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.

Multifunctional Additives as Zinc-Free Curatives for Sulfur Vulcanization

2006 ◽  
Vol 79 (4) ◽  
pp. 561-588 ◽  
Author(s):  
Geert Heideman ◽  
Jacques W. M. Noordermeer ◽  
Rabin N. Datta ◽  
Ben van Baarle
Keyword(s):  
Physical Properties ◽  
Model Compound ◽  
Vital Role ◽  
The State ◽  
Sulfur Vulcanization ◽  
Multifunctional Additives ◽  
System Inclusion ◽  
The Cost ◽  
Conventional Systems ◽  
Vulcanization Process

Abstract Concern about the release of eco-toxic zinc species from rubbers into the environment leads to an increasing interest in potential substitutes. This investigation reports on the application of Multifunctional Additives, amines complexed with fatty acids, for sulfur vulcanization of rubbers. Good physical properties can be obtained in s-SBR compounds using the MFA/S cure system, albeit at the cost of a shortened scorch time as compared to a ZnO/stearic acid system. Inclusion of ZnO lengthens the scorch time, though it reduces the state of cure and ultimate properties. The amount of ZnO used in the MFA-formulations is considerably lower than in the conventional systems. The introduction of CaO and MgO leads to an improvement in the state of cure and physical properties. Amines play a vital role in the vulcanization process, hence various amine-complexes have been synthesized and investigated as zinc-free curatives in s-SBR compounds. It is observed that the scorch time is related to the basicity of the amines. The results of Model Compound Vulcanization studies with MFAs reveal a fast decomposition of the accelerator and some differences in the distribution of the crosslinked products. The conclusion must be drawn, that the chemistry involved in the MFA-systems is fundamentally different from the conventional vulcanization systems.

Zinc Loaded Clay as Activator in Sulfur Vulcanization: A New Route for Zinc Oxide Reduction in Rubber Compounds

2004 ◽  
Vol 77 (2) ◽  
pp. 336-355 ◽  
Author(s):  
Geert Heideman ◽  
Jacques W. M. Noordermeer ◽  
Rabin N. Datta ◽  
Ben van Baarle
Keyword(s):  
Model Compound ◽  
Exchange Process ◽  
Zinc Level ◽  
Zinc Compounds ◽  
Ion Exchange Process ◽  
Rubber Compounds ◽  
Wide Range ◽  
Sulfur Vulcanization ◽  
Reduction Of Zno ◽  
Insight Into

Abstract Concern about the release of eco-toxic zinc species from rubbers into the environment leads to an increasing interest in potential substitutes. Although alternative metal oxides and zinc compounds as activators for sulfur vulcanization have been studied thoroughly, at present no viable alternative has been found to eliminate ZnO completely from rubber compounds, without significantly jeopardizing processing as well as performance characteristics. In this paper, the application of a new activator for sulfur vulcanization will be discussed. This activator is developed based on the assumption that an increase in the availability of Zn2+-ions could lead to a considerable reduction of ZnO in rubber compounds. Montmorillonite clay was used as carrier material and loaded with Zn2+-ions via an ion-exchange process. Application in a wide range of natural and synthetic rubbers has been explored. Results clearly demonstrate that this Zn-Clay can substitute conventional ZnO, retaining the curing and physical properties of the rubber products but reducing the zinc concentration with a factor 10 to 20. Model Compound Vulcanization studies have been used to gain an insight into the mechanism of this activator. It can be concluded that systems with Zn2+-ions on a support represent a new and novel route to reduce the zinc level, and therefore to minimize its environmental impact significantly.

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.

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.

Model Compound Vulcanization And IGC As Prediction Tools In Carbon Black Effect On Vulcanization

2002 ◽  
Vol 731 ◽  
Author(s):  
E. Vidal-Escales ◽  
M.P. Diago ◽  
S. Borrós
Keyword(s):  
Carbon Black ◽  
Active Sites ◽  
Inverse Gas Chromatography ◽  
Model Compound ◽  
Lack Of Information ◽  
Model Molecule ◽  
Wide Range ◽  
Surface Active ◽  
Vulcanization Process

AbstractThe influence of carbon black (CB) in a rubber formulation can be observed during the vulcanization process. However, looking through literature there seems to be a lack of information related to the role of CBs in vulcanization reaction. The present work is focused on the application of Model Compound Vulcanization (MCV) approach and Inverse Gas Chromatography (IGC) to predict the role of carbon black on vulcanization.Squalene was chosen as the model molecule of natural rubber to undergo the vulcanization in the presence of carbon black. This methodology gives rise to several advantages. On one hand, the model allows following the accelerator, vulcanization intermediate compounds, and even the crosslinked model molecule. Moreover, the similarity between the model and the polymer chain allows further extrapolation to discover the real sample's performance. In order to complete the information required IGC analysis was used. IGC has been performed using both dispersive and specific probes to elucidate a wide range of CB surface active sites.The application of this prediction tool to special grades revealed different effects that have been verified with real formulations in both cases.

