PVC-free Floor Covering (PVB)

Desired was a fineness of 80 % < 350 µm. With the present start size of > 20 cm. A manual precutting would be required. We don’t provide such a large mill and used a table top scissors to cut the sample into thin strips with ~ 2,5x10 cm.

A fineness of < 500 µm will be tricky for some plastic sample, surely a high-performance cyclone separator will be required for fine grinding. Because of this, we precut the sample with this result to < 4 mm already with the combined high-performance cyclone separator and sample exhauster. This optional equipment will chill samples and grinding parts and removes a ground sample out of the grinding chamber, within the moment it is capable to pass the used sieve cassette.

The 380 grams of < 2,5 cm wide precut sample was slowly fed into the mill which was equipped with a standard rotor with V-cutting edges and a sieve cassette with 4,0 mm square perforations for precutting.

The sample pusher was used every now and then to support feeding. It took 140 seconds (2:20 minutes) until the complete batch was fed and ground. The sound of grinding was typical and comminution was performed without problems.

The sample which passed the 4 mm sieve cassette will be used for fine grinding in our next trial.

Cleaning of the grinding chamber was performed rapidly by vacuuming with a soft brush.

Precut sample material of result 1 was used for this trial. With a fineness < 4 mm, the sample might be grindable to < 500 µm within the following step. We prepared a batch of 150 grams of < 4 mm sample and started to transfer the sample slowly into the grinding chamber.

The mill was equipped with our high-performance cyclone separator, the standard rotor with V-cutting edges and a sieve cassette with 0,5 mm trapezoidal perforations.

While we transferred the sample into the grinding chamber, the sound of comminution was typical. We stopped feeding of sample material after only 80 grams of < 4 mm sample was fed into the mill. The output seemed to stagnate after ~ 3 minutes. Also, the air flow of the cyclone collapsed at this point. Switching off and on, of the sample exhauster did not improve the air flow anymore. We interrupted the grinding process after a total grinding time of 4 minutes. We found and output of 50 grams inside the cyclones attached collecting glass.

About 95 % of the trapezoidal perforations were blocked with sample material. A Universal Cutting Mill PULVERISETTE 19 is not suitable to achieved the desired level of fineness.

Cleaning was performed by vacuuming with a soft brush. The sieve cassette was cleaned with a wired brush.

Typically, a Variable Speed Rotor Mill PULVERISETTE 14 premium line which was converted into a cutting mill can grind samples which don’t pass a Universal Cutting Mill PULVERISETTE 19 anymore. Eventually this type of mill would be capable to comminute the desired amount of 500 grams of precut sample as desired (see next result).

Our Variable Speed Rotor Mill PULVERISETTE 14 premium line can be converted into a cutting mill. With a knives gap of only 0,1 mm and a speed up to 18.000 rpm, much finer results can be realized, compared to a standard cutting mill (with a gap of ~ 0,2 mm and up to ~ 3000 rpm). For this type of cutting mill, a fine precutting is required.

We used the 4 mm output of result 1 for our grinding trial. A batch of 150 grams was used. The mill was equipped with our high-performance cyclone separator and sample exhauster. Sieve shells with 0,5 mm trapezoidal perforations were equipped for this trial.

The batch was slowly transferred into the feeding funnel. The sound of grinding was smooth. It took 4 minutes until the complete sample was fed and ground.

After comminution, only electrostatically charged fine sample dust remained inside the collecting vessel. The majority of trapezoidal perforations were not clogged with sample. We estimate that about 5-10 % of perforations were blocked with residues.

Surely higher amounts of sample could be ground this way. For a desired amount of 500 grams, we don’t expect that a cleaning step needs to be performed.

Finally, we also checked the grindability of the < 4 mm precut sample which sieve shells of 0,2 mm trapezoidal perforations.

We prepared a batch of 100 grams and started to feed the sample with a very low feed rate into the mill. The grinding sound was very smooth during the grinding process. After five minutes, we recognized that the air flow almost collapsed and interrupted the feeding process after five minutes. About 95 % of the trapezoidal perforations were blocked with sample material. A cleaning step would be required now. An output of 42 grams was packed from the cyclones collecting glass.

Residues inside the grinding chamber were removed by vacuuming with a soft brush. The sieve shells required brushing off with a wired brush. Final residues were removed with a lancet. Also compressed air could be used to support the cleaning of sieve shells.

We don’t recommend using 0,2 mm sieve shells for the comminution of your PVB sample material.