PET (several kind of pre forms & lids)

Before fine grinding to the desired fineness can be done, a pre grinding of sample is required. Therefore, sample can be precut with a band saw, also a Power Cutting Mill PULVERISETTE 25 will be capable to comminute the samples to an adequate start size for feeding to the Universal Cutting Mill PULVERISETTE 19.

Also the usage of the standard rotor with V-cutting edges is possible to use for the Power Cutting Mill PULVERISETTE 25.

With the biggest PET pre forms, the start size use to produce some difficulties with feeding. It takes about 20-30 seconds before the sample will be grabbed by the rotor knife and starts to be ground.

After a total time of 60 seconds, the complete pre form has been comminuted to < 4 mm. A bit of sample use to remain loose on top of the sieve cassette and can be removed easily by vacuuming with a soft brush.

Even higher amounts of sample can be pre ground this way.

The sample has been precut in result 1 by using the Power Cutting Mill PULVERISETTE 25.

Now a grinding to the desired fineness is possible. After the first minute of grinding, an output of 11 g has been found. After 3 minutes of grinding, output rose to 38 g. We aborted the grinding process after a total of 8 minutes with a maximum output of 41,5 g. It might be possible to run the machine longer, but by grinding of plastics, electrostatic charged sample will always remain inside of the grinding chamber.

Also in this case, a higher amount of sample remains loose inside of the grinding chamber and can be removed easily by vacuuming with a soft brush. A grinding of higher amounts is still possible.

As commented in result 1, also with Universal Cutting Mill PULVERISETTE 19, the usage of a standard rotor with V-cutting edges is plausible. With hardmetal tungsten carbide, you will have a much longer durability (compared to steel rotors).

One of the big pre forms has been precut with a band saw. Now the sample pieces use to be < 8 cm and can be fed to the protected funnel with sample pusher.

Two of the precut pieces with a total weight of ~ 50 g have been fed within 30 seconds. After 2 minutes, an output of 34 g has been achieved. After a total of 5 minutes, the output rose to 42,5 g.

Even higher amounts can be ground this way.

Also like in result 2, a bit of sample remains loose inside of the grinding chamber and can be removed by vacuuming with a soft brush.

Analogue result 1, we ground two further sizes of PET pre forms. There is one mid size black pre form with a maximum length of ~ 14,5 cm and one small blue pre form with ~ 9 cm length.

It took about 55 seconds for a grinding of the larger black pre form and about 15 s until the small blue pre form have been ground.

As usual, a small amount of pieces was lying loose on top of the sieve cassette after grinding.

Analogue result 2 & 3, a grinding of the other pre forms can be performed as well. For the black pre form, a pre cutting has been performed with a band saw to achieve pieces of < 7 cm. The small blue pre form has been fed as one intact piece.

With the black pre cut PET pre form, we achieved an output of 16 g after 2 minutes. After a total grinding time of 7 minutes, the output rose to 21,4 g.

The intact blue pre form achieved an output of 10,8 g after the first minute. Grinding has been aborted after 3 minute with an present output of 15,4 g. For both trails, we are guessing that a longer grinding time will improve the output lightly.

Electrostatic charged particles in the inside of the grinding chamber can be removed easily by vacuuming with a soft brush.

Also a grinding of higher amounts is possible.

Also red and green plastic lids can be ground directly without a previous reduction of size. Several lids have been fed directly to the machine. After the first minute of grinding, an output of ~ 13 g has been achieved. After 2 minutes, it rose to 15 g. After a total of 200 seconds, an output of 16,9 g has been found in the collecting vessel.

Still some particles are left over in the grinding chamber. These particles use to stick lightly by electrostatic charge and can be removed easily by vacuuming with a soft brush.

A grinding of higher amounts is still possible.