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.

The Determination of Free Sulfur by a Volumetric Method Part II

1933 ◽  
Vol 6 (4) ◽  
pp. 512-517
Author(s):  
W. D. Guppy
Keyword(s):  
Hydrogen Sulfide ◽  
Organic Compounds ◽  
Sulfur Compounds ◽  
Acetone Extract ◽  
Volumetric Method ◽  
Organic Sulfur Compounds ◽  
Vulcanized Rubber ◽  
Volumetric Determination ◽  
Free Sulfur

Abstract 1. The method previously described for the volumetric determination of free sulfur in vulcanized rubber has been compared with the older gravimetric methods in cases where other organic compounds containing sulfur are present in the vulcanizate. 2. The volumetric method gave lower results than the methods involving oxidation of the acetone extract in the case of vulcanized rubber containing aldehydeamine condensation products of thiouram disulfide compounds. This indicated that the sulfur combined with some organic compounds was not reduced by the reagents used. 3. The results with the accelerator tetraethylthiouram disulfide showed that in some cases part of the sulfur in organic compounds was reduced under the conditions of the reaction. 4. The acetone-soluble and the acetone-insoluble portions of brown substitute contain organic sulfur compounds. Part of the sulfur in these compounds was reduced to hydrogen sulfide by the action of nascent hydrogen. 5. The sulfur compounds present in white substitute were stable toward the reducing agents used in the estimation of free sulfur. 6. The sulfur compounds formed by the vulcanization of ebonite were in part reduced to hydrogen sulfide with tin and acid. Variations in the composition of the mixing and in the vulcanizing conditions altered the amount of these reducible compounds. 7. The volumetric method previously described cannot be used for the determination of the free sulfur in ebonite, brown substitute or in vulcanized rubber containing brown substitute. In the case of vulcanized rubber containing brown substitute or of ebonite the method can be used to determine the amount of sulfur in the acetone extract. 8. The volumetric method can be employed for the determination of the free sulfur in soft vulcanized rubber containing white substitute and in reclaimed rubber.

The Russell Effect with Rubber

1934 ◽  
Vol 7 (2) ◽  
pp. 309-313
Author(s):  
Avan Rossem ◽  
J. H. E. Hessels
Keyword(s):  
Prolonged Exposure ◽  
Mercury Vapor ◽  
Acetone Extract ◽  
Sodium Bisulfite ◽  
Gaseous Products ◽  
Acetone Extraction ◽  
Vulcanized Rubber ◽  
Low Concentrations ◽  
Quartz Mercury

Abstract (1) The Russell effect from raw rubber, after exposure to light and air, depends on three factors: (a) smoke components: smoked sheet shows a strong Russell effect owing to the presence of these components; Para does not because it is prepared with a different kind of smoke; (b) tackiness: most crepes show little Russell effect, but prolonged exposure after acetone extraction causes concurrent increases in both the Russell effect and tackiness; (c) acetone extract: the extract shows a strong Russell effect, but this is scarcely apparent when it is present in the rubber. (2) The gaseous products that cause the Russell effect are decomposed or driven off at 80° C. (3) These gaseous products are not the same as those formed by treatment with ozone. (4) Antioxidants for raw rubber do not affect the Russell effect, but sodium bisulfite weakens it. (5) Mastication or mixing with sulfur alone has little effect, but mixing with diphenylguanidine, triphenylguanidine or hexamethylenetetramine plus sulfur, or with mercaptobenzothiazole alone, considerably weakens the Russell effect. (6) Vulcanized rubber (normally or overcured, or oxidized by aging) shows a very weak Russell effect; this effect therefore will not detect incipient oxidation or a tendency to oxidation. (7) Quartz mercury vapor lamps are not suitable for experiments on the Russell effect, because the results are complicated by the ozone formed around them. (8) Ozone, even in very low concentrations (0.01 per cent or less), causes a strong Russell effect in both raw and vulcanized rubber.

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.

