Observation by 13C n.m.r. of H-crosslinks and methyl end groups due to main-chain scission in ethylene-propylene copolymers after γ-irradiation

O’Donnell, James H.; Whittaker, Andrew K.

doi:10.1016/0032-3861(92)90560-j

Cited by 22 publications

(63 citation statements)

References 19 publications

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“…This resonance is identified with hydroperoxides and/or dialkyl peroxides (peak a in Figure 1). In their solid-state 13 C NMR analysis of γ-irradiated, 13 C enriched polyethylene films, Assink et al 10 found a similar resonance at ∼85 ppm which they attributed to secondary hydroperoxides. (c) methyl ketones; (d) esters and/or peresters; (e) carboxylic acids and/or esters; (f) in-chain ketones; (g) ketals and/or acetals.…”

Section: Resultsmentioning

confidence: 95%

“…Radiation aging was conducted at the Low Intensity Cobalt Array (LICA) facility (Albuquerque, NM), which has been previously described in detail. 23 Samples were 13 C NMR spectroscopy. Samples of the PP powder were dissolved in 1,2,4-trichlorobenzene at 130°C.…”

Section: γ-Radiation Agingmentioning

confidence: 99%

“…Resonance integrals vs recycle delay time for 13 C DP/MAS spectra of a solid C(2) labeled polypropylene sample thermally aged at 109°C for ∼1 day 13. C resonances: (b) +60 to -10 ppm (main-chain carbons); (9) 85.3 ppm (tertiary hydroperoxides and/or dialkyl peroxides); ([) 74.2 ppm (tertiary alcohols); (2) ∼207 ppm (methyl ketones); (0) 170-175 ppm (esters and/or peresters); (O) 100-110 ppm (ketals and/ or acetals).…”

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confidence: 99%

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Solid-State ¹³C NMR Investigation of the Oxidative Degradation of Selectively Labeled Polypropylene by Thermal Aging and γ-Irradiation

et al. 2005

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Unstabilized polypropylene (PP) films having selective 13 C isotopic labeling were subjected to thermal aging at 50, 80, and 109°C and to γ-irradiation at 24 and 80°C. The oxidized films were examined using solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy. Dramatic differences were found in the type and distribution of oxidation products originating from the three carbon atom sites within the PP macromolecule (tertiary carbon, secondary carbon, and methyl side group). Most of the oxidation products that formed on the polymer chain originated through chemical reactions at the PP tertiary carbons. Under all of the aging conditions examined, tertiary peroxides (from the PP tertiary site) were the most abundant functional group produced. Also originating from the PP tertiary carbon were significant amounts of tertiary alcohols, together with several more minor products that included "chain-end" methyl ketones. No significant amount of peroxides or alcohols associated with the PP secondary carbon sites was detected. A substantial yield of carboxylate groups was identified (acids, esters, etc.). The majority of these originated from the PP secondary carbon site, from which other minor products also formed, including in-chain ketones. We found no measurable yield of oxidation products originating from reaction at the PP methyl group. Remarkably similar distributions of the major oxidation products were obtained for thermal aging at different temperatures, whereas the product distributions obtained for irradiation at the different temperatures exhibited significant differences. Time-dependent concentration plots have been obtained, which show the amounts of the various oxidation products originating at the different PP sites, as a function of the extent of material oxidation.

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Section: Resultsmentioning

confidence: 95%

Section: γ-Radiation Agingmentioning

confidence: 99%

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confidence: 99%

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Solid-State ¹³C NMR Investigation of the Oxidative Degradation of Selectively Labeled Polypropylene by Thermal Aging and γ-Irradiation

et al. 2005

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“…Note that the spectra magnified around 32 ppm are shown in (b). Signal assignment based on bibliographic survey for EPR in solution, the swollen, and solid states is summarized in Table 3 [38][39][40][41][42]. Spectral peaks existing in the chemical shift range from 45 to 46 ppm are due to CH 2 in the main chain located between methyl groups of propylene units.…”

Section: Resultsmentioning

confidence: 99%

“…Table 3 shows that most of the peak positions observed were somewhat lower than the average positions reported. It is well known that peak positions differ because of the solvent and sample states [38][39][40][41][42].…”

Section: Resultsmentioning

confidence: 99%

Mechanism elucidation of degradation dynamics of ethylene propylene rubber cable insulations sampled from nuclear power containment using additional aging

Fuse

Misaka

Homma

et al. 2016

IEEE Trans. Dielect. Electr. Insul.

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Ethylene propylene rubber insulation under operation for 16 years in boiling water reactor containments was subjected to additional thermal aging at 110°C. After 70 days of aging, the mechanical property of the insulation was decreased such that the limit guaranteeing durability against design-basis events was breached. This degradation rate is three times slower than that predicted on the basis of an accelerated aging test with control samples. Infrared spectroscopic analysis revealed suppression in the formation of carbonyl products in the service-used cables. According to the gel fraction measurement, cross-linking is the dominant reaction in such service cables. The unique slow degradation dynamics observed in service cables could be attributed to such oxidation control and the cross-linking reaction. The present study also conducts nuclear magnetic resonance analysis to elucidate the cross-linking point in the main chain.

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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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Observation by 13C n.m.r. of H-crosslinks and methyl end groups due to main-chain scission in ethylene-propylene copolymers after γ-irradiation

Cited by 22 publications

References 19 publications

Solid-State ¹³C NMR Investigation of the Oxidative Degradation of Selectively Labeled Polypropylene by Thermal Aging and γ-Irradiation

Solid-State ¹³C NMR Investigation of the Oxidative Degradation of Selectively Labeled Polypropylene by Thermal Aging and γ-Irradiation

Mechanism elucidation of degradation dynamics of ethylene propylene rubber cable insulations sampled from nuclear power containment using additional aging

Radiation Chemistry of Polymers

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Observation by 13C n.m.r. of H-crosslinks and methyl end groups due to main-chain scission in ethylene-propylene copolymers after γ-irradiation

Cited by 22 publications

References 19 publications

Solid-State 13C NMR Investigation of the Oxidative Degradation of Selectively Labeled Polypropylene by Thermal Aging and γ-Irradiation

Solid-State 13C NMR Investigation of the Oxidative Degradation of Selectively Labeled Polypropylene by Thermal Aging and γ-Irradiation

Mechanism elucidation of degradation dynamics of ethylene propylene rubber cable insulations sampled from nuclear power containment using additional aging

Radiation Chemistry of Polymers

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Solid-State ¹³C NMR Investigation of the Oxidative Degradation of Selectively Labeled Polypropylene by Thermal Aging and γ-Irradiation

Solid-State ¹³C NMR Investigation of the Oxidative Degradation of Selectively Labeled Polypropylene by Thermal Aging and γ-Irradiation