Mechanism of Protection against Ozone by N-Phenyl-N′-Isopropyl-p-Phenylenediamine

Разумовский, С. Д.

doi:10.5254/1.3547334

Cited by 16 publications

(22 citation statements)

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“…This pathway explains the degradation of rubber upon exposure to ozone. 34,35,42 Despite this consensus, two distinct proposals for the mechanism of primary ozonide formation have gained popularity: A concerted addition across the double bond (Criegee mechanism) 43 and a stepwise addition, where ozone reacts with an olefin to form a biradical intermediate which may subsequently collapse to the ozonide (DeMore mechanism). 44 Consensus increasingly indicates that the Criegee mechanism prevails in simple (i.e.…”

Section: Ozonation Mechanismsmentioning

confidence: 99%

“…[21][22][23][24][25][26][27][28][29][30][31] The O 3 chemistry of PPDs and the development of safer antiozonants are more elusive. Broadly speaking, it is believed that 6PPD protects tires in two distinct but overlapping ways: 32 (1) kinetic scavenging that consumes O 3 before it is able to react with the tire 3,33,34 and (2) subsequent formation of a protective film that prevents ozone permeation past the surface of the tire. 33,35,36 Not observed in all PPDs, 34 these protective films are likely comprised of PPD reaction products, [35][36][37] although details are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

“…Broadly speaking, it is believed that 6PPD protects tires in two distinct but overlapping ways: 32 (1) kinetic scavenging that consumes O 3 before it is able to react with the tire 3,33,34 and (2) subsequent formation of a protective film that prevents ozone permeation past the surface of the tire. 33,35,36 Not observed in all PPDs, 34 these protective films are likely comprised of PPD reaction products, [35][36][37] although details are poorly understood. Furthermore, an early and significant body of research into the ozone chemistry of PPDs failed to identify quinone byproducts, indicating that this work is incorrect or (at best) incomplete.…”

Section: Introductionmentioning

confidence: 99%

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Computational studies of rubber ozonation explain the effectiveness of 6PPD as an antidegradant and the mechanism of its quinone formation

Rossomme

Hart‐Cooper

Orts

et al. 2022

Preprint

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The discovery that the commercial rubber antidegradant 6PPD reacts with ozone (\ce{O3}) to produce a highly toxic quinone (6PPDQ) spurred a significant research effort into non-toxic alternatives. Identification of non-toxic alternatives has been hampered by lack of a detailed understanding of the mechanism of protection that 6PPD affords rubber compounds against ozone. Herein, we report high-level density functional theory studies into early steps of rubber and PPD ($p$-phenylenediamine) ozonation, identifying key steps that contribute to the antiozonant activity of PPDs. In this, we establish that our density functional theory approach can achieve chemical accuracy for many ozonation reactions, which are notoriously difficult to model. Using adiabatic energy decomposition analysis, we examine and dispel the notion that one-electron charge transfer initiates ozonation in these systems, as is sometimes argued. Instead, we find direct interaction between \ce{O3} and PPD carbon atoms is kinetically accessible, and that this motif is more significant than interactions with PPD nitrogens. The former pathway results in a hydroxylated PPD intermediate, which reacts further with \ce{O3} to afford 6PPD hydroquinone and, ultimately, 6PPDQ. This mechanism directly links the toxicity of 6PPDQ to the antiozonant function of 6PPD. These results have significant implications for development of alternative antiozonants, which are discussed.

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Section: Ozonation Mechanismsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Computational studies of rubber ozonation explain the effectiveness of 6PPD as an antidegradant and the mechanism of its quinone formation

Rossomme

Hart‐Cooper

Orts

et al. 2022

Preprint

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“…Andrews and Braden [16] assumed that when rubber containing PPD is exposed to the action of ozone, a less fl exible layer of ozonised PPD which is inert to any further ozone attack forms. The experimental results given above all indicate that the protective action of anti-ozonants is exerted by a trapping [17] or protective layer [8]. This means that a sequence of events such as the following can be postulated:…”

