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Judyta Kucharska - One of the best experts on this subject based on the ideXlab platform.
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Organic Zinc Salts as Pro-Ecological Activators for Sulfur Vulcanization of Styrene–Butadiene Rubber
Polymers, 2019Co-Authors: Magdalena Maciejewska, Anna Sowińska, Judyta KucharskaAbstract:Organic zinc salts and complexes were applied as activators for Sulfur Vulcanization of styrene-butadiene elastomer (SBR) in order to reduce the content of zinc ions in rubber compounds as compared with conventionally used zinc oxide. In this article, the effects of different organic zinc activators on the curing characteristics, crosslink densities, and mechanical properties of SBR as well as the aging resistance and thermal behavior of vulcanizates are discussed. Organic zinc salts seem to be good substitutes for zinc oxide as activators for Sulfur Vulcanization of SBR rubber, without detrimental effects to the Vulcanization time and temperature. Moreover, vulcanizates containing organic zinc salts exhibit higher tensile strength and better damping properties than vulcanizate crosslinked with zinc oxide. The application of organic zinc activators allows the amount of zinc ions in SBR compounds to be reduced by 70-90 wt % compared to vulcanizate with zinc oxide. This is very important for ecological reasons, since zinc oxide is classified as being toxic to aquatic species.
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organic zinc salts as pro ecological activators for Sulfur Vulcanization of styrene butadiene rubber
Polymers, 2019Co-Authors: Magdalena Maciejewska, Anna Sowińska, Judyta KucharskaAbstract:Organic zinc salts and complexes were applied as activators for Sulfur Vulcanization of styrene-butadiene elastomer (SBR) in order to reduce the content of zinc ions in rubber compounds as compared with conventionally used zinc oxide. In this article, the effects of different organic zinc activators on the curing characteristics, crosslink densities, and mechanical properties of SBR as well as the aging resistance and thermal behavior of vulcanizates are discussed. Organic zinc salts seem to be good substitutes for zinc oxide as activators for Sulfur Vulcanization of SBR rubber, without detrimental effects to the Vulcanization time and temperature. Moreover, vulcanizates containing organic zinc salts exhibit higher tensile strength and better damping properties than vulcanizate crosslinked with zinc oxide. The application of organic zinc activators allows the amount of zinc ions in SBR compounds to be reduced by 70-90 wt % compared to vulcanizate with zinc oxide. This is very important for ecological reasons, since zinc oxide is classified as being toxic to aquatic species.
Magdalena Maciejewska - One of the best experts on this subject based on the ideXlab platform.
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organic zinc salts as pro ecological activators for Sulfur Vulcanization of styrene butadiene rubber
Polymers, 2019Co-Authors: Magdalena Maciejewska, Anna Sowińska, Judyta KucharskaAbstract:Organic zinc salts and complexes were applied as activators for Sulfur Vulcanization of styrene-butadiene elastomer (SBR) in order to reduce the content of zinc ions in rubber compounds as compared with conventionally used zinc oxide. In this article, the effects of different organic zinc activators on the curing characteristics, crosslink densities, and mechanical properties of SBR as well as the aging resistance and thermal behavior of vulcanizates are discussed. Organic zinc salts seem to be good substitutes for zinc oxide as activators for Sulfur Vulcanization of SBR rubber, without detrimental effects to the Vulcanization time and temperature. Moreover, vulcanizates containing organic zinc salts exhibit higher tensile strength and better damping properties than vulcanizate crosslinked with zinc oxide. The application of organic zinc activators allows the amount of zinc ions in SBR compounds to be reduced by 70-90 wt % compared to vulcanizate with zinc oxide. This is very important for ecological reasons, since zinc oxide is classified as being toxic to aquatic species.
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Organic Zinc Salts as Pro-Ecological Activators for Sulfur Vulcanization of Styrene–Butadiene Rubber
Polymers, 2019Co-Authors: Magdalena Maciejewska, Anna Sowińska, Judyta KucharskaAbstract:Organic zinc salts and complexes were applied as activators for Sulfur Vulcanization of styrene-butadiene elastomer (SBR) in order to reduce the content of zinc ions in rubber compounds as compared with conventionally used zinc oxide. In this article, the effects of different organic zinc activators on the curing characteristics, crosslink densities, and mechanical properties of SBR as well as the aging resistance and thermal behavior of vulcanizates are discussed. Organic zinc salts seem to be good substitutes for zinc oxide as activators for Sulfur Vulcanization of SBR rubber, without detrimental effects to the Vulcanization time and temperature. Moreover, vulcanizates containing organic zinc salts exhibit higher tensile strength and better damping properties than vulcanizate crosslinked with zinc oxide. The application of organic zinc activators allows the amount of zinc ions in SBR compounds to be reduced by 70-90 wt % compared to vulcanizate with zinc oxide. This is very important for ecological reasons, since zinc oxide is classified as being toxic to aquatic species.
