阅读说明：本技术 超高分子量聚乙烯表面梯度交联方法及其应用 (Ultrahigh molecular weight polyethylene surface gradient crosslinking method and application thereof ) 是由 张宗涛 于 2020-11-06 设计创作，主要内容包括：本发明涉及一种超高分子量聚乙烯表面梯度交联方法及其应用。该超高分子量聚乙烯表面梯度交联方法包括超高分子量聚乙烯表面光引发剂扩散步骤和紫外光辐照交联步骤。该方法将光引发剂深度扩散进入超高分子量聚乙烯表面,紫外辐照后体材从表面向内部呈现梯度交联,由超级交联逐步转为低度交联或非交联,使得体材整体具有良好的韧性且表面具有良好的耐磨性。(The invention relates to a surface gradient crosslinking method of ultrahigh molecular weight polyethylene and application thereof. The gradient crosslinking method of the surface of the ultra-high molecular weight polyethylene comprises a step of diffusing an ultra-high molecular weight polyethylene surface photoinitiator and a step of ultraviolet irradiation crosslinking. According to the method, a photoinitiator is deeply diffused into the surface of the ultra-high molecular weight polyethylene, the body presents gradient crosslinking from the surface to the inside after ultraviolet irradiation, and the super crosslinking is gradually changed into low-degree crosslinking or non-crosslinking, so that the whole body has good toughness and the surface has good wear resistance.)

1. A method of crosslinking a surface layer of an ultra-high molecular weight polyethylene material, the method comprising the steps of:

(1) under the temperature higher than the melting point of the photoinitiator and the temperature lower than the melting point of the ultra-high molecular weight polyethylene, the photoinitiator is diffused from the surface of the base material to the inside and enters the surface layer of the ultra-high molecular weight polyethylene;

(2) irradiating the photoinitiator-diffused surface layer with ultraviolet light to crosslink the surface layer, thereby forming surface layer gradient crosslinked ultra-high molecular weight polyethylene.

2. The method of crosslinking of claim 1, wherein the ultrahigh molecular weight polyethylene base material is a non-ionically crosslinked ultrahigh molecular weight polyethylene.

3. The crosslinking method of claim 1, wherein the surface layer of the ultra-high molecular weight polyethylene substrate is a support surface layer of a medical implant.

4. The crosslinking method of claim 1, wherein the ultrahigh molecular weight polyethylene substrate comprises an antioxidant.

5. The crosslinking method of claim 4, wherein the antioxidant is selected from one or more of the group consisting of: vitamin E, tetrakis [ methylene (3, 5-di-tert-butylhydroxyhydrocinnamate) ] methane, thiodimethylenebis [3- [3, 5-di-tert-butyl-4-hydroxyphenyl ] propionate, octadecyl 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate, N' -hexane-1, 6-diylbis (3- (3, 5-di-tert-butyl-4-hydroxyphenylpropionamide)), phenylpropionic acid 3, 5-bis (1, 1-dimethyl-ethyl) -4-hydroxy-C7-C9 branched alkyl ester, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -2,4, 6-trimethylbenzene, 2, 4-bis (dodecylthiomethyl) -6-methylphenol, Triethylene glycol bis (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, 2 '-methylenebis (4-methyl-6-tert-butylphenol) monoacrylate, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione, the reaction product of benzylamine and 2,4, 4-trimethylpentene, 2, 4-bis (octylthio) -6- (4-hydroxy-3, 5-di-tert-butylanilino) -1,3, 5-triazine 5, 7-di-tert-butyl-3- (3, 4-dimethylphenyl) -3H-benzofuran-2-one, 2, 3' -methylenebis (4-methyl-6-tert-butylphenol), Tris (2, 4-di-tert-butylphenyl) phosphite, or pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ].

6. The crosslinking method of claim 4, wherein the antioxidant is vitamin E.

7. The crosslinking method of claim 4, wherein the antioxidant is present in an amount of 0.05 to 0.20 wt.%.

8. The crosslinking method of claim 4, wherein the antioxidant is present in an amount of 0.05 to 0.1 wt.%.

9. The crosslinking method of claim 1, wherein the photoinitiator is selected from one or more of the group consisting of: benzophenone, 4-chlorobenzophenone, 2-chlorobenzophenone, 4' -dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-chloroanthraquinone, p-chloroanthraquinone, benzyl sulfide, benzyl sulfoxide, phenyl sulfoxide, 4-acetylbiphenyl, anthrone, hexachlorobenzene.

10. The crosslinking method of claim 1, wherein the photoinitiator is benzophenone.

11. The crosslinking method of claim 1, wherein in step (1), the temperature of the diffusion is controlled to be between 50 ℃ and 134 ℃.

12. The crosslinking method according to claim 1, wherein in the step (1), the temperature of the diffusion is controlled to be 81 to 130 ℃.

13. The crosslinking method according to claim 1, wherein in step (2), the intensity of the ultraviolet radiation is 90mW/cm or more²。

14. The crosslinking method according to claim 1, wherein in step (2), the intensity of the ultraviolet radiation is 100mW/cm or more²。

15. The crosslinking method of claim 1, wherein the surface layer gradient crosslinks to a total depth of up to 3.5 mm.

16. The method of claim 1, wherein in the gradient crosslinking, the depth of the hypercrosslinking is up to 1.5 mm.

17. The crosslinking method of claim 1, wherein the photoinitiator has a diffusion of greater than 0.9mg/cm²。

18. Medical implant of ultra high molecular weight polyethylene, characterized in that the medical implant is partly or completely made of ultra high molecular weight polyethylene, the medical implant having at least one supporting surface layer made of ultra high molecular weight polyethylene, which is gradient cross-linked, wherein the supporting surface layer is super cross-linked, highly cross-linked and lowly cross-linked in this order from the outside to the inside of the surface.

19. The ultra high molecular weight polyethylene medical implant of claim 18, wherein the gradient crosslinks a total depth of up to 3.5 millimeters.

20. The ultra high molecular weight polyethylene medical implant of claim 18, wherein in the gradient cross-linking, the depth of the hypercrosslinking is up to 1.5 mm.

21. The ultra-high molecular weight polyethylene medical implant of claim 18, wherein the ultra-high molecular weight polyethylene contains an antioxidant.

22. The ultra high molecular weight polyethylene medical implant of claim 21, wherein the antioxidant is selected from one or more of the group consisting of: vitamin E, tetrakis [ methylene (3, 5-di-tert-butylhydroxyhydrocinnamate) ] methane, thiodimethylenebis [3- [3, 5-di-tert-butyl-4-hydroxyphenyl ] propionate, octadecyl 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate, N' -hexane-1, 6-diylbis (3- (3, 5-di-tert-butyl-4-hydroxyphenylpropionamide)), phenylpropionic acid 3, 5-bis (1, 1-dimethyl-ethyl) -4-hydroxy-C7-C9 branched alkyl ester, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -2,4, 6-trimethylbenzene, 2, 4-bis (dodecylthiomethyl) -6-methylphenol, Triethylene glycol bis (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, 2 '-methylenebis (4-methyl-6-tert-butylphenol) monoacrylate, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione, the reaction product of benzylamine and 2,4, 4-trimethylpentene, 2, 4-bis (octylthio) -6- (4-hydroxy-3, 5-di-tert-butylanilino) -1,3, 5-triazine 5, 7-di-tert-butyl-3- (3, 4-dimethylphenyl) -3H-benzofuran-2-one, 2, 3' -methylenebis (4-methyl-6-tert-butylphenol), Tris (2, 4-di-tert-butylphenyl) phosphite, or pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ].

23. The ultra high molecular weight polyethylene medical implant of claim 21, wherein the antioxidant is vitamin E.

24. The ultra high molecular weight polyethylene medical implant of claim 21, wherein the antioxidant is present in an amount of 0.05 to 0.20 weight percent.

25. The ultra high molecular weight polyethylene medical implant of claim 21, wherein the antioxidant is present in an amount of 0.05 to 0.1 wt%.

26. The ultra high molecular weight polyethylene medical implant of claim 18, wherein the average force to break of the 0.25 millimeter thick film of the outermost surface layer of the bearing surface layer is greater than 50.0 newtons.

27. The ultra-high molecular weight polyethylene medical implant according to claim 18, wherein the average equivalent degree of crosslinking of the outermost surface layer of the bearing surface layers is above 100 kGy.

28. The ultra high molecular weight polyethylene medical implant of claim 18, wherein the bearing surface layer of the medical implant is cross-linked by the cross-linking process of claim 1.

29. A medical joint comprising a first joint support and a second joint support; the ultra high molecular weight polyethylene medical implant of claim 18 between the first joint support and the second joint support.

30. The medical joint of claim 29, wherein the medical joint is an artificial knee joint, an artificial hip joint, an artificial condyle joint, an artificial elbow joint, an artificial wrist joint, an artificial finger joint, or an artificial shoulder joint.

Technical Field

The invention belongs to the field of high polymer materials, and particularly relates to an ultrahigh molecular weight polyethylene surface gradient crosslinking method and application thereof.

