Explanation using the example of PP/PE separation in PET bottle recycling: The pre-shredded material is fed into the separation tank via 2 screws below the water surfaces. Since PET is heavier than water, it sinks to the discharge organ for the sinking material and is guided out of the machine by means of a screw conveyor or a scraper chain conveyor. PP and PE, on the other hand, rise to the surface and are conveyed by various paddle drums connected in series to the floating material discharge, where they are pressed under water several times to separate any PET that may still be adhering. A separation tank is usually followed by a Frictionwasher, as this can separate large quantities of liquid from the material.