Electron spin resonance study of the reaction of aromatic hydrocarbons with oxygen

Lewis, I.C.; Singer, L. S.

doi:10.1021/j150604a011

Cited by 52 publications

(37 citation statements)

References 1 publication

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“…The residues resulting from the isothermal degradation of the PU/APP formulation show a splitting factor g around 2.0060. These high values of g strongly suggest the presence of oxygen in the free radical 29. The line shape gives information about the interaction between a spin system and its environment.…”

Section: Resultsmentioning

confidence: 90%

Mechanism of fire retardancy of polyurethanes using ammonium polyphosphate

Duquesne¹,

Bras²,

Bourbigot³

et al. 2001

J of Applied Polymer Sci

179

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ABSTRACT:In this work, we studied the mechanism of the fire retardancy of ammonium polyphosphate (APP) in polyurethane (PU). Indeed, according to the limiting oxygen index test, the efficiency of APP in PU coating was proven. On the one hand, thermogravimetric analyses showed that the addition of APP to PU accelerates the decomposition of the matrix but leads to an increase in the amount of high-temperature residue, under an oxidative or inert atmosphere. This stabilized residue acts as a protective thermal barrier during the intumescence-fire retardancy process. On the other hand, spectroscopic analysis of the charring materials using infrared spectroscopy, MAS NMR of the solid state, and ESR enables better understanding of the carbonization process and, consequently, of the intumescence phenomenon. It has been shown that the char resulting from PU consists of an aromatic carbonaceous structure which condenses and oxidizes at high temperature. In the presence of APP, a reaction between the additive and the polymer occurs, which leads to the formation of a phosphocarbonaceous polyaromatic structure. Moreover, this char is strongly paramagnetic. The presence of large radical species, such as a polyaromatic macromolecule trapping free radicals, was demonstrated. Both of these characteristics help to explain the fire-retardant performance of PU/APP.

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Section: Resultsmentioning

confidence: 90%

Mechanism of fire retardancy of polyurethanes using ammonium polyphosphate

Duquesne¹,

Bras²,

Bourbigot³

et al. 2001

J of Applied Polymer Sci

179

View full text Add to dashboard Cite

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“…This g -factor in Fig. 3B is typical of an oxygen-centered radical [39]. Further annealing of the matrix resulted in the appearance of a symmetrical singlet line with a g -factor of 2.0030, Δ H p–p = 2 G, and Δ H total -≤ 10.0 G (cf.…”

Section: Resultsmentioning

confidence: 91%

“…These organic-carbon centered radicals are defined by their hyper-fine splitting constants [38] but may also appear as a broad featureless spectrum depending on the environment [20]. Oxygen-centered radicals retain their aromatic structure while incorporating a substituent oxygen atom and exhibit g -factors in the range of 2.0029–2.0040 [39] and often appear as broad featureless spectrum. EPFRs are radical species formed on the surfaces of transition metal-containing particles by chemisorption of a molecular precursor and subsequent electron transfer from the organic to the metal [25,40].…”

Section: Resultsmentioning

confidence: 99%

Paramagnetic centers in particulate formed from the oxidative pyrolysis of 1-methylnaphthalene in the presence of Fe(III)2O3 nanoparticles

Herring¹,

Khachatryan²,

Lomnicki³

et al. 2013

Combustion and Flame

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The identity of radical species associated with particulate formed from the oxidative pyrolysis of 1-methylnaphthalene (1-MN) was investigated using low temperature matrix isolation electron paramagnetic resonance spectroscopy (LTMI-EPR), a specialized technique that provided a method of sampling and analysis of the gas-phase paramagnetic components. A superimposed EPR signal was identified to be a mixture of organic radicals (carbon and oxygen-centered) and soot. The carbon-centered radicals were identified as a mixture of the resonance-stabilized indenyl, cyclopentadienyl, and naphthalene 1-methylene radicals through the theoretical simulation of the radical’s hyperfine structure. Formation of these radical species was promoted by the addition of Fe(III)2O3 nanoparticles. Enhanced formation of resonance stabilized radicals from the addition of Fe(III)2O3 nanoparticles can account for the observed increased sooting tendency associated with Fe(III)2O3 nanoparticle addition.

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“…This was demonstrated by Siat et al 27 by an electron paramagnetic resonance study. It suggests that the beginning of the carbonization process during mixing occurs at 240°C 28,29 . So we considered this problem when processing the blend.…”

Section: Introductionmentioning

confidence: 99%

Intumescent PP Blends

Almeras

Bras

Bourbigot

et al. 2003

Polymers and Polymer Composites

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One way to improve the fire performance of polymers is by the development of intumescent systems. The addition of ammonium polyphosphate/polyamide-6 is known to provide flame retardancy in many polymers via an intumescent process. The development of appropriate formulations is limited by their mechanical properties. This study shows that polypropylene based intumescent blends are efficient fire retardant systems and that acceptable mechanical properties can be obtained. It is also shown that adding talc improves the mechanical properties of intumescent polypropylene formulations without decreasing their fire retardancy.

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Electron spin resonance study of the reaction of aromatic hydrocarbons with oxygen

Cited by 52 publications

References 1 publication

Mechanism of fire retardancy of polyurethanes using ammonium polyphosphate

Mechanism of fire retardancy of polyurethanes using ammonium polyphosphate

Paramagnetic centers in particulate formed from the oxidative pyrolysis of 1-methylnaphthalene in the presence of Fe(III)2O3 nanoparticles

Intumescent PP Blends

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