Section: Migration Of Antioxidantsmentioning

confidence: 99%

Migration of Additives in Rubber

Anthoine

Ignatz‐Hoover

2005

International Polymer Science and Technology

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The migration of compounding ingredients in rubber compounds before, during and after vulcanisation is recognised as an important factor in the overall properties and performance of rubber articles containing a number of layers, such as, for example, tyres or hoses. In certain cases, the migration of compounding ingredients can be benefi cial since the effect of waxes and paraphenylenediamines as anti-ozonants are largely determined by the migration mechanism if they are to provide optimum protection against degradation by ozone for rubber products in service. In addition, the dispersion of compounding ingredients such as oil, curing agents and antioxidants in rubber can be enhanced by diffusion. In other cases, however, diffusion at the interface between two rubber materials can be detrimental to performance by causing a change in the distribution of the individual materials which may result in a change in mechanical properties, a loss of adhesion or the action of antioxidants; the discolouration of lightcoloured products is another familiar example. This paper describes the fate of various chemical additives in uncured and cured rubber. It also provides an overview of earlier works and more recent information on the migration of compounding ingredients. Better understanding of this important compounding phenomenon could enable us to identify the optimum distribution of ingredients.

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“…2,3 The reaction of ozone with olefinic compounds is very rapid. 4 Substituents on the double bond that donate electrons increase the rate of reaction while electron-withdrawing substituents slow down the reaction. Thus, the rate of reaction with ozone decreases in the following order: polyisoprene Ͼ polybutadiene Ͼ polychloroprene.…”

Section: Introductionmentioning

confidence: 99%

Ozonolysis of model olefins—Efficiency of antiozonants

Huntink

Datta

Talma

et al. 2006

J of Applied Polymer Sci

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ABSTRACT:In this study, the efficiency of several potential long lasting antiozonants was studied by ozonolysis of model olefins. 2-Methyl-2-pentene was selected as a model for natural rubber (NR) and 5-phenyl-2-hexene as a model for styrene butadiene rubber (SBR). A comparison was made between the efficiency of conventional antiozonants like N-(1,3 dimethylbutyl)-NЈ-phenyl-p-phenylene diamine (6PPD), N-isopropyl-NЈ-phenyl-p-phenylene diamine (IPPD), and a mixture of diaryl p-phenylene diamines (Wingstay 100) and some newly synthesized antiozonants. The stearic acid salt of 6PPD (PPD-C18), 2,4,6-tris(4-(phenylamino)phenyl)-1,3-5-triazinane (ADPAT), and 4-pyrole diphenylamine (PDPA) showed a higher efficiency than the conventional antiozonants in both NR as well as SBR model system. Special attention was paid to the carboxylic acid salts of 6PPD such as PPD-C18, which has shown good long-term protection of passenger tire sidewall compounds. It was demonstrated that by varying the chain length, C7, C18, and C22, of the carboxylic acid part of the 6PPD salts, the ozone protection was not influenced under the selected test conditions. The 6PPD salts made from strong acids like succinic acid (SA) and methyl sulfonic acid (MSA) appeared to be less efficient than PPD-C18. It was also investigated whether the reactions between ozone and the double bonds of the model rubber could be measured online by a spectroscopic technique. It was demonstrated that near infrared spectroscopy is a suitable technique to study these reactions. FT Raman looked also a promising technique because of the high response factor of double bonds. However, the addition of p-phenylene diamines (PPDAs) to the sample solution resulted in a strong discoloration (dark brown) and therefore in a high fluorescence background signal. This technique can therefore not be used for the evaluation of staining antiozonants.

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Mechanism of Protection against Ozone by N-Phenyl-N′-Isopropyl-p-Phenylenediamine

Cited by 16 publications

References 0 publications

Computational studies of rubber ozonation explain the effectiveness of 6PPD as an antidegradant and the mechanism of its quinone formation

Computational studies of rubber ozonation explain the effectiveness of 6PPD as an antidegradant and the mechanism of its quinone formation

Migration of Additives in Rubber

Ozonolysis of model olefins—Efficiency of antiozonants

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