Patent ID: 8425815

Claim:
A method of making oxidation-resistant cross-linked highly crystalline polymeric material comprising: a) doping the polymeric material with an additive by introducing the additive into the polymeric material, wherein the polymeric material is in the form of a consolidated stock, resin powder, flakes, particles, powder, or a mixture thereof; b) heating the polymeric material to a temperature of above the melting point of the polymeric material and pressuring the heated polymeric material at about 10-1000 MPa; c) holding at this pressure and temperature; d) cooling the heated polymeric material to a temperature below the melting point of the polymeric material; e) releasing the pressure, thereby forming a highly crystalline polymeric material; and f) irradiating the highly crystalline polymeric material with ionizing radiation at a temperature that is between about 90° C. and below the melting point of the polymeric material, thereby forming a highly crystalline oxidation-resistant cross-linked polymeric material.