Heat Treatment of Vulcanized Rubber

1933 ◽  
Vol 6 (2) ◽  
pp. 225-231
Author(s):  
Takeo Fujiwara ◽  
Toshio Namiki
Keyword(s):  
Chemical Structure ◽  
Chloroform Extract ◽  
Rapid Decrease ◽  
Acetone Extract ◽  
Maximum Point ◽  
Total Sulfur ◽  
Vulcanized Rubber ◽  
Experimental Findings ◽  
Maximum Content ◽  
Control Samples

Abstract By heating samples of a rubber—sulfur system at 160° C., the following results in relation to the time of heating were obtained: 1. The maximum acetone extract was obtained after 0.5–1 hour of heating, and the amount decreased rapidly thereafter with increase in the time of heating until it became equal to or less than that of the control samples. 2. The maximum chloroform extract was obtained after 0.5 hour of heating, beyond which the amount decreased rapidly until it was less than that of the control samples. 3. The amount of total sulfur decreased, and this tendency to decrease is to be attributed to three factors. 4. There was also a rapid decrease in free sulfur. 5. The maximum combined sulfur content was reached after a certain time of heating, beyond which it decreased. The maximum point was reached after the acetone and chloroform extracts had reached their maximum values. 6. The maximum content of resinous substance was also obtained after a certain time. 7. The weights of the samples increased during the heating, and this increase was greater in over-vulcanized samples. A general discussion of these experimental findings leads to the conclusion that the processes of aging and reclaiming of rubber may both be attributed to a change in the chemical structure of the rubber molecules produced by heat in the presence of sulfur and oxygen. This investigation is an outcome of our work on reclaimed rubber. Thanks are due to Prof. Y. Tanaka for his kindly advice.

Biochemical Composition, Antibacterial and Anti-Biofilm Activities of Indian Medicinal Plants

2020 ◽  
Vol 18 ◽  
Author(s):  
Mulugeta Mulat ◽  
Fazlurrahman Khan ◽  
Archana Pandita
Keyword(s):  
Antibacterial Activity ◽  
Medicinal Plants ◽  
Pathogenic Bacteria ◽  
Chemical Constituents ◽  
Multidrug Resistant ◽  
Chloroform Extract ◽  
Acetone Extract ◽  
Biologically Active ◽  
Ocimum Sanctum ◽  
Agar Disc

Background: Medicinal plants have been used for treatments of various health ailments and the practices as a remedial back to thousands of years. Currently, plant-derived compounds used as alternative ways of treatment for multidrug-resistant pathogens. Objective: In the present study, various parts of six medical plants such as Solanum nigrum, Azadirachta indica, Vitex negundo, Mentha arvensis, Gloriosa superba, and Ocimum sanctum were extracted for obtaining biological active constituents. Methods: Soxhlet method of extraction was used for obtaining crude extracts. Agar disc diffusion and 96-well plate spectroscopic reading were used to detect the extract’s antibacterial and antibiofilm properties. Results: The obtained extracts were tested for antimicrobial and antibiofilm properties at 25 mg/mL concentrations. Maximum antibacterial activity was observed in O. sanctum chloroform extract (TUCE) against Staphylococcus aureus (24.33±1.52 mm), S. nigrum acetone extract (MAAC) against Salmonella Typhimurium (12.6 ± 1.5 mm) and Pseudomonas aeruginosa (15.0 ±2.0 mm). Only TUCE exhibited antibacterial activity at least a minimum inhibitory concentration of 0.781 mg/mL. Better antibiofilm activities were also exhibited by petroleum extracts of G. superba (KAPE) and S. nigrum (MAPE) against Escherichia coli, S. Typhimurium, P. aeruginosa and S. aureus. Moreover, S. nigrum acetone extract (MAAC) and O. sanctum chloroform extract (TUCE) were showed anti-swarming activity with a reduction of motility 56.3% against P. aeruginosa and 37.2% against S. aureus. MAAC also inhibits Las A activity (63.3% reduction) in P. aeruginosa. Conclusion: Extracts of TUCE, MAAC, MAPE, and KAPE were exhibited antibacterial and antibiofilm properties against the Gram-positive and Gram-negative pathogenic bacteria. GCMS identified chemical constituents are responsible for being biologically active.

The Chemical Structure Responsible for the Deactivating Effect of Compounds Which Protect Rubber from Deterioration by Oxygen

1951 ◽  
Vol 24 (3) ◽  
pp. 638-639
Author(s):  
Jean Le Bras ◽  
Jacques Le Foll
Keyword(s):  
Nitrogen Atom ◽  
Systematic Study ◽  
Chemical Structure ◽  
Thiol Group ◽  
Vulcanized Rubber ◽  
Thiol Form

Abstract One of the present authors has already offered evidence which indicates the existence of a deactivating effect, whereby vulcanized rubber is protected against deterioration by oxygen. This effect is evident with such compounds as mercaptobenzimidazole (I), mercaptobenzoxazole, and ethylene-bis (N,N′-phenylthiourea) (II), and the phenomenon seems to be connected in some way with the presence in the molecule of a thiol group united to a nitrogen atom under such conditions that the possible tautomerism between the thion and thiol forms (III) is probably displaced toward the thiol form. We have completed these earlier experiments by a more systematic study, which has included an examination of the influence of cyclization, the nature of the ring, and hetero atoms.

