Sulfur Bond in Vulcanizates Implications of Halogen Reactions

1947 ◽  
Vol 20 (3) ◽  
pp. 627-648
Author(s):  
S. R. Olsen ◽  
C. M. Hull ◽  
Wesley G. France
Keyword(s):  
Double Bond ◽  
Carbon Tetrachloride ◽  
Sulfur Atom ◽  
Side Reactions ◽  
Double Bonds ◽  
Vulcanized Rubber ◽  
Iodine Chloride ◽  
Allyl Sulfide ◽  
Sulfur Bond

Abstract 1. When iodine chloride is used for the determination of double bonds in sulfur-vulcanized rubber or GR-S, it undergoes side reactions induced by combined sulfur. 2. Bromine in carbon tetrachloride is believed to give a satisfactory measure of the double bonds in a rubber-sulfur vulcanizate dissolved in dichlorobenzene-chloroform mixture. 3. The relation of one double bond consumed per sulfur atom combined in the rubber-sulfur type vulcanizate was confirmed. 4. Organic accelerators (in the absence of metal activators) catalyze the combination of sulfur without altering the ratio of one double bond loss per sulfur atom combined. 5. The introduction of a metal oxide or soap, such as zinc, causes a different type of vulcanization, which results in less than one double bond consumed per sulfur atom combined. 6. The reactions of propyl sulfide, dodecyl sulfide, propyl disulfide, allyl sulfide, methallyl sulfide, and butylmethallyl sulfide with iodine chloride and with bromine, respectively, are described. 7. The behavior of rubber-sulfur vulcanizates resembles that of butylmethallyl sulfide in reactions with iodine chloride and bromine, respectively; this suggests an alkyl-allyl type sulfur bond. 8. The theory of vulcanization proposed by Armstrong, Little, and Doak, based on the α-methylenic concept of Farmer, is supported by the findings of this investigation.

Infrared Study of Some Structural Changes in Natural Rubber during Vulcanization

1958 ◽  
Vol 31 (4) ◽  
pp. 719-736 ◽  
Author(s):  
Frederic J. Linnig ◽  
James E. Stewart
Keyword(s):  
Double Bond ◽  
Gamma Rays ◽  
Structural Changes ◽  
Elemental Sulfur ◽  
Carboxyl Groups ◽  
Double Bonds ◽  
Infrared Study ◽  
Tetramethylthiuram Disulfide ◽  
Vulcanized Rubber ◽  
Double Bond Shift

Abstract A knowledge of the structure of vulcanized rubber is essential to the interpretation of vulcanization and oxidation studies and the physical properties of the material. In the present work an infrared study has been made of structures resulting from a number of different methods of vulcanization. Sulfur vulcanizates show the presence of a shifted double bond, originally observed by Sheppard and Sutherland. The presence of conjugated double bonds is also indicated. Accelerators such as tetramethylthiuram disulfide and zinc dibutyl dithiocarbamate increase the rate of the double-bond shift and reduce the amount of conjugated double bonds. Neither the double-bond shift nor conjugation is observed as a result of vulcanization with tetramethylthiuram disulfide alone, hydrogen sulfide and sulfur dioxide (Peachey process), a peroxide, or gamma rays. These result in a possible decrease in carbonyl structures, and in the case of the last three, possible increased absorption due to OH and ionized carboxyl groups. Apparently, the double-bond shift and conjugation are primarily phenomena related to the use of elemental sulfur. The other vulcanization systems studied evidently involve different mechanisms. An implication of the present work is that there may be a relationship between the reported ease of oxidation of sulfur vulcanizates, accelerated vulcanizates, and sulfurless vulcanizates (tetramethylthiuram disulfide alone), which decreases in the order named, and the probable amount of conjugation in the compound, which decreases in the same order.

