Chemical Unsaturation of Rubbers Vulcanized with Polynitro Compounds and Benzoyl Peroxide, and Its Possible Bearing on Vulcanization

1928 ◽  
Vol 1 (1) ◽  
pp. 101-105
Author(s):  
Harry L. Fisher ◽  
A. E. Gray
Keyword(s):  
Benzoyl Peroxide ◽  
Vulcanized Rubber ◽  
Chemical Combination ◽  
Sulfur Vulcanization

Abstract STUDIES on the chemical unsaturation of ordinary vulcanized rubber show that vulcanization has caused no change in the unsaturation of the rubber hydrocarbon beyond that which can satisfactorily be accounted for by the chemical combination of sulfur on the basis of one atomic equivalent of sulfur to a C5H8 group. If such is the case with sulfur vulcanization, it becomes very desirable to know whether there is any change in the unsaturation when rubber is vulcanized with substances other than sulfur, namely, polynitro compounds and benzoyl peroxide.

Vulcanization of Rubber. By Organic Peroxides or by Ammonium Persulphate

1930 ◽  
Vol 3 (2) ◽  
pp. 195-200 ◽  
Author(s):  
Iwan Ostromislensky
Keyword(s):  
Benzoyl Peroxide ◽  
Organic Peroxides ◽  
Ammonium Persulphate ◽  
Aluminium Powder ◽  
Metallic Oxides ◽  
Vulcanized Rubber ◽  
Viscous Mass ◽  
Metallic Aluminium ◽  
Short Time ◽  
Rubber Product

Abstract 1. Organic peroxides vulcanize rubber not only in the absence of sulphur but likewise without any foreign substances such as metallic oxides or accelerators of any kind. 2. Rubber vulcanized by means of an adequate amount of benzoyl peroxide (10 to 30 per cent.) gives a soft rubber product which does not differ in point of physical properties from products cured with sulphur, or rather with sulphur chloride. 3. The process of vulcanizing rubber with benzoyl Superoxide is completed in a relatively short time even at a fairly low temperature, sometimes even in two minutes at 119° C., corresponding to 13 pounds pressure. 4. Vulcanization of rubber by means of peroxides may lead to the formation of a soft, transparent and elastic product, which is almost entirely colorless. 5. The products in question vulcanized by means of various peroxides are gradually converted to a very sticky and viscous mass. 6. Sulphur protects the vulcanizates in question from such decomposition or oxidation. However, the products obtained in vulcanization of rubber with organic peroxides in the presence of sulphur are opaque. 7. As distinguished from sulphur, selenium, tellurium, their sulphides, metal oxides (in particular, lead oxide) as well as amines (aniline), tannic acid, and metallic aluminium powder not only do not protect the peroxide vulcanized rubber products from decomposition or oxidation but, on the contrary, they accelerate such processes quite considerably. 8. Benzoyl peroxide is the active vulcanizing agent in the process of heating rubber with a mixture of sulphur and benzoyl peroxide. 9. When rubber is subjected to the action of a mixture of some nitrobenzenes and benzoyl peroxides, vulcanization is effected exclusively by the nitrobenzenes, and the benzoyl peroxide remains altogether passive. 10. Ammonium persulphate vulcanizes rubber completely, resulting in a porous product which, generally speaking, is of small practical value.

Nonlinearity in the Dynamic Properties of Vulcanized Rubber Compounds

1954 ◽  
Vol 27 (1) ◽  
pp. 209-222 ◽  
Author(s):  
W. P. Fletcher ◽  
A. N. Gent
Keyword(s):  
Simple Shear ◽  
Dynamic Modulus ◽  
Dynamic Properties ◽  
Mechanical Vibration ◽  
Frequency Range ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Chemical Combination ◽  
Wide Range ◽  
Static Shear

Abstract Measurements are described of the dynamic properties of rubber, loaded with various amounts and types of filler, when subjected to mechanical vibration in simple shear at amplitudes from 0 to 3 per cent shear in the frequency range 20 to 120 c.p.s. The decrease of dynamic modulus with increasing amplitude is shown, for a wide range of filler types and concentrations, to be determined by the amount of stiffening produced by the filler. This relationship is not influenced by variations in the vulcanizing ingredients, reasonable variations in state of vulcanization, addition of softener, or imposition of static shear strain. Rubber compounds stiffened by mixture with, or chemical combination of, other polymers exhibit a smaller order of nonlinearity than that described above and also exhibit much lower hysteresis values within the amplitude range 0 to 3 per cent shear.