Analysis of Vulcanized Rubbers. Influence of Accelerators on the Determination of Free Sulfur by the Copper Spiral Method

1952 ◽  
Vol 25 (4) ◽  
pp. 956-958
Author(s):  
J. Mann
Keyword(s):  
Hydrogen Sulfide ◽  
Copper Sulfide ◽  
Acetone Extract ◽  
British Standard ◽  
Standard Methods ◽  
Vulcanized Rubber ◽  
Potential Source ◽  
Source Of Error ◽  
Free Sulfur

Abstract The copper spiral method is being inserted in a revised edition of the “British Standard Methods of Testing Vulcanized Rubber”, and this raises the question of what sulfur compounds react as “free” sulfur. In this method, “free” sulfur is considered to be that part of the sulfur which is present in the acetone extract and which reacts with a copper spiral, placed in the acetone during the extraction, with the production of copper sulfide, the amount of which can be estimated after its removal from the acetone. Since most accelerators contain sulfur, it is obvious that the presence of accelerators or accelerator fragments is a potential source of error. Fourteen accelerators of various types were therefore examined, and it was found that some react with copper, producing compounds which evolve hydrogen sulfide on treatment with hydrochloric acid.

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.

Determination of Free Sulfur in Vulcanized Rubber

1941 ◽  
Vol 14 (2) ◽  
pp. 520-524
Author(s):  
J. G. Mackay ◽  
C. H. J. Avons
Keyword(s):  
Barium Chloride ◽  
American Chemical Society ◽  
Chemical Society ◽  
Acetone Extract ◽  
Vulcanized Rubber ◽  
Factory Production ◽  
Usual Manner ◽  
Physical And Chemical ◽  
Free Sulfur

Abstract In a rubber laboratory controlling uniformity of factory production by physical and chemical testing, free sulfur is perhaps the most important determination. In this investigation recently described methods for determining free sulfur have been compared. A previous examination by one of the present authors of various methods of estimating free sulfur led to the adoption of a procedure comprising oxidation of the dried acetone extract by a mixture of nitric acid, perchloric acid and bromine, followed by evaporation with sodium chloride and hydrochloric acid before precipitation of sulfate in the usual manner with barium chloride. In the Avon laboratories considerable use has also been made of the method recommended by the Rubber Division of the American Chemical Society, in which bromine alone is used to oxidize the acetone extract, and the sulfate so produced is estimated gravimetrically as the barium salt. Both methods are accurate, but they are not sufficiently quick for effective factory control. Meantime there had been published several new methods of determining free sulfur which were claimed to be quicker than the older procedures. With the aim, therefore, of finding a rapid method more suited to the requirements of a control laboratory, the following methods have been compared. Methods 1 and 2 below were included as controls. As test-samples, 22 different general rubber products selected from factory production were used. Each product contained at least one sulfur-bearing ingredient in addition to the sulfur added to effect vulcanization.

Studies on the Acetone Extraction of Raw Rubber

1935 ◽  
Vol 8 (4) ◽  
pp. 604-612
Author(s):  
Hidemaro Endô
Keyword(s):  
Acid Value ◽  
Acetone Extract ◽  
Water Bath ◽  
Acetone Extraction ◽  
Saponification Value ◽  
Alcoholic Potash ◽  
Saponifiable Matter ◽  
Acetone Extracts ◽  
Hcl Solution

Abstract (1) For the determination of the saponification value of the acetone extract, 20 cc. 0.2 N alcoholic potash is added to the extract and the flask is heated on a water bath for 60 minutes. It is then titrated with 0.1 N HCl solution, using phenolphthalein as indicator. (2) When the saponification values of the acetone extracts of 8, 16, and 24 hours are compared, the saponification value of the 8 hour extract is seen to be high, while those of 16 and 24 hour extracts are low. This indicates (a) that the 8 hour extract contains a higher percentage of saponifiable matter than the 16 and 24 hour extracts; (b) the quantity of rubber hydrocarbon which is dissolved in the acetone extract increases with increasing time of extraction, and (c) the acid value of the acetone extract decreases during the period of extraction from 16 to 24 hours. (3) Regarding the saponification values (R) of the acetone extracts of 8, 16, and 24 hours, similar remarks may be made as in (2) above.

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