The Polarographic Determination of Organic Accelerators of Vulcanization

1941 ◽  
Vol 14 (4) ◽  
pp. 914-919 ◽  
Author(s):  
Gerard Proske
Keyword(s):  
Double Bond ◽  
Organic Compounds ◽  
Analytical Determination ◽  
Polarographic Method ◽  
Rubber Industry ◽  
Vulcanized Rubber ◽  
Color Reactions ◽  
Analytical Utility ◽  
Kjeldahl Nitrogen

Abstract In spite of the great importance which vulcanization accelerators have attained in the rubber industry, there is still an almost complete lack of analytical methods, both for determining the accelerator contents of rubber mixtures and for identifying accelerators in vulcanized rubber. Apart from the wholly unsatisfactory and uncertain method of deciding the existence of organic accelerators in vulcanized rubber by a Kjeldahl nitrogen determination, there is little of value in the literature. Twiss and Martin have described a few qualitative reactions of accelerators. Recently Shimada described some color reactions of accelerators with cobalt oleate, but the analytical utility of these reactions is very doubtful. Of far more promise than these is the polarographic method, the value of which in the analytical determination of a series of important accelerators was proved in an investigation which will be described in the present paper. It had already been proved in earlier polarographic investigations that organic compounds containing nitrogen with a double bond can be reduced electrolytically, provided groups with a tendency to rupture are close to the double bond. Shikata and Tachi have shown this to be true of azobenzene, and Winkel and Proske of dimethylquinoxaline.

scholarly journals Investigations of infra-red spectra. Determination of C-H frequencies (~3000 cm. -1 ) in paraffins and olefins, with some observations on “polythenes”

1940 ◽  
Vol 175 (961) ◽  
pp. 208-233 ◽  
Keyword(s):  
Double Bond ◽  
Carbon Tetrachloride ◽  
General Type ◽  
The Other ◽  
Hydrogen Atoms ◽  
Wave Numbers ◽  
Infra Red ◽  
Modes Of Vibration ◽  
Single Bonds

In a previous communication (1938) we described the results of an investigation into the infra-red absorption in the region of 3 µ of a number of hydrocarbons dissolved in carbon tetrachloride, with special reference to the absorption of ⟩CH 2 groups in different molecules. It was found that in many simple compounds the CH 2 group gave rise to two frequencies, essentially C-H valency vibrations, about 2857 and 2927 cm. -1 , and that from one compound to another these frequencies varied by only a few wave numbers. The lower frequency was identified with the mode of vibration in which the hydrogen atoms move in phase, while the other frequency was taken as the unsymmetrical mode of vibration. This assignment was substantiated by calculations with potential functions for molecules of the general type CH 2 — X , where X represents the rest of the molecule and is attached to the CH 2 group by single bonds. It was found that the CH frequencies of a CH 2 group are but little affected by the nature of X in saturated compounds, but that when the CH 2 group is attached to X by a double bond the CH frequencies are some 150 cm. -1 higher. In ethylene each CH 2 group has two CH valency modes of vibration, and since the CH 2 groups themselves can vibrate in or out of phase with one another, four CH frequency modes are possible for the C 2 H 4 molecule, two being Raman active and two infra-red active. In many molecules containing several CH 2 groups, similar coupling effects are important, and frequently four infra-red CH frequencies are observed.

Rubber, Polyisoprenes and Allied Compounds. VIII. The Formation of Dialkyl Sulfide Dihalides, and Its Bearing on the Problem of Determining the Unsaturation of Vulcanized Rubber

1946 ◽  
Vol 19 (2) ◽  
pp. 287-295
Author(s):  
George F. Bloomfield
Keyword(s):  
Zinc Oxide ◽  
Acetic Acid ◽  
Double Bond ◽  
Potassium Iodide ◽  
Sulfur Atom ◽  
Iodine Monochloride ◽  
Vulcanized Rubber ◽  
Dialkyl Sulfide ◽  
Dialkyl Sulfides ◽  
Halogen Acid