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novel ionic liquids as accelerators for the Sulfur Vulcanization of butadiene styrene elastomer composites
Industrial & Engineering Chemistry Research, 2013Co-Authors: Magdalena Maciejewska, Filip Walkiewicz, Marian ZaborskiAbstract:The aim of this work was to study the activity of novel benzalkonium and ammonium ionic liquids with 2-mercaptobenzothiazolate as accelerators in the Sulfur Vulcanization of butadiene–styrene elastomer (SBR). In this Article, the effect of the ionic liquids on the Vulcanization kinetics of the rubber compounds, the cross-link density, and the mechanical properties of the vulcanizates, as well as their resistance to thermal and UV aging, was studied. The application of novel ionic liquids allowed for the elimination of N-cyclohexyl-2-benzothiazolesulfenamide from SBR compounds and for the considerable reduction of the amount of 2-mercaptobenzothiazole present in rubber products. Synthesized salts seem to be good substitutes for standard accelerators in the Sulfur Vulcanization of SBR rubber, without the observation of any detrimental effects on the Vulcanization process, the physical properties, or the thermal stability of the obtained vulcanizates.
P. J. Nieuwenhuizen - One of the best experts on this subject based on the ideXlab platform.
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Zinc accelerator complexes.: Versatile homogeneous catalysts in Sulfur Vulcanization
Applied Catalysis A-general, 2001Co-Authors: P. J. NieuwenhuizenAbstract:This paper reviews homogeneous catalysis during the Sulfur Vulcanization of rubber by zinc dithiocarbamates and zinc mercaptobenzothiazolates. By means of quantumchemical calculations and model studies, individual reaction steps of the Vulcanization reaction sequence have been studied in detail. This has revealed that zinc accelerator complexes, such as the zinc dithiocarbamates and mercaptobenzothiazolates homogeneously catalyze a multitude of reactions during Sulfur Vulcanization. Among these are the formation, deSulfuration, but also the degradation, of Sulfur cross-links. In addition it could be shown that under oxidative conditions these zinc complexes catalyze the formation of diene and triene structures in the rubber. The zinc complexes are able to effect these reactions by (a) their ability to incorporate and activate Sulfur atoms and (b) their Lewis acidity, which enhances the reactivity of Sulfur Vulcanization intermediates.
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The First Theoretical and Experimental Proof of Polythiocarbamatozinc(ii) Complexes, Catalysts for Sulfur Vulcanization
Chemistry - A European Journal, 1998Co-Authors: P. J. Nieuwenhuizen, Andreas W. Ehlers, Johannes W. Hofstraat, Sander R. Janse, M.w.f. Nielen, Jan Reedijk, Evert Jan BaerendsAbstract:The existence of polythiocar- bamatozinc complexes, species pre- sumed to be involved in catalyzing Sulfur Vulcanization, has been studied by com- putational and mass-spectrometric tech- niques. Density functional calculations reveal that the Sulfuration energy of bis(trithiocarbamato)zinc(ii) is compara- ble to that of bis(phenyltrithiolato)- zinc(ii), a stable Sulfurated complex. Interestingly, the analogous nonsym- metrically Sulfurated complex (dithio- carbamato)(tetrathiocarbamato)zinc(ii) is energetically slightly more favorable. The calculations indicate that polythio- carbamatozinc complexes may indeed be involved in the Sulfur Vulcanization cascade, a conclusion corroborated by ensuing laser-desorption ionization (LDI) mass-spectrometric measure- ments on mixtures of dithiocarbamato- zinc(ii) complexes and elemental Sulfur. These demonstrate the presence of poly- thiocarbamatozinc ions that are sulfu- rated with up to eight additional Sulfur atoms.