Effect of Compound Ingredients on Adhesion between Rubber and Brass-Plated Steel Cord

2005 ◽  
Vol 78 (2) ◽  
pp. 175-187 ◽  
Author(s):  
Takeshi Hotaka ◽  
Yasuhiro Ishikawa ◽  
Kunio Mori
Keyword(s):  
Carbon Black ◽  
Physical Properties ◽  
Adhesive Strength ◽  
Crosslink Density ◽  
Condensation Reaction ◽  
Gel Formation ◽  
Vulcanized Rubber ◽  
Sulfur Vulcanization ◽  
Steel Cord ◽  
Carbon Gel

Abstract Effect of several ingredients in the rubber on adhesion characteristics between brass-plated steel cord and rubber was thoroughly investigated. Amine component is generated by N,N'-dicyclohexylbenzothiazole-sulphenamide- (DCBS) accelerated sulfur vulcanization, and it is known to promote stress-induced corrosion crack in the brass layer at the brass plated steel cord. Hexamethoxymethylmelamine (HMMM), which is formulated for the condensation reaction of RF resin, has a function to trap amines, which was found to effectively improve the adhesive strength in water-aged degradation. It was clarified that the physical properties of the vulcanized rubber such as crosslink density and strain modulus are also improved by trapping the residual amine accompanying improved adhesive strength for the formulation with HMMM. Influence of carbon black on concentration of the residual amine and adhesive strength was also studied. Amount of the amine was inversely proportional to the carbon gel content, while adhesive strength linearly increased with the level of carbon gel. It was assumed that the carbon black dose enhances the adhesive strength due to a preferential entrapment of the amine at the stage of carbon gel formation.

Effect of Reinforcing Pigments on Rubber Hydrocarbon

1942 ◽  
Vol 15 (2) ◽  
pp. 272-279
Author(s):  
F. S. Thornhill ◽  
W. R. Smith
Keyword(s):  
Tensile Strength ◽  
Specific Loss ◽  
Reinforcing Fillers ◽  
Chemical Combination ◽  
Reinforcing Value ◽  
Sulfur Vulcanization ◽  
Black Particle ◽  
Published Account ◽  
Rubber Stock ◽  
Reinforcing Filler

Abstract Several investigators have established that sulfur vulcanization of rubber involves chemical combination of sulfur and rubber hydrocarbon. A definite decrease in unsaturation of the rubber hydrocarbon as vulcanization progresses has been generally noted. While it has often been concluded that a double bond is saturated for each atomic equivalent of combined sulfur, recent work by Brown and Hauserdemonstrates that this conclusion cannot be applied in all cases. In certain compounds they found the loss in unsaturation with extent of vulcanization to be considerably less than anticipated on the basis above. Their results indicate that stocks reaching optimum cure with the least loss of unsaturation possess the greatest tensile strength. Although a considerable amount of work has been done on this problem, we have not found a published account of similar investigations performed on stocks containing significant loadings of reinforcing fillers. Since, as pointed out below, the nature of the bonding between such fillers and the rubber molecules has not been clearly defined, one is not justified in applying previous results obtained on stocks containing no reinforcing fillers to those bearing appreciable loadings of such substances. Accordingly one portion of the present investigation was concerned with determining the effect of various fillers on the course of sulfur vulcanization, as judged from combined sulfur and unsaturation values. As pointed out by Gehman and Field it is undoubtedly true that the black particle in a carbon-black-reinforced rubber stock is firmly attached to the rubber molecule. The nature of the bonding between the black and rubber has not been clearly defined. Some investigators maintain that the association is physical and involves definite forces of adhesion or adsorption; others have suggested the formation of primary valence linkages with rubber hydrocarbon. The opinion of the present authors is that if such linkages are formed, the ethylenic bonds of the rubber molecule would probably be involved. If this latter view is correct, then a specific loss in unsaturation of rubber hydrocarbon, due to the reinforcing filler, should occur. Thus the second objective of the present study was to determine whether it was possible by chemical means to detect such a linkage. If measurable, this effect, together with the surface area determinations reported previously, would be particularly valuable in estimating the reinforcing value of various fillers.

