Highly crystalline polyethylene
The present invention relates to methods for making highly crystalline polymeric material, for example, highly crystalline cross-linked and not cross-linked ultra-high molecular weight polyethylene (UHMWPE). The invention also provides methods of making additive-doped highly crystalline polymeric material using high pressure and high temperature crystallization processes, medical implants made thereof, and materials used therein.
1. A method of making a cross-linked and interlocked hybrid material for a medical device or implant, wherein the method comprises:
a) mixing a polymeric material with an antioxidant to form a polymeric blend;
b) compression molding of the polymeric blend to the counterface of second material, thereby forming an interlocked hybrid material having an interface between the polymeric blend and the second material; and
c) irradiating the interlocked hybrid material by electron beam radiation at an elevated temperature that is between about 90° C. and below the melting point of the polymeric blend, thereby forming cross-links in the polymeric blend and yielding a cross-linked and interlocked hybrid material for a medical device or implant, wherein: (i) the cross-linking strengthens the polymeric blend to minimize separation at the interface, (ii) the antioxidant provides resistance to post-irradiation oxidation, and (iii) the irradiation sterilizes the interface.
2. The method according to claim 1 , wherein the second material is porous so as to permit bony in-growth into the medical device or implant.
3. The method according to claim 2 , wherein the second material is metallic.
4. The method according to claim 2 , wherein the second material is non-metallic.
5. The method according to claim 1 , wherein the polymeric material is ultrahigh molecular weight polyethylene.
6. The method according to claim 1 , wherein the anti-oxidant is an α-tocopherol.
7. A method of making a medical device or implant comprising a cross-linked and interlocked hybrid material, wherein the method comprises:
a) mixing a polymeric material with an antioxidant to form a polymeric blend;
b) compression molding of the polymeric blend to the counterface of second material, thereby forming an interlocked hybrid material having an interface between the polymeric blend and the second material;
c) irradiating the interlocked hybrid material by electron beam radiation at an elevated temperature that is between about 90° C. and below the melting point of the polymeric blend, thereby forming cross-links in the polymeric blend and yielding a cross-linked and interlocked hybrid material for a medical device or implant, wherein: (i) the cross-linking strengthens the polymeric blend to minimize separation at the interface, (ii) the antioxidant provides resistance to post-irradiation oxidation, and (iii) the irradiation sterilizes the interface; and
d) machining the cross-linked and interlocked hybrid material to form the medical device or implant.
8. The method according to claim 7 , further comprising the step of e) sterilizing the medical device or implant.
9. The method according to claim 8 , wherein the sterilizing is by gas sterilization.
10. The method according to claim 8 , wherein the sterilizing is by ionizing radiation, wherein the antioxidant provides resistance to post-sterilization oxidation.
11. The method according to claim 7 , wherein the second material is porous so as to permit bony in-growth into the medical device or implant.
12. The method according to claim 11 , wherein the second material is metallic.
13. The method according to claim 11 , wherein the second material is non-metallic.
14. The method according to claim 7 , wherein the polymeric material is ultrahigh molecular weight polyethylene.
15. The method according to claim 7 , wherein the antioxidant is an α-tocopherol.
16. A method of making a cross-linked polymeric material for a medical device or implant, wherein the method comprises:
a) mixing a polymeric material with an antioxidant to form a polymeric blend; and
b) irradiating the polymeric blend by electron beam radiation at an elevated temperature that is between about 90° C. and below the melting point of the polymeric blend, thereby forming cross-links in the polymeric blend and yielding a cross-linked polymeric blended material for a medical device or implant, wherein: (i) the cross-linking increases wear resistance, and (ii) the antioxidant provides resistance to post-irradiation oxidation.
17. The method according to claim 16 , wherein the polymeric material is ultrahigh molecular weight polyethylene.
18. The method according to claim 16 , wherein the antioxidant is an α-tocopherol.
19. A method of making a medical device or implant comprising a cross-linked polymeric material, wherein the method comprises:
a) mixing a polymeric material with an antioxidant to form a polymeric blend;
b) consolidating the polymeric blend;
c) irradiating the consolidated polymeric blend by electron beam radiation at an elevated temperature that is between about 90° C. and below the melting point of the polymeric blend, thereby forming cross-links in the consolidated polymeric blend and yielding a cross-linked consolidated polymeric blended material for a medical device or implant, wherein: (i) the cross-linking increase wear resistance, and (ii) the antioxidant provides resistance to post-irradiation oxidation; and
d) machining the cross-linked consolidated polymeric material to form the medical device or implant.
20. The method according to claim 19 , further comprising the step of e) sterilizing the medical device or implant.
21. The method according to claim 20 , wherein the sterilizing is by gas sterilization.
22. The method according to claim 20 , wherein the sterilizing is by ionizing radiation, wherein the antioxidant provides resistance to post-sterilization oxidation.
23. The method according to claim 19 , wherein the polymeric material is ultrahigh molecular weight polyethylene.
24. The method according to claim 19 , wherein the antioxidant is an α-tocopherol.
25. The method according to claim 16 , wherein the polymeric blend is consolidated prior to the irradiation step.