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 Crosslinks in TMTD-Zinc Oxide-Natural Rubber Vulcanizates

1960 ◽  
Vol 33 (2) ◽  
pp. 394-397 ◽  
Author(s):  
C. G. Moore
Keyword(s):  
Zinc Oxide ◽  
Natural Rubber ◽  
Appreciable Amount ◽  
Dicumyl Peroxide ◽  
Swelling Properties ◽  
Tetramethylthiuram Disulfide ◽  
Chemical Studies ◽  
The Subject ◽  
Natural Rubber Vulcanizates ◽  
Recent Experimental Work

Abstract The mechanism of vulcanization of natural rubber (NR) by means of tetramethylthiuram disulfide (TMTD) and zinc oxide has been the subject of much recent experimental work and speculation. While such studies have clarified the kinetics and stoichiometry of TMTD decomposition and zinc dimethyldithiocarbamate formation, they have not directly aided our knowledge of the nature of the crosslinks in the resultant vulcanizate. It was earlier suggested that the vulcanizate contained only C—C crosslinks, comparable with those formed by means of di-tert-alkyl (and aralkyl) peroxides, while more recently, disulfide crosslinks have been proposed. However, neither of these views has been confirmed by direct chemical studies of the vulcanizate. Evidence is now presented which shows that there can be no appreciable amount of C—C crosslinking by the TMTD-ZnO combination, and this is consistent with the view that sulfur crosslinks predominate. This conclusion is based on the respective swelling properties in n-decane of dicumyl peroxide vulcanizates (containing only C—C crosslinks) and TMTD-ZnO vulcanizates, which have been treated with methyl iodide in vacuo at 80° C. This reagent is known to cause the fission of C—S and S—S bonds in variously constituted organic mono- and polysulfides and should therefore cause the fission of sulfur crosslinks in a vulcanizate with consequent degradation of the network (cf. Ref. 8), whereas there is no evidence that di-allylic C—C crosslinks can be similarly degraded.

Sulfur Vulcanization of Vinyl-Substituted Polysiloxanes

1957 ◽  
Vol 30 (2) ◽  
pp. 406-418
Author(s):  
K. E. Polmanteer ◽  
R. J. Koch
Keyword(s):  
Zinc Oxide ◽  
Stearic Acid ◽  
Calcium Oxide ◽  
Elemental Sulfur ◽  
Organic Polymers ◽  
Cross Link ◽  
Bivalent Metal ◽  
Organic Bases ◽  
Sulfur Vulcanization ◽  
Metal Dithiocarbamates

Abstract The vinyl content of the polysiloxane polymer affects the rate of vulcanization in such a way that the vulcanization time varies inversely with the vinyl concentration raised to a power less than 1. Furthermore, this power appears to be dependent upon the vinyl concentration, so that a stationary value cannot be quoted. Sulfur alone crosslinks only polysiloxane polymers of high vinyl content. A 4 mole per cent vinyl-containing polymer exhibited no vulcanization after 3 hours at 160° C with sulfur alone. Vulcanization times in the same range as those found with sulfur-vulcanizing organic polymers were obtained in this polysiloxane system by the proper choice of accelerators. Starting with the most active, compounds for accelerating or activating this vinyl-containing polysiloxane-sulfur system were: strong organic bases (TEPA), DPG, thiuram disulfides (TMTD), magnesium oxide, bivalent metal dithiocarbamates, thiazoles (MBT), weak organic bases (aniline), calcium oxide. Zinc oxide and litharge are inhibitors in this system to varying extents, depending on the accelerator present. Organic acids such as stearic acid inhibit vulcanization in this system. For recipes void of elemental sulfur, the following conclusions may be made: Accelerators that vulcanize vinyl-containing polysiloxanes without the aid of elemental sulfur follow very closely the list of compounds capable of vulcanizing organic polymers. (D.P.)c data indicated that two vinyl groups are involved in each cross link.

Sulfenamide Accelerated Sulfur Vulcanization of Natural Rubber in Presence and Absence of Dicumyl Peroxide

1970 ◽  
Vol 43 (6) ◽  
pp. 1311-1326 ◽  
Author(s):  
S. P. Manik ◽  
S. Banerjee
Keyword(s):  
Complex Formation ◽  
Stearic Acid ◽  
Natural Rubber ◽  
Methyl Iodide ◽  
Intermediate Complex ◽  
Radical Mechanism ◽  
Dicumyl Peroxide ◽  
Sulfur Vulcanization ◽  
Cross Links ◽  
Presence And Absence

Abstract Sulfuration by CBS acceleration both in presence and absence of ZnO and stearic acid with or without DCP has been studied in detail. It is observed that CBS increases the rate of DCP decomposition and decreases the crosslinking maxima due to DCP—ultimately leading to zero cross links with high amounts of CBS. In accordance with the observed sulfur decrease, free MBT formation, combined sulfur as MS etc., a predominantly radical mechanism has been presented, presumably not proceeding through intermediate complex formation. In mixes containing DCP together with sulfur, CBS, ZnO, and stearic acid crosslinks are found to be formed nearly additively, further confirmed by methyl iodide treatment of vulcanizates. Attempts have been made to interpret the results in terms of radical and polar mechanisms.