Analysis of the Mechanism of N-t-Butyl-2-Benzothiazole Sulfenamide Accelerated Sulfur Vulcanization of cis-Polyisoprene

1994 ◽  
Vol 67 (2) ◽  
pp. 348-358 ◽  
Author(s):  
M. R. Krejsa ◽  
J. L. Koenig ◽  
A. B. Sullivan
Keyword(s):  
Double Bond ◽  
Network Analysis ◽  
Mechanistic Studies ◽  
Exchange Reactions ◽  
Methyl Carbon ◽  
Double Bond Migration ◽  
Sulfur Vulcanization ◽  
Cis And Trans ◽  
Vulcanization Process

Abstract Results of previously published work involving network analysis and accelerator intermediate analysis of cis-polyisoprene were compared to help correlate and rationalize network/chemistry relationships. Both classical chemical probe network analysis and further NMR measurements (DEPT analysis) were used as necessary to verify NMR peak assignments. Furthermore, samples of the conventional formulation were vulcanized in the absence of zinc oxide and stearic acid to help elucidate the role of zinc in the vulcanization process. Polysulfidic dibenzothiazole accelerator intermediates were proposed to produce allylic substituted cis-polysulfides both with and without double bond migration, while zinc polysulfidic dibenzothiazole accelerator intermediates were proposed to produce allylic cis and trans polysulfides substituted structures with no double bond migration. Polysulfidic substitution on the isoprene methyl carbon was shown to result from exchange reactions during network maturation. The network-chemistry relationships were compared with earlier mechanistic studies and several points of agreement were noted.

2-t-Butylbenzothiazole Sulfenamide Accelerated Sulfur Vulcanization of Polyisoprene

1999 ◽  
Vol 72 (1) ◽  
pp. 65-73 ◽  
Author(s):  
M. H. S. Gradwell ◽  
M. J. van der Merwe
Keyword(s):  
Special Reference ◽  
Exchange Reaction ◽  
Differential Scanning Calorimeter ◽  
Reaction Mechanisms ◽  
Sulfur Vulcanization ◽  
Pendent Groups ◽  
Delayed Action

Abstract The mechanism of 2-t-butylbenzothiazole sulfenamide (TBBS) accelerated sulfur vulcanization of polyisoprene was investigated. Samples of compounded rubber were heated in a differential scanning calorimeter to preselected temperatures or degrees of vulcanization, the reaction stopped, and the products analyzed. TBBS polysulfides, formed from the reaction of TBBS with sulfur, react with the rubber chain to form benzothiazole pendent groups and free t-butylamine. The delayed action of TBBS accelerated sulfur vulcanization was shown to be due to an exchange reaction involving benzothiazole terminated pendent groups and TBBS. Crosslinking occurred very rapidly once the TBBS was depleted. Special reference was made to the role of the amine. Reaction mechanisms were proposed to account for the formation of products.

The Role of Uric Acid in the Acute Myocardial Infarction: A Narrative Review

Angiology ◽  
2021 ◽  
pp. 000331972110125
Author(s):  
Atalay Demiray ◽  
Baris Afsar ◽  
Adrian Covic ◽  
Masanari Kuwabara ◽  
Charles J. Ferro ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Uric Acid ◽  
Adverse Outcomes ◽  
Narrative Review ◽  
Background Information ◽  
Pathophysiological Role ◽  
Artery Disease ◽  
Pathologic Processes

Increased serum uric acid (SUA) levels have been associated with various pathologic processes such as increased oxidative stress, inflammation, and endothelial dysfunction. Thus, it is not surprising that increased SUA is associated with various adverse outcomes including cardiovascular (CV) diseases. Recent epidemiological evidence suggests that increased SUA may be related to acute myocardial infarction (AMI). Accumulating data also showed that elevated UA has pathophysiological role in the development of AMI. However, there are also studies showing that SUA is not related to the risk of AMI. In this narrative review, we summarized the recent literature data regarding SUA and AMI after providing some background information for the association between UA and coronary artery disease. Future studies will show whether decreasing SUA levels is beneficial for outcomes related to AMI and the optimum SUA levels for best outcomes in CV diseases.

scholarly journals Estrogen binding by leukocytes during phagocytosis,.

1977 ◽  
Vol 145 (4) ◽  
pp. 983-998 ◽  
Author(s):  
S J Klebanoff
Keyword(s):  
Chronic Granulomatous Disease ◽  
Reaction Mechanisms ◽  
Dehydrogenase Deficiency ◽  
Cell Types ◽  
Neutrophil Function ◽  
Granulomatous Disease ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Estrogen Binding ◽  
Two Populations

Estradiol binds covalently to normal leukocytes during phagocytosis. The binding involves three cell types, neutrophils, eosinophils, and monocytes and at least two reaction mechanisms, one involving the peroxidase of neutrophils and monocytes (myeloperoxidase [MPO]) and possibly the eosinophil peroxidase, and the second involving catalase. Binding is markedly reduced when leukocytes from patients with chronic granulomatous disease (CGD), severe leukocytic glucose 6-phosphate dehydrogenase deficiency, and familial lipochrome histiocytosis are employed and two populations of neutrophils, one which binds estradiol and one which does not, can be demonstrated in the blood of a CGD carrier. Leukocytes from patients with hereditary MPO deficiency also bind estradiol poorly although the defect is not as severe as in CGD. These findings are discussed in relation to the inactivation of estrogens during infection and the possible role of estrogens in neutrophil function.

Sign in / Sign up

Export Citation Format

Share Document