Materials for Extruder Barrel

4 Choice of Materials for Extruder Barrel and Screw Elements 

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The copolymers have been used in the manufacture of extruded pipe, moulded fittings and for other items of chemical plant. They are, however, rarely used in Europe for this purpose because of cost and the low maximum service temperature. Processing conditions are adjusted to give a high amount of crystallinity, for example by the use of moulds at about 90°C. Heated parts of injection cylinders and extruder barrels which come into contact with the molten polymer should be made of special materials which do not cause decomposition of the polymer. Iron, steel and copper must be avoided. The danger of thermal decomposition may be reduced by streamlining the interior of the cylinder or barrel to avoid dead-spots and by careful temperature control. Steam heating is frequently employed. 

There are many options for barrel material construction with most extruder barrel designed to withstand up to at least 10,000 psi (69 MPa) internal pressures higher pressure units [30,000 psi (210 MPa)] are manufactured for the injection molding processes since they operate at higher pressures. They have a minimum safety burst pressure of at least 50,000 psi (350 MPa). The need for corrosion and/or wear protection, cost, repair, or their combinations may determine the choice of materials. They can be made from a solid piece of metal. The most common material is carbon steel.6... 

Soy, and Other Legume Proteins Two quite different product types have been constructed by extrusion, high-density flaked structures for meat analogues, and lower density and crispy products for high-protein snacks. The latter uses conditions similar to that of starch-based cereal extrusion to obtain low bulk density in the expanded product the former uses a higher water content in the extruder barrel and lower exit temperatures to obtain a dense material with open pores or even flaked structmes. For these two types of processes, molecular changes in the extruder barrel are not dissimilar. Post-die structuring of the extrudates determines final product properties. 

An advantage of an extrusion device as a reactor is the combination of several chemical process operations into one piece of equipment with accompanying high space-time yields of product. An extruder reactor is ideally suited for continuous production of material after equilibrium is established in the extruder barrel for the desired chemical processes. 

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