A Global Model for Starve-Fed Nonconventional Single-Screw Extrusion of Thermoplastics

Abstract

ABSTRACT:A global computer model has been developed for starve-fed nonconventional single-screw extrusion. The model has been built by combining a new melt conveying model with recently developed melting models. Mixing screw equipped with dispersive mixing element of Maddock has been considered as an example for modeling. Extensive fully three-dimensional non-Newtonian Finite Element Method (FEM) computations have been performed to model the melt flow in mixing elements. Screw pumping characteristics have been computed and modeled for these elements at various power law indices. These characteristics have been implemented into the global model of the process. Computations were made for low-density polyethylene at various operating conditions. Fill factor, pressure, temperature, and melting profiles were simulated and validated experimentally. It has been confirmed by computation and experimentation that melting in starve-fed single-screw extruders is totally different compared with melting in flood-fed extruders. It is faster, and the screw length needed for melting extends with an increase of the flow rate. The screw is fully filled for some distance from the die only and starved beyond it. This distance is dependent on the flow rate and screw speed. C

A computer model for starve‐fed single‐screw extrusion of polymer blends

“…Tadmor et al [4][5][6] first developed a mathematical model of fusion of polymers in single-screw extruders, and later a composite model of the process that includes polymer solid conveying, polymer fusion and polymer melt conveying. [22,23] These models were confined to extrusion of thermoplastics. Experimental studies on mixing and fusion capabilities of starve fed extruders were performed, only.…”

“…[16][17][18][19] Wilczyński et al [15,20,21] first developed a mathematical model of fusion of polymers in starve fed single-screw extruders, and subsequently a composite model of the process, first for conventional screws, and later for non-conventional screws. [22,23] These models were confined to extrusion of thermoplastics.…”

“…13) ln η _blend = a 0 + a 1 lṅγ+a 11 ln 2γ +a 12 T lṅγ+a 2 T + a22 T General simulation characteristics of the starve-fed single-screw extrusion of polymer blends (an example)…”

Experimental study of melting of polymer blends in a starve fed single screw extruder

“…Using this model the authors developed a global model for conventional starve fed single screw extrusion process . Later, the global model has been extended to non‐conventional screw configurations . It is interesting to note that Luker used starving concepts to develop spiral fluted single screw extensional mixers with exceptional ability to compounding.…”

Optimization for Starve Fed/Flood Fed Single Screw Extrusion of Polymeric Materials

“…Up to date, there is a lack of optimization studies on single screw extrusion with metered feeding (starve fed extrusion) and counter-rotating twin screw extrusion, although the mathematical models of these global models for starve fed single screw extrusion [30][31][32] and global models for counter-rotating extrusion [33][34][35][36][37] have been recently developed.…”