Elimination of Sag in Plastic Pipe Extrusion
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D. N. Githuku
Abstract
Plastic pipe is produced by extruding molten polymer through an annular die. As the pipe leaves the die, it passes through a sizing sleeve and then a cooling tank where it solidifies slowly. For thick walled pipe, the inside of the pipe remains molten for as long as ten hours causing downward melt flow called sag. Sag can cause serious non-uniformity in pipe wall thickness. The conventional way to reduce sag is by manually adjusting the die eccentricity, until an acceptable wall thickness profile is achieved. This tedious trial and error procedure can take up to four attempts to get the right profile. In this paper a new way has been proposed to reduce sag, by rotating the pipe during cooling. A numerical simulation of sag flow while pipe is rotating, predicts that for rotational speeds between 0.1 to 10 rad/s, sag is virtually eliminated for thick walled, large diameter HDPE pipe extrusion.
© 1992, Carl Hanser Verlag, Munich
Articles in the same Issue
- Contents
- Contents
- Continuous Mixing and Compounds
- Starve-fed Flow in Co-Rotating Twin Screw Extruders
- Process for Improvement in Toughness of Unsaturated Polyester with Elastomer
- Mechanical Properties of Thermoplastic Polyurethane Blends and Copolymers of Styrene and Acrylonitrile
- Extrusion
- Mixing on Melting in Single Screw Extrusion
- Numerical Study of Slip at the Walls in the Extruder
- Elimination of Sag in Plastic Pipe Extrusion
- Fibers and Film
- Issues Concerning the Rate of Heat Transfer from a Spinline
- Skew Stretched Polycarbonate Films
- Molding
- Molecular Orientation in Injection-Molded Polypropylene Copolymers with Ethylene
- Melt-recrystallization of Talc-filled Polypropylene Injection Moldings
- Processing Characteristics of Thermoplastic Sheet Composites
- Rapid Communication of Recent Advances
- The Face-relief Strategy for Design of Profile Dies
Articles in the same Issue
- Contents
- Contents
- Continuous Mixing and Compounds
- Starve-fed Flow in Co-Rotating Twin Screw Extruders
- Process for Improvement in Toughness of Unsaturated Polyester with Elastomer
- Mechanical Properties of Thermoplastic Polyurethane Blends and Copolymers of Styrene and Acrylonitrile
- Extrusion
- Mixing on Melting in Single Screw Extrusion
- Numerical Study of Slip at the Walls in the Extruder
- Elimination of Sag in Plastic Pipe Extrusion
- Fibers and Film
- Issues Concerning the Rate of Heat Transfer from a Spinline
- Skew Stretched Polycarbonate Films
- Molding
- Molecular Orientation in Injection-Molded Polypropylene Copolymers with Ethylene
- Melt-recrystallization of Talc-filled Polypropylene Injection Moldings
- Processing Characteristics of Thermoplastic Sheet Composites
- Rapid Communication of Recent Advances
- The Face-relief Strategy for Design of Profile Dies
