Sulfur compounds as synergistic antioxidants

Chien, James C. W.; Boss, C.

doi:10.1002/pol.1972.150100602

Cited by 41 publications

(5 citation statements)

References 42 publications

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“…This mechanism is similar t o the one proposed by Chien a n d Boss (15) for the reaction of nickel dialkyldithiocarbamates with alkyl hydroperoxides. These workers did, however, propose that the hydroperoxide was the oxidizing species whereas we believe alkylperoxy radicals a r e the oxidizing species.…”

Section: Rerrction Meclianis~?lsupporting

confidence: 59%

Metal complexes as antioxidants. VI. An electron spin resonance study of the transient cupric complexes formed in the reaction of cupric dialkyldithiocarbamates with alkylperoxy radicals and alkyl hydroperoxides

Howard¹,

Tait²

1978

Can. J. Chem.

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The epr spectra of three intermediate copper(II) complexes formed by oxidation of bis[N,N-dialkyl(dithiocarbamato-S,S′)] copper(II) by alkyl hydroperoxides and alkylperoxy radicals are reported. Isotropic and anisotropic spectra of the complexes formed from alkylperoxy radicals enriched with 17O are consistent with the following structures: [Cu(S2CNR2)(OS2CNR2)] (I), [Cu(OS2CNR2)2] (II), and [Cu(OS2CNR2)(O2S2CNR2)] (III). The isotropic 17O hyperfine interaction of I is 19.2 G while the anisotropic spectrum of II indicates that the two oxygen nuclei are equivalent. The anisotropic 17O hyperfine splitting constants are consistent with a structure for these complexes in which the S—O bond(s) is directed out of the plane of the complex and not coordinated to the copper.

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Section: Rerrction Meclianis~?lsupporting

confidence: 59%

Metal complexes as antioxidants. VI. An electron spin resonance study of the transient cupric complexes formed in the reaction of cupric dialkyldithiocarbamates with alkylperoxy radicals and alkyl hydroperoxides

Howard¹,

Tait²

1978

Can. J. Chem.

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“…The catalysts are protic (RSO 2 H) or Lewis (SO 2 ) acids [56,57] The influence of the structure of the alkyl group, R, on the rate of cleavage in Reaction (4.48) has been correlated with the following order of increasing reactivity:…”

Section: Hydroperoxide Decomposersmentioning

confidence: 99%

Oxidative Degradation and Stabilisation of Mineral Oil-Based Lubricants

Aguilar

Mazzamaro

Rasberger

2009

Chemistry and Technology of Lubricants

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Thermally induced hydrocarbon oxidation is a self-accelerating autoxidation process and is divided into 'low'-, 30-120 • C, and 'high'-, >120 • C, temperature phases. The first has four stages -induction of radical chain reactions, propagation, branching and then termination. Mechanisms of these processes are described and discussed. Differences in hydrocarbon reactivity are related to molecular structure. For hydrocarbon oxidation >120 • C, the first stage is the same as low-temperature oxidation but with reduced selectivity and increased reactivity; second, the oxidation phase becomes diffusion controlled as hydrocarbon viscosities increase from progressive polycondensation of higher molecular weight products, causing varnish and sludge formation. Base oil oxidation stabilities depend upon their derivation, whether solvent neutral, hydrocracked or synthetic, and their response to antioxidant treatment. Lubricant oxidation control focuses on radical scavengers and hydroperoxide decomposers and their synergistic mixtures.Engine oils increasingly use phenolic and aminic antioxidants as radical scavengers with organometallic complex antioxidants. Sterically hindered phenols substituted at 2-and 6-positions by t-butyl groups are particularly effective, reacting successively with peroxy radicals to form stable cyclohexadieneone peroxides. Secondary amines as either two aryl or phenyl and naphthyl groups are very effective at eliminating four peroxy radicals per molecule. They are more effective by a ratio of 4:2 than the sterically hindered phenols below 120 • C. At higher temperatures a catalytic cycle is suggested as an extended stabilisation mechanism. Transition metal ions with two valence states, Fe 2+/3+ , Cu 1+/2+ , etc. as trace quantities of metal soaps catalyse/retard autoxidation according to concentration and/or combination of metals. They catalyse or inhibit oxidation by complexing and decomposing hydroperoxides or can also oxidise peroxy radicals and reduce alkyl radicals to inert products. Organomolybdenum complexes such as molybdenum dialkyldithiocarbamates, MDTC, are increasingly used to stabilise engine lubricants particularly because of synergy with other antioxidants such as alkylated diphenylamines. 107 R.M. Mortier et al. (eds.), Chemistry and Technology of Lubricants, 3rd edn.,

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“…It was revealed that the MBZ/445 complex exhibited excellent antioxidative ability for EPDM based on the results in our previous study. Thereby, the possible antioxidative mechanisms are proposed as following according to the previous reports . 445 is used as the primary antioxidants to capture the chain propagating hydroxyl/alkyl/alkoxyl/peroxy radicals before they can react with the polymer, while MBZ is used as the secondary antioxidants to decompose hydroperoxides into byproducts, alcohols and water, resulting in hindering the autocatalytic oxidation of rubber chains significantly.…”

Section: Resultsmentioning

confidence: 99%

Synergistic Effects of Amine‐Containing Antioxidants on the Aging Performances of Ethylene Propylene Diene Rubber

Li¹,

Zhou²,

Cao³

et al. 2020

ChemistrySelect

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In this study, two types of amine-containing antioxidants composed of 2-mercaptobenzimidazole zinc (MBZ) and 4,4'-bis (α, α-dimethylbenzyl) diphenylamine (445) were used to improve the thermo-oxidative aging resistance of ethylene propylene diene rubber (EPDM). The synergistic effects on the performances of EPDM and the corresponding aging mechanism were investigated by FTIR, tensile test, differential scanning calorimetry (DSC), rotary rheometer and other equipment. The results showed that the hardness increased gradually with the increasing aging time regardless of the type of antioxidants. Compared with the EPDM without antioxidants, the elongation retention of those samples with MBZ or 445 improved obviously. Additionally, the sample with the MBZ/445 complex showed the highest retention values at the same aging time. The antioxidative mechanisms were further analyzed by carbonyl index, activation energy and oxidation induction time, respectively. Results indicated that the degree of oxidation of EPDM using the MBZ/445 complex was much lower than other control systems during the aging process. As a result, the MBZ/445 complex was a favorable antioxidative additive for EPDM.[a] Dr.

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Sulfur compounds as synergistic antioxidants

Cited by 41 publications

References 42 publications

Metal complexes as antioxidants. VI. An electron spin resonance study of the transient cupric complexes formed in the reaction of cupric dialkyldithiocarbamates with alkylperoxy radicals and alkyl hydroperoxides

Metal complexes as antioxidants. VI. An electron spin resonance study of the transient cupric complexes formed in the reaction of cupric dialkyldithiocarbamates with alkylperoxy radicals and alkyl hydroperoxides

Oxidative Degradation and Stabilisation of Mineral Oil-Based Lubricants

Synergistic Effects of Amine‐Containing Antioxidants on the Aging Performances of Ethylene Propylene Diene Rubber

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