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zinc ii catalyzed disproportionation in rubber the mechanism of Sulfur Vulcanization revisited
Chemistry: A European Journal, 1997Co-Authors: P. J. Nieuwenhuizen, Jaap G. Haasnoot, Anthony L. Spek, Sandjai Timal, Jan ReedijkAbstract:Model studics have shown that cross-link precursors, that is, intermediates in the Sulfur Vulcanization of rubber, are transformed into cross-links by a nonsymmetric but regiosclective disproportionation mechanism. Thus, two equivalents of the cross- link precursor of thc type R-S-S-X are transformed into X-S-X and the actual cross-link R- S- S-S ~ R. Exchange of Sulfur atoms is a prerequisite. A mechanism dithiocarba- involving an S,i' reaction with an allylic moiety, suggested in the literature, has not been mate * homogeneous catalysis * ohservcd. The disproportionation reaction is catalyzed by rubber-soluble zinc dithio- carbamatc complexes, an important class of Vulcanization accelerators. By virtuc of ligand -functional-group exchange reactions these complexes serve to transport and exchange Sulfur atoms.
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Thiuram- and dithiocarbamate-accelerated Sulfur Vulcanization from the chemist's perspective; methods, materials and mechanisms reviewed
Rubber Chemistry and Technology, 1997Co-Authors: P. J. Nieuwenhuizen, Jan Reedijk, M. Van Duin, W. J. McgillAbstract:Abstract This paper describes research methodologies for the investigation of the mechanism of Vulcanization and discusses the reactivity of thiuram and dithiocarbamate chemicals. The combined knowledge is subsequently applied to thoroughly review the mechanism and chemistry of both thiuram- and dithiocarbamate-accelerated Sulfur Vulcanization. Integration of the original mechanistic ideas from the 1960s and the results obtained in the past three decades now have led to a more balanced appraisal of events during Vulcanization. Questions have been answered, solutions for old problems are proposed, and remaining fields of endeavor are identified.
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Sulfur Vulcanization of Simple Model Olefins, Part V: Double Bond Isomerization during Accelerated Sulfur Vulcanization as Studied by Model Olefins
Rubber Chemistry and Technology, 1997Co-Authors: P. Versloot, P. J. Nieuwenhuizen, Jan Reedijk, Jaap G. Haasnoot, M. Van Duin, J. PutAbstract:Abstract The Sulfur Vulcanization of unsaturated rubber has been studied with the use of various olefins as simple, low-molecular models. By treatment of these olefins with a mixture of zinc oxide, Sulfur, and tetramethylthiuram disulfide (TMTD) at 140 °C, a mixture of dialkenyl sulfides is obtained mimicking crosslinked rubber. Isomerization of the double bond may take place during this reaction, depending on the olefin used. The position of the double bond is on the one hand determined by crosslink formation mechanisms, and on the other hand by isomerization, which takes place at higher temperatures. The position of the equilibrium between isomeric alkenyl sulfides is determined by the increased stability of the sulfide which in itself results from an increased degree of alkyl substitution at the unsaturation. Due to the isomerization reaction, at higher temperatures no mechanism for crosslink formation can be discerned. At room temperature, however, a radical mechanism appears to be predominant during the Vulcanization process.
