Scale-up consideration for polymerization in a twin-screw extruder using 3-D numerical simulation

Scaling up a polymerization process in the fully filled screw elements of co-rotating twin-screw extruders was investigated with a 3-D Finite Volume Method. The simulation results show that, with identical mean residence time in the screw elements, the polymerization progression is accelerated when the screw diameter is increased. Moreover, the difference in conversion based on 1-D and 3-D models becomes more significant with increasing screw dimension, indicating that 1-D model can not predict the polymerization progression correctly in large extruders. The polymerization requires short screw length (L/D) to complete when the screw diameter is increased. This may be due to the fact that the heat loss through the barrel surface is more difficult to occur, and the non-uniformity in temperatures at the cross section of screw elements becomes more pronounced after scaling up.