3. Experimental results

The measurement techniques described in the previous section can be applied to any extrusion process. However, the experimental results presented here depend directly on the type of extruder used. One major difference concerns their mode of operation: while single-screw extruders are generally completely filled, with a flow rate imposed by the speed of rotation, this is not the case with twin-screw extruders or co-mixers, for which the flow rate is fixed by a metering device and is therefore largely independent of the speed of rotation, leading to partial filling of the machine.

A large number of experimental results have been published in the literature. However, some of these results must be treated with caution, as their quality is highly dependent on the measurement technique used, the extruder geometry and the operating conditions. The most numerous studies...