Engineering Analysis of Devolatilization in Modular Intermeshing Co-Rotating Twin Screw Extruders
Jongmin Keum, James L. White
The University of Akron
US
Keywords: extrusion, devolatilization,
In commercial manufacturing processes for most polymers there is a need to separate unreacted monomer, solvents and other low molecular weight components from these polymers. The devolatilization process has been carried out in various extruders such as single screw extruders, intermeshing co-rotating twin screw extruders and counter-rotating twin screw extruders. In early research, researchers considered the mechanism of devolatilization as a simple surface renewal and diffusion process in the devolatilization extrusion. However diffusion coefficients from experimental data were often orders of magnitude larger than what would be expected from such a system. Subsequently, other researchers have investigated these processes and found foaming which involves rapid bubble growth, coalescence and rupture.
In order to develop this area and solve these problems, we made a critical experimental study with various operation conditions and screw configurations. This includes studying additives (Nonane, Hexanol, p-Xylene) of varying polarity to molten thermoplastics including polyethylene, polystyrene and polyamide 12. We also devise a model for devolatilization which includes a model of area of the devolatilization, the regions of flow and the mass transfer coefficients in an intermeshing co-rotating twin screw extruder. The results of the model were compared with experiment