Abstract In determining the unsaturation of olefinic sulfides and disulfides by halogenation methods, the addition of halogen to the sulfur atom must be taken into account. The dihalides of dialkyl or dialkenyl sulfides react with aqueous potassium iodide partly to liberate iodine with regeneration of the sulfide, and partly to form halogen acid and dialkyl or dialkenyl sulfoxides. Correction for the latter reaction, which occurs extensively in the presence of alcohol or acetic acid, must be applied before reliable unsaturation values for dialkenyl sulfides can be obtained. With vulcanized rubber and iodine monochloride, the precise magnitude of the correction to be applied is uncertain, but this uncertainty can be removed by using bromine as the additive reagent. Simple rubber-sulfur vulcanizates show a loss of unsaturation corresponding to one double bond per sulfur atom combined up to at least 8 per cent of combined sulfur; vulcanizates accelerated with mercaptobenzothiazole in the presence of zinc oxide exhibit a substantially smaller loss of unsaturation. The dibromides of dialkyl sulfides readily yield a molecule of bromine to olefins, the reaction being practically exclusively additive.

The Determination of Unsaturation in Butadiene Synthetic Rubber

1948 ◽  
Vol 21 (4) ◽  
pp. 830-834
Author(s):  
P. P. Kobeko ◽  
E. K. Moskvina
Keyword(s):  
Carbon Tetrachloride ◽  
Natural Rubber ◽  
Carbon Disulfide ◽  
Addition Product ◽  
Butadiene Rubber ◽  
Synthetic Rubber ◽  
Iodine Chloride ◽  
Hydrolysis Of

Abstract 1. It has been found that synthetic rubber does not precipitate from a solution of dichloromethane by the addition of Wijs reagent, whereas natural rubber does precipitate under the same conditions. The reverse relation occurs with carbon disulfide as solvent. 2. A method has been developed for the determination of the unsaturation of butadiene rubber in solution in dichloromethane by the use of Wijs reagent. 3. It has been demonstrated that, by the use of a solution of iodine chloride in carbon tetrachloride, the reaction with rubber is complicated by the hydrolysis of iodine chloride during titration, but not by the substitution of hydrogen by halogen nor by the hydrolysis of the rubber-halogen addition product. 4. The possibility of obtaining accurate values for unsaturation by a calculation of this hydrolysis is demonstrated. 5. Two methods have been developed for the determination of the unsaturation of natural and butadiene rubbers.

Determination of Double Bonds in Ethylene Propylene Terpolymer Rubbers

1967 ◽  
Vol 40 (3) ◽  
pp. 936-946 ◽  
Author(s):  
R. Hank
Keyword(s):  
Double Bond ◽  
Conjugated Dienes ◽  
Butyl Rubber ◽  
Double Bonds ◽  
Ethylene Propylene ◽  
Qualitative And Quantitative ◽  
Considerable Success

Abstract Developments in the field of sulfur vulcanized unsaturated ethylene propylene terpolymer rubbers, also known as EPT rubbers, have progressed rapidly in recent years. Considerable success has been achieved in producing EPT rubbers from ethylene, propylene, and various dienes. Initial difficulties, involving introduction of double bonds into already known ethylene propylene copolymers, were soon overcome when it became clear that it was not the then commonly conjugated dienes such as butadiene and isoprene, but rather nonconjugated dienes, which were required for successful terpolymerization with ethylene and propylene, according to the Ziegler process. As with butyl rubber, it is sufficient, for vulcanization purposes, to incorporate one or two mole per cent of such dienes into the terpolymer. It is especially important, not only for polymerization, but also for rubber processing, to know the type and amount of unsaturation. In this article we wish first of all to report on double bond determinations in general and then, in particular, on qualitative and quantitative dicyclopentadiene determinations in ethylene propylene terpolymers. It is especially important, not only for polymerization, but also for rubber processing, to know the type and amount of unsaturation. In this article we wish first of all to report on double bond determinations in general and then, in particular, on qualitative and quantitative dicyclopentadiene determinations in ethylene propylene terpolymers.

scholarly journals Gas Chromatographic Determination of Fatty Acids in Oils with Regard to the Assessment of Fire Hazard

