ABSTRACT
An extruder is a standard piece of equipment used in rubber and plastic processing for such operations as injection and blow molding, for processing thermosetting resins, and for the hybrid process of injection blow molding. The apparatus is fed room temperature resin in the form of beads, pellets, or powders, or if rubbers are being processed, the feed material may be in the form of particulates or strips. The unit converts the feedstock into a molten polymer at sufficiently high pressure to enable the highly viscous melt to be forced through a nozzle into the mold cavity (injection-type molding) or through a die (e.g., blow molding or continuous extrusion of articles). In the initial portion of the extruder the polymer is conveyed along the extruder barrel and is compressed. The material is then heated until soft, eventually reaching a molten state. As fresh feed material enters, heat transfer takes place between the molten fluid and solid polymer. Once in the molten state, the extruder acts like a pump, transferring the molten polymer through the extruder channel building up pressure prior to flow through the discharge nozzle or die. The principal components of a single-screw extruder are illustrated in Figure 1. The machine has a motor drive, a gear train, and a screw that is keyed into the gear reducing train. The fluid layers between the screw flights and barrel wall maintain the screw balanced and centered. Principal design features of a single-screw extruder. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780203742853/0cc42c74-5683-414c-aca6-2272749eedf3/content/fig6_1.tif"/>