CURE CHARACTERISTICS OF DEVULCANIZED RUBBER:THE ISSUE OF LOW SCORCH

2017 ◽  
Vol 90 (3) ◽  
pp. 536-549 ◽  
Author(s):  
Anu Mary Joseph ◽  
Benny George ◽  
K. N. Madhusoodanan ◽  
Rosamma Alex
Keyword(s):  
Solvent Extraction ◽  
Natural Rubber ◽  
Main Chain ◽  
Process Safety ◽  
Original Sample ◽  
Vulcanized Rubber ◽  
Sulfur Vulcanization ◽  
Natural Rubber Vulcanizates ◽  
Devulcanized Rubber

ABSTRACT We investigate the reasons behind the observed low scorch during the revulcanization of devulcanized rubber. Mechanically devulcanized carbon black filled natural rubber vulcanizates originally cured by conventional vulcanization (CV), semiefficient vulcanization (semi EV), efficient vulcanization (EV), and peroxide systems as well as buffing dust obtained from pre-cured tread with known formulation were used. Revulcanization of these devulcanized samples using sulfur/sulfonamide system led to the following observations; irrespective of the type of sulfur cure system used for the initial vulcanization of the rubber, (i) the devulcanized samples cured without pre-vulcanization induction time and (ii) devulcanized samples prepared from peroxide vulcanized rubber cured with scorch safety. Based on the earlier reports that solvent extraction of devulcanized rubber did not improve the scorch time during revulcanization, the role of zinc bound non-extractable moieties was investigated using devulcanized rubber prepared from activator-free vulcanizates, which disproved the role of such moieties. This confirmed that the scorch reducing moieties should be attached to the rubber main chain, which can be unreacted crosslink precursors and cyclic sulfides left after the initial accelerated sulfur vulcanization of the original sample. The ability of pre-vulcanization inhibitor to induce scorch safety when devulcanized rubber is revulcanized as such, without adding any virgin rubber, proved that mercaptobenzothiazole (MBT) generated from crosslink precursors is the cause of low scorch. Acetone extracted devulcanized rubber samples prepared from tetramethyl thiuramdisulfide (TMTD) cured natural rubber, which does not follow the MBT pathway when revulcanized, cured with scorch safety, which further proved the role of MBT. Based on the previous reports and our results, it is obvious that powdering of rubber vulcanizate and devulcanization processes have no role on the low process safety of these materials, but it is inherent to the initial accelerated sulfur vulcanization chemistry undergone by these materials.

Vulcanization Accelerators

2009 ◽  
Vol 36 (7) ◽  
pp. 49-55
Author(s):  
Tomoyuki Komatsu
Keyword(s):  
Vulcanized Rubber ◽  
Sulfur Vulcanization ◽  
Vulcanization Accelerator

Vulcanization accelerators are important for sulfur vulcanization. Sulfur vulcanization is performed by heating the rubber to which sulfur was added. But, it proceeds very slowly in the absence of a vulcanization accelerator, and the properties of the vulcanized rubber are inferior. Vulcanization accelerator promotes the vulcanization reaction and improves the quality of the rubber. This report describes fundamentals of the vulcanization accelerator.

The Law of Absorption of Carbon Dioxide by Rubber as a Function of the Time

1932 ◽  
Vol 5 (4) ◽  
pp. 604-607
Author(s):  
C. Cheneveau
Keyword(s):  
Carbon Dioxide ◽  
Wash Water ◽  
Vulcanized Rubber ◽  
Lime Water ◽  
Chemical Combination ◽  
Long Time ◽  
The Law ◽  
Coefficients Of Absorption ◽  
Absorption Measurements

