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Transverse orientation dies for solid‐state extrusion of polymers. Part I: Process mechanics
Author(s) -
Mascia L.,
Zhao J.
Publication year - 1991
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760310908
Subject(s) - extrusion , materials science , die (integrated circuit) , transverse plane , composite material , perpendicular , polymer , polyethylene , deformation (meteorology) , shear (geology) , orientation (vector space) , geometry , structural engineering , nanotechnology , mathematics , engineering
Solid‐state extrusion of crystalline polymers is a well‐known technique to produce monoaxial orientation in filaments and films. This is essentially achieved by extruding or drawing the polymer through a convergent die at temperatures below its melting point. Biaxial orientation in die drawing processes has been achieved by adding extensional forces in the transverse direction at the die exit, as in the case of tubular products. In the present study, billets of poly(tetrafluoropolyethylene) (PTFE) and ultrahigh‐molecular‐weight polyethylene (UHMWPE) were subjected to simultaneous deformations in the longitudinal and transverse directions, by means of dies featuring converging and diverging walls perpendicular to each other, to produce extrudates exhibiting a predominant orientation in the transverse direction. Two geometries, producing a nominal state of pure shear deformations, by maintaining constant the cross‐section area at entry and exit, were examined to determine the relationship between die geometry, yielding and frictional properties of the polymer and extrusion forces. The effects of die geometry and processing conditions are analyzed in Part 2.