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Polymers (Processing) (Classifications of Shaping Processes (Extruded…

- - - - Extruder Screw
        
        divided into sections to serve several functions
        
        Feed Section ( feedstock is moved from hopper and preheated)
        
        Compression section (Polymer is transformed into fluid, air mixed with pellets is extracted from melt, and material is compressed)
        
        Metering Section (Melt is homogenized and sufficient pressure developed to pump it through die opening)
        
        Extrusion of Solid Profiles
        
        regular shapes such as
        
        Rounds
        
        Squares
        
        irregular cross section such as
        
        Structural shapes
        
        Door and window moldings
        
        Automobile trim
        
        House siding
  - - - Die End of Extruder
        
        progress of polymer melt through barrel leads ultimately to the die zone
        
        before reaching die, the melt passes through a screen pack (series of wire meshes supported by stiff plate containing small axial holes)
        
        Functions of Screen pack
        
        Filter out contaminants and hard lumps
        
        build pressure in metering section
        
        straighten flow of polymer melt and remove its memory of circular motion from screw
      - Die Configurations and Extruded Products
        
        the shape of the die orifice determines the cross-sectional shape of the extrudate
        
        common die profiles and corresponding extruded shapes
        
        Solid profiles
        
        Hollow profiles, such as tubes
        
        Wire and cable coating
        
        Sheet and film
        
        Filaments