Oxidative aging of natural rubber vulcanizates. Part III. Crosslink scission in monosulfidic networks

Colclough, T.; Cunneen, J. I.; Higgins, George M.

doi:10.1002/app.1968.070120205

Cited by 25 publications

(10 citation statements)

References 24 publications

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“…-It is well known that sulfide bridges (especially monosulfide and disulfide bridges) decompose POOH in a non-radical way. [46][47][48] More generally, sulfide bridges (P 2 S) can progressively be transformed into sulfur structures with an increasing degree of oxidation (see Scheme 9): First, in sulfoxide (P 2 SO) and sulfenic acid (PSOH), then in sulfone (P 2 SO 2 ) and sulfinic acid (PSO 2 H), then in sulfonic acid (PSO 3 H), and finally in sulfuric acid (SO 4 H 2 ). This series of consecutive transformations delays and slows down the oxidation reaction, particularly when comparing sulfur vulcanized elastomers with their starting linear polymer.…”

Section: Theoretical Chemical Levelmentioning

confidence: 99%

“…. ., 17) are elementary rate constants and chemical yields, respectively (h) From a practical point of view, it is more convenient to use an apparent yield c 1 for the formation efficiency of carbonyls owing to the high uncertainty on the nature of these species, but also the value of their corresponding molar extinction coefficients 60 (i ) c S accounts for b-scission efficiency of PO radicals ( j) c 4 and c 5 account respectively for the coupling efficiency of radical species (k) c 16 and c 17 account for the efficiency of the Colclough's mechanism, 47 which involves the breaking of a C-S bond A system of 17 non-linear differential equations can be derived from this mechanistic scheme for reactive species only, by applying the classical rules of chemical kinetics…”

Section: Appendix A: Thermal Oxidation Kinetics Of a Stabilized And Smentioning

confidence: 99%

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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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Section: Theoretical Chemical Levelmentioning

confidence: 99%

Section: Appendix A: Thermal Oxidation Kinetics Of a Stabilized And Smentioning

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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“…The oxidative reaction can result in scission of main rubber chains and the crosslinks 39–41 . This in turn results in losses in tensile strength and mechanical attributes 39–42 …”

Section: Resultsmentioning

confidence: 99%

“…The oxidative reaction can result in scission of main rubber chains and the crosslinks. [39][40][41] This in turn results in losses in tensile strength and mechanical attributes. [39][40][41][42] As shown in Figure 2, the three main mechanical properties (tensile strength, elongation at break, and percent moduli) of the aged PVNR films were barely affected relative to the unaged PVNR films so long as the aging treatment was mild (70 C, 7 days).…”

Section: Thermal Aging Of Pvnr Filmsmentioning

confidence: 99%

Compositing prevulcanized natural rubber with multiwalled carbon nanotubes to make antistatic films

Wiroonpochit

Keawmaungkom

Chisti

et al. 2022

Polymers for Advanced Techs

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Natural rubber was prevulcanized using ultraviolet (UV) light and the resulting prevulcanized natural rubber (PVNR) was composited with multiwalled carbon nanotubes (MWCNT) as a conductive filler, to make films suitable for antistatic gloves.These films were characterized in terms of mechanical properties and electrical resistivity. Effects of type of UV radiation and other specifics of the production process, on mechanical properties of neat PVNR were first investigated. This was followed by an investigation of the effects of surfactant type on the dispersion of MWCNT in water and the PVNR matrix. Four surfactants with different headgroups were used in preparing MWCNT dispersions that were then mixed with the PVNR latex to form the different films. As a consequence of its milk-like turbidity, the natural rubber latex was found to require deeply penetrating UVA light for satisfactory prevulcanization.Sodium dodecyl sulfate (SDS) was the best surfactant for dispersing MWCNT both in water and in PVNR matrix. SDS resulted in MWCNT-PVNR composite films with the least electrical resistivity and good mechanical properties for making antistatic gloves.SDS did not interfere with stress transfer at NR-MWCNT interface. SDS was superior to the other surfactants because its head group had a charge opposite to that on the NR surface and lacked a benzene ring that would have interacted strongly with the hydrophobic surface of MWCNT.

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“…PHYSICAL APPROACH An EPDM network can be characterized by only two structural quantities well known to have a direct impact on mechanical properties [51][52][53] :…”

Section: Resultsmentioning

confidence: 99%

PEROXIDE CROSS-LINKING OF EPDMs HAVING HIGH FRACTIONS OF ETHYLENIC UNITS

Shabani

Colin

Marque

et al. 2014

Rubber Chemistry and Technology

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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. ABSTRACTThe considerable amount of research in the literature has practically allowed the elucidation of the mechanism of peroxide cross-linking of ethylene-propylene-diene-monomer rubber (EPDM), which occurs through a radical chain reaction initiated by the thermal decomposition of the peroxide molecule. According to this radical chain reaction, all types of labile hydrocarbon bonds (i.e., allylic, methynic, and methylenic CH bonds) would be exposed to alkoxy radicals and involved in the formation of the elastomeric network. However, for high fractions of ethylenic units (typically !60 mol.%), simple chemical kinetics and thermochemical analyses have shown that the radical attack would essentially occur on the methylenic CH bonds. Starting from this assertion, a simplified mechanistic scheme has been proposed for the three commercial EPDMs under study. The corresponding kinetic model, derived from this new scheme by using the basic concepts of the chemical kinetics, provides access to the changes in concentration of the main reactive chemical functions (against exposure time), among which are double bonds and changes in cross-linking density. The validity of these predictions has been eventually successfully verified by five distinct analytical techniques frequently used for studying the cross-linking of rubbers.

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Oxidative aging of natural rubber vulcanizates. Part III. Crosslink scission in monosulfidic networks

Cited by 25 publications

References 24 publications

Chemo-Mechanical Model for Predicting the Lifetime of Epdm Rubbers

Chemo-Mechanical Model for Predicting the Lifetime of Epdm Rubbers

Compositing prevulcanized natural rubber with multiwalled carbon nanotubes to make antistatic films

PEROXIDE CROSS-LINKING OF EPDMs HAVING HIGH FRACTIONS OF ETHYLENIC UNITS

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