Evolution of morphology in UHMWPE following accelerated aging: The effect of heating rates

Kurtz, Steven M.; Pruitt, Lisa A.; Crane, Deborah J.; Edidin, Avram A.

doi:10.1002/(sici)1097-4636(199907)46:1<112::aid-jbm13>3.3.co;2-l

Cited by 4 publications

(5 citation statements)

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“…Several studies have reported an increase in PE crystallinity upon ageing, [15,18,[51][52][53][54] and this behaviour has been related to a rearrangement of the polymeric chains as a result of their increased mobility due to thermal ageing. [52] However, for EtO-sterilized samples, this effect appeared less pronounced [51] ; on the other hand, thermally unstabilized XLPE samples submitted to accelerated ageing did not display any increase in crystallinity, [55] as well as XLPE and UHMWPE components after 2 years of real-time shelf ageing. [56] In those components, the oxidation index, as determined by IR spectroscopy, was extremely low (less than 0.1).…”

Section: Discussionmentioning

confidence: 99%

Comparative micro‐Raman study on standard, cross‐linked and vitamin E‐blended polyethylene acetabular cups after long‐term in vitro testing and ageing

Taddei

Pavoni

Affatato

2017

J Raman Spectroscopy

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Ultra‐high molecular‐weight polyethylene has been used in total joint replacement for the last three decades. Many attempts have been made to improve the wear behaviour of this material. Highly cross‐linked polyethylene (XLPE) has been developed to decrease the wear rate, while the addition of stabilizers such as vitamin E has been proposed to slow the oxidation processes. In this study, we compared the wear behaviour of conventional ultra‐high molecular‐weight polyethylene, XLPE and vitamin E‐added XLPE acetabular cups for total hip arthroplasty. The samples were run for five million cycles on a hip joint simulator (first test), then underwent an accelerated ageing treatment, were tested again for two million cycles (second test) and finally were run for another two million cycles in presence of third‐body particles (third test). Our study showed that vitamin E‐added XLPE cups had a better wear behaviour only in the long‐term and more severe testing conditions: in the third test, they underwent the lowest increase in wear rate. Micro‐Raman spectroscopy allowed us to analyse the wear degradation of the cups on a molecular scale, and differences in the wear mechanisms were revealed. The presence of vitamin E did not prevent structural changes upon the first test, while it did in ageing and in the second test. In the third test, more significant structural changes were observed; the XLPE cups, which lost the lowest mass, had the most modified articular surface. These morphological aspects should be taken into account, together with gravimetric wear rates, in the characterization of wear degradation. Copyright © 2017 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Comparative micro‐Raman study on standard, cross‐linked and vitamin E‐blended polyethylene acetabular cups after long‐term in vitro testing and ageing

Taddei

Pavoni

Affatato

2017

J Raman Spectroscopy

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“…30 Previously it has been reported that even though oxidised retrieved polyethylene samples have increased percentage crystallinity, it is uncommon for thermally aged samples to show any significant increase in crystallinity. 30,31…”

Section: Discussionmentioning

confidence: 99%

“…crosslinking) is likely to alter the oxidation mechanism. 31 Future work will evaluate the concentration of free radicals in the polyethylene prior to ageing in order to better understand the oxidation rate. 43…”

Section: Discussionmentioning

confidence: 99%

Chemical stability of oil-infused polyethylene

2020

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Ultra-high molecular weight polyethylene (UHMWPE) can be made radiopaque for medical imaging applications through the diffusion of an iodised oil-based contrast agent (Lipiodol Ultra Fluid). A similar process is used for Vitamin E incorporated polyethylene which provides antioxidant properties. This study aimed to investigate the critical long-term properties of oil-infused medical polyethylene after 4 weeks of accelerated thermal ageing. Samples treated with an oil (Vitamin E or Lipiodol) had a higher oxidation stability than currently used medical grade polyethylene, indicated by a smaller increase in oxidation index after ageing (Vitamin E + 36%, Lipiodol +40%, Untreated +136%, Thermally treated +164%). The tensile properties of oil treated polyethylene after ageing were significantly higher than the Untreated and Thermally treated controls (p<0.05) indicating less mechanical degradation. There was also no alteration in the percentage crystallinity of oil treated samples after ageing, though the radiopacity of the Lipiodol treated samples reduced by 54% after ageing. The leaching of oil with time was also investigated; the leaching of Lipiodol and Vitamin E followed the same trend and reached a steady state by two weeks. Overall, it can be concluded that the diffusion of an oil-based fluid into polyethylene not only increases the oxidative and chemical stability of polyethylene but also adds additional functionality (e.g. radiopacity) providing a more suitable material for long–term medical applications.

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“…[1][2][3] Different parameters like particle size and shape, sintering enhancers, sintering temperature and pressure, and particle morphology have significant effect on sintering behavior of polyethylene. [4][5][6][7][8] The influence of molecular weight on the mechanical properties of sintered UHMWPE was attributed to chain diffusion at the particles interface. 9 It is known that there is an optimum pressure for compression molding of polymeric powders.…”

Section: Introductionmentioning

confidence: 99%

The unique effect of chain entanglements and particle morphology on the sintering of ultrahigh molecular weight polyethylene

Hosseinnezhad

Talebi

Rezaei

2016

Journal of Elastomers & Plastics

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Nascent ultrahigh molecular weight polyethylene (UHMWPE) is a thermoplastic material, consisting of nodular-fibrillar structure making it too much porous. At the present work, the effect of both particle morphology and chain entanglements on the sintering of UHMWPE was investigated. Neck growth for particles of three different commercial grades was determined as a function of time at isothermal sintering temperatures. A comparison between the experimental data and predictions from a theoretical model based on Maxwell constitutive equations revealed a complicated effect of particle size and morphology. It was observed that at early stages of sintering, Bellehumeur’s model was in an excellent agreement with the experimental data, while it was deviated at late stages when the neck growth ratio ( y/ a) exceeds 0.8. Unlike commercially entangled samples, melted disentangled powder particles did not flow toward each other even after a long time had elapsed. Disentangled UHMWPE pellets, sintered for 10 min near the melting temperature, showed great transparency indicating low air voids and developing the sintering process, while grain boundaries remained undeveloped for entangled pellets.

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Evolution of morphology in UHMWPE following accelerated aging: The effect of heating rates

Cited by 4 publications

References 0 publications

Comparative micro‐Raman study on standard, cross‐linked and vitamin E‐blended polyethylene acetabular cups after long‐term in vitro testing and ageing

Comparative micro‐Raman study on standard, cross‐linked and vitamin E‐blended polyethylene acetabular cups after long‐term in vitro testing and ageing

Chemical stability of oil-infused polyethylene

The unique effect of chain entanglements and particle morphology on the sintering of ultrahigh molecular weight polyethylene

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