Heats of Reaction of Natural Rubber with Sulfur

1970 ◽  
Vol 43 (6) ◽  
pp. 1275-1293 ◽  
Author(s):  
N. Bekkedahl ◽  
J. J. Weeks
Keyword(s):  
Hydrogen Sulfide ◽  
Standard Deviation ◽  
Natural Rubber ◽  
Volume Change ◽  
Side Reaction ◽  
Enthalpy Change ◽  
Heat Of Reaction ◽  
Use Of Data ◽  
Heats Of Reaction

Abstract An adiabatic copper calorimeter was used to determine the heats of vulcanization of pale crepe natural rubber with sulfur for mixtures varying in composition from 0 to 32 per cent added sulfur. The side reaction that produces hydrogen sulfide was avoided by using reaction temperatures near 155° C. Heats of reaction at 25° C and at 155° C are reported. The enthalpy change at 25° C for compounds containing up to about 18 per cent sulfur is given in joules per gram of vulcanizate by the equation, ΔH25=−21.1·S with a standard deviation of 11 J/g. Here S is the percentage of combined sulfur. Above 18 per cent sulfur the heat of reaction at 25° C remains approximately constant at 380 ± 8 J/g. A comparison is made between the heat of vulcanization and the volume change on vulcanization, both as functions of combined sulfur, by making use of data in the literature.

Heats of formation of RuO4, RuO42−, and related compounds

1969 ◽  
Vol 47 (4) ◽  
pp. 581-586 ◽  
Author(s):  
E. E. Mercer ◽  
D. T. Farrar
Keyword(s):  
Sodium Periodate ◽  
Heats Of Formation ◽  
Basic Solution ◽  
Heat Of Reaction ◽  
Kcal Mole ◽  
Heats Of Reaction ◽  
Related Compounds

The heat of reaction of ruthenium metal with bromine in basic solution, according to the equation[Formula: see text]has been measured calorimetrically. In addition, the heat of oxidation of barium ruthenate hydrate by sodium periodate to form RuO4(aq) has been determined. From these heats of reaction, and several other heats measured here, the heats of formation of several ruthenium species have been calculated. The more important of these are: Na2RuO4(aq), ΔHf = −224.1 ± 0.8; RuO42−(aq), ΔHf = −109.4 ± 1.0; RuO4(aq), ΔHf = −57.5 ± 1.1; RuO4(l), ΔHf = −57.0 ± 1.1 kcal/mole.

Studies of the Vulcanization of Rubber. X. The Vulcanization of Natural Rubber with a Mixture of Sulfur Dioxide and Hydrogen Sulfide

1953 ◽  
Vol 26 (3) ◽  
pp. 559-566 ◽  
Author(s):  
B. A. Dogadkin ◽  
F. Keifetz
Keyword(s):  
Tensile Strength ◽  
Hydrogen Sulfide ◽  
Sulfur Dioxide ◽  
Natural Rubber ◽  
Sulfur Content ◽  
Spatial Network ◽  
Smooth Curves ◽  
Multiple Cycles

Abstract 1. The dynamics of the changes of the properties of rubber during vulcanization by a mixture of sulfur dioxide and hydrogen sulfide, in distinction from conventional vulcanization by sulfur, is expressed by smooth curves. No vulcanization optimum is observed. 2. With multiple cycles of vulcanization, the increase of bound sulfur content above 3 per cent results in a decrease of tensile strength. 3. Changes of tensile strength of the vulcanizate dependent on changes of sulfur content are attributable to the influence of the density of the spatial network on the orientation processes during deformation.

Studies of the Hard Rubber Reaction. I. Heat of Reaction

1963 ◽  
Vol 36 (4) ◽  
pp. 1059-1070 ◽  
Author(s):  
M. L. Bhaumik ◽  
D. Banerjee ◽  
Anil K. Sircar
Keyword(s):  
Thermal Analysis ◽  
Hydrogen Sulfide ◽  
Differential Thermal Analysis ◽  
Exothermic Reaction ◽  
Heat Evolution ◽  
Linear Increase ◽  
Heat Of Reaction ◽  
Dehydrogenation Reaction ◽  
Rate Of Reaction

Abstract A method for the determination of the heat of the hard-rubber reaction by the application of differential thermal analysis is reported. The heat of reaction was determined with stocks containing different rubber/sulfur ratios and also with a 68/32 stock, preheated to contain different amounts of combined sulfur. Heat evolution is observed first with samples containing about 7 per cent sulfur and therefrom the amount of heat evolved shows a nearly linear increase up to 30 per cent sulfur. With increasing combined sulfur in the 68/32 stock, the quantity of exothermic heat gradually diminishes; so also does the temperature of initiation, i.e., the temperature at which heat evolution appears to begin. Initiation of the exothermic reaction appears to be a function of composition and temperature of the mass. An increase in the rate of reaction was observed when the composition reached 0.5 g-atom of sulfur per isoprene unit. An endothermic dehydrogenation reaction is observed at the end of the hard-rubber reaction. This, however, does not affect the determination of exothermic heat, because there is similar dehydrogenation taking place in the reference material (ebonite) which almost balances this heat loss. The final product has a lower sulfur content due to loss of sulfur as hydrogen sulfide.

