Claims
- 1. An irradiated composition comprising a polymer, said composition having a gradient of cross-linking perpendicular to the direction of irradiation.
- 2. The composition of claim 1, wherein said polymer is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, very low density polyethylene, ultra high molecular weight polyethylene, and high molecular weight polyethylene.
- 3. The composition comprising of claim 1, wherein the polymer is an alloy of two or more polymers selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, very low density polyethylene, ultra high molecular weight polyethylene, and high molecular weight polyethylene.
- 4. The composition of claim 1, wherein the polymer is ultra high molecular weight polyethylene.
- 5. A method of making a cross-linked composition comprising an irradiated polymer, said cross-linked composition having a gradient of cross-linking perpendicular to the direction of irradiation, said method comprising:
(A) shielding a part of composition comprising a polymer; and (B) irradiating said partially shielded composition of (A) to yield the cross-linked polymer.
- 6. The method of claim 5, wherein said polymer is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, very low density polyethylene, ultra high molecular weight polyethylene, and high molecular weight polyethylene.
- 7. The method of claim 6, wherein the polymer is ultra high molecular weight polyethylene.
- 8. The method of claim 5, wherein irradiation step comprises one or more, in any order, of the procedures selected from the group consisting of procedures (a)-g):
(a) (i) heating the polymer to at or above the melting temperature of the polymer, and
(ii) irradiating the polymer in the molten state; (b) (i) providing the polymer at or below room temperature, and
(ii) irradiating the polymer; (c) (i) providing the polymer at or below room temperature, and
(ii) irradiating the polymer with a high enough total dose and/or at a fast enough dose rate to generate enough heat in the polymer to result in at least a partial melting of the crystals of the polymer; (d) (i) providing the polymer at or below room temperature,
(ii) irradiating the polymer, and (iii) heating the irradiated polymer to at or above the melting temperature of the polymer; (e) (i) heating the polymer to a temperature above room temperature and below the melting temperature, and
(ii) irradiating the heated polymer; (f) (i) heating the polymer to a temperature above room temperature and below the melting temperature,
(ii) irradiating the heated polymer, and (iii) heating the irradiated polymer to at or above the melting temperature of the polymer; and (g) (i) heating the polymer to a temperature above room temperature and below the melting temperature, and
(ii) irradiating the heated polymer with a high enough total dose and/or at a fast enough dose rate to generate enough heat in the polymer to result in at least a partial melting of the crystals of the polymer.
- 9. The method of claim 5, wherein said shield is made from a material selected from the group consisting of ceramics, metals, glasses and polymers.
- 10. A medical prosthesis comprising an irradiated polymer, said prosthesis having a gradient of cross-linking perpendicular to the direction of irradiation.
- 11. The medical prosthesis of claim 10, wherein said polymer is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, very low density polyethylene, ultra high molecular weight polyethylene, and high molecular weight polyethylene.
- 12. The medical prosthesis of claim 10, wherein the polymer is an alloy of two or more polymers selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, very low density polyethylene, ultra high molecular weight polyethylene, and high molecular weight polyethylene.
- 13. The medical prosthesis of claim 10, wherein the polymer is ultra high molecular weight polyethylene.
- 14. A method of making a medical prosthesis comprising an irradiated polymer, said medical prosthesis having a gradient of cross-linking perpendicular to the direction of irradiation, said method comprising:
(A) shielding a part of a composition comprising said polymer; and (B) irradiating said partially shielded composition.
- 15. The method of claim 14, wherein said polymer is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, very low density polyethylene, ultra high molecular weight polyethylene, and high molecular weight polyethylene.
- 16. The method of claim 14, wherein the polymer is ultra high molecular weight polyethylene.
- 17. The method of claim 14, wherein irradiation step comprises one or more, in any order, of the procedures selected from the group consisting of procedures (a)-(g):
(a) (i) heating the polymer to at or above the melting temperature of the polymer, and
(ii) irradiating the polymer in the molten state; (b) (i) providing the polymer at or below room temperature, and
(ii) irradiating the polymer; (c) (i) providing the polymer at or below room temperature, and
(ii) irradiating the polymer with a high enough total dose and/or at a fast enough dose rate to generate enough heat in the polymer to result in at least a partial melting of the crystals of the polymer; (d) (i) providing the polymer at or below room temperature,
(ii) irradiating the polymer, and (iii) heating the irradiated polymer to at or above the melting temperature of the polymer; (e) (i) heating the polymer to a temperature above room temperature and below the melting temperature, and
(ii) irradiating the heated polymer; (f) (i) heating the polymer to a temperature above room temperature and below the melting temperature,
(ii) irradiating the heated polymer, and (iii) heating the irradiated polymer to at or above the melting temperature of the polymer; and (g) (i) heating the polymer to a temperature above room temperature and below the melting temperature, and
(ii) irradiating the heated polymer with a high enough total dose and/or at a fast enough dose rate to generate enough heat in the polymer to result in at least a partial melting of the crystals of the polymer.
- 18. The method of claim 14, wherein said shield is made from a material selected from the group consisting of ceramics, metals, glasses and polymers.
RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional Application Serial No. 60/254,560, filed Dec. 12, 2000, which is incorporated by reference.
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/US01/47507 |
12/11/2001 |
WO |
|