Free Radicals in Polyolefins Initiated with Ultraviolet and Ionizing Radiation

Rånby, Bengt; Carstensen, P.

doi:10.1021/ba-1967-0066.ch018

Cited by 22 publications

(12 citation statements)

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“…2, No. 5,1971 light without any filters. The light of a wavelength longer than 280 mµ could cause a similar change as shown in Figure 15 but only to a small extent.…”

Section: Spectrum Change On Warmingmentioning

confidence: 99%

“…2, No. 5,1971 the energy absorbed by carbonyl groups as follows (a) a transfer of energy from the doubly excited carbonyl groups, causing ionization in the chain or the breakage of the C-H bond in a neighbouring methylene group, (b) hydrogen atom abstraction from a methylene group by an adjacent excited carbonyl group. They concluded that the latter mechanism was the more likely.…”

Section: Absorption Of Energy Of Lightmentioning

confidence: 99%

“…Formation of carbon monoxide was reported after UV-irradiation of polyethylene. 23 · 24 Therefore the Norrish-type I reaction of carbonyl groups seems to be a primary reaction for radical formation when polyethylene is irradiated with UV-light at -196°C, although the Norrish-type II reaction is also important for polymer degradation.2 5 The observation of acyl radicals, as will be described later, shows validity of this mechanism, and according to the Norrish-type I reaction, ESR spectra observed after UV-irradiation can be explained reasonably as described in the next section.…”

Section: H · +-Ch2-ch2-ch2-----+-ch2-ch-ch2-+h2 ( 4)mentioning

confidence: 99%

“…Ranby,et al,3 claimed the existence of a fiveline spectrum due to the free radicals -CH2CH2 · but this interpretation is not conclusive. 5 Recently we pointed out that two more lines were observed on both sides of the six-line spectrum 6 and the presence of the free radicals of the type -CH2-C-CH2-was proposed. However as I CH3 described in the results section, the ESR spectrum observed at -l 96°C can be thought to be composed of two six-line spectra with separations of about 30 and 22 gauss, and the total widths of the two spectra are about 155 and 110 gauss, respectively.…”

Section: Identification Of Free Radicalsmentioning

confidence: 99%

“…2, No. 5,1971 to a larger extent. In order to mm1m1ze this thermal effect by irradiation, most experiments were carried out by using nitrogen-filled samples and applying the UV-D25 filter.…”

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confidence: 96%

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Electron Spin Resonance Study of Polyethylene Irradiated with Ultraviolet Light

Tsuji

Seiki

1971

Polym J

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ESR Spectrum of polyethylene irradiated with ultraviolet light at -196°C was composed of a superposition of two six line spectra, whose total widths were about 155 and _110 gauss, respectively. Free radicals responsible for these two spectra are -CH2-CH-CH2-and -CH2-CH2·. The latter radicals were very reactive and abstracted hydrogen atoms from other parts of polymers to produce former radicals. During the warm-up process, a sharp single! spectrum appeared at about -125°C, which was C=O

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“…2, No. 5,1971 light without any filters. The light of a wavelength longer than 280 mµ could cause a similar change as shown in Figure 15 but only to a small extent.…”

Section: Spectrum Change On Warmingmentioning

confidence: 99%

Section: Absorption Of Energy Of Lightmentioning

confidence: 99%

Section: H · +-Ch2-ch2-ch2-----+-ch2-ch-ch2-+h2 ( 4)mentioning

confidence: 99%

Section: Identification Of Free Radicalsmentioning

confidence: 99%

mentioning

confidence: 96%

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Electron Spin Resonance Study of Polyethylene Irradiated with Ultraviolet Light

Tsuji

Seiki

1971

Polym J

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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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Radiation Chemistry of Polymers

Hill

Whittaker

2016

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 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 main reaction pathways. 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 radiolysisin vacuo, the effect of the presence of dissolved oxygen on the reaction pathways is also briefly addressed.

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Free Radicals in Polyolefins Initiated with Ultraviolet and Ionizing Radiation

Cited by 22 publications

References 0 publications

Electron Spin Resonance Study of Polyethylene Irradiated with Ultraviolet Light

Electron Spin Resonance Study of Polyethylene Irradiated with Ultraviolet Light

Radiation Chemistry of Polymers

Radiation Chemistry of Polymers

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