Heats of Vulcanization of Synthetic Rubbers

1944 ◽  
Vol 17 (2) ◽  
pp. 404-411 ◽  
Author(s):  
P. L. Bruce ◽  
R. Lyle ◽  
J. T. Blake
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Chemical Reactions ◽  
Side Reaction ◽  
Heat Evolution ◽  
Butyl Rubber ◽  
Vulcanized Rubber ◽  
Principal Reaction ◽  
Low Sulfur ◽  
Quantity Of Heat

Abstract 1. The heats of vulcanization for natural rubber and Buna-S are nearly equal. The data for both materials indicate two different chemical reactions during vulcanization. At low sulfur percentages, the principal reaction forms soft vulcanized rubber and is accompanied by little or no heat evolution. Above the 2 per cent sulfur region, a second reaction predominates, forming hard rubber and producing a relatively large quantity of heat. 2. The presence of an accelerator (Santocure) in Buna-S has little, if any, effect on heat of vulcanization. 3. The addition of carbon black to Buna-S lowers the heat of vulcanization in the region above 4 per cent sulfur. The calories evolved in a 10 per cent sulfur compound decrease linearly with percentage of carbon black. 4. The heats of vulcanization of Buna-N (Hycar OR-15) indicate the presence of two chemical reactions. Unlike natural rubber and Buna-S, the ebonite reaction does not predominate until the sulfur concentration is raised above 10 per cent. 5. The heat of vulcanization of Butyl rubber with sulfur is equal to the heat evolved with natural rubber containing 0.6 per cent sulfur. If one sulfur atom reacts per double bond, the maximum amount combining would be 0.72 per cent sulfur. During the vulcanization of Butyl rubber with p-quinone dioxime and lead peroxide, a large amount of heat is evolved by a side reaction between the vulcanizing agents. The reaction involving the Butyl rubber produces about 6 calories per gram, a considerably higher value than the 1 calorie produced by sulfur vulcanization. 6. The heat of vulcanization of Neoprene-GN without added agents corresponds to a value for smoked sheet rubber containing 4.5 per cent sulfur. The addition of zinc oxide and magnesia decreases the heat of vulcanization.

The solubility of potassium from soil illites. V. Interlayer hydrogen ions; heats of reaction; and synopsis

Soil Research ◽  
1967 ◽  
Vol 5 (2) ◽  
pp. 203 ◽  
Author(s):  
BM Tucker
Keyword(s):  
Calcium Chloride ◽  
Calcium Ions ◽  
Temperature Rise ◽  
Chloride Solution ◽  
Calcium Chloride Solution ◽  
Hydrogen Ion ◽  
Heat Of Reaction ◽  
Hydrogen Ions ◽  
Kcal Mole ◽  
Heats Of Reaction

When potassium is readsorbed at interlayer sites in soil illites after displacement in calcium chloride solution, hydrogen ions are released in proportions ranging from 1/6 to 1/10 of the potassium adsorbed. This supports the conclusions of earlier work that release of potassium by calcium ions from these sites requires the intervention of hydrogen ions in the approximate ratio of one hydrogen ion to three calcium ions. The release of potassium increased about 1.4 times for a temperature rise from 10 to 30�C. The heat of reaction was 3 or 4 kcal/mole potassium released. This is consistent with a reaction between ions and charged sites as the heats of many ionic reactions are of this magnitude; and it appears to be less than the heats of decomposition of the clay mineral lattice. A summary of the findings of Parts I-V of this series appears in the Synopsis

Heat of Reaction Measurements of Sodium Borohydride Alcoholysis

2005 ◽  
Author(s):  
Jinsong Zhang ◽  
T. S. Fisher ◽  
Jay P. Gore ◽  
P. Veeraraghavan Ramachandran
Keyword(s):  
Ethylene Glycol ◽  
Sodium Borohydride ◽  
Aqueous System ◽  
Heat Of Reaction ◽  
New Approach ◽  
On Demand ◽  
Heats Of Reaction ◽  
Prior Literature ◽  
Storage Methods ◽  
The Cost

On-board hydrogen storage has been identified as one of the most challenging technical barriers to the transition from gasoline to hydrogen powered vehicles. The Hydrogen-On-Demand™ system patented by Millenium Cell Inc. uses sodium borohydride and water to generate hydrogen when needed. The system has many advantages over other types of storage methods such as compressed hydrogen, liquid hydrogen and metal hydrides. Nevertheless, the cost of making and regenerating sodium borohydride is too high. A recently filed patent indicates that sodium borohydride alcoholysis (e.g. using ethylene glycol) may offer some advantages over the aqueous system in terms of regeneration, which may significantly reduce the cost to regenerate sodium borohydride. To begin evaluating the energy efficiency of this new approach, this work experimentally characterizes the heat of reaction of sodium borohydride with ethylene glycol. The heat of reaction was measured to be approximately 220 kJ/mol (exothermic). For the sodium borohydride and water reaction, two different heat of reaction values have been reported in prior literature. The present work shows that the heats of reaction for both sodium borohydride hydrolysis and alcoholysis are both near 220 kJ/mol exothermically.

