The ESR spectra of tetramethylthiuram disulphide and its copper complex

Degtyarev, L. S.; Ganyuk, L. N.

doi:10.1016/0032-3950(64)90335-1

Cited by 8 publications

(7 citation statements)

References 6 publications

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“…85 Skinner's work suggests that the presence of an accelerator enables an efficient substitution in allylic position, which agrees with the conclusions of Bateman et al 2 , Lautenschlaeger 86-88 and Kresja and Koenig. 34,81 In the 1960s a radical mechanism that did not include crosslink precursors was advocated for the conversion of accelerator polysulfides into crosslinks; [89][90][91][92][93] specifically,…”

Section: Formation Of Crosslinkmentioning

confidence: 99%

Sulfur Vulcanization of Natural Rubber for Benzothiazole Accelerated Formulations: From Reaction Mechanisms to a Rational Kinetic Model

Ghosh

Katare

Patkar

et al. 2003

Rubber Chemistry and Technology

215

228

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The chemistry of accelerated sulfur vulcanization is reviewed and a fundamental kinetic model for the vulcanization process is developed. The vulcanization of natural rubber by the benzothiazolesulfenamide class of accelerators is studied, where 2-(morpholinothio) benzothiazole (MBS) has been chosen as the representative accelerator. The reaction mechanisms that have been proposed for the different steps in vulcanization chemistry are critically evaluated with the objective of developing a holistic description of the governing chemistry, where the mechanisms are consistent for all reaction steps in the vulcanization process. A fundamental kinetic model has been developed for accelerated sulfur vulcanization, using population balance methods that explicitly acknowledge the polysulfidic nature of the crosslinks and various reactive intermediates. The kinetic model can accurately describe the complete cure response including the scorch delay, curing and the reversion for a wide range of compositions, using a single set of rate constants. In addition, the concentration profiles of all the reaction intermediates as a function of polysulfidic lengths are predicted. This detailed information obtained from the population balance model is used to critically examine various mechanisms that have been proposed to describe accelerated sulfur vulcanization. The population balance model provides a quantitative framework for explicitly incorporating mechanistically reasonable chemistry of the vulcanization process.

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Section: Formation Of Crosslinkmentioning

confidence: 99%

Sulfur Vulcanization of Natural Rubber for Benzothiazole Accelerated Formulations: From Reaction Mechanisms to a Rational Kinetic Model

Ghosh

Katare

Patkar

et al. 2003

Rubber Chemistry and Technology

215

228

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“…13, No. vulcanizing temperatures (28). CuDMDC has a very strong esr signal and has led to misinterpretations in the past (11,15,29).…”

Section: Reaction Schemementioning

confidence: 99%

Sulfur Vulcanization of Hydrocarbon Diene Elastomers

Coleman¹,

Shelton²,

Koenig³

1974

Product R&D

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his whole lorge Sweat to work Out Achilles his armour" Sir Thomas brow^ Michael M. Coleman receiued his B.Sc. in chemical technology at Borough Polytechnic, London, En. gland, in 1968 and his M.S. and Ph.D. in macromolecular science from Case Western Reserue lJniversit2 in 1971 and 1973, respectivi mer Chemicals Departmenl ny as a research chemist ii to obtaining his undergradL an analytical chemist for nine years in Zambia and England Dr Coleman has seueral Dublications in the fiela on the ay.

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“…This signal was assigned to the thiuram radical Me 2 NCS 2 • . 4 If TMTD was heated followed by quenching to -56 °C, a singlet was observed at g ) 2.02 and was assigned to a persulfenyl radical Me 2 NCS 3 • . 5 In addition, a weak signal at g ) 2.006 was recorded after heating TMTD for 120 min to 145 °C; this signal was assigned to an unknown carbon radical.…”

Section: Introductionmentioning

confidence: 99%

Homolytic Dissociation of the Vulcanization Accelerator Tetramethylthiuram Disulfide (TMTD) and Structures and Stabilities of the Related Radicals Me₂NCS_n^• (n = 1−4)

Steudel

Mak

et al. 2006

J. Org. Chem.

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The homolytic dissociation of the important vulcanization accelerator tetramethylthiuram disulfide (TMTD) has been studied by ab initio calculations according to the G3X(MP2) and G3X(MP2)-RAD theories. Homolytic cleavage of the SS bond requires a low enthalpy of 150.0 kJ mol-1, whereas 268.0 kJ mol-1 is needed for the dissociation of one of the C-S single bonds. To cleave one of the SS bonds of the corresponding trisulfide (TMTT) requires 191.1 kJ mol-1. Me2NCS2* is a particularly stable sulfur radical as reflected in the low S-H bond dissociation enthalpy of the corresponding acid Me2NC(=S)SH (301.7 kJ mol-1). Me2NCS2* (2B2) is a sigma radical characterized by the unpaired spin density shared equally between the two sulfur atoms and by a 4-center (NCS2) delocalized pi system. The ESR g-tensors of the radicals Me2NCSn* (n = 1-3) have been calculated. Both TMTD and the mentioned radicals form stable chelate complexes with a Li+ cation, which here serves as a model for the zinc ions used in accelerated rubber vulcanization. Although the binding energy of the complex [Li(TMTD)]+ is larger than that of the isomeric species [Li(S2CNMe2)2]+ (12), the dissociation enthalpy of TMTD as a ligand is smaller (125.5 kJ mol-1) than that of free TMTD. In other words, the homolytic dissociation of the SS bonds of TMTD is facilitated by the presence of Li+ ions. The sulfurization of TMTD in the presence of Li+ to give the paramagnetic complex [Li(S3CNMe2)2]+ is strongly exothermic. These results suggest that TMTD reacts with naked zinc ions as well as with the surface atoms of solid zinc oxide particles in an analogous manner producing highly reactive complexes, which probably initiate the crosslinking process during vulcanization reactions of natural or synthetic rubber accelerated by TMTD/ZnO.

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The ESR spectra of tetramethylthiuram disulphide and its copper complex

Cited by 8 publications

References 6 publications

Sulfur Vulcanization of Natural Rubber for Benzothiazole Accelerated Formulations: From Reaction Mechanisms to a Rational Kinetic Model

Sulfur Vulcanization of Natural Rubber for Benzothiazole Accelerated Formulations: From Reaction Mechanisms to a Rational Kinetic Model

Sulfur Vulcanization of Hydrocarbon Diene Elastomers

Homolytic Dissociation of the Vulcanization Accelerator Tetramethylthiuram Disulfide (TMTD) and Structures and Stabilities of the Related Radicals Me₂NCS_n^• (n = 1−4)

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The ESR spectra of tetramethylthiuram disulphide and its copper complex

Cited by 8 publications

References 6 publications

Sulfur Vulcanization of Natural Rubber for Benzothiazole Accelerated Formulations: From Reaction Mechanisms to a Rational Kinetic Model

Sulfur Vulcanization of Natural Rubber for Benzothiazole Accelerated Formulations: From Reaction Mechanisms to a Rational Kinetic Model

Sulfur Vulcanization of Hydrocarbon Diene Elastomers

Homolytic Dissociation of the Vulcanization Accelerator Tetramethylthiuram Disulfide (TMTD) and Structures and Stabilities of the Related Radicals Me2NCSn• (n = 1−4)

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Homolytic Dissociation of the Vulcanization Accelerator Tetramethylthiuram Disulfide (TMTD) and Structures and Stabilities of the Related Radicals Me₂NCS_n^• (n = 1−4)