Highly crystalline cross-linked oxidation-resistant polyethylene
The present invention relates to methods for making highly crystalline cross-linked polymeric material, for example, highly crystalline cross-linked ultra-high molecular weight polyethylene (UHMWPE). The invention also provides methods of making antioxidant-doped highly crystalline cross-linked polymeric material using high pressure and high temperature crystallization processes, medical implants made thereof, and materials used therein.
1. A method of making an oxidation resistant, cross-linked polymeric blend comprising:
a) mixing a polymeric material with one or more additives to form a polymeric blend in the absence of a supercritical fluid;
b) consolidating the polymeric blend;
c) irradiating the polymeric blend by ionizing radiation, thereby forming a cross-linked polymeric blend;
d) mechanically deforming the cross-linked polymeric blend below its melting point, thereby forming a mechanically deformed cross-linked polymeric blend; and
e) annealing the mechanically deformed cross-linked polymeric blend at a temperature that is above or below the melting point, thereby forming an oxidation resistant cross-linked polymeric blend.
2. The method of claim 1 , wherein the polymeric material is a polyolefin, a polypropylene, a polyamide, a polyether ketone, or a mixture thereof.
3. The method of claim 2 , wherein polyolefin is selected from a group consisting of a low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), or a mixture thereof.
4. The method of claim 1 , wherein the polymeric material is polymeric resin powder, polymeric flakes, polymeric particles, or a mixture thereof or an additive.
5. The method of claim 1 , wherein the radiation dose is between about 25 and about 1000 kGy.
6. The method of claim 1 , wherein the radiation dose is about 65 kGy, about 75 kGy, about 150 kGy or about 200 kGy.
7. The method of claim 1 , wherein the radiation is a gamma irradiation.
8. The method of claim 1 , wherein the radiation is an electron beam irradiation.
9. The method of claim 1 further comprising:
a) doping the cross-linked polymeric blend with an antioxidant by diffusion in the absence of a supercritical fluid, thereby forming an antioxidant-doped cross-linked polymeric blend; and
b) annealing the antioxidant-doped, cross-linked polymeric blend at a temperature below the melting point of the antioxidant-doped, cross-linked polymeric blend, thereby forming a cross-linked, oxidation resistant and homogenized polymeric blend.
10. The method of claim 1 further comprising:
a) machining the oxidation resistant cross-linked polymeric blend, thereby forming an oxidation resistant cross-linked medical implant;
b) doping the oxidation resistant cross-linked medical implant with an additive by diffusion in the absence of a supercritical fluid, thereby forming an additive-doped oxidation resistant cross-linked medical implant; and
c) annealing the additive-doped polymeric blend at a temperature below the melting point of the additive-doped polymeric blend, thereby forming a medical implant comprising an additive-doped and homogenized polymeric blend.
11. The method of claim 1 , wherein the polymeric material is irradiated at a temperature between about room temperature and about the peak melting temperature of the polymeric blend.
12. The method of claim 1 , wherein the polymeric blend is irradiated at a temperature above the peak melting point of the polymeric blend.
13. The method of claim 1 , wherein at least one additive is an antioxidant.
14. A method of claim 1 , wherein at least one additive is vitamin E.
15. The method in claim 1 , wherein the additive concentration is about 0.01 wt/wt %, 0.02 wt/wt %, 0.05 wt/wt %, 0.1 wt/wt %, 0.2 wt/wt %, 0.5 wt/wt %, or 1.0 wt/wt %.
16. The method according to claim 1 , wherein the polymeric blend contains more than one antioxidant.
17. The method of claim 1 , wherein the cross-linked polymeric blend is mechanically deformed at a temperature below the melting point of the cross-linked polymeric blend.
18. The method of claim 1 , wherein the annealing is carried out in air for at least for one minute to about 5 hours or more at about 130° C.
19. The method of claim 1 , wherein the cross-linked polymeric blend is mechanically deformed uniaxially.
20. The method of claim 1 , wherein the cross-linked polymeric blend is mechanically deformed to a compression ratio of about 2.5 at about 130° C.