The Synergistic Effect of Natural Rubber on the Crystallization of Lithium Poly(Isoprene)S (Coral Rubber)

1972 ◽  
Vol 45 (5) ◽  
pp. 1303-1314 ◽  
Author(s):  
M. J. Brock ◽  
Marjorie J. Hackathorn
Keyword(s):  
Synergistic Effect ◽  
Natural Rubber ◽  
Silver Nitrate ◽  
Induction Period ◽  
Volume Change ◽  
Crystallization Rate ◽  
Similar Species ◽  
Retarding Effect ◽  
Seeding Effect ◽  
Crystallizable Polymer

Abstract The influence of silver nitrate on the crystallization of poly(isoprene)s has been demonstrated as well as the synergistic effect of natural rubber on the crystallization of lithium catalyzed poly(isoprene). This synergism does not appear to be a “seeding” effect in the strictly definitive sense, since no seed crystals are actually added. In this case a better description of this effect might be cocrystallization where nucleation is promoted by the addition of a quantity of a highly regular similar species. Actually there is a good probability that the nucleating crystals themselves contain segments of the synthetic poly(isoprene). This conclusion is supported by the data shown in Figure 6 for a 50/50 mixture of natural rubber and a noncrystallizable Alfin polymer. The dilato meter curve for this mixture indicates that the 50 per cent non-crystallizable polymer has a slight retarding effect on the induction period for the crystallization of the natural rubber but the crystallization rate of the natural rubber in the 50/50 mixture is quite rapid up to the total volume change expected for natural rubber portion of the mixture. However, in the presence of 50 per cent of a crystallizable lithium poly(isoprene) (also shown in Figure 6), the crystallization rate of this mixture is much slower due to co crystallization. The proposed change from head-tail cis-1,4 addition to tail-head cis-4,1 addition whenever a 3,4 unit is introduced into the polymer chain seems to explain the experimental crystallinity data obtained in these studies. In addition, it raises some questions about the polymerization mechanisms involved and resulting from the orientation of a 3,4 unit being added to the growing end of a polydienyl chain.

Volume Changes in the Stretching of Vulcanized Natural Rubber

1951 ◽  
Vol 24 (4) ◽  
pp. 767-772 ◽  
Author(s):  
Geoffrey Gee ◽  
Jan Stern ◽  
L. R. G. Treloar
Keyword(s):  
Tensile Stress ◽  
Natural Rubber ◽  
Volume Change ◽  
Isotropic Material ◽  
Volume Changes ◽  
Change Mechanism ◽  
Hydrostatic Component

Abstract Measurements are presented of the volume changes accompanying small (≯100%) elongations of vulcanized natural rubber completely free from undissolved particles. The small expansions found agree with those calculated from the known compressibility of rubber and the hydrostatic component of the stretching force. It is pointed out that this volume change mechanism applies generally to any isotropic material, and does not contribute significantly (in rubber) to the tensile stress.

Volume change and gas transport at uniaxial deformation of filled natural rubber

1987 ◽  
Vol 22 (10) ◽  
pp. 3470-3476 ◽  
Author(s):  
W. F. Reichert ◽  
M. K. Hopfenm�ller ◽  
D. G�ritz
Keyword(s):  
Natural Rubber ◽  
Volume Change ◽  
Gas Transport ◽  
Uniaxial Deformation

Anaerobic fructolysis, lactic acid and heat production of bull spermatozoa

1964 ◽  
Vol 159 (975) ◽  
pp. 291-296 ◽  
Keyword(s):  
Lactic Acid ◽  
Standard Deviation ◽  
Heat Production ◽  
Metabolic Pathways ◽  
Enthalpy Change

A comparison has been made of the fructose broken down, lactic acid produced and heat evolved by washed anaerobic bull spermatozoa. On the average, 19·5% more fructose was broken down than lactic acid produced (standard deviation 2·0%, 95% fiducial limits 15·2 and 23·8%). The amount of heat produced by the spermatozoa was on the average only 9·7% more than the heat expected on the basis of the enthalpy change associated with the breakdown of that part, 80·5%, of the fructose which was broken down to lactic acid. The standard deviation of the 9·7% was 3·4 %, with 95% fiducial limits 2·3 and 17·1%. The implications of these findings are discussed in relation to the metabolic pathways in anaerobic bull spermatozoa.

Sign in / Sign up

Export Citation Format

Share Document