The Reaction Mechanism of Thiuram Disulfide Vulcanization of Poly-1,5-Dienes, Particularly of Natural Rubber

1957 ◽  
Vol 30 (2) ◽  
pp. 393-396
Author(s):  
G. Blelstein ◽  
W. Scheele
Keyword(s):  
Reaction Mechanism ◽  
Natural Rubber ◽  
Temperature Dependence ◽  
Reaction Kinetics ◽  
Experimental Work ◽  
Complete Solution ◽  
Experimental Results ◽  
Present Treatment ◽  
Final Interpretation ◽  
Kinetics Of

Abstract In previous publications on thiuram vulcanization we confined ourselves to the presentation and discussion of our extensive experimental work. We had investigated quantitatively the conversion of thiuram disulfides and were in a position to describe the kinetics of thiuram vulcanization. Such investigations are, of course, of particular value to technology for information about the rate and temperature dependence of vulcanization reactions. Our experiments were therefore not primarily designed to determine the details of reaction mechanism, which we had hitherto treated with restraint, and experience shows that the study of reaction kinetics does not always provide the key to a complete solution. All the same, it now seems reasonable to pick out some of the results we have obtained, and so consider the question of a reaction mechanism for thiuram vulcanization. We should, however, like to state, that although the present treatment concerns matters which may include some pertinent points, it does not necessarily represent a final interpretation. It is to be stressed, that any postulated reaction mechanism must explain what we regard as a stoichiometrical, i.e., concentration and temperature independent conversion of thiuram disulfide to zinc dithiocarbamate. The following experimental results thus formed the basis of our considerations:

scholarly journals A kinetic study of rabbit muscle pyruvate kinase

1973 ◽  
Vol 131 (2) ◽  
pp. 223-236 ◽  
Author(s):  
S. Ainsworth ◽  
N. Macfarlane
Keyword(s):  
Reaction Mechanism ◽  
Kinetic Study ◽  
Pyruvate Kinase ◽  
Random Order ◽  
Experimental Results ◽  
Rabbit Muscle ◽  
Dead End ◽  
Inhibition Constants ◽  
Muscle Pyruvate Kinase ◽  
Kinetics Of

The paper reports a study of the kinetics of the reaction between phosphoenolpyruvate, ADP and Mg2+ catalysed by rabbit muscle pyruvate kinase. The experimental results indicate that the reaction mechanism is equilibrium random-order in type, that the substrates and products are phosphoenolpyruvate, ADP, Mg2+, pyruvate and MgATP, and that dead-end complexes, between pyruvate, ADP and Mg2+, form randomly and exist in equilibrium with themselves and other substrate complexes. Values were determined for the Michaelis, dissociation and inhibition constants of the reaction and are compared with values ascertained by previous workers.

Vulcanization of Elastomers. 40. Vulcanization of Natural Rubber and Synthetic Rubber with Sulfur in Presence of Sulfenamides. III

1965 ◽  
Vol 38 (1) ◽  
pp. 189-203 ◽  
Author(s):  
W. Scheele ◽  
J. Helberg
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Natural Rubber ◽  
Rate Constants ◽  
Sulfur Concentration ◽  
Kcal Mole ◽  
Synthetic Rubber ◽  
Chemical Constitution ◽  
Induction Times ◽  
Kinetics Of

Abstract Vulcanization of natural rubber with sulfur was studied in presence of six sulfenamides, to determine the effect of the chemical constitution of the sulfenamide on sulfur decrease and on crosslinking. The results can be condensed as follows: (1) The kinetics of sulfur disappearance is in every respect qualitatively independent of the chemical constitution of the sulfenamide. (2) For the sulfenamides investigated, the smallest and largest rate constants for sulfur decrease differed only by a factor of two. (3) Greater differences are encountered in the induction times for sulfur decrease and for crosslinking. The latter are notably longer than those for sulfur disappearance. (4) The same activation energy, 23 kcal/mole, is derived from the temperature dependence of the induction times for all the sulfenamides. (5) The dissociation of sulfenamides in solution and their reaction with mercaptobenzothiazole were investigated further. The results provide the basis for a proposed reaction mechanism, which is presented in detail and can account for a number of the features typical of sulfenamide-accelerated vulcanization. (6) The drop in sulfur concentration goes at practically the same rate, if one introduces, instead of N, N-dicyclohexyl-2-benzothiazolesulfenamide, the corresponding ammonium mercaptide in equimolar concentration.

Kinetics of autothermal thermophilic aerobic digestion – application and extension of Activated Sludge Model No 1 at thermophilic temperatures

2007 ◽  
Vol 56 (9) ◽  
pp. 137-145 ◽  
Author(s):  
R. Kovács ◽  
P. Miháltz ◽  
Zs. Csikor
Keyword(s):  
Mathematical Model ◽  
Activated Sludge ◽  
Temperature Dependence ◽  
Decay Rates ◽  
Experimental Results ◽  
Aerobic Digestion ◽  
Activated Sludge Model ◽  
Thermophilic Aerobic Digestion ◽  
Autothermal Thermophilic Aerobic Digestion ◽  
Kinetics Of

The application of an ASM1-based mathematical model for the modeling of autothermal thermophilic aerobic digestion is demonstrated. Based on former experimental results the original ASM1 was extended by the activation of facultative thermophiles from the feed sludge and a new component, the thermophilic biomass was introduced. The resulting model was calibrated in the temperature range of 20–60 °C. The temperature dependence of the growth and decay rates in the model is given in terms of the slightly modified Arrhenius and Topiwala-Sinclair equations. The capabilities of the calibrated model in realistic ATAD scenarios are demonstrated with a focus on autothermal properties of ATAD systems at different conditions.