Background

Currently, the crosslinking process for Ultra High Molecular Weight Polyethylene (UHMWPE) that is commercially used in prosthetic joints is bulk crosslinking. The bulk crosslinking is crosslinking of the whole material through radiation of ionizing rays with specific energy, does not relate to chemical reaction, and belongs to a physical crosslinking method. Ionizing radiation includes gamma rays, beta rays, x rays, electron beam radiation, and the like. The crosslinking method has the advantages that the side chains of the polyethylene molecules are crosslinked, so that the wear resistance of the material is improved; the disadvantage is that this process also cuts the main chain leading to a decrease in toughness. Both wear resistance and toughness are not compatible (document 1). When the degree of crosslinking exceeds 100kGy, the use of the monolithic material is limited by the fact that it is too brittle (at present, the highest degree of crosslinking in the orthopaedic commercial sector is about 100 kGy).

There is also a surface-crosslinked ultrahigh molecular weight polyethylene (documents 2 to 6, 16). The advantage is that the crosslinking is only carried out on the surface layer, the inside of the body is kept with low crosslinking or not crosslinked, and the wear resistance and the toughness can be obtained simultaneously. The surface crosslinking may be physical crosslinking or chemical crosslinking. Since the first surface cross-linking patent publication in 2000, several patents have been published. For example, document 2 employs peroxide chemical crosslinking or low energy electron beam physical crosslinking of pure ultra-high molecular weight polyethylene. With both methods of document 2, the surface of the ultrahigh molecular weight polyethylene is oxidized, so that it is necessary to remove the surface oxide layer. However, the result of removing the surface oxide layer was that the abrasion resistance was not as good as that of 100kGy crosslinked polyethylene as the bulk material. Document 3 introduces a large amount of antioxidant (1-2 wt%) in bulk and reduces the amount of antioxidant on the surface, followed by irradiation with a large dose of electron beam (300kGy) to achieve surface and bulk crosslinking. The method overcomes the defect of polyethylene surface oxidation, but a large amount of antioxidant also softens the polyethylene base material, the material becomes brittle through bulk crosslinking, and the cost of crosslinking through large-dose electron beam radiation is too high.

Documents (4-6) adopt gamma rays to integrally pre-crosslink ultra-high molecular weight polyethylene, then coat a photoinitiator, and the photoinitiator makes the polyethylene generate a crosslinking reaction under the catalysis of ultraviolet light, belonging to chemical crosslinking. The crosslinking process comprises soaking the pre-crosslinked ultra-high molecular weight polyethylene coated with photoinitiator in 65 deg.C warm water at low dose (50 mW/cm)²) Ultraviolet light, with an average wavelength of 350 nm, achieves surface crosslinking. The energy of the long-wavelength ultraviolet light (about 350 nm) is very low, no ionization effect is generated, and the ultraviolet light cannot crosslink polyethylene per se. There are two examples of this approach. One example is toThe material is subjected to surface crosslinking, and the material shows good surface wear resistance. Here, theIs a highly crosslinked ultra-high molecular weight polyethylene, which is a trademark of the Schott company, crosslinked by 30kGy gamma ray and annealed 3 times. However, the disadvantage is that the bulk is highly crosslinked and the bulk becomes brittle. Another example is the cross-linking of ultra-high molecular weight polyethylene (trade mark) with gamma radiation of about 30kGy) The surface of the material is crosslinked, and the material has good toughness. The cobalt chromium alloy and the PEEK with the wear resistance of the surface and the smooth surface are opposite to each other, and the cobalt chromium alloy and the PEEK also show better wear resistance. The disadvantage is that the depth of crosslinking is not clear. The depth depends on the soaking time of the ultra-high molecular weight polyethylene in the photoinitiator solution. Although the claims describe crosslinking depths of 0.2 to 1.0 mm, no experimental data are provided. Documents (4-6) mention a method of applying a photoinitiator to the surface of ultra-high molecular weight polyethylene by vapor deposition, but also do not support the examples. After a period of clinical use, when the cobalt-chromium alloy ball head becomes rough, the worry of grinding through a polyethylene surface cross-linked layer exists.

In summary, the surface crosslinking method is theoretically superior to the bulk crosslinking method, and can meet the dual requirements of wear resistance and toughness, but the disclosed surface crosslinked ultra-high molecular weight polyethylene has the defects which are not overcome yet, so that the surface crosslinked ultra-high molecular weight polyethylene is not commercialized yet. The current prosthetic joint with the lowest clinical wear rate is ceramic to ceramic. Zirconia toughened alumina ceramic (trade name: alumina ceramic)Ceramic) is ground on a hip joint testing machine, and the volume wear rate is 0.118 +/-0.036 mm³/10⁶Cyclically, the rate of wear cannot be determined clinically (documents 10 to 11). Standard high-crosslinking ultrahigh molecular weight polyethylene ball on marketThe clinical volume wear rate of the alumina ceramic counter-grinding toughened by the zirconia is 29.61mm³/10⁶And (4) circulating, wherein the linear wear rate is 0.1 mm/year. The grinding produced at 0.1 mm/year just reaches the limit of osteolysis (document 12). However, the ceramic-to-ceramic material has the disadvantages of harsh noise, brittle material, and high cost. The highly crosslinked ultrahigh molecular weight polyethylene has a disadvantage of brittleness and a higher wear rate of 0.15 mm/year with cobalt-chromium alloy (document 13).

Therefore, there is a clinical need for ultra-high molecular weight polyethylene that is ultra-wear resistant; it should have the same wear resistance as ceramics but no noise of ceramics, and it should have the same toughness as conventional ultra high molecular weight polyethylene.

Disclosure of Invention

The invention aims to meet the clinical requirements, overcome the defects of the existing surface cross-linked ultrahigh molecular weight polyethylene and provide the ultrahigh molecular weight polyethylene with more wear-resistant surface and more tough body.

In order to achieve the purpose, the invention provides the following technical scheme:

the invention provides a crosslinking method of a surface layer of an ultrahigh molecular weight polyethylene material, which comprises the following steps:

(1) diffusing the photoinitiator into the surface of the ultrahigh molecular weight polyethylene base material from the surface of the base material to the inside at a temperature higher than the melting point of the photoinitiator and lower than the melting point of the ultrahigh molecular weight polyethylene;

(2) irradiating the photoinitiator-diffused surface layer with ultraviolet light to crosslink the surface, thereby forming surface layer gradient crosslinked ultra-high molecular weight polyethylene.

In another preferred embodiment, the ultrahigh molecular weight polyethylene base material is nonionic crosslinked ultrahigh molecular weight polyethylene.

In another preferred example, step (1) and step (2) of the crosslinking method are performed in a closed space.

In another preferred example, step (1) and step (2) of the crosslinking method are performed in a nitrogen atmosphere; preferably, the pressure of the nitrogen atmosphere is 1 atmosphere.

In another preferred embodiment, the ultra-high molecular weight polyethylene substrate surface layer is a support surface layer of a medical implant.

In another preferred example, the medical implant is partially or entirely made of an ultra-high molecular weight polyethylene material.

In another preferred embodiment, the ultrahigh molecular weight polyethylene base material is uncrosslinked ultrahigh molecular weight polyethylene.

In another preferred embodiment, the medical implant is preformed.

In another preferred example, the medical implant is an orthopedic medical implant.

In another preferred example, the ultra-high molecular weight polyethylene base material contains an antioxidant.

In another preferred embodiment, the antioxidant is selected from one or more of the following group: vitamin E, tetrakis [ methylene (3, 5-di-tert-butylhydroxyhydrocinnamate) ] methane, thiodimethylenebis [3- [3, 5-di-tert-butyl-4-hydroxyphenyl ] propionate, octadecyl 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate, N' -hexane-1, 6-diylbis (3- (3, 5-di-tert-butyl-4-hydroxyphenylpropionamide)), phenylpropionic acid 3, 5-bis (1, 1-dimethyl-ethyl) -4-hydroxy-C7-C9 branched alkyl ester, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -2,4, 6-trimethylbenzene, 2, 4-bis (dodecylthiomethyl) -6-methylphenol, Triethylene glycol bis (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, 2 '-methylenebis (4-methyl-6-tert-butylphenol) monoacrylate, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione, the reaction product of benzylamine and 2,4, 4-trimethylpentene, 2, 4-bis (octylthio) -6- (4-hydroxy-3, 5-di-tert-butylanilino) -1,3, 5-triazine 5, 7-di-tert-butyl-3- (3, 4-dimethylphenyl) -3H-benzofuran-2-one, 2, 3' -methylenebis (4-methyl-6-tert-butylphenol), Tris (2, 4-di-tert-butylphenyl) phosphite, or pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ].

In another preferred embodiment, the antioxidant is vitamin E.

In another preferred embodiment, the antioxidant is present in an amount of 0.05 to 0.20 wt.%.

In another preferred embodiment, the antioxidant is present in an amount of 0.05 to 0.1 wt.%.

In another preferred embodiment, the antioxidant is present in an amount of 0.1 wt%.

In another preferred embodiment, the photoinitiator is selected from one or more of the following group: benzophenone, 4-chlorobenzophenone, 2-chlorobenzophenone, 4' -dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-chloroanthraquinone, p-chloroanthraquinone, benzyl sulfide, benzyl sulfoxide, phenyl sulfoxide, 4-acetylbiphenyl, anthrone, hexachlorobenzene.

In another preferred embodiment, the photoinitiator is benzophenone.

In another preferred example, in the step (1), the temperature of the diffusion is controlled between 50 ℃ and 134 ℃.

