 minutes were required. With the higher feed rate, the system temperature rose to 42 °C (still not problematic to grind higher amounts). After the complete kilogram was comminuted, still only ~ 20 % of openings inside the sieve shells were clogged.

We merged remaining and ground sample from the collecting vessel with the sample inside the cyclones attached collecting glass by switching on the sample exhauster and pushing ground sample into the tube which is connecting the cyclone.

Electrostatically charged rests of sample were removed by vacuuming with a soft brush. The grinding parts were placed into an ultrasonic cleaner for several minutes to remove the last traces of sample. Also, a small needle like tool could be used to free a few trapezoidal openings from residues. A wired brush (made of brass) could be used to remove a higher amount of residues inside smaller sieve shells.