Experimental and theoretical study of twin-screw extrusion of polypropylene

The flow of a polypropylene in a self-wiping corotating twin-screw extruder was characterized by measuring the pressure, temperature, and residence ti me along the screw profile. The influence od the operating conditions (feed rate, screw speed, barrel temperature) and screw profile was studied. Flow modeling was performed using the Ludovic(R) software and measured and calc ulated pressure, temperature, residence time,and energy consumption were co mpared. The values of the temperature close to the melting zone were overes timated by the model, which considers instantaneous melting upon the first restrictive screw element. If the program assumes that melting occurs at th e screw location identified experimentally, a correct description of the te mperatures along the screw profile is produced. The influence of the proces sing conditions (feed rate, screw speed, barrel temperature, screw profile) is well described by the model. These results put in evidence the importan ce of including an adequate melting model in the modeling of the twin-screw extrusion process. (C) 2000 John Wiley & Sons, Inc.