In another preferred example, in the step (1), the temperature of the diffusion is controlled between 50 ℃ and 130 ℃.

In another preferred example, in the step (1), the temperature of the diffusion is controlled between 81 ℃ and 130 ℃.

In another preferred example, in the step (1), the temperature of the diffusion is controlled between 90 ℃ and 130 ℃.

In another preferred embodiment, in step (1), the diffusion time is controlled to be less than 24 hours (e.g., 0.1 to 24 hours).

In another preferred embodiment, in step (1), the diffusion time is controlled to be less than 12 hours (e.g., 0.1 to 12 hours).

In another preferred embodiment, in step (1), the diffusion time is controlled to be less than 8 hours (e.g., 0.1 to 8 hours).

In another preferred example, in the step (1), the diffusion time is 0.5 to 8 hours.

In another preferred example, in the step (1), the diffusion time is 1 to 4 hours.

In another preferred embodiment, the photoinitiator diffuses into the surface layer of the ultrahigh molecular weight polyethylene substrate to a depth of 3.5 mm.

In another preferred embodiment, the photoinitiator may diffuse into the surface layer of the ultra-high molecular weight polyethylene substrate to a depth of 1-3 mm, 1-2.5 mm, or 1-2 mm.

In another preferred example, in the step (1), after the photoinitiator is diffused into the surface layer of the ultra-high molecular weight polyethylene substrate, the method further comprises the following steps: the surface layer with the photoinitiator diffused was cooled to room temperature.

In another preferred example, in the step (2), the intensity of the ultraviolet radiation is more than or equal to 90mW/cm²

In another preferred example, in the step (2), the intensity of the ultraviolet radiation is more than or equal to 100mW/cm²。

In another preferred example, in the step (2), the intensity of the ultraviolet radiation is more than or equal to 150mW/cm²。

In another preferred example, in the step (2), the intensity of the ultraviolet radiation is more than or equal to 170mW/cm²。

In another preferred example, in the step (2), the intensity of the ultraviolet radiation is 90-250mW/cm²Or 90-200mW/cm²。

In another preferred example, in the step (2), the intensity of the ultraviolet radiation is 100-250mW/cm²Or 100-200mW/cm²。

In another preferred example, in the step (2), the intensity of the ultraviolet radiation is 150-250mW/cm²Or 150-²。

In another preferred example, in the step (2), the intensity of the ultraviolet radiation is 170-250mW/cm²Or 170-200mW/cm²。

In another preferred example, in the step (2), the irradiation time of the ultraviolet light is controlled to be 20 minutes or more (for example, 20 to 200 minutes or 20 to 100 minutes).

In another preferred example, in the step (2), the irradiation time of the ultraviolet light is controlled to be 40 minutes or more (e.g., 40 to 200 minutes or 40 to 100 minutes).

In another preferred example, in the step (2), the irradiation time of the ultraviolet light is controlled to be 60 minutes or more (for example, 60 to 200 minutes or 60 to 100 minutes).

In another preferred example, in the step (2), the ultraviolet irradiation depth is up to 3.5 mm.

In another preferred example, in the step (2), the ultraviolet irradiation has a depth of 1 to 3 mm, 1 to 2.5 mm, 1 to 2 mm, or 1 to 1.5 mm.

In another preferred example, in step (2), after the surface layer is crosslinked, the method further comprises a cleaning step: soaking the surface of the gradient cross-linked ultrahigh molecular weight polyethylene in an organic solvent; and after soaking, drying the surface to obtain the cleaned ultrahigh molecular weight polyethylene with the surface layer subjected to gradient crosslinking.

In another preferred example, in the step (2), the cleaning step further comprises a sterilization step after: sterilizing the cleaned ultra-high molecular weight polyethylene surface with gradient cross-linking of the surface layer; the sterilization is any one of gamma ray sterilization, ETO sterilization or gas plasma sterilization.

In another preferred embodiment, the total depth of the surface layer gradient cross-linking is up to 3.5 mm.

In another preferred embodiment, the total depth of the surface layer gradient cross-linking is up to 3 mm.

In another preferred embodiment, the total depth of the surface layer gradient cross-linking is up to 2.5 mm.

In another preferred embodiment, in the gradient crosslinking, the depth of the hypercrosslinking is up to 1.5 mm.

In another preferred embodiment, in the gradient crosslinking, the depth of the hypercrosslinking is up to 1 mm.

In another preferred example, the diffusion amount of the photoinitiator in the surface layer of the ultrahigh molecular weight polyethylene material is more than 0.9mg/cm²。

In another preferred example, the diffusion amount of the photoinitiator in the surface layer of the ultrahigh molecular weight polyethylene material is more than 1.11mg/cm²。

In another preferred example, the diffusion amount of the photoinitiator in the surface layer of the ultrahigh molecular weight polyethylene base material is 0.9-10 mg/cm²。

In another preferred example, the diffusion amount of the photoinitiator in the surface layer of the ultrahigh molecular weight polyethylene material is 1-8 mg/cm²。

In a second aspect of the invention, an ultra high molecular weight polyethylene medical implant is provided, the medical implant being partly or completely made of ultra high molecular weight polyethylene, the medical implant having at least one bearing surface layer made of ultra high molecular weight polyethylene, the bearing surface layer being gradient cross-linked, wherein the bearing surface layer is super cross-linked, highly cross-linked and lowly cross-linked in that order from the outside to the inside of the surface.

In another preferred embodiment, the total depth of gradient cross-linking is up to 3.5 mm.

In another preferred embodiment, the total depth of gradient cross-linking is up to 3 mm.

In another preferred embodiment, the total depth of gradient cross-linking is up to 2.5 mm.

In another preferred embodiment, in the gradient crosslinking, the depth of the hypercrosslinking is up to 1.5 mm.

In another preferred embodiment, in the gradient crosslinking, the depth of the hypercrosslinking is up to 1 mm.

In another preferred embodiment, the ultra-high molecular weight polyethylene contains an antioxidant.

In another preferred embodiment, the antioxidant is selected from one or more of the following group: vitamin E, tetrakis [ methylene (3, 5-di-tert-butylhydroxyhydrocinnamate) ] methane, thiodimethylenebis [3- [3, 5-di-tert-butyl-4-hydroxyphenyl ] propionate, octadecyl 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate, N' -hexane-1, 6-diylbis (3- (3, 5-di-tert-butyl-4-hydroxyphenylpropionamide)), phenylpropionic acid 3, 5-bis (1, 1-dimethyl-ethyl) -4-hydroxy-C7-C9 branched alkyl ester, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -2,4, 6-trimethylbenzene, 2, 4-bis (dodecylthiomethyl) -6-methylphenol, Triethylene glycol bis (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, 2 '-methylenebis (4-methyl-6-tert-butylphenol) monoacrylate, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione, the reaction product of benzylamine and 2,4, 4-trimethylpentene, 2, 4-bis (octylthio) -6- (4-hydroxy-3, 5-di-tert-butylanilino) -1,3, 5-triazine 5, 7-di-tert-butyl-3- (3, 4-dimethylphenyl) -3H-benzofuran-2-one, 2, 3' -methylenebis (4-methyl-6-tert-butylphenol), Tris (2, 4-di-tert-butylphenyl) phosphite, or pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ].

In another preferred embodiment, the antioxidant is vitamin E.

In another preferred embodiment, the antioxidant is present in an amount of 0.05 to 0.20 wt.%.

In another preferred embodiment, the antioxidant is present in an amount of 0.05 to 0.1 wt.%.

In another preferred embodiment, the antioxidant is present in an amount of 0.1 wt%.

In another preferred embodiment, the bearing surface layer of the medical implant is cross-linked by the cross-linking method according to the first aspect of the invention.

In another preferred embodiment, the average breaking force of the 0.25 mm thick film of the outermost surface layer of the supporting surface layer is more than 50.0 newtons.

In another preferred example, the average equivalent crosslinking degree of the outermost surface layer of the support surface layer is 100kGy or more.

In a third aspect, the present invention provides a medical joint comprising a first joint support and a second joint support; between the first joint supports and the second joint supports there is an ultra high molecular weight polyethylene medical implant according to the second aspect of the invention.

In another preferred example, the medical joint may be any artificial joint, such as an artificial hip joint, an artificial shoulder joint, an artificial knee joint, an artificial condyle joint, an artificial elbow joint, an artificial wrist joint, an artificial finger joint, and the like.

In another preferred example, when the medical joint is a hip joint, the first joint support is a cup; the second joint support is a femoral head.

It is to be understood that within the scope of the present invention, the above-described features of the present invention and those specifically described below (e.g., in the examples) may be combined with each other to form new or preferred embodiments. Not to be reiterated herein, but to the extent of space.

The invention has the advantages that:

the U.S. drug administration (FDA) classifies ultra-high molecular weight polyethylene (UHMWPE) prosthetic joint materials into four categories. The first type is traditional ultra-high molecular weight polyethylene, the degree of crosslinking is lower than 40kGy, and the polyethylene is invented and put into clinical use since 1960. The second type is highly crosslinked ultra-high molecular weight polyethylene, with a degree of crosslinking of 50-100kGy, which was invented since the 1990's and was put into clinical use. The third type is highly cross-linked ultra-high molecular weight polyethylene containing an antioxidant, the degree of cross-linking is 100kGy, and the polyethylene is invented and put into clinical use since 2005. The fourth class of materials, which have been invented since 2000 but not clinically used, are others, such as surface cross-linked ultra-high molecular weight polyethylene. The surface cross-linked ultrahigh molecular weight polyethylene obtained by the invention is surface gradient cross-linked ultrahigh molecular weight polyethylene, the cross-linking degree and chemical components of the surface gradient cross-linked ultrahigh molecular weight polyethylene cover the first three types of materials, and the surface gradient cross-linked ultrahigh molecular weight polyethylene belongs to the fourth type.

