Polycaprolacton (PCL)

For a grinding of thermoplastic samples with melting points < 60 °C and glass transition temperatures about -72 °C, we recommend a cryogenic comminution.

With our Vibratory Micro Mill PULVERISETTE 0 and the optional Cryo-Box, sample and grinding equipment will be chilled directly inside liquid nitrogen (-196 °C). The less of sample will be used, the faster the grinding sound be. With desired amount of 6 grams, it could take very long until all particles will be hit and ground. Typically, about 2-5 grams of sample are used for grinding.

We used 6 grams of the PCL sample and placed it into the mortar made of zirconium oxide (ZrO2). The 50 mm Ø grinding ball was added and the mortar was placed into the Cryo-Box. After fixing the box on the vibrating disk, we flushed the mortar with liquid nitrogen (LN2). We started to grind the sample with about 3,0 mm amplitude. Evaporating LN2 was replaced with fresh liquid nitrogen. In the beginning of the trial, more of LN2 would be consumed, until sample and equipment have the same temperature as the nitrogen.

Within the first 10 minutes, we fed about one liter of liquid nitrogen. After 10 minutes, plenty of fine ground particles were covering the available surfaces because of the electrostatic charge.

We proceeded grinding inside liquid nitrogen. After 15 Minutes, a total of 1,5 Liters of LN2 was used. After finally 30 minutes of grinding, finally 1,8 liters of LN2 were needed.

A lot of very fine particles could not be brushed out because of electrostatic charge. We found up to ~ 500 µm large particles inside the brushed-out sample material. A lot of sample was ground as fine as desired (< 200 µm).

Mortar and grinding ball were cleaned with soapy water after they reached room temperature again. For an intensive cleaning, it is possible to grind a proper amount of sand and water.