AN EXPERIMENTAL-STUDY ON PLASTICATING SINGLE-SCREW EXTRUSION

An experimental study was conducted with a plasticating single-screw extruder, which had the following screw dimensions: (a) the diameter (D) of 6.35 cm; (b) the total extruder length of 24 D; (c) the length of the feed section of 3 D; (d) the length of the tapered section of 4 D; and (e) the length of the metering section of 17 D. The extruder had nine pressure transducers which were mounted, almost equally spaced along the extruder axis, on the wall of the extruder barrel, so that we could measure axial pressure profiles during extrusion. Also measured in our study were the solid-bed width profiles in the screw channel by conducting tracer experiments (i.e., screw 'pushout' experiments). For the study, a high-pressure low-density polyethylene and a high-density polyethylene were used. Experimental results were analyzed using the reported Lee-Han melting model. Theoretical predictions of axial pressure profiles were found to be in good agreement with results. Of particular note are the theoretical predictions that for the particular screw configurations used, which has short feed and tapered sections, and extrusion conditions employed, there was considerable solid-bed acceleration in the tapered section of the screw.