Filled and reinforced

The corotating twin-screw extruders developed by Maris, based in Rosta (Turin, Italy), for plastics and rubber compounding are available with a D/d (larger diameter/smaller diameter) ratio of 1.55 (M/HT range), 1.65 (HS), and 1.78 (VM) for processing different materials which require different stress values.
The different geometry of the extruders modifies the shear rate in the screw channel with varying speed of rotation. Therefore the D/d rate is a key factor in process optimization, influencing the free volume of the screw, i.e., the ability of the extruder to draw in material.