Abstract 1. As the form of the curves shows, factice does not appear to obey the law for rubber. Calculations give values which, in relation to the observed values, show deviations of 8.5 per cent for brown factice and 13.7 per cent for white factice, whereas Table I gives smaller deviations for the different rubbers. 2. Crude rubber absorbs more than the same rubber cut into pieces, which indicates that the latter has become less porous. The absorption measurements can therefore give an idea of the porosity. It is a curious fact that if crude or cut-up rubber is boiled with alcohol the same value for the coefficient of absorption is obtained. 3. Vulcanized rubber or rubber mixed with mineral or organic fillers absorbs carbon dioxide in the same way. 4. Although Reychler has assumed that carbon dioxide dissolves in rubber, it should be noted that the law of the phenomenon of absorption is identical to that of monomolecular chemical combination. Might there not be formed therefore a compound with one of the components of the rubber? In any case, it is extremely difficult to remove the carbon dioxide from rubber, even after subjecting it to a vacuum for a long time. Moreover, if successive experiments are repeated on a single sample, it is found that the coefficients of absorption become smaller and smaller. This indicates that more and more carbon dioxide remains in the rubber. The coefficient of absorption for plantation rubber at the end of four tests changed from 0.165 to 0.141 and did not regain its value at the end of 50 days' standing. Upon washing the rubber at this stage, traces of carbon dioxide were detected in the wash water by means of lime water. 5. The study of the k coefficients, which may be called diffusion coefficients, likewise gives information about a rubber. 6. A sample left for one whole day in carbon dioxide did not appear to have altered, as judged by its elongation and tensile strength. 7. Without desiring to draw any definite conclusions from this work, it is believed that more complete tests such as those described would doubtless be of value in obtaining information about the constitution or the quality of different rubbers.

Studies in the Vulcanization of Rubber. VII. Unsaturation of Rubber Vulcanized with Nitro Compounds and Benzoyl Peroxide

1937 ◽  
Vol 10 (4) ◽  
pp. 735-742
Author(s):  
John T. Blake ◽  
Phillip L. Bruce
Keyword(s):  
Benzoyl Peroxide ◽  
Chemical Reaction ◽  
Nitro Compounds ◽  
Unsaturated Hydrocarbon ◽  
Secondary Reaction ◽  
Double Bonds ◽  
Decomposition Products ◽  
Vulcanized Rubber ◽  
Chemical Theory

Abstract RUBBER is primarily an unsaturated hydrocarbon. Sulfur adds to its double bonds during vulcanization to form soft and hard vulcanizates. In the formation of soft vulcanized rubber, unsaturation is reduced several per cent by the chemical addition of sulfur. Spence and Scott (10) showed that the proportion of combined sulfur corresponds exactly to the decrease in unsaturation, and therefore that sulfur combination consists entirely of addition to the double bonds of rubber. The studies of one of the authors (1) on the vulcanization of rubber with nitro compounds indicate that these substances or their decomposition products combine with rubber. Van Rossem (8) also showed that vulcanization with benzoyl peroxide is accompanied by a decrease in extractable material, indicating that either the reagent or its decomposition products combine chemically with the rubber. The natural expectation would be that addition to the double bonds occurs and that the unsaturation decreases correspondingly. Van Rossem's proposed mechanism for the vulcanization with benzoyl peroxide would involve no change in unsaturation. Fisher and Gray (2) applied Kemp's method (4) in determining the iodine numbers of a single vulcanizate of each of four compounds. The vulcanizing agents involved were m-dinitrobenzene, trinitrotoluene, and benzoyl peroxide. Their unsaturation values agreed closely with calculated values for the unvulcanized compounds. They concluded from their results that “Ordinary vulcanization is an unknown or undetermined type of change in the hydrocarbon involving no change in the unsaturation and that chemical union of sulfur is a secondary reaction.” If true, this evidence is a serious blow to the chemical theory of vulcanization which postulates that a chemical reaction is essential for the process. The present paper offers evidence that the vulcanization of rubber with these reagents does involve change in its unsaturation.

