Sulfur Vulcanization of Hydrocarbon Diene Elastomers

Coleman, Michael M.; Shelton, J. Reid; Koenig, Jack L.

doi:10.1021/i360051a002

Cited by 68 publications

(68 citation statements)

References 41 publications

(66 reference statements)

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“…In the case of sulfur systems, the discussion concerning the nature of the reactions involved in the vulcanization process, i.e. ionic or free radical pathways, is still ongoing [1][2][3][4]. Several works conclude that radical mechanisms are required to justify the crosslink structures formed on NR after the vulcanization with sulfur [2][3][4][5][6]: sulfur cross-links of different lengths, mainly polysulfidic bonds, pendant groups, cyclic sulfides and cis/trans isomerization of the double bonds and/or conjugated sequences in the polymer backbone [7].…”

Section: Introductionmentioning

confidence: 99%

“…They are classi-fied as conventional (CV), semi-efficient (semi-EV) and efficient (EV) systems depending on the accelerator/sulfur ratio (usually in a range between 0.2 and 12, for the extreme cases). The NR samples usually show different and characteristic mechanical and viscoelastic properties, fatigue and ageing resistance according to the sulfur/accelerator system employed in the vulcanization process [1,7]. On the other hand, vulcanization of NR with organic peroxides provides materials with higher concentration of non-elastic network defects and rubber network structures characterized by the formation of C-C cross-links with more heterogeneous spatial distribution, as compared to the samples vulcanized with sulfur-accelerators [6].…”

Section: Introductionmentioning

confidence: 99%

“…The application to other vulcanization systems, e.g. sulfur based systems, has been limited to model compounds or the analysis of the vulcanization system without rubber [1]. Recently, ESR has been applied to study the polybutadiene vulcanization mechanism [13].…”

Section: Introductionmentioning

confidence: 99%

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ESR investigation of NR and IR rubber vulcanized with different cross-link agents

Posadas¹,

Malmierca²,

Jiménez³

et al. 2016

Express Polym. Lett.

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Abstract. This study evaluates the formation of radical species in natural rubber (NR) and poly-isoprene rubber (IR) during the vulcanization process and the uniaxial deformation of the formed networks by means of Electron Spin Resonance (ESR). Vulcanization of NR and IR always shows a radical pathway, where the different vulcanization systems dictate the concentration of radical species in the course of this complex process. The greatest concentration of radicals were detected during the vulcanization with sulfur/accelerator based on efficient systems (EV), followed by conventional (CV) and sulfur donor systems, whereas azide and organic peroxide agents showed smaller concentration of radicals. Independently of the vulcanization system, certain amount of radicals was detected on the vulcanized samples after the end of the vulcanization process. Comparison between different matrices demonstrates that NR always shows higher concentration of radicals than IR in the vulcanization process as well as during uniaxial deformation, fact that could be associated to the presence of nonrubber components in NR.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

ESR investigation of NR and IR rubber vulcanized with different cross-link agents

Posadas¹,

Malmierca²,

Jiménez³

et al. 2016

Express Polym. Lett.

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“…However, the mechanism of the reaction remains unclear, despite extensive literature on the subject. It is commonly suggested [1][2][3][4] that the reaction is initiated by sulfuration of the accelerator to give a polysulfidic zinc complex, although such complexes have not been separated. Zn 2 (dmtc) 4 is only sparingly soluble in rubber but is said to be rendered more soluble through coordination with nitrogen bases or zinc carboxylates.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the proposals for the involvement of pendant groups in the vulcanization process are based on circumstantial evidence. [1][2][3][4] Geyser and McGill 33 proposed that the reaction proceeds via a concerted mechanism without the formation of a true intermediate, the crosslinking of polysulfidic thiuram pendant groups being immediate in the presence of Zn 2 (dmtc) 4 , which catalyzes their crosslinking. The catalytic crosslinking by Zn 2 (dmtc) 4 (and zinc stearate) of pendant groups formed in compounds containing TMTD and sulfur was demonstrated by a number of authors.…”

Section: Introductionmentioning

confidence: 99%

Effect of water and hydrogen sulfide in zinc dimethyldithiocarbamate accelerated sulfur vulcanization

Shumane

Gradwell

McGill

2002

J of Applied Polymer Sci

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Rubber and the model compound 2,3-dimethyl-2-butene (TME) are vulcanized with zinc dimethyldithiocarbamate [Zn 2 (dmtc) 4 ] accelerated sulfur formulations. When heated in dry nitrogen, Zn 2 (dmtc) 4 is stable at vulcanization temperatures. However, it shows a mass increase when heated in moist nitrogen, indicating strong coordination with water; in a nitrogen/H 2 S atmosphere rapid degradation to dimethyldithiocarbamic acid (Hdmtc) and ZnS occurs. Model compound studies show that crosslinked sulfides are essentially bis(alkenyl) and confirm the absence of accelerator terminated pendant groups in the vulcanizates, while the ease with which rubber vulcanizates crystallize on cooling in a density column also suggests that pendant groups are largely absent. However, the rates of crystallization, measured as the time for the crystallization process to go to 50% completion, are slower in lightly crosslinked gels than in peroxide cures of similar crosslink density, particularly in the vulcanizates cured in a vacuum; this is interpreted as an indication that some residual pendant groups are present in Zn 2 (dmtc) 4 vulcanizates. Water promotes the rate of crosslink formation in both rubber and TME systems, and it is suggested that the strong coordination of water with zinc in Zn 2 (dmtc) 4 promotes its reactivity. The H 2 S liberated in the vulcanization process promotes decomposition of Zn 2 (dmtc) 4 to Hdmtc, and this reaction makes an important contribution to the amount of Hdmtc that is formed in situ. The importance of Hdmtc as an accelerator and its role in providing alternative routes to crosslink formation in Zn 2 (dmtc) 4 accelerated sulfur vulcanization are discussed. It is suggested that water, which is liberated when Hdmtc reacts with ZnO to form Zn 2 (dmtc) 4 , activates newly formed Zn 2 (dmtc) 4 molecules; and this accounts for the beneficial influence of ZnO in Zn 2 (dmtc) 4 formulations.

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Spectroscopies I have known?Award address: Philips ACS Award in Applied Polymer Science

Koenig¹

1998

J. Appl. Polym. Sci.

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This review paper demonstrates the development of a number of spectroscopic techniques for the characterization of polymers including dispersive infrared, laser-excited Raman spectroscopy, Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance spectroscopy, and nuclear magnetic resonance imaging. A discussion is given of the roles that these techniques have in the arsenal of the polymer scientist and the nature of the contributions from the author's laboratory.

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Sulfur Vulcanization of Hydrocarbon Diene Elastomers

Cited by 68 publications

References 41 publications

ESR investigation of NR and IR rubber vulcanized with different cross-link agents

ESR investigation of NR and IR rubber vulcanized with different cross-link agents

Effect of water and hydrogen sulfide in zinc dimethyldithiocarbamate accelerated sulfur vulcanization

Spectroscopies I have known?Award address: Philips ACS Award in Applied Polymer Science

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