The surface gradient crosslinked ultra-high molecular weight polyethylene obtained by the process method breaks through the technical limits of the first three types of polyethylene, and can expand the application range of the polyethylene. The super wear resistance of the surface gradient crosslinked ultra-high molecular weight polyethylene can completely replace ceramics, and the brittle fracture of the ceramics becomes history. The surface gradient crosslinked ultra-high molecular weight polyethylene of the invention is used for replacing metal, and the sensitivity of metal ions to patients and the toxicity of trumpetcreeper can be fundamentally eliminated. Because the bulk material of the surface gradient crosslinked ultra-high molecular weight polyethylene is not crosslinked, the artificial joint prepared by the method does not need metal as mechanical support any more, so that the manufacturing cost can be saved by more than 50 percent. Moreover, with the surface gradient crosslinked UHMWPE of the present invention, the parts can be made quite thin, minimizing osteotomy. At present, the wear resistance and toughness of the artificial joint made of the bulk crosslinked ultra-high molecular weight polyethylene are not compatible, so that doctors recommend that patients implanted in the joint do not have severe exercises such as running, jumping or mountain climbing, and patients using the artificial joint made of the surface gradient crosslinked ultra-high molecular weight polyethylene of the present invention are not limited to such.

The process method of the invention is improved as follows:

first, the prior art step of gamma-ray bulk pre-crosslinking is eliminated.

Secondly, the photoinitiator is diffused to the depth of more than 1.0 mm on the surface of the polyethylene by adopting a high-temperature gas phase diffusion method under the condition that the temperature is higher than the melting point of the photoinitiator.

Thirdly, high dose ultraviolet irradiation (> 100 mW/cm)²) So as to ensure that the deeply diffused photoinitiator and the ultra-high molecular weight polyethylene complete crosslinking.

The process improvement of the three aspects achieves remarkable technical effects:

firstly, the process method has no gamma-ray integral pre-crosslinking, so that the main chain of the polyethylene molecule can not be cut off, and the defect that the body becomes brittle is overcome. The surface gradient crosslinked ultrahigh molecular weight polyethylene of the invention increases the two-dimensional tensile fracture toughness along with the increase of the crosslinking degree. This is unexpectedly the opposite of the data disclosed in the prior art (see fig. 1, 2, 3, 6).

Secondly, the surface of the ultra-high molecular weight polyethylene subjected to surface gradient crosslinking presents super crosslinking, the crosslinking degree can be improved to more than 250kGy, and the thickness of the super crosslinking exceeds 1.0 mm.

Thirdly, the total depth of the surface gradient cross-linking of the surface gradient cross-linked ultrahigh molecular weight polyethylene of the invention exceeds 1.0 mm.

Fourthly, a very small amount of antioxidant (<0.1 wt%) is introduced into the polyethylene surface layer, and the surface layer does not need to be removed because the surface is not oxidized, so that the super wear resistance of the polyethylene surface is kept. In the case of a rough surface of the cobalt chromium alloy ball, still have a lower wear rate than the equivalent composition ultra high molecular weight polyethylene, which is highly crosslinked at 100 kGy.

Drawings

FIG. 1 shows the two-dimensional tensile breaking force versus crosslinking depth for a surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E0.25 mm film (example eight).

FIG. 2 shows the equivalent degree of crosslinking versus crosslinking depth for a surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E0.25 mm film (example eight).

FIG. 3 shows the two-dimensional tensile toughness of a surface hypercrosslinked ultra-high molecular weight polyethylene GUR1020E0.25 mm film as a function of crosslinking depth (example eight).

Figure 4 shows the two-dimensional tensile break force versus crosslinking depth for surface crosslinked ultra high molecular weight polyethylene 0.25 mm films of prior art CN102276864 and US 9132209.

Figure 5 shows the two-dimensional tensile fracture toughness of surface cross-linked ultra high molecular weight polyethylene 0.25 mm films of prior art CN102276864 and US9132209 as a function of cross-linking depth.

FIG. 6 shows a graph comparing the two-dimensional tensile toughness versus equivalent cross-linking degree for the present application and another prior art (example eight).

Fig. 7 shows a schematic diagram of a two-dimensional film tensile mechanical test.

FIG. 8 shows the force at break versus elongation curve for a surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E (example eight) film compared to other polyethylene films, where the area under the curve is the film two-dimensional tensile fracture toughness. In the figure, the upper curve (a) is data of example eight of the present invention; the lower curve (b) is a non-crosslinked ultra-high molecular weight polyethylene GUR 1020; the middle curve (c) is 100kGy gamma ray high cross-linked ultra-high molecular weight polyethylene GUR 1020E.

FIG. 9 shows the two-dimensional tensile break force of ultra high molecular weight polyethylene GUR1020E0.25 mm film as a function of gamma ray dose using a gamma ray bulk crosslinking method.

FIG. 10 shows the two-dimensional tensile break force of ultra high molecular weight polyethylene GUR 10200.25 mm thin films as a function of gamma ray dose using a gamma ray bulk crosslinking method.

FIG. 11 is a graph showing the variation of the ultraviolet irradiation intensity with the surface depth of the ultra-high molecular weight polyethylene in the crosslinking process of the present invention.

Figure 12 shows a comparison of wear test results for two 44 mm diameter hip joints made by the method of the present application and the prior art, respectively. The low wear curve is the surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E of the present invention and the high wear curve is the gamma ray highly crosslinked (100kGy) ultra high molecular weight polyethylene GUR 1020E.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings in order to more clearly understand the objects, features and advantages of the present invention. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the present invention, but are merely intended to illustrate the spirit of the technical solution of the present invention.

In the following description, for the purposes of illustrating various disclosed embodiments, certain specific details are set forth in order to provide a thorough understanding of the various disclosed embodiments. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of the specific details. In other instances, well-known devices, structures and techniques associated with this application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

Throughout the specification and claims, the word "comprise" and variations thereof, such as "comprises" and "comprising," are to be understood as an open, inclusive meaning, i.e., as being interpreted to mean "including, but not limited to," unless the context requires otherwise.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It should be noted that the term "or" is generally employed in its sense including "and/or" unless the context clearly dictates otherwise.

The "surface gradient crosslinked ultra high molecular weight polyethylene" obtained by the process of the present invention may also be referred to herein as "surface hypercrosslinked ultra high molecular weight polyethylene".

Tensile breaking force of two-dimensional film: means the highest force to break or the ultimate force to break of a two-dimensional stretch of a 0.25 mm thick film using the ASTM F2977-13 standard.

Tensile fracture toughness of two-dimensional film: means the work done by stretching a 0.25 mm thick film in two dimensions until it breaks, using the ASTM F2977-13 standard.

Equivalent degree of crosslinking: when both crosslinking methods achieve the same tensile breaking force of the two-dimensional film, they have the same degree of crosslinking. Equivalent degrees of crosslinking can also be obtained theoretically by measuring the crosslinking density (crosslink density) or the Trans-vinylene (Trans-vinylene) index. The unit of equivalent degree of crosslinking is kGy.

To date, the test methods used for bulk materials have not been suitable for gradient crosslinking. The invention is inspired by the mathematical differential method, and adopts the film test of document 15, and takes a 0.25 mm film in a gradient layer to carry out the two-dimensional tensile mechanical test layer by layer according to the standard of ASTMF 2183. And (3) carrying out radiation crosslinking correction on the two-dimensional stretching data to obtain the equivalent crosslinking degree. The two-dimensional tensile breaking force for the ultra-high molecular weight polyethylene GUR1020E containing 0.1 wt% vitamin E was linearly related to the gamma ray dose in the range of 0-250kGy (FIG. 9), but the linear relationship for the ultra-high molecular weight polyethylene GUR1020 containing no vitamin E did not hold in the range of 100-250kGy (FIG. 10).

The invention selects gamma-ray integral cross-linking as a correction method and ultraviolet light auxiliary photoinitiator surface cross-linking as a corrected method. For example, for ultra high molecular weight polyethylene GUR1020E containing 0.1 wt% vitamin E, the equivalent degree of crosslinking is obtained from the corrected straight line formula shown in FIG. 9:

equivalent degree of crosslinking (two-dimensional film tensile breaking force-33.02)/0.109

Super crosslinking: the equivalent crosslinking degree is larger than gamma rays with the dosage of 100kGy, and the two-dimensional tensile breaking force of the ultra-high molecular weight polyethylene film with the thickness of 0.25 mm is larger than 50 newtons.

High crosslinking: the equivalent crosslinking degree is between 50 and 100kGy of gamma rays, and the two-dimensional tensile breaking force of the ultra-high molecular weight polyethylene film with the thickness of 0.25 millimeter is between 38.5 and 50 newtons.

Low degree of crosslinking: the equivalent crosslinking degree is between 30 and 50kGy of gamma rays, and the two-dimensional tensile breaking force of the ultra-high molecular weight polyethylene film with the thickness of 0.25 millimeter is between 36 and 38.5 newtons.

