Electronic Theses and Dissertations

Identifier

943

Date

2013

Document Type

Thesis

Degree Name

Master of Science

Major

Physics

Concentration

Materials Science

Committee Chair

Muhammad Shah Jahan

Committee Member

John Hanneken

Committee Member

Firouzeh Sabri

Abstract

PEEK (polyether ether ketone) is a biocompatible, semicrystalline thermoplastic that is mechanically strong and thermally stable; it is also generally considered to be radiation resistant. Interactions of PEEK with radiation, such as X-ray and UV, may bring chemical changes such as from the simultaneous occurrence of crosslinking and chain scission, which may also impact on the macroscopic properties of material. Past research work on PEEK is concentrated mostly on the study of the effect of energetic radiations like gamma-irradiation and electron beam radiation. In a recent study, Awaja et al. detected free radicals in plasma-treated PEEK at room temperature. The lifetimes of the radicals were found to be approximately 24 hours. In another study, Li et al. observed radiation-induced radicals at liquid nitrogen (77 K), and at room temperature, for UV-, gamma- and e-beam-irradiated PEEK; the gamma- and e-beam-induced radicals decayed in less than 20 minutes at room temperature, and the UV-induced radicals decayed in about 24 hours. While no structural information about the radicals was provided, these authors suggested that the residual radicals (present in as-received PEEK before irradiation) and the UV-induced radicals were similar or identical. Awaja et al., however, noted that the residual radicals could be produced during the manufacturing process. In this research work, we have used electron spin resonance to find the effects of UV- and X-irradiation on four types of PEEK. UV-and X-radiation appear to produce the same type of induced free radicals, which are observable for longer times than previously reported. In essence, we have found that radiation-induced radical formation may be more significant than previously thought for PEEK materials. Additional work is needed to further characterize the radiation-induced free radicals and their long- term consequences.

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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