Solid phase deformation process

Details Solid phase deformation process Solid phase deformation process

1989-07-13

1992-03-17

Thurlow, Jeffery

Plastic and nonmetallic article shaping or treating: processes

Direct application of fluid pressure differential to...

Including hydrostatic or liquid pressure

264126, 264235, 264236, 264323, 26433117, 264333, B29B 1112

Patent

active

050966545

ABSTRACT:
A process for the solid phase deformation of orientable, semi-crystalline, thermoplastic, polymeric material, in particular polyethylene, is provided in which an improvement of the mechanical properties of the polyethylene is achieved. The process for producing a product from linear polyethylene includes forming a workpiece which is to be extruded in the solid phase by consolidating a mass of solid particulate linear polyethylene under heat and pressure. The resulting workpiece is subjected to heat treatment under pressure to cause the polyethylene to crystallize in an extended chain morphology and to have a melting point of at least 139.5.degree. C. and a density of at least 0.98 g/cm.sup.3. Thereafter the workpiece of polyethylene is deformed in the solid phase to provide a polyethylene product by, for example, passage through a die, the workpiece being subjected to a deformation extrusion ratio of at least 3 and preferably 3 to 25. The process in accordance with the invention allows more efficient processing of linear polyethylene having a weight average molecular weight of greater than 350,000 than had hitherto been possible.

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