Non-crosslinking: the equivalent crosslinking degree is less than 30kGy dosage gamma ray, and the two-dimensional tensile breaking force of the ultra-high molecular weight polyethylene film with the thickness of 0.25 mm is less than 36 newtons.

Crosslinking depth: the distance from one level of crosslinking to another.

Gradient cross-linking total depth: the surface hypercrosslinking gradually decays to the distance of in vivo non-crosslinking, i.e. the sum of the depth or thickness of hypercrosslinking, high crosslinking and low crosslinking.

Aspects of the present invention are described in detail below.

Base material

The base material used in the present invention may be uncrosslinked ultrahigh molecular weight polyethylene (e.g., Ticona) produced by TiconaE.g., GUR1020 or GUR 1050). The substrates used in the present invention may or may not contain an antioxidant. The optional antioxidants may be selected from any one or more of the following: vitamin E, vitamin C,1010、1035、1076、1098、11135、1130、1520、1726、245、3052、3114、5057、565、HP-136、168 or pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate]See table 1. The content of the antioxidant is 0.05-0.20 wt%; for example, 0.1% by weight is preferable. The base material used in the present invention may preferably be an uncrosslinked ultrahigh molecular weight polyethylene containing 0.1% by weight of vitamin E, which may be referred to as uncrosslinked ultrahigh molecular weight polyethylene (0.1% by weight of vitamin E) or uncrosslinked ultrahigh molecular weight polyethylene (0.1% by weight of ViE). For example, the uncrosslinked ultra high molecular weight polyethylene GUR1020 containing 0.1 wt% vitamin E may be referred to as ultra high molecular weight polyethylene GUR1020E for short, or GUR1020E for short.

TABLE 1 continuation

TABLE 1 continuation

TABLE 1 continuation

The substrate of the present invention may be treated by a surface diffusion process and a surface crosslinking process. Preferably, the surface cross-linking process may be further followed by a surface cleaning process and a surface sterilization process.

The substrate of the present invention may also be subjected to preliminary processing and further processing of the substrate prior to the surface diffusion process, the substrate being first processed into a component, e.g., a medical implant. The medical implant in the present invention refers to a part which can be implanted into an animal body (e.g., a human body). In another preferred embodiment, the medical implant is used as a wear resistant insert in an artificial joint (e.g., hip, shoulder, knee, etc.).

The introduction of the individual steps of the surface gradient crosslinking method of the present application will be described below.

Preliminary working (shaping)

The base material of the present invention can be primarily processed into ultra-high molecular weight polyethylene materials in various forms (for example, rectangular plates or bars) by molding or extrusion. This step may be performed by a manufacturer including: orthopedics synthesis, Ltd, uk, Medical science and technology, Inc, america, Medical Polymer, Inc, and Restoration Medical Polymer, Inc.

Further processing

The preliminarily processed ultra-high molecular weight polyethylene material (e.g., rectangular plate or bar) can be further processed into various forms of ultra-high molecular weight polyethylene parts, such as small plates or artificial joints, by means of machining. The resulting part may be subjected to a series of processes as described below. The surface of the component may be cleaned with a solvent such as acetone to remove impurities from the surface prior to performing the following process.

Surface diffusion process

The photoinitiator is diffusion impregnated into the wear surface of the processed ultra high molecular weight polyethylene part (e.g., a small flat plate or an artificial joint). The photoinitiators which may be used according to the invention may be one or more selected from the group consisting of: benzophenone, 4-chlorobenzophenone, 2-chlorobenzophenone, 4' -dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-chloroanthraquinone, p-chloroanthraquinone, benzyl sulfide, benzyl sulfoxide, phenyl sulfoxide, 4-acetylbiphenyl, anthrone, hexachlorobenzene. Benzophenone is preferred.

Taking benzophenone as an example of the photoinitiator, the surface diffusion process of benzophenone may include the following steps: ultra high molecular weight polyethylene parts (e.g., ultra high molecular weight polyethylene GUR1020E tablets or artificial joints) were placed on an aluminum plate. The aluminum plate was placed in a stainless steel diffusion vessel. The container is filled with solid benzophenone powder. The side of the container is provided with a ventilating pipeline; the pipeline is connected with a mechanical pump for vacuumizing the container, nitrogen is introduced again after vacuumizing, and circulation is carried out for three times. The vessel was kept sealed and the nitrogen pressure was about one atmosphere. The whole stainless steel container is put into a low-temperature oven, the photoinitiator benzophenone and the ultra-high molecular weight polyethylene part are simultaneously heated to a certain temperature, and the photoinitiator benzophenone and the ultra-high molecular weight polyethylene part are diffused on the surface of the ultra-high molecular weight polyethylene part for a period of time at the certain temperature. And after the surface of the ultra-high molecular weight polyethylene is diffused by the photoinitiator, cooling the ultra-high molecular weight polyethylene part to room temperature.

The temperature of diffusion is controlled between 50 ℃ and 134 ℃. The minimum diffusion temperature should exceed the melting point of benzophenone by about 49 deg.c and keep benzophenone in a liquid state. Liquid benzophenones have a relatively high saturated vapor pressure. The diffusion temperature is improved, so that the benzophenone gas can be rapidly and deeply diffused to the ultra-high molecular weight polyethylene, and the process time is saved. The maximum diffusion temperature should be about 134 ℃ below the melting point of the ultra-high molecular weight polyethylene. Above 134 c the ultra high molecular weight polyethylene is deformed. Preferred diffusion temperatures are between 50 ℃ and 130 ℃, more preferably between 80 ℃ and 130 ℃, and most preferably between 90 ℃ and 130 ℃. The diffusion time is controlled to be less than 24 hours, more preferably less than 12 hours, most preferably less than 8 hours. For large-size parts and large-scale production, the diffusion temperature and time should be adjusted accordingly.

Surface cross-linking process

After the diffusion is completed and cooled to room temperature, the aluminum plate with the ultra-high molecular weight polyethylene part (e.g., ultra-high molecular weight polyethylene GUR1020E tablet or artificial joint) placed therein is placed in a stainless steel container for crosslinking. The stainless steel vessel for crosslinking and the stainless steel vessel for diffusion are the same. A ventilating pipeline is arranged on the side surface of the container; the pipeline is connected with a mechanical pump and used for vacuumizing the container, nitrogen is introduced again after vacuumizing, circulation is carried out for three times, the container is kept sealed, and the pressure of the nitrogen is about one atmosphere. The top of the container is provided with a transparent glass top cover; an ultraviolet lamp is arranged on the transparent glass top cover. Crosslinking is carried out under ultraviolet irradiation.

The uv lamp may be any commercially available brand. The average wavelength of ultraviolet irradiation is 320-390 nm; preferably 365 nm. Selection of UV by modulationThe power and irradiation distance of the lamp control the irradiation intensity of the ultraviolet light. The irradiation intensity of the ultraviolet light on the surface of the ultra-high molecular weight polyethylene is controlled to be more than or equal to 90mW/cm²Preferably ≥ 100mW/cm²More preferably 150mW/cm or more²Most preferably 170mW/cm or more². The irradiation time of the ultraviolet light should be controlled to be more than or equal to 20 minutes, preferably more than or equal to 40 minutes, and most preferably more than or equal to 60 minutes.

A material or part of diffused and cross-linked ultra high molecular weight polyethylene (e.g., ultra high molecular weight polyethylene GUR1020E) is machined into a plurality of circular sheets. The diameter of the circular slice is 25.4 mm; the thickness of the circular thin sheet is 0.5 mm, 1.0 mm, 1.5 mm, 2 mm, 2.5 mm and 3 mm, respectively. And (3) overlapping the sheets, placing an ultraviolet light intensity tester below the sheets, and testing the curve of the ultraviolet light intensity changing along with the thickness change of the sheets. Taking the ultra-high molecular weight polyethylene GUR1020E as an example, the results are shown in FIG. 11: the ultraviolet light intensity decays as the thickness of the sheet increases. Thus, providing a sufficiently high intensity of uv light is one of the requirements for increasing the depth of crosslinking of the surface layer.

When ultraviolet light is irradiated, the color of the surface of the ultrahigh molecular weight polyethylene diffused by the photoinitiator benzophenone gradually changes from dark yellow to light white. There was no color change on the surface of the ultra high molecular weight polyethylene that had not been diffused with the photoinitiator benzophenone upon irradiation with ultraviolet light. Thus, the photoinitiator benzophenone participates in the surface crosslinking of the ultrahigh molecular weight polyethylene under the action of ultraviolet light. And as the crosslinking proceeded, the color tended to stabilize, indicating that benzophenone was gradually depleted. When the surface is not diffused by the photoinitiator, the ultraviolet light irradiates the ultrahigh molecular weight polyethylene, and the surface of the ultrahigh molecular weight polyethylene has no color change all the time, which indicates that no crosslinking reaction occurs at the time.

Surface cleaning process

After the diffusion and the crosslinking of the surface of the ultra-high molecular weight polyethylene part are finished, the surface of the part is cleaned. The cleaning method comprises the following steps: and (3) soaking the ultra-high molecular weight polyethylene part in an organic solvent to remove the unreacted photoinitiator benzophenone and the soluble byproduct of the phenol. The organic solvent may be selected from the group consisting of: acetone, ethanol, methanol, isopropanol, diethyl ether, etc. The organic solvent is preferably acetone. After the surface of the ultra high molecular weight polyethylene part is cleaned, the part is placed in a forced air oven to dry (e.g., 70 ℃ for 1 hour).

