Sulfur Linkage in Vulcanized Rubber. Acetone Extraction of Vulcanizates

1949 ◽  
Vol 22 (1) ◽  
pp. 8-15 ◽  
Author(s):  
M. L. Selker ◽  
A. R. Kemp
Keyword(s):  
Methyl Iodide ◽  
Acetone Extraction ◽  
Vulcanized Rubber ◽  
Rubber Stock ◽  
Soft Rubber ◽  
Free Sulfur

Abstract 1. For the soft rubber stock SB1A, there is no evidence for the change: polysulfide → free sulfur on acetone extraction. 2. Evidence for the change: polysulfide → other sulfur links on acetone extraction is indicated by increased reactivity of extracted SB1A to methyl iodide. 3. Natural and GR-S ebonites lose about one-third of their combined sulfur on reaction with methyl idode at 24° C. Trimethylsulfonium iodide is found in large quantities. 4. Neither extraction experiments nor methyl iodide reactions offer evidence for occurrence of polysulfides in 32 per cent sulfur natural ebonite.

Investigations of the Reversion of Vulcanized Rubber under Heat

1952 ◽  
Vol 25 (2) ◽  
pp. 241-250 ◽  
Author(s):  
Uma Shankar
Keyword(s):  
Free Energy ◽  
Hydrogen Sulfide ◽  
Methyl Iodide ◽  
Energy Of Activation ◽  
Cross Linking ◽  
Molar Free Energy ◽  
Vulcanized Rubber ◽  
Free Energy Of Activation ◽  
Equilibrium Swelling ◽  
Free Sulfur

Abstract (1) During reversion of a vulcanizate, the breakdown of cross-linkages, including those of polysulfides, predominates over any simultaneous reformation of cross-linkages. (2) The reverting modulus falls exponentially with time. (3) The calculated molar free energy of activation is 33.3 ± 1.7 kcal., irrespective of the temperature or the atmosphere of cure or the composition of the mix, and is sufficient to rupture an —S—S— bond. (4) The degree of cross-linking, estimated from the equilibrium swelling measurements in benzene, falls during reversion. (5) The exclusion of oxygen during curing does not prevent reversion if the temperature is high enough to supply the energy needed to break up the cross-linkages. (6) During reversion in nitrogen, hydrogen sulfide is freely evolved, and the C/H ratio rises above the value for C5H8. (7) Evidence for the formation and breakdown of polysulfides during reversion is provided by an increase in free sulfur and a decrease in combined sulfur during a given cure, and the methyl iodide reaction of the reverted vulcanizates.

Studies of Hard Rubber Reactions. VI. Liberation of So-Called Free Sulfur and Changes in the Acetone Extract of Vulcanized Rubber by Repeated Extraction and Heating

1940 ◽  
Vol 13 (3) ◽  
pp. 598-603 ◽  
Author(s):  
Seiiti Numaziri
Keyword(s):  
Sulfur Compound ◽  
Acetone Extract ◽  
Acetone Extraction ◽  
Vulcanized Rubber ◽  
Rubber Product ◽  
Free Sulfur

Abstract 1. True Free Sulfur.—In the case of the pure rubber-sulfur compound, as shown in the graph, the quantity of true free sulfur liberated from the thermally active hard rubber product by 120 minutes' cure was generally a little greater than that from the thermally nonactive sample with 300 minutes' cure. During the whole course of the extraction and heating, there occurs a lowest point in the true free sulfur curve, which increases again. In view of this fact, liberation of free sulfur can not be attributed to the insufficiency of the acetone extraction but is probably attributable to depolymerization of the vulcanizate or the like. 2. Acetone Extract.—Although purified rubber was used, the corrected acetone extract due to the formation of resinous substances from the depolymerized or aged hard rubber product showed relatively high values at the beginning of extraction and heating. To some extent, the change in acetone followed a course similar to that of the true free sulfur.

Determination of Free Sulfur in Vulcanized Rubber Mixtures

1952 ◽  
Vol 25 (2) ◽  
pp. 365-370 ◽  
Author(s):  
Horst Frey
Keyword(s):  
Acetone Extraction ◽  
Vulcanized Rubber ◽  
Widespread Acceptance ◽  
Free Sulfur

Abstract Numerous papers on the determination of free sulfur in rubber mixtures have been published. Most of these are in the older literature, and they offer various methods for determining free sulfur. In principle the methods can be divided into two general groups. The procedures described in the first and larger group involve preliminary acetone extraction before the actual determination of the free sulfur, whereas the methods comprising the second group, which include only two different procedures, do not involve acetone extraction. Of these two methods, only that of Oldham, Baker, and Craytor has found widespread acceptance.

