In the field of plastics technology, the process of extrusion is widespread and important. It is employed in the compounding and pelletising of plastics materials, in their conversion into products (such as profiles, pipe, hose, sheet, film or bottles) and in the coating of wires, cables, paper, board or foil. A major reason for its use is the screw extruder's ability to melt efficiently and pump continuously large amounts of plastics materials. The understanding of the melting/pumping operation of the extruder and the development of larger and faster-running machines so as to give higher outputs have been given great attention and the results have been widely published. However, the whole manufacturing technology for extruded products has also developed, particularly in recent years. This has occurred not only by the use of modern screw extruders, but also by the incorporation of improved process control systems, the better design of dies and extrudate handling machinery and by the utilisation of improved plastics materials and additives. It is the purpose of this book to present selected topics which contribute to, or exemplify, these developments in extrusion-based processes.