Surface disinfection process

After the surface of the ultra-high molecular weight polyethylene part is cleaned, the surface of the part can be disinfected. The sterilization method includes any one of gamma ray sterilization, ETO sterilization, or gas plasma sterilization.

After the above process, the obtained surface gradient crosslinked ultra-high molecular weight polyethylene part was tested as follows:

two-dimensional tensile mechanical property test (light beating)

The two-dimensional tensile mechanical property test of the present invention was carried out generally according to the method of ASTM F2977-13 (document 7), while being adjusted in two ways: one is that the thickness of the test sample is changed from 0.508+0.005/-0.008 mm to 0.250+0.005/-0.008 mm; secondly, the diameter of the inner hole of the grinding tool is changed from 3.8 mm to 3.4 mm. The thickness of the test sample is reduced to precisely measure the gradient cross-linking, and the reduction of the diameter of the inner hole of the grinding tool is to avoid the sliding test error caused by the reduction of the thickness of the sample (document 8). For the surface gradient crosslinked UHMWPE samples of the present invention, cylindrical samples with a diameter of 6.350+0.000/-0.127 mm were taken from the body. A film was obtained in layers of 0.25 mm from the outside to the inside in this order from the abraded surface (reference 9), and a two-dimensional tensile mechanical test was carried out in accordance with the adjusted ASTM F2977-13 method to obtain a curve of a change in two-dimensional tensile breaking force of the film with the elongation of the film (see fig. 7 for a schematic diagram of the film stretching method). Specifically, in the test, the two-dimensional film is clamped in a small hole, the hemispherical metal needle pushes the film upwards until the film is broken, and the curve of the breaking stress and the elongation of the film is recorded. The final breaking force is the two-dimensional tensile breaking force of the film; the area under the curve is the film two-dimensional tensile fracture toughness. The curve end point is the maximum breaking force and the area under the curve is the fracture toughness. Six separate measurements were made for each experimental selection and the mean and standard error were calculated.

Correction of degree of equivalent crosslinking

Processing the ultra-high molecular weight polyethylene GUR1020 and the ultra-high molecular weight polyethylene GUR1020E into films with the diameter of 6.350+0.000/-0.127 mm and the thickness of 0.250+0.005/-0.008 mm, filling the films into air-isolated Mylar aluminum foil bags, mechanically pumping the films to be vacuum, introducing nitrogen, circulating the films for three times, keeping the vacuum sealing state, carrying out gamma ray crosslinking, and then carrying out annealing treatment at 80 ℃. And (4) carrying out two-dimensional tensile mechanical property test on the obtained sample. The radiation dose of gamma ray and the final breaking force of the two-dimensional tensile mechanical property test are plotted to obtain the radiation crosslinking correction straight line of the ultra-high molecular weight polyethylene GUR1020E (figure 9). This calibration straight line can be used for the equivalent cross-linking degree calibration of the surface cross-linked ultra high molecular weight polyethylene GUR 1020E. As a result, the equivalent crosslinking degree of the ultra-high molecular weight polyethylene GUR1020 containing no vitamin E has a linear relationship only in the range of 0-100kGy, and the tensile breaking force of the two-dimensional film is basically kept unchanged after exceeding 100kGy, and the average value fluctuates between 50-53N (figure 10). The equivalent cross-linking degree correction is not suitable for the ultra high molecular weight polyethylene GUR 1020.

The equivalent degree of crosslinking can also be obtained theoretically by measuring the crosslinking density (crosslink density) according to astm d 2765. The higher the degree of crosslinking, the greater the crosslinking density. The measurement of crosslink density is an indirect measurement method in which crosslinked ultra-high molecular weight polyethylene is dissolved in xylene at 130 ℃ and the change in weight before and after dissolution is measured to calculate the swelling ratio (Swell ratio). The swelling ratio was converted to the crosslinking density. For the ultra-high molecular weight polyethylene with low to high crosslinking degree, the xylene absorption amount is higher, and the crosslinking density test is more accurate. However, the super cross-linked ultra-high molecular weight polyethylene has extremely low xylene absorption amount, is limited by the precision of a balance, and has large measurement error. So the present invention is not used.

The equivalent crosslinking degree can also be theoretically obtained by measuring the Trans-vinylene index (TVI) by infrared spectroscopy according to ASTM D2381. The higher the degree of crosslinking, the larger the TVI. TVI is also an indirect test method, which measures 965cm in the infrared spectrum of ultra-high molecular weight polyethylene^-1Absorption peaks and 965cm^-1And 1900cm^-1Ratio of absorption peak area. The present invention tested TVI but with a higher errorIs large.

Surface gradient crosslinking degree curve

The basis for testing the degree of crosslinking is a correction line formula shown in fig. 9, and the two-dimensional tensile breaking force is in direct proportion to the dosage of gamma rays. By the breaking force of the film, a degree of crosslinking equivalent to that of gamma rays or the like is obtained, which is called an equivalent degree of crosslinking. For the surface-hypercrosslinked ultrahigh molecular weight polyethylene sample of the present invention or the surface-crosslinked ultrahigh molecular weight polyethylene sample in the literature, a 0.25 mm film was sequentially taken from the bearing wear surface in a gradient layer, and a two-dimensional tensile breaking force depth curve (fig. 1 and 4) was tested to obtain a surface crosslinking degree depth curve (fig. 2) and a surface toughness depth curve (fig. 3 and 5).

Abrasion test

Abrasion test in GermanyThe abrasion test machine for the hip joint C6/2-07 adopts ISO4242-1 standard. The applied force is a Bawell (Paul) curve simulating human walking, the median angle is 30 degrees (corresponding to clinical 45 degrees), the flexion/extension is +25 degrees/-18 degrees, the adduction/abduction is-4 degrees/+ 7 degrees, the cycle period is 1.0 Hz, the maximum force is 3000 newtons, and the temperature is 37.0 +/-2.0 ℃. Four samples were selected as the test group and four samples as the control group. Three samples per set were used for abrasion testing and one sample was used for water loss absorption correction.

The test set samples were a surface hypercrosslinked ultra high molecular weight polyethylene of the present invention, a 44.2 mm diameter concave hemispherical hip joint and a surface roughened 44.0 mm diameter convex cobalt chromium alloy hemispherical hip joint counter-ground.

The control samples were ultra high molecular weight polyethylene, a 44.2 mm diameter concave hemispherical hip joint, and a surface roughened 44.0 mm diameter convex cobalt chromium alloy hemispherical hip joint pair mill, manufactured by yoyo biotechnology limited and already marketed in the united states as gamma-ray highly cross-linked (100 kGy).

The abrasion medium is 632.4ml/L deionized water, 367.6ml/L bovine serum water solution, EDTA 2.73g/L, gentamicin 10ml/L, amphotericin 10 ml/L. The roughening treatment of the cobalt-chromium alloy semispherical surface adopts the process of document 14. And (3) putting the polished cobalt-chromium alloy hemisphere into a rolling ball mill, wherein the rotating speed is 40 revolutions per minute, and the ball milling time is 30 minutes. The milling medium was 500 ml, 90 ml of alumina powder with a particle size of 500 and 200 ml of plastic with a particle size of SP 2.

Experiment group one: preparation of surface hypercrosslinked ultra-high molecular weight polyethylene GUR1020E

The non-crosslinked ultra-high molecular weight polyethylene GUR1020E (i.e., non-crosslinked ultra-high molecular weight polyethylene GUR1020 containing 0.1 wt% vitamin E) was selected from compression molding, and is manufactured by British orthopedics Synthesis, Inc.

Processing the compression molding rectangular bar into an ultrahigh molecular weight polyethylene part: a plate of 65 mm x 45 mm x 8 mm, a plate of 65 mm x 8 mm diameter, or a hemispherical cup of 44.20 mm diameter and 4.5 mm thickness.

The ultra high molecular weight polyethylene part was placed on an aluminum plate, which was then placed in a stainless steel container. The bottom of the container was placed with benzophenone powder (benzophenone from Sigma Aldrich under the trade name Reagent)99%). The top of the container is a transparent glass top cover. Vacuumizing, introducing nitrogen, circulating for three times, keeping the pressure of the nitrogen in the container at about one atmosphere and keeping the container in a sealed state. And then heating the stainless steel container to a specified temperature, preserving the heat for a period of time, cooling to room temperature, taking out the ultra-high molecular weight polyethylene part, and finishing the diffusion process. Placing the surface of the ultrahigh molecular weight polyethylene diffused with acetophenone under an ultraviolet lamp for irradiation and crosslinking, wherein the average wavelength is about 365 nanometers, and the surface irradiation intensity is 175mW/cm²The irradiation time was 60 minutes. The intensity of the UV light was maintained at about 50mW/cm at a depth of about 0.7 mm below the surface²(see FIG. 11). This is the same as the uv irradiation intensity of the material surface in CN102276864 and US 9828474.

Table 2 lists various examples based on different diffusion temperatures and times for benzophenone.

