Surface cross‐linked ultra high molecular weight polyethylene by emulsified diffusion of dicumyl peroxide

Abstract

Cross-linking improves the wear resistance of ultrahigh molecular weight polyethylene (UHMWPE) used in hip and knee implants. Free radicals, generated by ionizing radiation or chemically, react to form cross-links. Limiting cross-linking to the articulating surface of the implant is desirable to enable high wear resistance on the surface and higher strength and toughness in the bulk. We investigated the diffusion of emulsified dicumyl peroxide (DCP) into vitamin E-blended UHMWPE (0.1 and 0.3 wt. % vitamin-E) with subsequent thermal decomposition in situ to obtain surface cross-linking with the objective of achieving surface wear rate equivalent or lower than that of current clinically available materials. We diffused emulsified DCP at 100°C followed by in situ decomposition at 150°C. We also assessed the effect of having vitamin-E in the DCP emulsion. The oxidative stability of the treated samples increased with increasing vitamin E concentration in the blend and by incorporating vitamin E into the peroxide emulsion. The impact strength of a surface cross-linked, 0.3 wt% vitamin E blended UHMWPE prepared using this method was superior to a clinically available irradiated and melted highly cross-linked UHMWPE while the wear resistance was comparable. These results showed the feasibility of surface cross-linking using emulsified peroxide diffusion as a method of making tough and wear resistant joint implant bearing surfaces. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1517-1523, 2018.

Surface cross‐linked UHMWPE using peroxides

“…This is presumably due to increased penetration depth of peroxide with increased temperature during doping. In further analysis, the mechanical testing of surface cross‐linked UHMWPE using diffusion of emulsified peroxides similar to what was shown here corroborated improved toughness compared to uniformly cross‐linked UHMWPEs …”

“…An additional benefit of this method would be the limitation of the cross‐linking to the surface regions of a UHMWPE implant, which has been shown to lead to the improvement of the fatigue strength and toughness of radiation cross‐linked material . The improvement in toughness by surface cross‐linking using peroxide diffusion was further corroborated in tibial preform‐sized UHMWPE components in a separate study . Similarly, the two formulations, which showed POD wear rates comparable to clinically available highly cross‐linked UHMWPEs (DCP doping at 100°C for 4 h followed by decomposition at 130°C for 4h and P130 doping at 120°C for 4h followed by decomposition at 180°C for 4 h) can be used with implant‐shaped preforms and be subjected to device testing such as hip joint simulation.…”

“…While peroxide crosslinking of UHMWPE adversely affects its oxidation resistance, the presence of the antioxidant addressed this problem. An additional benefit of this method would be the limitation of the cross‐linking to the surface regions of a UHMWPE implant, which has been shown to lead to the improvement of the fatigue strength and toughness of radiation cross‐linked material . The improvement in toughness by surface cross‐linking using peroxide diffusion was further corroborated in tibial preform‐sized UHMWPE components in a separate study .…”

Research into the thermal stability and mechanical properties of vitamin E diffusion modified irradiation cross-linked graphene oxide/ultra-high molecular weight polyethylene composites

“…Osteolysis, as a clinical problem, has been the driving force behind the development of UHMWPE. 1,2 During the last 20 years, cross-linking [3][4][5][6] and lling with graphene oxide (GO) [7][8][9][10][11] have been widely used to enhance the performance of UHMWPE. Cross-linked materials and materials with added GO have shown remarkable increases in longterm overall survival in total joint replacements around the world, due to signicantly improved mechanical properties.…”

A review of recent advances in tribology

“…Other coatings such as sol-gel coating [342], TiCuN solid solution coating [343], etc., were also investigated. Surface treatments included the use of emulsified diffusion of dicumyl peroxide to cross-linking UHWMEP [344] and boriding for Ti6Al4V alloy [345]. It is interesting to note that apart from improving wear resistance, the release from metallic ions, which is being increasingly recognized as a potential problem of metallic biomaterials, was also prevented from coatings [340].…”