2017 ◽  
Vol 25 (40) ◽  
pp. 73-81 ◽  
Author(s):  
Alica Bartošová ◽  
Tomáš Štefko
Keyword(s):  
Fatty Acids ◽  
Double Bond ◽  
Spontaneous Combustion ◽  
Unsaturated Fatty Acids ◽  
Fire Hazard ◽  
Accurate Determination ◽  
Coconut Oil ◽  
Double Bonds ◽  
Self Heating

Abstract The aim of the paper was to study and research the application of processing gas chromatographic method for the rapid and accurate determination of the composition of different types of oils, such as substances with the possibility of an adverse event spontaneous combustion or self-heating. Tendency to spontaneous combustion is chemically characterized mainly by the amount of unsaturated fatty acids, which have one or more double bonds in their molecule. Vegetable oils essentially consist of the following fatty acids: palmitic, stearic, oleic, linoleic, and linoleic. For the needs of assessment, the fire hazard must be known, in which the double bond is present, as well as their number in a molecule. As an analytical method, GCMS was used for determination of oils content. Three types of oil were used - rapeseed, sunflower, and coconut oil. Owing to the occurrence of linoleic acid C18:2 (49.8 wt.%) and oleic acid C18:1 (43.3 wt.%) with double bonds, sunflower oil is the most prone to self-heating. The coconut and rapeseed oils contain double bond FAME in lesser amount, and their propensity to self-heating is relatively low.

Radiochemical Investigation of Polymer Unsaturation. Reaction of Butyl Rubber with Radiochlorine

1963 ◽  
Vol 36 (4) ◽  
pp. 1071-1080
Author(s):  
I. C. McNeill
Keyword(s):  
Free Radical ◽  
Double Bond ◽  
Side Effects ◽  
Butyl Rubber ◽  
Small Scale ◽  
Substitution Process ◽  
Vacuum Line ◽  
Iodine Chloride

Abstract The reaction between chlorine and butyl rubber is of interest for two reasons: because of the industrial importance of the reaction the mechanism of which has not been fully understood, and because of the possibility of using it as a method for the determination of unsaturation. By the use of (36Cl)-chlorine, it has been possible to study the reaction on a conveniently small scale, the radiochlorine being manipulated quantitatively by a vacuum line technique. It has been shown that the reaction with chlorine is freer from side effects than the iodine chloride reaction. Two atoms of chlorine are incorporated in the polymer for each double bond originally present. These are incorporated not by addition but by a substitution process which is probably not free-radical in nature. A mechanism is proposed for the reaction. Radiochlorine is demonstrated to be potentially a useful reagent for investigating very low unsaturations in polymers.

Sulfur Linkage in Vulcanized Rubbers. I. Reaction of Methyl Iodide with Sulfur Compounds

1944 ◽  
Vol 17 (2) ◽  
pp. 303-330
Author(s):  
M. L. Selker ◽  
A. R. Kemp
Keyword(s):  
Double Bond ◽  
Methyl Iodide ◽  
Sulfur Atom ◽  
Direct Evidence ◽  
Chemical Nature ◽  
Sulfur Compounds ◽  
Double Bonds ◽  
The One ◽  
Direct Attack

Abstract For many years the rubber chemist, in trying to explain the chemical nature of the vulcanization of rubber, was limited by two accepted theories: (1) Sulfur adds at the double bonds of the hydrocarbon, and (2) one atom of sulfur combines for each double bond saturated in the reaction. Therefore it was concluded that only one type of sulfur linkage would occur in vulcanizates. However, it was impossible on this basis to propose a hypothesis to account for all the facts. The few bits of direct evidence available have semed to support the theory of “one sulfur for each double bond saturated”. Since it is difficult to make any direct attack on this problem and since the art of vulcanization has far surpassed the science, it was not until 1938 that grave doubt was thrown on the generality of the “one sulfur atom per double bond saturated” theorem. The work of Brown and Hauser indicated that there were wide variations in the number of sulfur atoms combined for each double bond saturated, depending on the type of acceleration used. Four years later Thornhill and Smith pointed out that, in compounds containing reinforcing channel blacks, no loss of unsaturation could be detected on combination of sulfur during vulcanization. Thus the relation between sulfur combination and changes in unsaturation is at present obscure.

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