Electronic Theses and Dissertations

Identifier

3749

Date

2016

Document Type

Thesis

Degree Name

Master of Science

Major

Physics

Concentration

Materials Science

Committee Chair

M. Shah Jahan

Committee Member

Firouzeh Sabri

Committee Member

Xiao Shen

Abstract

In this research, free radical analyses were performed using electron spin resonance (ESR) technique for two groups of orthopedic ultra-high molecular weight polyethylene (UHMWPE). In the first group, Group A, two UHMWPE resins, GUR 4150 and Hylamer (Himont 1900) were investigated. These materials were provided by the Medical-Device Industry members of the NSF-Industry/University Center for Biosurfaces (IUCB), a partnership program between the State University of New York at Buffalo (SUNY Buffalo) and the University of Memphis (1997-2011). The present study is a part of the ongoing research project which was undertaken in 1998. The long-term effects of temperature (23°C, 37°C and 75°C) upon free radicals in inert environments and in the presence of oxygen (open air) were investigated. ESR spectra recorded in the present study (t = 18 years) indicate the presence of oxygen-induced polyenyle radicals in all samples aged at 23°C or 37°C in open air, with a greater concentration at 23°C. At 75°C in open air, there were no detectable radicals. While the total concentration of radicals in all samples decreased by two orders of magnitude in 18 years, the present data showed that, at 23°C, it decreased less in Hylamer than in GUR 4150, by a factor 2/3. In inert environments, both GUR 4150 and Hylamer showed similar concentration (slightly higher concentration at 23°C than at 37°C). Compared to GUR 4150, Hylamer showed the presence of 0.6, 0.9, 1.0, 1.1 and 1.3 times more radicals at 23°C (air), 37°C (air), 23°C (inert), 37°C (inert) and 75°C (inert), respectively. In terms of radical type (alkyl, allyl, polyenyle, dienyle and trienyle), only a minor difference was found between GUR 4150 and Hylamer. For the second group, Group B, free radical analyses were performed on vitamin E-containing UHMWPE (GUR 1020) following post-gamma (30 kGy) shelf aging for 10 years at 23°C (room temperature) in open air. Vitamin E (α-tocopherol) was consolidated with GUR 1020 at a concentration level varying between 0% (no vitamin E) and 20% in 2006. The ESR measurements conducted immediately after gamma irradiation in 2006 showed a decrease in free radical concentration by an order of magnitude due to vitamin E. In 10 years (2016), the radical concentration was reduced by another order of magnitude; i. e. from ~1017 to ~1015 radicals per gram in all samples, with or without vitamin E. No measurable difference between radical concentrations was found as a function of vitamin E.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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