Sulfur Linkage in Vulcanized Rubber. Reaction of Methyl Iodide with Sulfur Compounds

1949 ◽  
Vol 22 (1) ◽  
pp. 1-7
Author(s):  
M. L. Selker
Keyword(s):  
Methyl Iodide ◽  
Room Temperature ◽  
Sulfur Compounds ◽  
Point Of View ◽  
Secondary Reaction ◽  
Reaction Products ◽  
Sulfide Sulfur ◽  
Vulcanized Rubber ◽  
Allyl Sulfide

Abstract The work described here is an extension of the study of the reaction of methyl iodide with sulfur compounds originally begun with the purpose of using such data in determining the sulfur linkage in vulcanized rubber. A previous paper dealt with the reactions of methyl iodide with propanethiol, propyl sulfide, propyl disulfide, allyl sulfide, and thiophene. This article adds to the list, n-butyl methallyl sulfide, allyl disulfide, allyl tetrasulfide, n-propyl tetrasulfide, and trithiane. The removal of combined sulfur from vulcanized rubber as trimethylsulfonium iodide on treatment with methyl iodide at room temperature was persuasive evidence of the presence of sulfide sulfur linked to allylic type residues. The evidence offered, however, did not constitute exclusive proof because it was not known whether still other types of sulfur linkage would also yield trimethylsulfonium iodide. To shed more light on this question, the sulfur linkages most likely to occur in vulcanizates—the allyl-alkyl monosulfide, diallyl and dialkyl di- and polysulfide—were investigated. The trithiane reaction is of interest mostly from the point of view of the reaction of overcured stocks or secondary reaction products stemming from the original polysulfides. The reactions were carried out using the method described in a previous paper.

scholarly journals Quantitative Analysis of Free Sulfur Content in the Vulcanized Rubber by HPLC

2008 ◽  
Vol 81 (2) ◽  
pp. 39-43
Author(s):  
Kazumi NAKAYAMA ◽  
Tomoko WATANABE ◽  
Yoshito OHTAKE ◽  
Mutsuhisa Furukawa
Keyword(s):  
Quantitative Analysis ◽  
Sulfur Content ◽  
Vulcanized Rubber ◽  
Free Sulfur

The Distribution of Combined Sulfur in Vulcanized Rubber and Its Bearing on the Sulfide Linkage Theory of Vulcanization

1939 ◽  
Vol 12 (2) ◽  
pp. 191-199
Author(s):  
I. Williams
Keyword(s):  
Physical Properties ◽  
Direct Evidence ◽  
Cross Linking ◽  
Direct Relation ◽  
Vulcanized Rubber ◽  
Free Sulfur

Abstract No direct evidence exists to support the sulfide linkage theory of vulcanization, which assumes that cross-linking of the molecules with sulfur would retain the elasticity and decrease the plasticity of the rubber. The following facts do not favor the sulfide linkage theory of vulcanization : (1) Vulcanized rubber can be peptized under conditions which do not appear to rupture a sulfide linkage. (2) No direct relation exists between the physical properties of vulcanized rubber and the amount of combined sulfur. (3) No direct relation exists between the ease of peptization and the physical properties of the vulcanizate. (4) Combined sulfur appears to assist the solvation of rubber. Rubber vulcanized with thiuram disulfides in the absence of free sulfur has poor physical properties but peptizes with difficulty. An increase in combined sulfur without a corresponding improvement in physical properties assists solvation. (5) Rubber having the best physical properties is also the most heterogeneous with respect to sulfur. The sulfide linkage theory would suggest that an even distribution of sulfur would produce the best physical properties. (6) Fractions of peptized vulcanizates, on evaporation of their solutions, leave insoluble vulcanized films, which shows that linkage by means of primary forces is unnecessary for producing the vulcanized condition.

The Determination of Free Sulfur in Soft Vulcanized Rubber by a Volumetric Method

1932 ◽  
Vol 5 (3) ◽  
pp. 360-362 ◽  
Author(s):  
W. D. Guppy
Keyword(s):  
Hydrogen Sulfide ◽  
Sulfuric Acid ◽  
Organic Compounds ◽  
Subsequent Oxidation ◽  
Vulcanized Rubber ◽  
Elementary State ◽  
Previously Treated ◽  
Mineral Sulfides ◽  
Free Sulfur

Abstract The methods so far proposed for the determination of the free sulfur in vulcanized rubber depend upon the removal of the sulfur by extraction of the rubber with hot acetone, and subsequent oxidation to sulfuric acid of the sulfur in the extract. The extract is liable however to contain, in addition to sulfur in the elementary state, organic compounds containing sulfur derived from the rubber resins, accelerator, or antioxidant. In the subsequent oxidation this sulfur will be oxidized to sulfuric acid to an extent which depends on the method of oxidation used. In the present work, a method of analysis has been developed which is more rapid than the existing methods, and in which it is considered that the determination of the sulfur present in the elementary state is less likely to be affected by organic compounds containing sulfur. It has been found that when vulcanized rubber placed in contact with a metal, such as tin or aluminum, is boiled in hydrochloric acid, hydrogen sulfide is generated by the action of the nascent hydrogen produced. This reaction occurred with rubber which had been previously treated with acid alone to decompose metallic sulfides, but no hydrogen sulfide was obtained from rubber which had been previously extracted with acetone and was free from metallic sulfides. As these results showed that the reactions were not due to the presence of mineral sulfides, or of sulfur combined with the rubber, it was concluded that the hydrogen sulfide was formed by the reduction of the free sulfur.

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