Experimental Investigation of Polymer Pellets Melting Mechanisms in Vane Extruders

Vane extruders are novel polymer-processing equipments, which are composed of a number of vane plasticizing and conveying units (VPCUs). With the vane extruder and the visualization VPCU device, the melting phenomenon of high-density polyethylene (HDPE) pellets under different operation conditions was investigated. It was shown that the positive displacement conveying mechanism and mandatory deformation of particles made the melting evolution in vane extruders totally different from screw extruders. The length of solid conveying and melting zone in vane extruders was much shorter, and the island-sea melting model was formed instead of Tadmor's melting model. Plastic energy dissipation, friction energy dissipation, and viscous energy dissipation were very important sources of heat energy for polymer particles melting in vane extruders. The eccentricity of VPCU, leading to the compression and deformation of particles, was a decisive factor in polymer melting in vane extrusion. Owing to the eccentricity, mechanical energy was dissipated into heat via the deformation of HDPE particles and the thermo-mechanical history was shortened remarkably. (C) 2013 Wiley Periodicals, Inc.