ORIENTED, SEMI-CRYSTALLINE POLYMER PRODUCTS

A thick-walled, seamless, rigid non-porous conduit (Y) having a substantially uniform wall thikkness which is not less than about 0.5 percent of the outside diameter consisting essentially of an oriented crystalline thermoplastic polymer characterized by a structure comprised of radially compressed discrete, platelet-like spherulitic crystalline aggregates (A!) and having a combination of good ultimate tensile strength and low temperature tensile impact strength. The conduit is fabricated by solid state hydrostatic extrusion of a substantially non-oriented semi-crystalline thermoplastic polymer preform (X) which may contain up to about60 weight percent filler. The polymer is substantially simultaneously elongated in both circumferential and axial directions by compressive forces with the circumferential elongation being at least 100 percent. The apparatus used to produce the product is a hydrostatic extrusion press which includes an annular orifice in which the thermoplastic polymer is elongated substantially simultaneously circumferentially and axially with the circumferential elongation being at least 100 percent. Means for maintaining the rigidity of tooling and the hydrostatic extrusion fluid pressure while providing a film of the fluid on the preform for lubricity are provided in the apparatus. A sheet (F) substantially uniform in thickness and having substantially the microstructure and properties of the conduit and excellent drawability may be made from the conduit by slitting and heat deformation. Articles of manufacture may be made by solid state deformation processing of the conduit or the sheet, such as vacuum drawing.