Table 2: list of examples

The weight change of the plate or hemispherical cup before and after diffusion was measured and divided by the exposed area to obtain the weight per unit area of benzophenone diffused into the surface layer of ultra high molecular weight polyethylene GUR1020E (Table 3).

Table 3: weight per unit area of benzophenone diffused into surface layer of ultra high molecular weight polyethylene GUR1020E (unit: mg/cm)²)

As can be seen from Table 3, the amount of benzophenone diffused per unit area was 1.112mg/cm under the conditions of 80 ℃ for 4 hours². If the temperature rises to 120 ℃, the diffusion capacity of the benzophenone per unit area rises to 7.568mg/cm². If the diffusion time is reduced to 2 hours, the diffusion amount per unit area of benzophenone is reduced to 5.095mg/cm². Therefore, the temperature rise and the time extension are both beneficial to increasing the diffusion of the benzophenone.

And soaking the part sample after surface crosslinking in acetone to remove the unreacted benzophenone and the soluble byproduct of the phenol. The cleaned part samples were machined to 0.25 mm film. The two-dimensional tensile mechanical properties were measured according to the adjusted ASTM F2977-13 method, and the final breaking force was shown in Table 4. The equivalent crosslinking degree is shown in Table 5 by the correction of the straight line shown in FIG. 9.

Table 4: surface cross-linked ultra-high molecular weight polyethylene GUR1020E surface 0.25 mm thick film two-dimensional tensile breaking force, unit: newton

Table 5: equivalent crosslinking degree of 0.25 mm thick film on surface of surface crosslinked ultra-high molecular weight polyethylene GUR1020E, unit: kGy

80℃

90℃

100℃

110℃

120℃

125℃

1 hour

185±39

239±23

1.5 hours

170±18

2 hours

214±15

266±23

304±98

2.3 hours

286±32

323±38

4 hours

106±21

As can be seen from tables 4 and 5:

in example one, the surface cross-linked UHMWPE GUR1020E film with a 0.25 mm surface thickness had a two-dimensional tensile ultimate breaking force of 45.25 + -2.38 newtons, an equivalent cross-linking degree of 106 + -21 kGy, and was highly cross-linked with a commercial 100kGy gamma ray in Table 6 as a wholeThe final breaking force (46.79 +/-1.5 newtons) and the crosslinking degree (100kGy) of the ultra-high molecular weight polyethylene GUR020E 0.25 film with the thickness of 0.25 mm are not obviously different, so that the ultra-high molecular weight polyethylene film belongs to surface high crosslinking.

Examples two to twelve, the surface-crosslinked UHMWPE GUR1020E film with a surface thickness of 0.25 mm has a two-dimensional tensile ultimate breaking force of between 52.34 + -1.96 Newton and 69.35 + -4.20 Newton, an equivalent degree of crosslinking of between 170 + -18 kGy and 323 + -38 kGy, well in excess of that of the commercially available 100kGy gamma ray film which is highly crosslinked overallThe two-dimensional tensile ultimate breaking force 46.79 + -1.5 (Table 6) of ultra-high molecular weight polyethylene GUR020E 0.25 film 0.25 mm thick was thus surface hypercrosslinked.

Table 6: commercial monolithic highly crosslinked ultra-high molecular weight polyethylene 0.25 mm thick film two-dimensional tensile ultimate breaking force and fracture toughness

Comparing the two-dimensional tensile breaking forces of the surface hypercrosslinked ultra-high molecular weight polyethylene GUR1020E0.25 mm thick film of the present invention (e.g., example eight), the uncrosslinked ultra-high molecular weight polyethylene GUR 10200.25 mm thick film and the 100kGy gamma ray bulk crosslinked ultra-high molecular weight polyethylene GUR1020E0.25 mm thick film, it was found that the surface hypercrosslinked ultra-high molecular weight polyethylene GUR1020E film of example eight had a higher breaking force than the uncrosslinked ultra-high molecular weight polyethylene GUR1020 film and the 100kGy gamma ray bulk crosslinked ultra-high molecular weight polyethylene GUR1020E film. The results are shown in FIG. 8.

The ultra-high molecular weight polyethylene surface hypercrosslinking of the invention further extends to depth, and the degree of crosslinking attenuates with the increase of depth, and is characterized by gradient crosslinking.

Table 7 shows the two-dimensional tensile breaking force, the equivalent crosslinking degree and the fracture toughness as a function of depth for the surface hypercrosslinked ultrahigh molecular weight polyethylene GUR1020E0.25 mm thick film prepared in example six. The equivalent degree of crosslinking of the surface was 214. + -. 15kGy, decreasing to 99. + -. 11kGy at 1.0 mm, to 49. + -. 3kGy at 1.5 mm, and finally to 3. + -. 11kGy (i.e., no crosslinking) at 2.5 mm. This indicates that the film has a surface gradient cross-linking depth of about 1.5 mm, with a hypercrosslinking depth of about 1.0 mm and a high cross-linking depth of about 0.5 mm. Below 2.0 mm, to the range of conventional gamma-ray sterilized ultra high molecular weight polyethylene (0-40kGy), with a total depth of surface gradient crosslinking of about 2.0 mm.

Table 7: example six surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E0.25 films 0.25 mm thick had two dimensional tensile break force, equivalent degree of crosslinking and fracture toughness as a function of depth.

Depth, mm

0

0.5

1

1.5

2

2.5

Breaking force, Newton

57.23±1.66

51.47±0.84

44.44±1.17

38.92±0.31

35.71±1.19

33.84±1.27

Equivalent degree of crosslinking, kGy

214±15

162±8

99±11

49±3

20±11

3±11

Fracture toughness, Newton millimeter

144.9±12.6

140.7±16.6

129.3±12.1

119.7±3.7

113.3±5.2

116.4±8.1

Fig. 1 and 2 show the gradient cross-linking characteristics of the surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E prepared in example eight. The film with the thickness of 0.25 mm on the outermost surface has the two-dimensional stretching final breaking force as high as 62.50 +/-2.50 newtons and the equivalent crosslinking degree of 262 +/-23 kGy. The thickness of the surface hypercrosslinked layer corresponding thereto increases to 1.5 mm, the thickness of the hypercrosslinked layer is about 1.0 mm, and below 2.5 mm the transition to low or even non-crosslinked. The ultra high molecular weight polyethylene gradient crosslinks had a total depth of about 3.0 millimeters.

Surprisingly, the fracture toughness of the surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E film of the present invention varied with depth with the same trend as the equivalent degree of crosslinking (see FIG. 2, FIG. 3, Table 6). While figure 6 further shows that the fracture toughness and equivalent crosslinking degree of the surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E film prepared in example eight is proportional, while the fracture toughness and equivalent crosslinking degree of the conventional gamma-ray bulk crosslinked ultra high molecular weight polyethylene film is inversely proportional. Here, the data for gamma-ray crosslinked polyethylene were obtained from the 0.50 mm film test results of journal of orthopedics (J.Othop Res) 2006, Chapter 24:2021-2027, M.Chimu et al, which were converted to 0.25 mm film fracture toughness. It is possible that the surface hypercrosslinked ultrahigh molecular weight polyethylene of the present invention has a crosslinked main chain and no broken side chain; and the conventional gamma-ray crosslinked ultra-high molecular weight polyethylene also breaks the side chains while crosslinking the main chain, so that the final breaking force of the two-dimensional stretching of the conventional gamma-ray crosslinked ultra-high molecular weight polyethylene at a low dose (0-100kGy) linearly increases with the increase of the gamma dose, but the final breaking force remains basically unchanged by a high dose (100-250kGy), and the crosslinking degree does not increase any more (Table 8, FIG. 10).

Table 8: two-dimensional tensile final breaking force and breaking toughness of gamma-ray integrally-crosslinked ultra-high molecular weight polyethylene 0.25 mm thick film are changed along with change of gamma-ray crosslinking dosage

Fig. 12 shows a comparison of two 44 mm diameter hip wear test results, i.e. the surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E of the present invention and gamma highly cross linked (100kGy) ultra high molecular weight polyethylene GUR1020E and roughened cobalt chrome, respectively, made by the method of the present application and the prior art. The surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E prepared in example eight showed lower wear loss than the gamma highly crosslinked (100kGy) ultra high molecular weight polyethylene GUR1020E ground with roughened cobalt chromium alloy under the same conditions. The wear loss of the surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E of the present invention was 1.0 times lower than the gamma highly crosslinked (100kGy) ultra high molecular weight polyethylene GUR1020E at one million cycles.

In a mathematical simulation of the experimental data of FIG. 12, the wear loss (W) of the surface hypercrosslinked ultra high molecular weight polyethylene GUR1020E of the present invention is related to the cycle number (C): w ═ (99 ± 16) (C)^{1/(3.14±0.05)}. The wear (W) of gamma-highly crosslinked (100kGy) ultra high molecular weight polyethylene GUR1020E is related to the number of cycles (C) by: w ═ (203 ± 39) (C)^{1/(1.51±0.05)}. Calculated by the formula, the wear loss of the surface super-crosslinked ultra-high molecular weight polyethylene GUR1020E is 1.6 times and 2.0 times lower than that of gamma-ray highly crosslinked (100kGy) ultra-high molecular weight polyethylene GUR1020E when twenty million cycles and three million cycles are obtained.