21. The method of claim 1 , wherein the cross-linked polymeric blend is heated to a temperature between above the room temperature and below the melt, and then mechanically deformed.
22. The method of claim 1 , wherein the cross-linked polymeric blend is heated to a temperature of about 130° C., and then mechanically deformed.
23. The method of claim 1 , wherein the polymeric blend is compression molded to a second material, and wherein the second material is a porous material.
24. The method of claim 1 , wherein the polymeric blend is compression molded to a second material, and wherein the second material is metallic.
25. A method of making an oxidation resistant cross-linked blend of polymeric material comprising:
a) blending the polymeric material with one or more additives in the absence of a supercritical fluid;
b) consolidating the blend; and
c) irradiating the blend of polymeric material with ionizing radiation at an elevated temperature that is above room temperature and below the melting point of the blend of polymeric material, thereby forming a cross-linked blend of polymeric material.
26. The method of claim 25 , wherein at least one of the additives is an antioxidant.
27. The method of claim 25 , wherein the polymeric material is a polyolefin, a polypropylene, a polyamide, a polyether ketone, or a mixture thereof.
28. The method of claim 27 , wherein polyolefin is selected from a group consisting of a low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), or a mixture thereof.
29. The method of claim 25 , wherein the polymeric material is irradiated at a temperature between about room temperature and less than about 155° C.
30. The method of claim 25 , wherein the blend of polymeric material is irradiated at a temperature of about 90° C.
31. The method of claim 25 , wherein the blend of polymeric material is irradiated at a temperature of about 100° C.
32. The method of claim 25 , wherein the blend of polymeric material is irradiated at a temperature of about 110° C.
33. The method of claim 25 , wherein the blend of polymeric material is irradiated at a temperature of about 120° C.
34. The method of claim 25 , wherein the blend of polymeric material is irradiated at a temperature of about 130° C.
35. The method of claim 25 , wherein the blend of polymeric material is irradiated at a temperature of about 135° C.
36. The method of claim 25 , wherein the irradiation dose is more than 1 kGy to 100 kGy, or more.
37. A method of making oxidation resistant cross-linked and interlocked hybrid material comprising:
a) blending the polymeric material with one or more additives, thereby forming a polymeric blend in the absence of a supercritical fluid;
b) compression molding the polymeric blend to the counterface of a 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 with ionizing radiation at an elevated temperature that is above room temperature and below the melting point of the polymeric blend, thereby forming a cross-linked and interlocked hybrid material.
38. The method of claim 37 , wherein the second material is a metallic mesh or back, a non-metallic mesh or back, a tibial tray, a patella tray, or an acetabular shell.
39. The method of claim 37 , wherein the polymeric material is a polyolefin, a polypropylene, a polyamide, a polyether ketone, or a mixture thereof.
40. The method of claim 39 , wherein polyolefin is selected from a group consisting of a low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), or a mixture thereof.
41. The method of claim 37 , wherein the interlocked hybrid material is irradiated at a temperature between about room temperature and less than about 155° C.
42. The method of claim 37 , wherein the interlocked hybrid material is irradiated at a temperature of about 90° C.
43. The method of claim 37 , wherein the interlocked hybrid material is irradiated at a temperature of about 100° C.
44. The method of claim 37 , wherein the interlocked hybrid material is irradiated at a temperature of about 110° C.
45. The method of claim 37 , wherein the interlocked hybrid material is irradiated at a temperature of about 120° C.
46. The method of claim 37 , wherein the interlocked hybrid material is irradiated at a temperature of about 130° C.
47. The method of claim 37 , wherein the interlocked hybrid material is irradiated at a temperature of about 135° C.
48. The method of claim 37 , wherein the irradiation dose is more than 1 kGy to 100 kGy, or more.
49. The method of claim 37 , wherein the second material is a porous.
50. The method of claim 37 , wherein the second material is metallic.