Modeling and Experimental Studies on Polymer Melting and Flow in Injection Molding

Injection molding, in addition to extrusion, is the most important technology in the polymer processing industry. When modeling injection molding, the global approach is necessary to take into account the solid polymer transport, polymer melting and the polymer melt flow. The model of polymer melting is fundamental for the development of such a global injection molding model. In the paper, the state-of-the-art of modeling and experimentation of the flow and melting in injection molding machines has been presented and discussed. It has been concluded that the existing mathematical models have no strong experimental basis. Therefore, experimentation of the polymer flow and melting in the injection molding machine has been performed, and the effect of processing conditions: the screw speed, the plasticating stroke and the back pressure on the process course has been investigated. Starving in the beginning sections of the screw has been observed, which was not presented in the literature so far. The novel concepts of injection molding modeling have been discussed.

Modeling of Twin Screw Extrusion of Polymeric Materials

An issue of modeling of twin-screw extrusion of polymeric materials is reviewed. The paper is written in honor of Prof. James L. White who was a pioneer in studying this issue. A global approach to process modeling is presented which includes solid polymer transport, polymer plasticating, and the flow of molten polymer. The methodology of CFD modeling of twin-screw extrusion is presented as well as the examples of this modeling which show the details of the process. Optimization and scaling of twin-screw extrusion are also covered. And finally, the future prospects of developments and research of twin screw extrusion is discussed.

Fundamentals of Global Modeling for Polymer Extrusion

A review paper is presented on modeling for polymer extrusion for both single screw and twin-screw extrusion. An issue of global modeling is discussed, which includes modeling for solid conveying, melting, melt flow, and co-operation of the screw/die system. The classical approach to global modeling of the extrusion process, which is based on separate models for each section of the screw, i.e., solid transport section, melting and pre-melting sections, and the melt flow section is presented. In this case, the global model consists of the elementary models. A novel continuous concept of global modeling based on CFD (Computational Fluids Dynamics) computations is also presented, and a concept of using the DEM (Discrete Element Method) computation coupled with CFD computations is discussed.

Melting Model for Starve Fed Single Screw Extrusion of Thermoplastics

Previous experimental studies of the polymer behavior in a starve fed single screw extrusion process have shown that contiguous solids melting mechanism which is observed for flood fed extrusion was not observed for starve fed extrusion. A new two-stage physical model of polymer melting in a starve fed single screw extrusion has been proposed with conductive mechanism for melting in the partially filled region and dispersed melting mechanism in the fully filled region. Mathematical models have been proposed for melting in both those regions. The models have been validated experimentally.

A Global Model for Closely Intermeshing Counter-rotating Twin Screw Extruders with Flood Feeding

A composite model has been developed to simulate the extrusion process for intermeshing counter-rotating twin-screw extruders. An experimentally based melting model, solids conveying model, and new improved metering model, were combined to develop this formulation. The procedure for global design of a flood feed intermeshing counter-rotating twin screw extruder is presented. Illustrative calculations are made for polyvinyl chloride and high density polyethylene in this type of machines with different screw designs. Computations are made for axial variation of the fill factor, pressure, temperature and melting profiles. Simulations were found to match with experimental results well. The model was also applied to scale-up.