W. J. Mcgill - One of the best experts on this subject based on the ideXlab platform.
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Dimethylammonium dimethyldithiocarbamate-accelerated Sulfur Vulcanization. II. Vulcanization of rubbers and model compound 2,3-dimethyl-2-butene
Journal of Applied Polymer Science, 2001Co-Authors: M. Shumane, M. H. S. Gradwell, W. J. McgillAbstract:Rubber and model compound 2,3-dimethyl-2-butene were vulcanized for various times with dimethylammonium dimethyldithiocarbamate [(dma)dmtc]-accelerated Sulfur formulations in the absence of ZnO. Model compound systems were analyzed by HPLC, and no reaction intermediates containing pendent groups were found. Crosslinked sulfides, characterized by 1H-NMR, were found to be essentially bis(alkenyl). Residual curatives were extracted from rubber compounds vulcanized for various times and analyzed by HPLC. Compounds, cured to various crosslink densities, were found to crystallize readily in a density column at subambient temperatures. This supports evidence from model compound systems that pendent groups are largely absent from vulcanizates. It is suggested that a reaction mechanism, similar to that applicable to zinc dimethyldithiocarbamate-accelerated Sulfur Vulcanization, may be applicable with (dma)dmtc accelerated formulations. Very limited crosslinking occurred on heating compounds under vacuum, and this can be attributed largely to the rapid loss of (dma)dmtc from rubber at elevated temperatures. However, the slower rate of crystallization on cooling of the gels, compared to the rate in press-cured vulcanizates of similar crosslink density, was interpreted as evidence that some pendent groups did form during heating with (dma)dmtc/Sulfur. Crosslinking of such pendent groups may be inhibited by the loss of (dma)dmtc, that, like zinc dimethyldithiocarbamate, may catalyze their crosslinking, and/or to the loss under vacuum of dimethyldithiocarbamic acid that would form thiol pendent groups that would rapidly crosslink with thiuram pendent groups. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3074–3083, 2001
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Benzothiazole‐accelerated Sulfur Vulcanization. I. 2‐Mercaptobenzothiazole as accelerator for 2,3‐dimethyl‐2‐butene
Journal of Applied Polymer Science, 2000Co-Authors: B. Morgan, W. J. McgillAbstract:2,3-Dimethyl-2-butene (TME) was used as a model compound for polyisoprene in a study of 2-mercaptobenzothiazole (MBT)-accelerated Sulfur Vulcanization. Mixes that contained curatives only were heated in a DSC to various temperatures, while those that also contained TME were heated isothermally at 150°C in evacuated, sealed glass ampules. Heated mixtures were analyzed for residual curatives, intermediates, and reaction products by HPLC. It is proposed that MBT forms polysulfidic species (BtSxH) in the presence of Sulfur and that these react with TME via a concerted, substitutive reaction pathway to form polysulfidic hydrogen-terminated pendent groups of varying Sulfur rank (TME–SxH). MBT is released as a by-product of this reaction. Crosslinking occurs slowly as a result of the interaction of polythiol pendent groups, the rate being dependent on the pendent group concentration. H2S is released on crosslinking. 2,3-Dimethyl-2-butene–1-thiol was synthesized and reacted in the presence of Sulfur to confirm the formation of crosslinked products (TME–Sx–TME). Benzothiazole-terminated pendent groups (TME–SxBt) were not observed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1377–1385, 2000
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Benzothiazole‐accelerated Sulfur Vulcanization. III. 2‐Bisbenzothiazole‐2,2′‐disulfide as accelerator for 2,3‐dimethyl‐2‐butene
Journal of Applied Polymer Science, 2000Co-Authors: B. Morgan, W. J. McgillAbstract:2-Bisbenzothiazole-2,2'-disulfide (MBTS)-accelerated Sulfur Vulcanization, in the absence of ZnO, was studied using 2,3-dimethyl-2-butene (TME) as a model for polyisoprene. Reactions were carried out in sealed tubes at 150°C and the residual curatives, intermediates, and products were analyzed by HPLC at various stages of the reaction. The formation of accelerator-terminated polysulfidic pendent groups is accompanied by the liberation of 2-mercaptobenzothiazole (MBT) and more MBT is liberated on crosslinking. Bis(alkenyl)-crosslinked products with varying degrees of Sulfuration result. It was shown that crosslinking by a reaction between pendent groups and the model compound, and by disproportionation of pendent groups, leads to limited crosslinking. H 2 S was not evolved during crosslinking. 2,3-Dimethyl-2-butene-benzothiazole disulfide (TME-S 2 Bt) and 2,3-dimethyl-2-butene-1-thiol (TME-SH) were synthesized and it was shown that rapid crosslinking occurs between TME-S x Bt and TME-S x H (where x > 1), the reaction liberating MBT.
