Dimethylammonium dimethyldithiocarbamate-accelerated sulfur vulcanization. II. Vulcanization of rubbers and model compound 2,3-dimethyl-2-butene

2001 ◽  
Vol 82 (12) ◽  
pp. 3074-3083 ◽  
Author(s):  
M. Shumane ◽  
M. H. S. Gradwell ◽  
W. J. Mcgill
Keyword(s):  
Model Compound ◽  
Sulfur 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.

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.

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.

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.

Chemical Structures in CIS-1, 4-Polybutadiene Vulcanizates. Model Compound Approach

1970 ◽  
Vol 43 (3) ◽  
pp. 549-571 ◽  
Author(s):  
E. C. Gregg ◽  
S. E. Katrenick
Keyword(s):  
Molecular Weight ◽  
Calibration Curve ◽  
Model Compound ◽  
Chemical Compounds ◽  
Alkyl Derivative ◽  
Chemical Structures ◽  
Sulfur Vulcanization ◽  
Before And After ◽  
Chemical Crosslinks ◽  
In Cis

Abstract We studied the vulcanization reaction of one curing recipe for cis-1,4-polybutadiene (CB). The curing recipe was zinc oxide (ZnO), diphenylguanidine (DPG), 2,2′-bis(benzothiazolyl) disulfide (MBTS), and sulfur and it produced only polysulfidic crosslinks. Devulcanization of this CB vulcanizate by phenyllithium solution permitted a comparison of the molecular weight of the CB before and after vulcanization. A small but measurable reduction of the molecular weight of the rubber occurred as a result of the vulcanization reaction. Reaction of the curing recipe in cis, cis-1,5-cyclooctadiene (COD) permitted the study of the fate of the curing chemicals in the vulcanizate because COD is an accurate chemical model for CB. This study showed that: 1. The vulcanization reaction consumes none of the DPG and none of the ZnO. 2. An insoluble coating forms on the ZnO and separates it from the vulcanization reaction during at least part of the reaction. 3. All of the MBTS reacts to form one compound: an S-alkyl derivative of 2-mercaptobenzothiazole attached to the rubber molecule at a point next to a thiacyclohexene ring. 4. All the sulfur reacts to form crosslinks and intramolecular rings. The rings are three-, five-, and six-membered thiacycloalkanes and five- and six-membered thiacycloalkenes. Some of the rings are isolated and some are next to crosslinks. 5. The three-membered rings are episulfide and they are very likely the key intermediate to the formation of the cyclic and crosslink structures. 6. The crosslinks are polysulfidic and occur singly and as clusters of two and four. The more crosslinks in a cluster, the less unsaturation in its vicinity. The four-link cluster has no unsaturation and occurs as two pairs with thiacyclopentane rings between. The sum of the single crosslinks and clusters of crosslinks in the model network agrees with the number of elastically effective chemical crosslinks found in the CB vulcanizate as measured by swelling in benzene. The elastically effective chemical crosslinks in the vulcanizate were calculated by the Flory-Rehner equation and the Moore-Watson calibration curve. This agreement proves that the theory of rubber elasticity in the form of the Flory-Rehner equation and the Moore-Watson calibration curve may be used to count the number of elastically effective chemical crosslinks in a sulfur vulcanizate. Three new chemical compounds and a new method for quantitatively titrating mercaptans are disclosed. The success of this technique recommends it for further study of sulfur vulcanization by other recipes and the study of other vulcanizate changes.

Chemistry of Various Accelerators in an E-SBR Model Compound

2006 ◽  
Vol 79 (1) ◽  
pp. 1-25 ◽  
Author(s):  
C. C. Pierre ◽  
S. Datta ◽  
R. N. Datta ◽  
A. G. Talma
Keyword(s):  
Reaction Kinetics ◽  
Model Compound ◽  
Reaction Products ◽  
Sulfur Vulcanization ◽  
Analytical Tools