Elucidating the reaction kinetics of lithium–sulfur batteries by operando XRD based on an open-hollow S@MnO2 cathode

2019 ◽  
Vol 7 (12) ◽  
pp. 6651-6658 ◽  
Author(s):  
Shaozhuan Huang ◽  
Lixiang Liu ◽  
Ye Wang ◽  
Yang Shang ◽  
Lin Zhang ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Reaction Mechanism ◽  
Reaction Kinetics ◽  
Lithium Sulfur Batteries ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Lithium Sulfur

This work studied the reaction mechanism and kinetics of Li–S batteries via operando XRD and quantitative analysis based on different cathode structures.

Crystallization in Natural Rubber. IV. Temperature Dependence

1956 ◽  
Vol 29 (3) ◽  
pp. 794-805
Author(s):  
A. N. Gent
Keyword(s):  
Stearic Acid ◽  
Natural Rubber ◽  
Temperature Dependence ◽  
Experimental Work ◽  
Crystallization Process ◽  
Vulcanized Rubber ◽  
Maximum Value ◽  
Similar Temperature Dependence ◽  
Similar Temperature

Abstract Considerable experimental work on the crystallization of unstrained natural rubber, both vulcanized and unvulcanized, has been described previously. The rate of crystallization of raw rubber increases as the temperature at which the crystallization occurs is reduced, until a maximum value is attained at about −26° C. On lowering the temperature further, the rate decreases continuously. A similar temperature dependence is found for vulcanized rubber, although the rate at any given temperature is lower. Small quantities of certain impurities, for example, stearic acid, greatly increase the rate of crystallization of raw rubber. Such impurities are normally present in plantation smoked-sheet rubber, on which many of the reported measurements of rates of crystallization have been made. The measurements now reported have, therefore, been made with a purified rubber (deproteinized pale crepe) containing negligible quantities of the relevant impurities. Peroxide vulcanizates prepared from such a rubber have also been examined. The crystallization process was followed dilatometrically.

Studies of the Vulcanization of High Elastic Polymers. V. Vulcanization of Natural Rubber by Tetramethylthiuram Monosulfide and Sulfur

1956 ◽  
Vol 29 (1) ◽  
pp. 48-62 ◽  
Author(s):  
Walter Scheele ◽  
Georg Bielstein
Keyword(s):  
Natural Rubber ◽  
Temperature Dependence ◽  
Order Reaction ◽  
Experimental Results ◽  
First Order Reaction ◽  
First Order ◽  
Temperature Range ◽  
Quantitative Formation ◽  
Energy Relationships

Abstract The vulcanization of natural rubber (pale crepe) by tetramethylthiuram monosulfide and sulfur (1 mole monosulfide per gram-atom of sulfur) has been studied in the temperature range from 90° to 150° C. The following results were obtained : 1. During vulcanization, the concentration of the thiuram monosulfide and also of the sulfur decreases. 2. In accordance with a first-order reaction, about 66 mole-per cent of zinc dithiocarbamate is formed (calculated on the amount of thiuram monosulfide added). Thus the same relationships were found as in vulcanization with thiuram disulfides. 3. The vulcanization of rubber with thiuram monosulfide and sulfur is, therefore, nothing else than vulcanization by thiuram disulfide, whose quantitative formation precedes the actual vulcanization reaction. 4. In no stage of vulcanization could thiuram disulfide be detected with certainty in the extracts of the vulcanizates. It must be assumed, therefore, that it reacts with the rubber instantly after it is formed. 5. The velocity constants derived for the dithiocarbamate formation at the various temperatures both from the experimental results and from the graphical presentations have been given, and their temperature dependence has been discussed. At lower temperatures, the influence of the prior interaction of the monosulfide with sulfur makes its influence on the energy relationships felt. 6. It is once more emphasized that in thiuram vulcanization it cannot be a question of a vulcanization with sulfur. In this connection we take a decided stand also with regard to the results of the more recent investigations of Craig and his coworkers.

scholarly journals Insights into Thermal Degradation Behaviors and Reaction Kinetics of Medical Waste Infusion Bag and Nasal Oxygen Cannula

Processes ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 27
Author(s):  
Lifan Zhang ◽  
Jiajia Jiang ◽  
Tengkun Ma ◽  
Yong Pan ◽  
Yanjun Wang ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Thermal Degradation ◽  
Reaction Kinetics ◽  
Three Dimensional ◽  
Inert Atmosphere ◽  
Medical Waste ◽  
Zero Order ◽  
Heating Rates ◽  
Degradation Behaviors ◽  
Kinetics Of

The thermal degradation behaviors and reaction kinetics of medical waste infusion bag (IB) and nasal oxygen cannula (NOC) were investigated under inert atmosphere with the heating rates of 5, 10, 15, and 25 K·min−1. Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS), and Friedman were employed to estimate the activation energy. Coats–Redfern and Kennedy–Clark methods were adopted to predict the possible reaction mechanism. The results suggested that the reaction mechanism of IB pyrolysis was zero-order, and that of NOC pyrolysis was concluded that zero-order for the first stage and three-dimensional diffusion Jander equation for the second stage. Based on the kinetic compensation effect, the reconstructed reaction models for IB and NOC pyrolysis were elaborated by introducing adjustment functions. The results indicated that the reconstructed model fitted well with the experimental data. The results are helpful as a reference and provide guidance for the determination of IB and NOC degradation behaviors and the simulation of parameters.

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