ZINC OXIDE VERSUS MAGNESIUM OXIDE REVISITED. PART 1

2012 ◽  
Vol 85 (1) ◽  
pp. 38-55 ◽  
Author(s):  
Manuel Guzmán ◽  
Berta Vega ◽  
Núria Agulló ◽  
Ulrich Giese ◽  
Salvador Borrós
Keyword(s):  
Zinc Oxide ◽  
Environmental Impact ◽  
Natural Rubber ◽  
Metal Oxides ◽  
Environmental Effects ◽  
Model Compound ◽  
Rubber Industry ◽  
Sulfur Vulcanization ◽  
Activator System

Abstract Zinc oxide is a widely used compound in the rubber industry due to the excellent properties that it shows as activator, and consequently, its role in the mechanism of accelerated sulfur vulcanization has been extensively studied. Due to the increased concern about its environmental effects, several research studies have been carried out in order to substitute it with different metal oxides such us MgO. The effect of the activator system in order to minimize the environmental impact of the rubber goods has been explored. The work developed is presented in two parts. In Part 1, the influence of different mixtures of ZnO and MgO on the vulcanization of natural rubber has been investigated. In Part 2, model compound vulcanization has been used to study the role of MgO on the mechanism to gain a better understanding of the differences shown in Part 1.

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.

Plasma Polymerized Primers for Rubber to Metal Bonding: Characterization of the Interphase

1995 ◽  
Vol 385 ◽  
Author(s):  
Y. M. Tsai ◽  
F. J. Boerio ◽  
Dong K. Kim
Keyword(s):  
Zinc Oxide ◽  
Free Radicals ◽  
Carbon Black ◽  
Stearic Acid ◽  
Natural Rubber ◽  
Rubber Compound ◽  
Carbonyl Groups ◽  
Double Bonds ◽  
Metal Bonding

ABSTRACTPlasma polymerized acetylene films contained mono- and di-substituted acetylene groups, aromatic groups, and carbonyl groups which resulted from reaction of residual free radicals with oxygen when the films were exposed to the atmosphere. There was some evidence for formation of acetylides in the interphase between the films and the substrates. Reactions occurring in the interphase between the plasma polymerized films and natural rubber were simulated using a model rubber compound consisting of a mixture of squalene, zinc oxide, carbon black, sulfur, stearic acid, diaryl-p-diphenyleneamine, and N,N-dicyclohexylbenzothiazole sulfenamide (DCBS). Zinc oxide and cobalt naphthenate reacted with stearic acid to form zinc and cobalt stearates. The stearates reacted with the benzothiazole sulfonamide moiety of DCBS and with sulfur to form zinc and cobalt accelerator complexes and perthiomercaptides. The complexes and perthiomercaptides reacted with squalene and the plasma polymer to form pendant groups which eventually disproportionated to form crosslinks between squalene and the primer. Migration of double bonds during reaction of the model rubber compound with the films resulted in formation of conjugated double bonds in squalene.

ZINC OXIDE VERSUS MAGNESIUM OXIDE REVISITED. PART 2

2012 ◽  
Vol 85 (1) ◽  
pp. 56-67 ◽  
Author(s):  
Manuel Guzmán ◽  
Berta Vega ◽  
Núria Agulló ◽  
Salvador Borrós
Keyword(s):  
Zinc Oxide ◽  
Environmental Impact ◽  
Natural Rubber ◽  
Metal Oxides ◽  
Environmental Effects ◽  
Model Compound ◽  
Rubber Industry ◽  
Sulfur Vulcanization ◽  
Activator System

Abstract Zinc oxide is a widely used compound in the rubber industry due to the excellent properties that it shows as an activator and, consequently, its role in the mechanism of accelerated sulfur vulcanization has been extensively studied. Due to the increased concern about its environmental effects, several research studies have been carried out in order to substitute it with different metal oxides such us MgO. The effect of the activator system in order to minimize the environmental impact of the rubber goods has been explored. The work developed is presented in two parts. In Part 1, the influence of different mixtures of ZnO and MgO in the vulcanization of natural rubber has been investigated. In Part 2 of the study, model compound vulcanization has been used to study the role of MgO on the mechanism to gain a better understanding of the differences shown in the first part.

Reinforcement of Natural Rubber with Silanized Precipitated Silica Nanofiller

2005 ◽  
Vol 78 (5) ◽  
pp. 793-805 ◽  
Author(s):  
A. Ansarifar ◽  
N. Ibrahim ◽  
M. Bennett
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Zinc Oxide ◽  
Reaction Mechanism ◽  
Energy Density ◽  
Natural Rubber ◽  
Elemental Sulfur ◽  
Stored Energy ◽  
Tear Strength ◽  
Precipitated Silica

Abstract The effect of a large amount of precipitated amorphous white silica nanofiller, pre-treated with bis[3-triethoxysilylpropyl-)tetrasulfide (TESPT), on the mechanical properties of a sulfur-cured natural rubber (NR) was studied. TESPT chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulfur-cure. The silica particles were fully dispersed in the rubber, which was cured primarily by using sulfur in TESPT, or, by adding a small amount of elemental sulfur to the cure system. The cure was also optimized by incorporating sulphenamide accelerator and zinc oxide into the rubber. The hardness, tear strength, tensile strength, and stored energy density at break of the vulcanizate were substantially improved when the filler was added. Interestingly, these properties were also enhanced when the rubber was cured primarily by using sulfur in TESPT.

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