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benzothiazole accelerated Sulfur Vulcanization i 2 mercaptobenzothiazole as accelerator for 2 3 dimethyl 2 butene
Journal of Applied Polymer Science, 2000Co-Authors: B. Morgan, W. J. McgillAbstract:2,3-Dimethyl-2-butene (TME) was used as a model compound for polyisoprene in a study of 2-mercaptobenzothiazole (MBT)-accelerated Sulfur Vulcanization. Mixes that contained curatives only were heated in a DSC to various temperatures, while those that also contained TME were heated isothermally at 150°C in evacuated, sealed glass ampules. Heated mixtures were analyzed for residual curatives, intermediates, and reaction products by HPLC. It is proposed that MBT forms polysulfidic species (BtSxH) in the presence of Sulfur and that these react with TME via a concerted, substitutive reaction pathway to form polysulfidic hydrogen-terminated pendent groups of varying Sulfur rank (TME–SxH). MBT is released as a by-product of this reaction. Crosslinking occurs slowly as a result of the interaction of polythiol pendent groups, the rate being dependent on the pendent group concentration. H2S is released on crosslinking. 2,3-Dimethyl-2-butene–1-thiol was synthesized and reacted in the presence of Sulfur to confirm the formation of crosslinked products (TME–Sx–TME). Benzothiazole-terminated pendent groups (TME–SxBt) were not observed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1377–1385, 2000
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The role of dimethyldithiocarbamic acid in accelerated Sulfur Vulcanization
Journal of Applied Polymer Science, 1999Co-Authors: S. R. Shelver, M. H. S. Gradwell, M. Shumane, W. J. McgillAbstract:Polyisoprene/tetramethylthiuram disulfide (TMTD)/Sulfur compounds were vulcanized under a variety of conditions. TMTD does not decompose to tetramethylthiourea (TMTU) at Vulcanization temperatures as has been suggested, neither is it formed as an integral part of the crosslinking process. Instead, it results from the attack of dimethylamine, released on decomposition of dimethyldithiocarbamic acid (Hdmtc), on TMTD. It is demonstrated that the formation of TMTU in vulcanizates may be overlooked, as it is readily lost in the work-up for HPLC analysis. Hdmtc is shown to play an essential role in the crosslinking process in polyisoprene/TMTD/Sulfur formulations, and its removal from the system during Vulcanization severely impedes crosslinking. Polysulfidic thiuram-terminated pendent groups are formed, in part, by the interaction of tetramethylthiuram polysulfides with the polymer chain, but largely by an exchange between Hdmtc and polysulfidic thiol pendent groups. The latter are formed when Sulfurated Hdmtc reacts with the polymer chain. Crosslinking of thiuram-terminated pendent groups is slow, and in the absence of ZnO crosslinking results from reaction between polysulfidic thiuram pendent groups and thiols. Crosslinking is delayed until the bulk of the accelerator is bound to the polymer chain, at which point the concentration of free thiuram groups, in the form of Hdmtc, is low, and exchanges between newly formed thiol pendent groups and Hdmtc is less frequent, permitting crosslinking of thiuram pendent groups with these newly formed thiol pendent groups. Data to support the proposed reaction mechanism is presented. Hdmtc on its own accelerates Sulfur Vulcanization and acts as a catalyst for the reaction, being regenerated in the crosslinking process. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1371–1379, 1999
Jan Reedijk - One of the best experts on this subject based on the ideXlab platform.
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The First Theoretical and Experimental Proof of Polythiocarbamatozinc(ii) Complexes, Catalysts for Sulfur Vulcanization
Chemistry - A European Journal, 1998Co-Authors: P. J. Nieuwenhuizen, Andreas W. Ehlers, Johannes W. Hofstraat, Sander R. Janse, M.w.f. Nielen, Jan Reedijk, Evert Jan BaerendsAbstract:The existence of polythiocar- bamatozinc complexes, species pre- sumed to be involved in catalyzing Sulfur Vulcanization, has been studied by com- putational and mass-spectrometric tech- niques. Density functional calculations reveal that the Sulfuration energy of bis(trithiocarbamato)zinc(ii) is compara- ble to that of bis(phenyltrithiolato)- zinc(ii), a stable Sulfurated complex. Interestingly, the analogous nonsym- metrically Sulfurated complex (dithio- carbamato)(tetrathiocarbamato)zinc(ii) is energetically slightly more favorable. The calculations indicate that polythio- carbamatozinc complexes may indeed be involved in the Sulfur Vulcanization cascade, a conclusion corroborated by ensuing laser-desorption ionization (LDI) mass-spectrometric measure- ments on mixtures of dithiocarbamato- zinc(ii) complexes and elemental Sulfur. These demonstrate the presence of poly- thiocarbamatozinc ions that are sulfu- rated with up to eight additional Sulfur atoms.
