Tetramethylthiuram Disulfide Vulcanization of Extracted Rubber. V. Low Molecular Products and the Mechanism of Zinc Oxide Activation

1951 ◽  
Vol 24 (2) ◽  
pp. 275-284 ◽  
Author(s):  
David Craig ◽  
W. L. Davidson ◽  
A. E. Juve
Keyword(s):  
Palmitic Acid ◽  
Good Yield ◽  
Main Product ◽  
Complete Removal ◽  
Tetramethylthiuram Disulfide ◽  
Short Path Distillation ◽  
Sulfur Vulcanization ◽  
Identical Part ◽  
Acidic Nature ◽  
Vulcanization Process

Abstract The essential features of TMTD vulcanization, as revealed by compounding tudies, were discussed in Part I of this series. Thus, TMTM, a product of TMTD vulcanization, and an active accelerator of sulfur vulcanization, was found to be an inhibitor, and ZnDMDC, a main product of TMTD vulcanization, in the presence of ZnO was found to be devoid of activating properties. As a replacement of ZnO, which is a potent activator, ZnDMDC displayed only mild activating effects. Zinc palmitate was even more potent than ZnO. Zinc sulfide was somewhat less active than ZnO. Palmitic acid and DMADC had little or no effect on the cure. The second paper reported that TMTD could be prepared in good yield by the reaction of TMTM with sulfur and also, as a result of radiosulfur techniques, that the four sulfur atoms in the TMTD molecule are chemically identical. Part II also reported that ZnO reacted with TMTD to form sulfur and ZnDMDC in good yield. Other reactions of TMTD were discussed. Part III, in presenting a short-path distillation technique for studying vulcanizates, reported that the nearly complete removal of zinc from the TMTD vulcanizate is not accompanied by devulcanization. Part IV reported on the behavior of rubber as an acid. This behavior results in the liberation of palmitic acid from zinc palmitate. From the comparison of the reaction of TMTD with acids and the reaction of rubber with TMTD, it was inferred that rubber is an OH-containing acid. Acids in the work reported were found to react rather slowly with TMTD to form dimethylamides and sulfur in good yield. The acidic nature of rubber did not seem to be great enough to contribute in any fundamental way to the vulcanization process. The present paper describes further studies of the TMTD vulcanization problem.

Sulfur Vulcanization of Simple Model Olefins, Part V: Double Bond Isomerization during Accelerated Sulfur Vulcanization as Studied by Model Olefins

1997 ◽  
Vol 70 (1) ◽  
pp. 106-119 ◽  
Author(s):  
P. Versloot ◽  
J. G. Haasnoot ◽  
P. J. Nieuwenhuizen ◽  
J. Reedijk ◽  
M. van Duin ◽  
...  
Keyword(s):  
Double Bond ◽  
Isomerization Reaction ◽  
Radical Mechanism ◽  
Formation Mechanisms ◽  
Molecular Models ◽  
Tetramethylthiuram Disulfide ◽  
Alkyl Substitution ◽  
Sulfur Vulcanization ◽  
The One ◽  
Vulcanization Process

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.

Tetramethylthiuram Disulfide Vulcanization of Extracted Rubber. I. Introduction and Compounding

1951 ◽  
Vol 24 (2) ◽  
pp. 254-262 ◽  
Author(s):  
David Craig ◽  
A. E. Juve ◽  
W. L. Davidson
Keyword(s):  
Zinc Oxide ◽  
Palmitic Acid ◽  
Zinc Sulfide ◽  
Main Product ◽  
Tetramethylthiuram Disulfide ◽  
Effective Activator

Abstract (1) Large dosages of TMTM inhibit TMTD vulcanization or vulcanization with sulfur. (2) The desirability of up to about 1.5 phr zinc oxide for TMTD vulcanization was confirmed. If an unusually large amount of TMTD (10 phr) is used, a well vulcanized stock may be obtained without zinc activation. (3) Palmitic acid displays only a mild activating effect on TMTD vulcanization. (4) Zinc dimethyldithiocarbamate, a main product of TMTD vulcanization, is not an activator for a TMTD-zinc oxide recipe. (5) Dimethylammonium dimethyldithiocarbamate does not activate TMTD-zinc oxide formulations. (6) Zinc sulfide is an effective activator for TMTD vulcanization.

Activators in Accelerated Sulfur Vulcanization

2004 ◽  
Vol 77 (3) ◽  
pp. 512-541 ◽  
Author(s):  
Geert Heideman ◽  
Rabin N. Datta ◽  
Jacques W. M. Noordermeer ◽  
Ben van Baarle
Keyword(s):  
Reaction Mechanisms ◽  
Model Compound ◽  
Background Information ◽  
Zinc Compounds ◽  
Chemical Mechanisms ◽  
Sulfur Vulcanization ◽  
Multifunctional Additives ◽  
Vulcanization Process