Abstract Sulfur vulcanization was carried out with 5-phenyl hex-2-ene serving as a model of e-SBR. Various accelerators have been used to study and compare the reactivity in a system containing sulfur and activators. Both HPLC and GC-MS analytical tools were used to identify the reaction products. It has been observed that the vulcanization in the presence of N-cyclohexyl-2-benzothiazole sulfenamide (CBS) generates a large amount of 2-marcaptobenzothiazole (MBT), which continuously increases and finally decreases suggesting further participation in vulcanization generating new crosslinks. The sulfenamide, N-cyclohexyl-4,6 dimethyl-2-pyrimidine sulfenamide (CDMPS) behaves different. Although it generates considerable amount of corresponding thiol, (4,6-dimethyl pyrimidine-2-thiol, DMMP) at the beginning of the reaction, no decrease has been observed during the course of further reaction suggesting that the accelerator, DMMP, somehow remains deactivated and therefore no changes in network is feasible. Identical differences exist between bis(2,2′benzothiazyl) disulfide (MBTS) and corresponding bis (4-methyl-2,2′benzothiazyl)disulfide (M-MBTS) in the reaction kinetics.

Influence of zinc oxide during different stages of sulfur vulcanization. Elucidated by model compound studies

2005 ◽  
Vol 95 (6) ◽  
pp. 1388-1404 ◽  
Author(s):  
G. Heideman ◽  
R. N. Datta ◽  
J. W. M. Noordermeer ◽  
B. van Baarle
Keyword(s):  
Zinc Oxide ◽  
Model Compound ◽  
Sulfur Vulcanization

An Appropriate Model Compound for the Accelerated Sulfur Vulcanization of Polyisoprene: I. The Mechanism of Bisbenzothiazole-2,2′-Disulfide Accelerated Vulcanization of Squalene in the Absence of ZnO

2006 ◽  
Vol 79 (1) ◽  
pp. 135-151 ◽  
Author(s):  
L. G. Boretti ◽  
C. D. Woolard
Keyword(s):  
Model Compound ◽  
Gel Permeation Chromatography ◽  
Realistic Model ◽  
Model Compounds ◽  
Whole Process ◽  
Gel Permeation ◽  
Sulfur Vulcanization ◽  
Pendent Groups

Abstract Model compound vulcanization is a useful technique for studying the mechanism of accelerated sulfur vulcanization. A technique based on gel permeation chromatography is presented which allows for the use of squalene as model compound. Squalene is shown to be a more realistic model compound for polyisoprene vulcanization in that the release of 2-mercaptobenzothiazole accompanies the formation of crosslinks. This situation accurately mirrors the situation in polyisoprene, unlike simpler model compounds such as 2-methyl-2-pentene. It is likely that a realistic model compound requires the presence of at least 2 isoprene units to allow for reactions at adjacent methylenic carbons. A mechanism for bisbenzothiazole-2,2′-disulfide vulcanization is proposed where the reaction of bisbenzothiazole-2,2′-polysulfides with squalene occurs in a concerted fashion to produce pendent groups and no 2-mercaptobenzothiazole. These pendent groups then react slowly with methylenic hydrogens on squalene to produce initial crosslinks and 2-mercaptobenzothiazole. The latter then reacts, in the presence of sulfur, with squalene to produce polysulfidic thiols which in turn react rapidly with benzothiazole groups to form further crosslinks and more 2-mercaptobenzothiazole. The whole process is autocatalytic.

Determination of Organic Bases by Ion-Pair Extraction Polarography Using Orange II as Counter Ion

1992 ◽  
Vol 57 (11) ◽  
pp. 2272-2278 ◽  
Author(s):  
Václav Koula ◽  
Daria Kučová ◽  
Jiří Gasparič
Keyword(s):  
Model Compound ◽  
Differential Pulse ◽  
Ion Pair ◽  
Differential Pulse Polarography ◽  
Orange Ii ◽  
Organic Bases ◽  
Counter Ion ◽  
Pulse Polarography ◽  
Ammonium Compounds

The combination of ion-pair extraction and differential pulse polarography is shown to be a method suitable for the determination of 10-7 mol l-1 concentrations of organic bases of quaternary ammonium compounds. Orange II (4-[2-hydroxy-1-naphtyl]azobenzenesulfonic acid) was found to be an appropriate polarographically active counter-ion. The proposed method was used for the determination of tetrapentylammonium bromide (as model compound), Septonex ([1-(ethoxycarbonyl)-pentadecyl]trimethylammonium bromide) and codeine.

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