Solid state deformation processing of crosslinked high molecular weight polymeric materials

A method of processing a crosslinked polymeric material, the material in a bulk form characterized by an axial direction, and further characterized by a cross section having an area A in a transverse section perpendicular to the axial direction, the method comprising

• heating the polymeric material to a compression deformable temperature;
• deforming the heated material by extruding it through a die that changes the dimensions of the cross-section, but that leaves the cross-sectional area A essentially unchanged;
• and
• cooling the extruded material.

A method of making a medical implant bearing component, comprising:

• crosslinking a UHMWPE bulk material to produce a free radical concentration greater than 0.06×1015 spins per gram;
• heating the crosslinked UHMWPE to a compression deformable temperature;
• extruding the heated UHMWPE, in the form of an elongate bulk material comprising a main axis defining an axial direction, and further characterized by a cross-section perpendicular to the axial direction, the extruding being though a die that has a shape different from that of the cross-section, but having an area essentially the same as the area of the cross-section;
• and
• further processing the extruded UHMWPE to make the bearing component.