Krzysztof Wilczyński

A Computer Model for Single-Screw Plasticating Extrusion

Abstract A fully predictive computer model has been developed for a single-screw plasticating extrusion (with conventional screws). The model takes into account five zones of the extruder (hopper, solids conveying, delay zone, melting zone, melt conveying) and the die, and describes an operation of the extruder-die system, making it possible to predict a mass flow rate of the polymer, pressure and temperature profiles along the screw channel and in the die, solid bed profile, and power consumption. Moreover, mixing degree, temperature fluctuation and viscoelastic properties of the polymer are estimated. The simulation parameters are the material and rheological properties of the polymer, the screw, hopper and die geometry, and the operating conditions (screw speed and barrel temperature profile). Such a comprehensive approach to the modeling of extrusion creates the possibility of optimizing the process, for example, from the point of view of the quality of extrusion. The model has been verified experimen...

Chemomechanical Systems: Study of Contraction and Mechanical Work of Poly(Acrylonitrile) Gel Fibers

Abstract A fully predictive computer model SSEM (Single-Screw Extrusion Model) has been developed for the single-screw plasticating extruders (with conventional and mixing screws). The model takes into account five zones of the extruder (hopper, solids conveying, delay zone, melting zone, and melt conveying) and the die, and it describes an operation of the extruder-die system, making it possible to predict the mass flow rate of the polymer, the pressure and temperature profiles along the screw channel and in the die, the solid-bed profile, and power consumption. Moreover, the mixing degree, the temperature fluctuation, and the viscoelastic characteristic of the polymer are evaluated. The model also makes it possible to predict the morphological changes of the polymer blend during the compounding process in the single-screw extruder. The simulation parameters are the material and rheological properties of the polymer, the screw, hopper, and die geometry, and the operating conditions (screw speed and barre...

Multipurpose Computer Model for Screw Processing of Plastics

The state-of-the-art has been presented for computer modeling of screw processing of plastics. A new generalized approach for modeling of this class of plastics processing techniques has been proposed. Single screw extrusion, twin screw extrusion, as well as injection molding are discussed. Various types of feeding machines, including flood feeding and starve feeding, are considered. An idea for a multipurpose computer system for comprehensive modeling of screw processing has been presented. A problem of optimization of screw processing has also been discussed.

Evaluating screw performance in a single-screw extrusion process

Abstract The ability of a screw to manufacture products of good quality with high productivity and low cost is called its performance. At the design stage of an extrusion process, evaluation of screw performance is very important and can be realized on the basis of experimental and theoretical investigations.

Computer Modeling for Single-Screw Extrusion of Wood–Plastic Composites

Experimental and theoretical studies have been performed on the single-screw extrusion of wood–plastics composites. Experimental research has been carried out on the flow and melting of polypropylene (PP)-based composites with different wood flour (WF) content in the single-screw extruder. Based on these experimental observations, elementary models of the process phenomena have been proposed and a global model of the process has been developed. This global computer model includes the models of solid conveying, melting dependent on the wood flour content, melt flow in the screw, and melt flow in the die. 3-D non-Newtonian finite element method (FEM) screw pumping characteristics have been applied to model the melt flow in the metering section of the screw. The model predicts the extrusion output, pressure and temperature profiles, melting profile, and power consumption. The model has been validated experimentally. An effect of material slip on the extruder operation has been discussed including both slipping in the screw/barrel surfaces and in the extruding die.

Studies for Polyblend Behaviour in Screw Extrusion and Injection Molding Processes

Polyblend behaviour in the screw extrusion and injection molding processes was studied. Melting mechanisms for LDPE/PS polyblend were investigated, as well as a morphology development was observed. The break‐up mechanism and fibrillation, as well as coalescence were clearly visible. A computer model developed for screw extrusion was applied to study material behaviour. The model is based on the flow field description in the machine.