The Mobility of Sulfur Bonds in Soft Rubber and Ebonite

1956 ◽  
Vol 29 (1) ◽  
pp. 67-70 ◽  
Author(s):  
G. A. Blokh ◽  
L. F. Chuprina
Keyword(s):  
Soviet Union ◽  
Tetramethylthiuram Disulfide ◽  
Large Group ◽  
Vulcanized Rubber ◽  
The Soviet Union ◽  
Number Of Factors ◽  
Sulfur Vulcanization ◽  
Sulfur Radicals ◽  
Soft Rubber

Abstract Much attention has been devoted to the problem of the sulfur and oxygen bonds in vulcanized rubber in numerous studies of both Soviet and foreign scholars. In the Soviet Union, the works of a large group of investigators, including B. A. Dogadkin, A. D. Zai˘onchovskii˘, P. A. Rebinder, A. P. Pisarenko, A. S. Kuzminskii˘, and others, have dealt with this problem. The nature of the sulfur structures formed in soft vulcanized rubbers depends on a number of factors, including the nature of the accelerators. It was shown in one work that sulfur vulcanization in the absence of sulfur-bearing accelerators leads to the formation of relatively weak polysulfide bonds. We assume that here a group of different polysulfide bonds is formed at the expense of the passage of octatomic ring sulfur structures into open linear sulfur radicals. For vulcanized rubbers which contain sulfur and diphenylguanidine in their recipe, the group of polysulfide bonds evidently constitutes an excellent criterion of their characteristic vulcanization structures. A number of rubber products, including cable and insulation rubbers, which do not contain sulfur as a vulcanizing agent are also known. In this case vulcanization takes place at the expense of the decomposition of tetramethylthiuram disulfide (thiuram vulcanization). Here stronger intermolecular monosulfide sulfur bonds are formed at the expense of the atomic sulfur, which is liberated during the decomposition of thiuram:

Identification of Carbon Black by Surface-Area Measurements

1943 ◽  
Vol 16 (3) ◽  
pp. 687-691
Author(s):  
F. H. Amon ◽  
W. R. Smith ◽  
F. S. Thornhill
Keyword(s):  
Carbon Black ◽  
Surface Area ◽  
Point Of View ◽  
Curing Temperature ◽  
Single Type ◽  
Surface Areas ◽  
Vulcanized Rubber ◽  
Chemical Combination ◽  
Black Surface ◽  
Rubber Stock

Abstract In general then, we may conclude that carbon black can be recovered from rubber stocks with unchanged surface-area. The nitric acid technique is the most effective method of effecting the separation. The digestion temperature must be controlled to between 60° and 70° C, for a total of not more than 3 to, 4 hours. This method of identifying the carbon black in an unknown rubber stock is directly applicable only in the presence of a single type of carbon black. If blends of blacks are employed in the material under investigation, some secondary identification is also required. The nonimpingement-type blacks, for example, are readily identified by microscopic observation. From the known surface-areas of these materials and the total per cent carbon present in the stock, a fairly positive identification of the blend can be made. The fact that carbon black can be recovered quantitatively and with unchanged surface-area from vulcanized rubber stocks appears to lend impetus to a physical concept of carbon black reinforcement. This point of view implies that any chemical combination between the ingredients of the rubber stock and the carbon black would be evidenced by some alteration in the surface of the latter. A few experiments were performed in an attempt to establish to what extent this concept was valid. One hundred grams of Grade-6 carbon black were intimately mixed with 6.6 grams of sulfur. This is about the ratio in which they are present in a standard rubber batch. Samples of this mixture were subjected to the standard curing temperature of 134° C for 30, 60, and 90 minutes. The free sulfur was then extracted for 40 hours with acetone ,and the combined sulfur on the carbon was determined. Values of 0.16, 0.21, and 0.4 per cent combined sulfur were obtained. The original sample of Grade-6 carbon black had a surface-area of 108 square meters per gram. The extracted sample of black containing 0.4 per cent of combined sulfur had a surface-area of 109 square meters per gram. These values are identical within experimental error. While unaltered surface-area need not necessarily be interpreted as evidence of complete lack of surface reactions, it is the authors' opinion that the extent of chemical combination at the carbon black surface is very small. This interpretation is in accord with the views expressed in a previous publication3, where it was suggested that the chief role of carbon black in rubber reinforcement may rest on its ability to orient the chains of rubber molecules and thus alter the extent and type of rubber-sulfur bonds normally formed in non-reinforced rubber stocks.

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