Synthesis, characterization and ESR study of the γ-radiolysis of aromatic polyesters containing isomeric naphthalene links

Hill, David J. T.; Choi, Bong-Ku; Ahn, Hung-Kun; Choi, E‐Joon

doi:10.1002/(sici)1097-0126(199910)48:10<956::aid-pi254>3.0.co;2-n

Cited by 7 publications

(3 citation statements)

References 9 publications

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“…When the microwave power was increased, we discovered that a weak shoulder beside the single peak was slowly appearing, which is called R 2 . The microwave power saturation method was used to confirm and differentiate the two kinds of free radical 21, 22. The saturated characteristic curves of the microwave power of R 1 and R 2 are presented in Fig 4.…”

Section: Resultsmentioning

confidence: 99%

“…The microwave power saturation method was used to confirm and differentiate the two kinds of free radical. 21,22 The saturated characteristic curves of the microwave power of R 1 and R 2 are presented in Fig 4. The curve of R 1 indicates that it is easily saturated by the microwave power, and that the power saturation occurs at power levels greater than 6.4 mW. R 2 is observed clearly as the microwave power increases to 64 mW; in addition, R 2 does not easily saturate to microwave power.…”

Section: Electron Spin Resonancementioning

confidence: 99%

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Thermal crosslinking behavior of poly (aryl ether ketone) copolymers containing naphthalene moieties

Niu

Wang

Zhang

et al. 2004

Polymer International

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A series of poly[(ether ether ketone)‐co‐(ether naphthalene ether ketone)] (P(EEK‐co‐ENEK)) copolymers were heated under a variety of conditions. The thermal crosslinking behavior was monitored by differential scanning calorimetry (DSC), electron spin resonance (ESR) and wide‐angle X‐ray diffraction (WAXD). The results indicate that under a non‐oxidative environment such as nitrogen P(EEK‐co‐ENEK) is more stable, while under oxidative conditions a crosslinking reaction takes place that causes a reduction in the crystallizability of the copolymers, and an increase in the concentration of free radicals on the copolymer. ESR results suggest that the crosslinking reaction proceeds via free radicals. Subsequently two kinds of free radicals were characterized: one is an RO• type free radical and the other is a naphthalene ring free radical. Copyright © 2004 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 99%

Section: Electron Spin Resonancementioning

confidence: 99%

Thermal crosslinking behavior of poly (aryl ether ketone) copolymers containing naphthalene moieties

Niu

Wang

Zhang

et al. 2004

Polymer International

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“…Polymers superior to polyimides are eagerly desired with respect to resistance to degradation by high‐energy radiation. The radiation chemistry of fluorine‐containing aromatic polymers has been investigated, including polyimides,25–29 poly(phosphine oxide)s,30 and polyesters 31–34. However, all these polymers contain fluorine atoms as a form of trifluoromethyl pendant or 1,1,1,3,3,3‐hexafluoroisopropylidene group.…”

Section: Introductionmentioning

confidence: 99%

Influence of electron beam irradiation on properties of fluorine‐containing poly(aryl ether ketone)s

Kimura

Tabuchi

Nishichi

et al. 2003

J of Applied Polymer Sci

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ABSTRACT:The influence of electron beam irradiation on the properties of fluorine-containing poly(aryl ether ketone)s (F-PEK), derived from 2,3,4,5,6-pentafluorobenzoic acid, was examined. Irradiation was performed with an electron beam at a dose of 3.63 ϫ 10 3 Gy s Ϫ1 for which the corresponding doses were 29.0, 51.0, and 94.5 MGy. Tensile strength at break increased up to a dose of 29.0 MGy and then decreased very slightly with irradiation. Elongation at break was more susceptible to irradiation and decreased drastically to one tenth at a dose of 29.0 MGy. Young's modulus was enhanced by the irradiation. F-PEKs were changed from elastic materials to strong and brittle materials by irradiation. Relaxation of the viscoelastic property shifted toward higher temperature by irradiation. These tensile and viscoelastic property changes were attributed to the formation of a bulkier and more rigid structure by crosslinking. The fluorine atoms attached to the 1,4-phenylene moiety in F-PEKs were surprisingly susceptible to the irradiation and were completely lost at a dose of 29.0 MGy. The -electron conjugated aromatic structure was concurrently developed during irradiation. Further, polar functional groups such as carboxyl group and ester group were generated by chain scission and rearrangement. The F-PEKs retained their good transparency and the thermal stability was significantly improved after irradiation.

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Radiation Chemistry of Polymers

Hill

Whittaker

2004

Encyclopedia of Polymer Science and Technology

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Polymeric materials are exposed to high energy radiation either deliberately to alter their properties or inadvertently during their use in high dose environments. As a consequence, an understanding of how radiation modifies the polymer structure, and hence properties, is essential for many applications. In addition, the understanding of the degradation of polymers with light or heat can benefit from knowledge of the reaction pathways of radical and charged species formed on irradiation with high energy photons. This article aims to provide a broad overview of the fundamental processes occurring during radiolysis of polymers. This is achieved through a discussion of the interaction of high energy photons with matter, and the subsequent reactions of mainly radical intermediates. Polymers either cross‐link or degrade on exposure to radiation, and the final properties of the polymers depend critically on the balance of these two main reaction pathways. A number of examples are taken from the literature to illustrate how the tendency to undergo cross‐linking or main‐chain scission depends on the polymer structure. The overall yield of reactions can be greatly reduced by the introduction of aromatic groups into the polymer structure. On the other hand, yields can be increased by the inclusion of radiation‐sensitive groups such as sulfones. Similarly, the rates of reactions and the balance between cross‐linking and scission can depend sensitively on the radiolysis temperature. While this review focuses on a discussion of the reactions occurring on radiolysis in vacuo, the effect of the presence of dissolved oxygen on the reaction pathways is also discussed.

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Synthesis, characterization and ESR study of the γ-radiolysis of aromatic polyesters containing isomeric naphthalene links

Cited by 7 publications

References 9 publications

Thermal crosslinking behavior of poly (aryl ether ketone) copolymers containing naphthalene moieties

Thermal crosslinking behavior of poly (aryl ether ketone) copolymers containing naphthalene moieties

Influence of electron beam irradiation on properties of fluorine‐containing poly(aryl ether ketone)s

Radiation Chemistry of Polymers

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