ABSTRACT
The instabilities have different origins: they may be of thermal, hydrodynamic, or chemical nature. Because some of them are dependent on the scale of the equipment, experiment design is important when a reactive extrusion process has to be developed on laboratory equipment and successively scaled up to larger size machines. During reactive extrusion a polymer-monomer mixture exists those changes from pure monomer to pure polymer. Reactive extrusion processes with large viscosity changes can severely be hampered by the possible occurrence of instabilities, resulting in a sudden transition to an operating mode with low conversions or in severe oscillations during the process. Thermal considerations learn that most extrusion polymerization processes occur under local runaway conditions. Hydrodynamic considerations lead to the contention that there are two stable operating points in reactive extrusion, one with a large fully filled length and a high conversion and one with a small fully filled length and a low conversion.