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zinc ii catalyzed disproportionation in rubber the mechanism of Sulfur Vulcanization revisited
Chemistry: A European Journal, 1997Co-Authors: P. J. Nieuwenhuizen, Jaap G. Haasnoot, Anthony L. Spek, Sandjai Timal, Jan ReedijkAbstract:Model studics have shown that cross-link precursors, that is, intermediates in the Sulfur Vulcanization of rubber, are transformed into cross-links by a nonsymmetric but regiosclective disproportionation mechanism. Thus, two equivalents of the cross- link precursor of thc type R-S-S-X are transformed into X-S-X and the actual cross-link R- S- S-S ~ R. Exchange of Sulfur atoms is a prerequisite. A mechanism dithiocarba- involving an S,i' reaction with an allylic moiety, suggested in the literature, has not been mate * homogeneous catalysis * ohservcd. The disproportionation reaction is catalyzed by rubber-soluble zinc dithio- carbamatc complexes, an important class of Vulcanization accelerators. By virtuc of ligand -functional-group exchange reactions these complexes serve to transport and exchange Sulfur atoms.
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Thiuram- and dithiocarbamate-accelerated Sulfur Vulcanization from the chemist's perspective; methods, materials and mechanisms reviewed
Rubber Chemistry and Technology, 1997Co-Authors: P. J. Nieuwenhuizen, Jan Reedijk, M. Van Duin, W. J. McgillAbstract:Abstract This paper describes research methodologies for the investigation of the mechanism of Vulcanization and discusses the reactivity of thiuram and dithiocarbamate chemicals. The combined knowledge is subsequently applied to thoroughly review the mechanism and chemistry of both thiuram- and dithiocarbamate-accelerated Sulfur Vulcanization. Integration of the original mechanistic ideas from the 1960s and the results obtained in the past three decades now have led to a more balanced appraisal of events during Vulcanization. Questions have been answered, solutions for old problems are proposed, and remaining fields of endeavor are identified.
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Sulfur Vulcanization of Simple Model Olefins, Part V: Double Bond Isomerization during Accelerated Sulfur Vulcanization as Studied by Model Olefins
Rubber Chemistry and Technology, 1997Co-Authors: P. Versloot, P. J. Nieuwenhuizen, Jan Reedijk, Jaap G. Haasnoot, M. Van Duin, J. PutAbstract:Abstract The Sulfur Vulcanization of unsaturated rubber has been studied with the use of various olefins as simple, low-molecular models. By treatment of these olefins with a mixture of zinc oxide, Sulfur, and tetramethylthiuram disulfide (TMTD) at 140 °C, a mixture of dialkenyl sulfides is obtained mimicking crosslinked rubber. Isomerization of the double bond may take place during this reaction, depending on the olefin used. The position of the double bond is on the one hand determined by crosslink formation mechanisms, and on the other hand by isomerization, which takes place at higher temperatures. The position of the equilibrium between isomeric alkenyl sulfides is determined by the increased stability of the sulfide which in itself results from an increased degree of alkyl substitution at the unsaturation. Due to the isomerization reaction, at higher temperatures no mechanism for crosslink formation can be discerned. At room temperature, however, a radical mechanism appears to be predominant during the Vulcanization process.
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Sulfur Vulcanization of simple model olefins part v double bond isomerization during accelerated Sulfur Vulcanization as studied by model olefins
Rubber Chemistry and Technology, 1997Co-Authors: P. Versloot, P. J. Nieuwenhuizen, Jan Reedijk, Jaap G. Haasnoot, M. Van Duin, J. PutAbstract:Abstract The Sulfur Vulcanization of unsaturated rubber has been studied with the use of various olefins as simple, low-molecular models. By treatment of these olefins with a mixture of zinc oxide, Sulfur, and tetramethylthiuram disulfide (TMTD) at 140 °C, a mixture of dialkenyl sulfides is obtained mimicking crosslinked rubber. Isomerization of the double bond may take place during this reaction, depending on the olefin used. The position of the double bond is on the one hand determined by crosslink formation mechanisms, and on the other hand by isomerization, which takes place at higher temperatures. The position of the equilibrium between isomeric alkenyl sulfides is determined by the increased stability of the sulfide which in itself results from an increased degree of alkyl substitution at the unsaturation. Due to the isomerization reaction, at higher temperatures no mechanism for crosslink formation can be discerned. At room temperature, however, a radical mechanism appears to be predominant during ...
