The oxidation mechanism of polypropylene: contribution of 13C-NMR spectroscopy

Vaillant, Daniel; Lacoste, J.; Dauphin, G.

doi:10.1016/0141-3910(94)90205-4

Cited by 50 publications

(62 citation statements)

References 12 publications

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“…Likewise, a resonance in the range 83-85 ppm was observed in high-temperature, solution-state 13 C NMR analyses of aged polyethylene 8 and polypropylene, 12 and these workers also identified the peak with hydroperoxide groups.…”

Section: Resultsmentioning

confidence: 91%

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: 91%

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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“…The oxidative degradation of PP has been reported to proceed by a free radical chain reactive mechanism to form a carbonyl group (CO) via a reaction involving hydroperoxide group (ROOH) formation 1–9. Therefore, IR spectrometry is a powerful tool for studying the oxidative degradation mechanism of PP.…”

Section: Resultsmentioning

confidence: 99%

“…Isotactic polypropylene (iPP) has been widely applied for commercial products in the form of fibers and films. However, iPP, which has tertiary carbon atoms, is known to be very vulnerable to oxidative degradation under the influence of elevated temperature and sunlight 1–8. The degradation chemistry of iPP has been very extensively studied and has long been recognized as a free radical chain reaction,9 which leads to polymer chain to scission.…”

Section: Introductionmentioning

confidence: 99%

Improvement of the photostability of isotactic polypropylene by the incorporation of ethylene

Alam

Nakatani

Goss

et al. 2002

J of Applied Polymer Sci

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ABSTRACT:The effect of the incorporation of ethylene on the photostability of isotactic poly(propylene) (iPP) was studied with the aim of improving the photostability. iPP was prepared with a random ethylene sequence (ethylenepropylene random copolymer, rPP), and the photooxidative degradation behavior was compared with that of homogeneous iPP. Both samples were thermally post-treated under vacuum to ensure the same crystallinity. The degradation behavior was studied by infrared spectroscopy (IR), gel permeation chromatography (GPC), and temperature rising elution fractionation (TREF) measurements. The rates of hydroperoxide and carbonyl formation in the irradiated iPP increased with irradiation time for Ͼ 192 h, whereas those in the irradiated rPP are almost constant after 96 h. The change in molecular weight with the irradiation time showed similar behavior, suggesting that the degradation reaction in the irradiated rPP was suppressed after 96 h. The degradation behavior of rPP was thought to be due to the dissociation of the methyl group, which leads to the termination of degradation.

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“…Its further application, however, has been considerably restricted due to the poor weatherability of PP material which is vulnerable to the effect of sunlight and thermal oxidation and consequently easy to degrade. Therefore, many studies have been conducted to investigate the degradation of PP material in natural and artificial accelerated weathering conditions [1][2][3][4][5][6][7][8]. Natural weathering can give the most practical and faithful data regarding the variation of the properties of the material used in a given natural environment.…”

Section: Introductionmentioning

confidence: 99%

Microstructure studies of isotactic polypropylene under natural weathering by positron annihilation lifetime spectroscopy

Zhu

Liao

et al. 2015

J Polym Res

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The microstructure evolution of isotactic polypropylene (PP) exposed to subtropical humid climate of Guangzhou of China, were investigated by gel permeation chromatography, Fourier transform infrared spectroscopy, differential scanning calorimeter, dynamic mechanical analysis and positron annihilation lifetime spectroscopy. Positron data showed that the free volume of PP matrix decreased with involving a shrinking of the free volume hole sizes as the extent of weathering degradation of PP aggravated. The shrinkage of free volume hole sizes may be traced to the loss of mobility of molecules of PP matrix. The increase of the glass transition temperature substantiated undoubtedly the decrease of molecular mobility of PP chains. The increase in crystallinity might increase the amount of rigid amorphous fraction of PP matrix, which induced the loss of molecular mobility. Furthermore, the decrease of orthopositronium formation ought to be correlated to the increase in crystallinity and the increasing amount of scavenchers which were in this work represented by the carbonyl groups.

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The oxidation mechanism of polypropylene: contribution of 13C-NMR spectroscopy

Cited by 50 publications

References 12 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

Improvement of the photostability of isotactic polypropylene by the incorporation of ethylene

Microstructure studies of isotactic polypropylene under natural weathering by positron annihilation lifetime spectroscopy

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The oxidation mechanism of polypropylene: contribution of 13C-NMR spectroscopy

Cited by 50 publications

References 12 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

Improvement of the photostability of isotactic polypropylene by the incorporation of ethylene

Microstructure studies of isotactic polypropylene under natural weathering by positron annihilation lifetime spectroscopy

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Product

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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