First electron spin resonance identification of a nitrogen peroxy radical as intermediate in the photooxidation of 2,2,6,6-tetramethylpiperidine derivatives

Faucitano, A.; Buttafava, A.; Martinotti, F.; Bortolus, Pietro

doi:10.1021/j150650a034

Cited by 38 publications

(12 citation statements)

References 2 publications

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“…It seemed interesting to us to clarify the nitroxyl formation from the initial amine. The three-step mechanism proposed by Faucitano et al [27] was chosen, but this mechanism cannot explain the UV analysis results. As a matter of fact, if TMQ-NH disappears only by reaction with POO radicals, its rate of disappearance must be given by:…”

Section: Methodsmentioning

confidence: 99%

Polyethylene stabilization against thermal oxidation by a trimethylquinoleine oligomer

Richaud

Colin

Monchy-Leroy³

et al. 2009

Polymer Degradation and Stability

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Section: Methodsmentioning

confidence: 99%

Polyethylene stabilization against thermal oxidation by a trimethylquinoleine oligomer

Richaud

Colin

Monchy-Leroy³

et al. 2009

Polymer Degradation and Stability

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“…In the case of amine stabilizers such as Chimassorb 2020, the "active" forms of stabilizers (nitroxy and alkoxyl amine) are generated from >NeH groups. Despite some controversies, it seems that the following mechanism based on the Faucitano's work [34,35] can be employed [36]:…”

Section: Kinetic Modeling and Strategy For Estimating Rate Constantsmentioning

confidence: 99%

Thermal oxidation of poly(dicyclopentadiene) - Effect of phenolic and hindered amine stabilizers

Huang

Gac

Richaud

2021

Polymer Degradation and Stability

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The thermal oxidation of stabilized polydicyclopentadiene was deeply studied here for the first time. Three kinds of antioxidants (phenolic antioxidant BHT, monomeric hindered amine in alkoxylated form Tinuvin 123 and oligomeric hindered amine Chimassorb 2020) were compared at the same concentrations. Tinuvin 123 was observed to me more efficient than Chimassorb 2020 because of the "activated" nature of alkoxyamine in Tinuvin 123. Results were simulated using a completed version of previously established kinetic model for thin PDCPD films in order to be able to make reliable lifetime prediction of stabilized PDCDP.

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“…The active species is a free radical, namely, the nitroxy radical (.NO ), which can be directly incorporated into the polymer matrix during the processing operation or be formed by oxidation of hindered amine (.NH) in the early periods of exposure. 40,41 There is a relative consensus on the fact that .NO radicals are unable to initiate new oxidation reactions, but efficiently scavenge P radicals in order to form an alkoxy amine (.NOP). 42,43 In addition, .NO radicals would be regenerated according to a two-step reaction: .NOP would decompose into hydroxyl amine (.NOH) that would then react with PO 2 radicals to give a .NO radical and a POOH.…”

Section: Theoretical Chemical Levelmentioning

confidence: 99%

Chemo-Mechanical Model for Predicting the Lifetime of Epdm Rubbers

Colin

Hassine²,

Nait-Abelaziz

2019

Rubber Chemistry and Technology

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A chemo-mechanical model has been developed for predicting the long-term mechanical behavior of EPDM rubbers in a harsh thermal oxidative environment. Schematically, this model is composed of two complementary levels: The “chemical level” calculates the degradation kinetics of the macromolecular network that is introduced into the “mechanical level” to deduce the corresponding mechanical behavior in tension. The “chemical level” is derived from a realistic mechanistic scheme composed of 19 elementary reactions describing the thermal oxidation of EPDM chains, their stabilization against oxidation by commercial antioxidants but also by sulfide bridges, and the maturation and reversion of the macromolecular network. The different rate constants and chemical yields have been determined from a heavy thermal aging campaign in air between 70 and 170 °C on four distinct EPDM formulations: additive free gum, unstabilized and stabilized sulfur vulcanized gum, and industrial material. This “chemical level” has been used as an inverse resolution method for simulating accurately the consequences of thermal aging at the molecular (concentration changes in antioxidants, carbonyl products, double bonds, and sulfide bridges), macromolecular (concentration changes in chain scissions and cross-link nodes), and macroscopic scales (weight changes). Finally, it gives access to the concentration changes in elastically active chains from which are deduced the corresponding changes in average molar mass MC between two consecutive cross-link nodes. The “mechanical level” is derived from a modified version of the statistical theory of rubber elasticity, called the phantom network theory. It relates the elastic and fracture properties to MC if considering the macromolecular network perfect, and gives access to the lifetime of the EPDM rubber based on a relevant structural or mechanical end-of-life criterion. A few examples of simulations are given to demonstrate the reliability of the chemo-mechanical model.

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First electron spin resonance identification of a nitrogen peroxy radical as intermediate in the photooxidation of 2,2,6,6-tetramethylpiperidine derivatives

Cited by 38 publications

References 2 publications

Polyethylene stabilization against thermal oxidation by a trimethylquinoleine oligomer

Polyethylene stabilization against thermal oxidation by a trimethylquinoleine oligomer

Thermal oxidation of poly(dicyclopentadiene) - Effect of phenolic and hindered amine stabilizers

Chemo-Mechanical Model for Predicting the Lifetime of Epdm Rubbers

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