Gear pumps find an increasing market within the rubber industry. Besides their classical use at the tip of the screw they are in use as complete plastication unit. Thus gear pump extruders can be used to strain temperature sensitive compounds, The investigations, presented in the article deal with this kind of machines. The test results show that it is possible to strain at a very low temperature level. The practical tests demonstrate also critical regions of the pump, By measurement of the rheological behaviour and of the vulcanisation reaction it can be shown, that there is no substancial change, This is valid for material passing through the pump and the slide bearings at the shafts of the pump.