Theoretical and Experimental Investigations of the Melting of Pellets in Co-Rotating Twin-Screw Extruders

Abstract

Knowledge of the plasticizing behavior in tightly intermeshing, co-rotating twin-screw extruders is of crucial importance for assessing the compounding process. Experiments were conducted on a laboratory extruder in order to establish the parameters that influence the melting process. Solidified samples of material were taken from the screw and microtome cuts produced from the plasticizing section. These were then assessed on the basis of image analysis. This visualization of the solid and molten phases which are present simultaneously together with the distribution of the two phases made it possible to quantify the reduction that occurs in the amount of solid material over the length of the screw configuration employed.A model is additionally presented for the calculation of the melting lengths and the melting profiles. This works on the basis of individual particles which are uniformly dispersed in the polymer melt. Allowance is made for the temperature increase in the solid material conveying section. A comparison of calculated and experimentally determined melting lengths revealed a satisfactory level of agreement.International Polymer Processing downloaded from www.hanser-elibrary.com by Kungliga Tekniska on August 20, 2015For personal use only.

A Composite Model for Solid Conveying, Melting, Pressure and Fill Factor Profiles in Modular Co -Rotating Twin Screw Extruders

“…If one makes the assumption that the heat convection in the melt layer in Eq. (5) may be neglected the increase in thickness of the melt layer, H m , along the screw axis x 1 may be shown to be [19] …”

Melting phenomena and mechanisms in polymer processing equipment

“…Based on observations of the solid bed in the kneading block region they reported that melting takes place by VED in a melt layer, and also suggested that a modified single-screw Tadmor melting model may be adequate to simulate melting in this region. 14 Potente et al also studied melting in twin- 15 screw extruders with a number of screw configurations and suggested a melting simulation model. Experimentally, they concluded that there are three distinct regions in the evolution of melting: The aforementioned studies suggest that fully intermeshing corotating twin-screw extruders carry out the melting elementary step very efficiently and rapidly in fully filled arrays of matching pairs of kneading disks, which induce bulk shear and compressive deformations and flows of the solid particulates, mixtures of particulates and melts, and molten polymer with suspended unmelted particulates.…”

“…Although there have been a few studies reporting on the particulate deformation in melting kneading blocks, none has addressed the issue of heat 8,12,13,15,16 generation during particulate plastic deformation, except for the melting investigations of polymer mixing studies. The presentwork addresses the 7,9,17 MELTING PHENOMENA AND MECHANISMS issue of PED in Co-TSE melting kneading blocks as well as during simple compressive deformations.…”

Manufacturing of Polymer Blends Using Polymeric and Low Molecular Weight Reactive Compatibilizers

“…More ambiguously stated similar developments are given by Potente and his coworkers [151,152] in 1996 and 1999 and by Canedo [153] in 1999. A better and more readable presentation of such a development was given by Vergnes [154,155] in 1996-1998.…”