Abstract This review provides relevant background information about the vulcanization process, as well as the chemistry of thiuram- and sulfenamide-accelerated sulfur vulcanization with emphasis on the role of activators, to lay a base for further research. It commences with an introduction of sulfur vulcanization and a summary of the reaction mechanisms as described in literature, followed by the role of activators, particularly ZnO. The various possibilities to reduce ZnO levels in rubber compounding, that have been proposed in literature, are reviewed. A totally different approach to reduce ZnO is described in the paragraphs about the various possible roles of multifunctional additives (MFA) in rubber vulcanization. Another paragraph is dedicated to the role of amines in rubber vulcanization, in order to provide some insight in the underlying chemical mechanisms of MFA systems. Furthermore, an overview of Model Compound Vulcanization (MCV) with respect to different models and activator/accelerator systems is given. In the last part of this review, the various functions of ZnO in rubber are summarized. It clearly reveals that the role of ZnO and zinc compounds is very complex and still deserves further clarification.

Effect of Sulfur and Dicumyl Peroxide on Vulcanization of Natural Rubber with Tetramethylthiuram Disulfide and Zinc Oxide

1970 ◽  
Vol 43 (6) ◽  
pp. 1294-1310 ◽  
Author(s):  
S. P. Manik ◽  
S. Banerjee
Keyword(s):  
Zinc Oxide ◽  
Stearic Acid ◽  
Natural Rubber ◽  
Reaction Mechanisms ◽  
Elemental Sulfur ◽  
Initial Rate ◽  
Dicumyl Peroxide ◽  
Tetramethylthiuram Disulfide ◽  
Sulfur Vulcanization ◽  
Salient Features

Abstract The salient features of both non-elemental sulfur vulcanization by TMTD and elemental sulfur vulcanization promoted by TMTD both in presence and absence of ZnO and stearic acid have been studied. TMTD increases the rate of DCP decomposition and lowers the crosslinking maxima due to DCP depending on its concentration. However, with higher amounts of TMTD the initial rate of crosslinking is increased with the increased amount of TMTD, while crosslinking maxima are still lowered due to reversion. ZnO or ZnO-stearic acid, however, seems to alter the entire course of the reaction. Both the crosslink formation and TMTD decomposition are much higher in presence of ZnO or ZnO-stearic acid, but stearic acid seems to have no effect. The reaction mechanisms for TMTD accelerated sulfuration in absence and presence of ZnO have also been studied.

The Vulcanization of Elastomers. 20. Sulfur Vulcanization Accelerated with Thiuram Compounds. I

1959 ◽  
Vol 32 (1) ◽  
pp. 139-149 ◽  
Author(s):  
Walter Scheele ◽  
Adolf Franck
Keyword(s):  
Reaction Order ◽  
Accurate Determination ◽  
Sulfur Concentration ◽  
Quantitative Investigation ◽  
Tetramethylthiuram Disulfide ◽  
First Order ◽  
Sulfur Vulcanization ◽  
Complicated Course ◽  
Peak Value

Abstract The present paper deals with the results of an orientating, quantitative investigation of sulfur vulcanization accelerated by thiuram disulfide, with tetramethylthiuram disulfide as the representative example. It was found: In the sulfur cure of natural rubber with tetramethylthiuram disulfide at different TMTD:S ratios, the rates of TMTD decrease and dithiocarbamate formation increase with increasing sulfur concentration, the TMTD content being kept constant. The rates practically do not change any further when the compounds contain 6 gram atoms of sulfur per mole of thiuram disulfide. The peak value of dithiocarbamate formation increases with the increase of sulfur concentration and reaches a constant end value of about 90 mole per cent based on the amount of original thiuram disulfide, when the stocks contain 4 gram atoms of sulfur per mole thiuram disulfide. This end value is identical to the end value of dithiocarbamate formation in the reaction of thiuram disulfide with zinc oxide (in the absence of rubber). The crosslinking, as measured by the change of reciprocal equilibrium swelling per time unit is also a reaction whose rate increases with the sulfur concentration to the point where the compounds contain 6 gram atoms of sulfur per mole of thiuram disulfide. The optimum degrees of crosslinking are roughly proportional to the sulfur concentration; at high sulfur levels the vulcanizates tend to revert. As in the pure TMTD vulcanization, the TMTD decrease as well as the dithiocarbamate formation are always first order reactions. The reversion at higher sulfur levels as well as the complicated course of the increase of combined sulfur during vulcanization render all but impossible an accurate determination of the reaction order for the crosslinking at higher sulfur levels. Nevertheless, in vulcanizations with 1 mole TMTD per 1 or 2 gram atoms of sulfur the crosslinking is a first order reaction.

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

2003 ◽  
Vol 76 (3) ◽  
pp. 592-693 ◽  
Author(s):  
Prasenjeet Ghosh ◽  
Santhoji Katare ◽  
Priyan Patkar ◽  
James M. Caruthers ◽  
Venkat Venkatasubramanian ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Natural Rubber ◽  
Reaction Mechanisms ◽  
Population Balance ◽  
Balance Model ◽  
Population Balance Model ◽  
Wide Range ◽  
Sulfur Vulcanization ◽  
Vulcanization Process ◽  
Single Set

Abstract 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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