Kinetic studies in the chemistry of rubber and related materials. III. Thermochemistry and mechanisms of olefin oxidation

Bolland, J. L.; Gee, Geoffrey

doi:10.1039/tf9464200244

Cited by 156 publications

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“…I t has been fairly generally assumed that in the temperature range in which pyrolyses in static systems normally occur the ally1 radical has sufficient resonance stabilization to render it incapable of propagating reaction chains (7, p. 126). The resonance stabilization energy has been esti~iiated by Coulson (8) to be 15.4 kcal/mole and by Bolland and Gee (9) to be 18.7 kcal/mole. Semenov (10) ascribes to the allyl radical a reactivity less than that of benzyl ancl a delocalization energy of 23 Itcal/mole.…”

Section: Introductionmentioning

confidence: 98%

Reactions of Allyl Radicals With Olefins

Bryce¹,

Ruzicka²

1960

Can. J. Chem.

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A study has been made of the ~nechanisms of the reactions of allyl radicals, produced thermally from diallyl, with various hydrocarbons in the temperature range 460-506' C. The allyl radical is capable of abstracting hydrogen from certain hydrocarbons and of adding to olelinic double bonds a t these temperatures. The rates of formation of the principal products in the reactions between allyl and I-butene, propylene, and ethylene are linearly related to the square root of the diallyl concentration. Mechanisms are proposed t o account for the reaction products formed. I n addition t o reacting readily with olehns the allyl radical is observed to sensitize the decomposition of n-butane a t 506' C. The implications of the present results with respect to inhibition in pyrolysis of hydrocarbons are discussed briefly. INTRODUCTIONThe information available in the literature on the reactivity of the allyl radical has been reviewed briefly in an earlier paper (1). The formation of ally1 has been proposed as the primary step in the pyrolysis of diallyl ( I ) , propylene (2), allyl bromide (3, 4), isobutene (5), and 1-butene (6). The action of propylene as an inhibitor for certain organic deco~iipositions has been commonly ascribed to the for~iiation of allyl by hydrogen abstraction from the propylene by active radicals like ~ilethyl and ethyl. I t has been fairly generally assumed that in the temperature range in which pyrolyses in static systems normally occur the ally1 radical has sufficient resonance stabilization to render it incapable of propagating reaction chains (7, p. 126). The resonance stabilization energy has been esti~iiated by Coulson (8) to be 15.4 kcal/mole and by Bolland and Gee (9) to be 18.7 kcal/mole. Semenov (10) ascribes to the allyl radical a reactivity less than that of benzyl ancl a delocalization energy of 23 Itcal/mole.The formation of ally1 has been observed directly in the pyrolysis of ally1 iodide and of cliallyl using a mass spectrometer with a flow system a t temperatures between 690 and 890" C (11). The mechanism of decomposition of this latter compound in a static system a t temperatures between 460 and 520" C can best be understoocl ( I ) on the assumption that the primarl-step involves a split into two allyl radicals which call subsequently abstract hydrogen to form propylene or add to olefinic double bonds to for111 the cyclic unsaturated products \vliicll are formed in substantial amounts. The co~iclusio~i that ally1 abstracts hydrogen readily under these conditions is in agree~iient \vith recent results of I\ilcKesby arid Gordon (12).The prcsent study mas undertalcen to demonstrate more clearly the nature of all31 reactivity and to gain further insight into the mechanism of its reaction with unsaturated hydrccarbons. Reactions with 1-butene were of particular interest because of WOI-I; done previously in this laboratory on the pyrolysis of this compound (G), the results of which provided strong evidence for reactions between it and the allyl radical. EXPERIRIIENTALThe substan...

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Section: Introductionmentioning

confidence: 98%

Reactions of Allyl Radicals With Olefins

Bryce¹,

Ruzicka²

1960

Can. J. Chem.

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“…Le schéma standard d'oxydation des polymères hydrocarbonés, développé par Bolland et Gee [16] aété adapté pour décrire le vieillissement thermique de la matrice PEEK. Sa version finale est résumée ci-dessous : -Amorçage :…”

Section: Proposition De Schéma Mécanistiqueunclassified

Proposition d’un modèle cinétique pour la dégradation thermique de la matrice PEEK

Courvoisier

Bicaba

Colin

2016

Matériaux & Techniques

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Mots clés : PEEK / vieillissement thermique / oxydation / réticulation / modèle cinétiqueAbstract -Proposal of a kinetic model for the thermal degradation of PEEK matrix. The thermal degradation of poly(ether ether ketone) (PEEK) has been studied in air at solid (rubbery) state typically from 523 to 593 K, i.e. in a never explored temperature interval. The modifications of the PEEK structure have been monitored at both molecular and macromolecular scales with two complementary analytical techniques. IR spectrophotometry in a transmission mode has allowed detecting four degradation products: phenols, benzoic acid, phenyl benzoate and fluorenone. Calorimetric analysis has clearly put in evidence that crosslinking is largely predominant over chain scissions. An oxidation mechanistic scheme of the PEEK matrix has been proposed on this basis of results, but also on the basis of all the experimental results reported in the literature at molten state. A kinetic model has been derived from this scheme and its validity has been successfully checked from the changes in the concentrations of degradation products and the glass transition temperature in air at 523 K. The corresponding values of the model parameters have been discussed.

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“…Bolland & Gee (1946) have tried to understand the phenomenon by studying the thermal-oxidation of polyolefin and rubbers. The mechanism they have developed could be applied successfully to a large number of polymers such as a polymer matrix of composite materials.…”

Section: Chemical Processesmentioning

confidence: 99%