Document 14 discloses Saxite 40 mmAnd roughening the opposite grinding results of the cobalt chromium alloy. After one million and two million cycles,the abrasion loss of the surface-hypercrosslinked ultra-high molecular weight polyethylene GUR1020E of the present invention is 99 + -16 mg and 124 + -20 mg, and the abrasion loss ratio of the surface-hypercrosslinked ultra-high molecular weight polyethylene GUR1020E of the present invention is 260 + -60 mg and 400 + -80 mg1.6 times and 2.2 times lower. The higher the cycle number, the higher the wear phase differenceThe larger the multiple. Corresponding to the longer the patient walks, the longer the patient is used. It can be seen that the present invention makes a significant technical advance. Moreover, the ultra-low wear rates of the present invention are unexpected as previously noted.

Experiment group two: preparation of surface super-crosslinked ultra-high molecular weight polyethylene GUR1020

The surface super-crosslinked ultra-high molecular weight polyethylene is prepared by adopting two base materials of GUR1020 and GUR1020E according to the diffusion process and the crosslinking process of the experimental group I. Wherein, the diffusion conditions of the experimental group are 110 ℃ and 3.0 hours; the crosslinking condition is ultraviolet light 175mW/cm²The irradiation was carried out for 1.0 hour.

As a result: the surface super cross-linked ultra-high molecular weight polyethylene GUR1020E film with the surface thickness of 0.25 mm has the final breaking force of 54.3 +/-1.2N in two-dimensional tensile mechanics and the equivalent cross-linking degree of 187 kGy. The surface super-crosslinked ultra-high molecular weight polyethylene GUR1020 surface layer 0.25 mm film has a two-dimensional tensile mechanical final breaking force of 55.2 +/-3.91N and an equivalent crosslinking degree exceeding 100 kGy.

It can be seen that the difference of the final breaking force of the two-dimensional tensile mechanics is within the error range after the two base materials are treated under the same condition. The diffusion and crosslinking method of the present invention is also applicable to ultra high molecular weight polyethylene GUR1020 which does not contain an oxidizing agent.

Comparative experiment

Comparative experiments were carried out with reference to CN102276864, US9828474, the process of example 1.

This comparative experimental group employed two matrices: one base body isUltra-high molecular weight polyethylene (GUR1020) prepared according to the method of US5414049 and crosslinked by 30.9kGy gamma rays in the protection of nitrogen; the other matrix isUltra-high molecular weight polyethylene (GUR1020), prepared according to the method of US7517919, was irradiated with gamma rays of about 30kGy and heat treated three times at 130 ℃ in succession under nitrogen protection. Both substrates were 65 mm x 45 mmX 8 mm plate. And soaking the flat plate in 11.1mg/ml benzophenone solution, taking out after one minute, and airing in air at room temperature to finish the surface coating of the benzophenone.

The weight was weighed with an electronic balance of accuracy 0.1 mg, and the change in weight before and after coating of the substrate was recorded, divided by the total surface area of the plate, to obtain the coating weight per unit area.A plate andthe weight gain of the flat plate is 0.00688mg/cm²About one thousandth of the diffusion of benzophenone in the experimental group of the invention (see table 3).

A glass cup is filled with deionized water, nitrogen is introduced for bubbling, oxygen in the water is removed, and the temperature is heated to 65 ℃. The ultra-high molecular weight polyethylene substrate coated with benzophenone is connected with a stainless steel sheet, and the ultra-high molecular weight polyethylene is settled at the bottom of the glass cup by gravity, and the surface of the glass cup is covered by water. Irradiating the surface of the ultra-high molecular weight polyethylene material by using ultraviolet light with the average wavelength of 365 nanometers and the intensity of 52mW/cm²And the time was 1 hour, surface crosslinking was completed. The surface cross-linked ultra-high molecular weight polyethylene is washed by acetone and water, and a film with the thickness of 0.25 mm is prepared layer by layer from the cross-linked surface through mechanical processing, and the two-dimensional tensile mechanical property test is carried out.

FIG. 4 shows the surface cross-linking obtained in a comparative experimentAnd0.25 mm film two-dimensional tensile break force versus crosslinking depth. Wherein the content of the first and second substances,the 0.25 mm film two-dimensional tensile break force of 48.6 newtons,the two-dimensional tensile break force of the 0.25 mm film was 33.58N. According to the relation between the two-dimensional tensile breaking force and the crosslinking degree of the ultra-high molecular weight polyethylene GUR1020 (figure 10),the corresponding degree of crosslinking is 100kGy,the corresponding degree of crosslinking is 30 kGy.

FIG. 4 shows the surface cross-linking obtained in a comparative experimentAndthe 0.25 mm film two-dimensional tensile break force was almost unchanged with depth. This indicates that the thickness of the surface cross-links obtained by this method is extremely thin, not exceeding 0.25 mm.

FIG. 5 shows the surface cross-linking obtained in a comparative experimentAndthe two-dimensional tensile fracture toughness of the 0.25 mm film is related to the crosslinking depth. The trend is the same as in fig. 4, with the tensile fracture toughness at the surface being essentially the same as in vivo, up to about 100 newton millimeters. Further, the method is described as having a very thin surface cross-linking thickness of not more than 0.25 mm.

Summary of the invention

Table 9 shows a comparison of the surface-hypercrosslinked ultrahigh molecular weight polyethylene obtained according to the process of the invention with the surface-crosslinked ultrahigh molecular weight polyethylene obtained by the comparative process (cf. example 1 of CN102276864 and US 9828474).

TABLE 9

Firstly, in the diffusion process of the present invention, the high temperature diffusion method is adopted to permeate the photoinitiator (such as benzophenone) into the surface of the ultra-high molecular weight polyethylene, and the amount of the photoinitiator introduced into the surface layer is large (>0.9mg/cm²) And the depth of the base body can be up to 3.0 mm. In contrast, the comparative method employed a room temperature coating method, and the amount of photoinitiator introduced into the skin layer was small (about 0.006 mg/cm)²) And penetrates to a depth of less than 0.25 mm into the matrix (fig. 4, fig. 5).

Secondly, the crosslinking process of the invention adopts high-intensity ultraviolet light (UV-light)>100mW/cm²) Irradiation, and contrast method using low intensity ultraviolet light (A)<100mW/cm²) And (5) irradiating. High intensity uv irradiation causes the deep-diffused photoinitiator to react with the ultra-high molecular weight polyethylene, producing deep cross-linking. The depth of surface cross-linking in the present invention is greater than 1.0 mm, while the depth of surface cross-linking in the comparative method is less than 0.25 mm.

Finally, the grinding experiment of the ultra-high molecular weight polyethylene with super cross-linked surface adopts a roughened cobalt-chromium alloy ball to carry out grinding; in contrast, the comparative method was conducted using a polished cobalt-chromium alloy ball for the counter-grinding test of the surface-crosslinked ultra-high molecular weight polyethylene. The experimental conditions of the invention are harsher and are closer to extreme clinical conditions.

All documents referred to herein are incorporated by reference into this application as if each were individually incorporated by reference. Furthermore, it should be understood that various changes and modifications of the present invention can be made by those skilled in the art after reading the above teachings of the present invention, and these equivalents also fall within the scope of the present invention as defined by the appended claims.

Reference documents:

j. Catherin et al, "The effect of radiation dose on The tensile and impact toughness of highly crosslinked and remelted ultra-high molecular weight polyethylene (The effect of radiation dose on The tensile and impact toughness)", J.biomed.Mat.Res., No.2, Chapter 97B, p.333.

2.US 6494917。

3. The "Surface crosslinked UHMWPE" of Eblou, Oldham et al allows the Use of Larger Femoral Heads in Total Joints (Surface Cross-Linked UHMWPE Can Enable the Use of Large ferromagnetic Heads in Total Joints), "journal of orthopedics (Orthop Res), 31:59-66(2013).

4.CN 102276864。

5.US 9132209。

6.US 9951190。

ASTM F2977-13, "Standard Test Method for two-dimensional tensile mechanical Properties Testing of Polymeric Biomaterials Used in Surgical Implants".

8. Yabebu Bilitz et al, "FEA-based DOE research solved the sample slip in the two-dimensional tensile mechanical property test of highly crosslinked UHMWPE film (FEA-based DOE stuck solutions sheet in thin film small punch test of high hly cross-sliced UHMWPE)," UHMWPE Poster No.1966 of the 2016 society for orthopedics research (ORS 2016Annual Meeting Poster No. 1966).

9. Dong Yu Lei Dong et al, "ceramic on ceramic or ceramic on polyethylene for total hip arthroplasty: systematic evaluation and Meta-analysis of Prospective randomization Studies (Ceramic on Ceramic or Ceramic on polyethylene for Total Hip mapping: A systematic Review and Meta-analysis of productive randomised students), J.Chinese, 5.5.5.9, Chapter 128, page 1223. sub.1231.

10. "Wear Performance of cermet Hip Bearings" by Yonn Reds et al, public scientific library, www.plosone.org, chapter 8, 2013, 8.8 (PLOS ONE | www.plosone.org, August 2013| Volume 8| Issue 8| e 73252).

11. Colduba LA et al "method of creating an abrasive composition for wear testing(Method creating biological compositions for near testing) "posters 2290 of 55 th annual meeting of the institute of orthopedics & university (Poster No.2290, 55)^th Anneal meeting of the orthopedic research society)。

12.US2016/02155117A1。