Oxidation of gamma-irradiated ultrahigh molecular weight polyethylene

Coote, Christopher F.; Hamilton, John; McGimpsey, W. Grant; Thompson, Robert W.

doi:10.1002/1097-4628(20000912)77:11<2525::aid-app22>3.0.co;2-i

Cited by 27 publications

(31 citation statements)

References 14 publications

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“…However, this process causes CH and CC bond scission, which then initiates the oxidation of the free radicals formed, followed by a series of reactions leading to the potential formation of hydroperoxides, alcohols, carbonyls, acids, and esters 9–14. If components are stored in air for a considerable time, a maximum oxidation at a depth of 1–2 mm in the subsurface can develop, with a consequent loss of mechanical properties due to molecular weight reduction 12–15. It has been documented that this process leads to smaller polymer chains and a loss of mechanical strength and abrasion resistance 14, 16–18.…”

Section: Introductionmentioning

confidence: 99%

Modeling the oxidative degradation of ultra‐high‐molecular‐weight polyethylene

Medhekar

Thompson

Wang

et al. 2002

J of Applied Polymer Sci

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ABSTRACT:Understanding the sequence of reactions that occur in ultra-high-molecular-weight polyethylene (UHMWPE) following 60 Co ␥ irradiation has been the focus of numerous experimental studies. In the study reported here, we have incorporated recent experimental findings into a mathematical model for UHMWPE oxidation. Simulation results for shelf aging and accelerated aging are presented. It is shown that very reasonable simulations of shelfaging and accelerated-aging data can be obtained. It is also shown that simulations of shelf aging in reduced oxygen environments predict that the subsurface peaks of ketones will be shifted to the exterior surface. In vivo aging can be simulated if we assume that the oxygen level in the synovial fluid is about one-eighth that of atmospheric levels. Some reduced irradiation doses are predicted to significantly reduce the ketone formation for shelf-aging periods of up to 10 years.

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Section: Introductionmentioning

confidence: 99%

Modeling the oxidative degradation of ultra‐high‐molecular‐weight polyethylene

Medhekar

Thompson

Wang

et al. 2002

J of Applied Polymer Sci

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“…Free radicals created during polymer production and sterilization become sites for oxidation [20]. Oxygen is entrapped in the polymer and diffuses into it during production, shelf life, and use in amounts large enough to allow propagation of oxidation [6,18,20]. Oxidation accelerates wear and may lead to pitting, delamination, and fracture of the liner resulting from embrittlement and loss in fatigue properties [19].…”

Section: Discussionmentioning

confidence: 99%

“…This contrasts with d-transition metals for which the d-electron shell leads to strong directional bonding and reactivity that can make them pro-oxidants [16]. The Ln + 3 ion is a hard Lewis acid that strongly coordinates to oxygen in ligands and exhibits high coordination numbers ( [ 6). Consequently, lanthanides may be effective scavengers for oxygen-containing species, including radicals.…”

Section: Introductionmentioning

confidence: 99%

Europium Stearate Additives Delay Oxidation of UHMWPE for Orthopaedic Applications: A Pilot Study

Gallardo

Carpentieri

Michel

et al. 2011

Clinical Orthopaedics &Amp; Related Research

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Background Ultrahigh-molecular-weight polyethylene (UHMWPE) is used as an articulating surface in prosthetic devices. Its failure under various mechanisms after oxidation is of utmost concern. Free radicals formed during the sterilization process using high-energy irradiation result in oxidation. Europium, an element of the lanthanide family, has a unique electron configuration with an unusual lack of preference for directional bonding and notable bonding to oxygen. Because of this, it currently is used in studies for stabilization of polymers such as polyvinyl chloride. Questions/purposes We asked whether europium stearate could enhance the oxidation resistance after irradiation in nitrogen of UHMWPE. Methods Conventional nonirradiated and gammairradiated in nitrogen UHMWPE were compared with polyethylene doped with 375 ppm and 3750 ppm europium(III) stearate under the same treatment conditions. Chemical characterization was performed by Fourier transform infrared (FTIR) microspectroscopy using 200-lm thin films. The oxidation of doped samples with time was compared with that of conventional samples using accelerated oven aging. The types of oxidation products were identified by FTIR and quantified per material and treatment condition as indications of the oxidation level and mechanism. Results The generation rate of hydroperoxides and ketones was decelerated proportionally with concentration of europium stearates. The oxidative mechanism appeared similar to that of conventional polyethylene with the same types of measurable end products as ketones and hydroperoxides. Yet, the rate of generation of the latter appeared to be slowed down by the action of europium stearate. Conclusions Europium stearate mixed in UHMWPE decelerated the oxidation reactions triggered by gamma irradiation in nitrogen, seemingly without major alteration of the oxidation mechanism.

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“…Therefore, the trapped radicals due to irradiation do not play the role of main initiators after long storage in air. If the fiber is kept in air after irradiation, oxide and hydroperoxide will be generated (Premnath et al, 1996;Coote et al, 2000). When a polymer is irradiated in air at room temperature, the atmospheric oxygen reacts with free radicals created on the polymer backbone to form diperoxides (POOP) and hydroperoxides (POOH).…”

Section: Graft Polymerizationmentioning

confidence: 99%