Chemical Structure of Vulcanized Rubber

1939 ◽  
Vol 12 (1) ◽  
pp. 43-55
Author(s):  
J. R. Brown ◽  
E. A. Hauser
Keyword(s):  
Chemical Structure ◽  
Empirical Knowledge ◽  
Extensive Investigation ◽  
Practical Application ◽  
True Nature ◽  
Rubber Industry ◽  
Vulcanized Rubber ◽  
Metallic Salts ◽  
Other Substances

Abstract A CENTURY ago, Charles Goodyear in America and Th. Hancock in England found that the properties of crude rubber could be greatly improved by heating it with sulfur. The product resulting was more elastic, more resistant to tear and abrasion, less affected by solvents, and decidedly less thermoplastic. The treatment of rubber to give these desired properties is known generally as vulcanization and must be considered as the basis for the enormous growth of the rubber industry and the extensive use of rubber products in our everyday life. Broadly speaking, vulcanization involves the reaction, in some fashion, of sulfur with rubber. Extensive investigation has revealed other substances, such as benzoyl peroxide or polynitrobenzenes, which can transform rubber into a “vulcanized” condition. Experience has also shown that metallic salts of zinc or lead and especially certain organic compounds called “accelerators” greatly affect the rate of vulcanization, and these are favorably employed in practice. A vast amount of empirical knowledge has been gained which has greatly improved the practical application of vulcanization and the quality of rubber products, but which has failed as yet to reveal a complete picture of the true nature of the process.

scholarly journals Manufacturing of amber particles suitable for composite fibre melt spinning

2016 ◽  
Vol 70 (2) ◽  
pp. 51-57
Author(s):  
Inga Ļ Ļašenko ◽  
Sergejs Gaidukovs ◽  
Jūlija Rombovska
Keyword(s):  
Melt Spinning ◽  
Chemical Structure ◽  
Polyamide 6 ◽  
Polyamide Fibre ◽  
Ball Mills ◽  
Composite Fibre ◽  
Before And After ◽  
The Matrix ◽  
Average Size ◽  
Experimental Findings

Abstract Polyamide fibre containing amber particles was fabricated. The amber particles were obtained by grinding technology using planetary ball-mills. Scanning electron microscopy and granulometry testing were used to characterise the structure and the size of prepared amber particles. Fourier transform infrared spectroscopy was used to analyse the chemical structure of the amber particles. The amber particles were characterised with average size up to 3 μm. The chemical composition of amber before and after the grinding remained unchanged. The amber particles were melt-extruded using polyamide 6 as the matrix. Melt spinning processing was used to fabricate polyamide-amber filaments. Pre-oriented yarns and fully drawn yarns were obtained after hotdrawing experiments. Reported experimental findings of amber composite fibre could be important for textile applications.

Studies of the Vulcanization of Rubber

1952 ◽  
Vol 25 (2) ◽  
pp. 209-229 ◽  
Author(s):  
Shu Kambara ◽  
Kumakazu Ohkita
Keyword(s):  
Organic Compounds ◽  
Chemical Structure ◽  
Room Temperature ◽  
Great Influence ◽  
Cross Linking ◽  
Oxidizing Agent ◽  
Vulcanized Rubber ◽  
Cross Linkage ◽  
Bridge Type ◽  
The Difference

Abstract In this study much information about the method of distinguishing the state in which sulfur is combined in simple organic compounds consisting of carbon, hydrogen, and sulfur was obtained, and a new theory of vulcanization was postulated as a result of its application to vulcanized rubber. When activated sulfur reacts with rubber, it first adds to the double bonds, forming thioketones, which in turn, as a characteristic of these radicals, combine with each other, with the formation of a thioether structure. This transformation of thioketone into thioether takes place, not only during vulcanization, but also gradually after vulcanization. Because of the presence of thioketone, treatment of vulcanized rubber with hydrazine, forms a new network, that is, a ketoazine cross-linkage. Combined sulfur of the thioketone type was determined by an oxidizing agent, and as the difference of this value and total combined sulfur a method of determining bridge type of combined sulfur has been proposed. By this method, it was found that, even in ebonite, about one-third of the combined sulfur is the thioketone type, and that the bridge type is only about two-thirds of the total. The thioketone type of combined sulfur in soft vulcanized rubber is transformed gradually into the thioether type of cross-linkage when allowed to stand at room temperature, and this transformation is accelerated when the temperature is raised. In the case of hard rubber, this phenomenon is also observable, but the rate of this transformation is much slower compared to the former. This tendency is the same in the case of ketoazine cross-linking when rubber vulcanizates are treated with hydrazine. From these facts, it seems that the distribution of the thioketone radicals is not uniform, and the magnitude of the probability for collision of these radicals to form cross-linkages has a great influence on the properties of rubber after vulcanization. That is, the property of the vulcanizate is greatly affected by the fact whether the thioketone radicals in the vulcanizates are comparatively uniformly distributed or whether they exist in sectional groups or in colonies. The authors are the first to advance this postulate concerning the chemical structure of vulcanized rubber and its transformation. We believe that when the study is extended, using this postulation, problems such as aging and the differences in the properties of vulcanized rubber accelerated with various accelerators will become clear. Moreover, we believe that it will be of interest to physicists studying rubber elasticity to suggest this idea of colony of cross-linkages. We are now carrying on researches on these problems, and we shall report on them later.

A Study of the Mechanism of the Deactivation Effect

1954 ◽  
Vol 27 (1) ◽  
pp. 157-164 ◽  
Author(s):  
Jacques Le Foll
Keyword(s):  
Chemical Structure ◽  
A Priori ◽  
Natural Aging ◽  
Chain Scission ◽  
Nitro Compounds ◽  
Active Part ◽  
Relaxation Phenomena ◽  
Chain Molecules ◽  
Vulcanized Rubber ◽  
The Subject

Abstract The only method by which significant differences between the effects of antioxygenic agents and deactivating agents can be detected has been found to be a study of relaxation phenomena. An investigation by this method has also furnished further support to the theories of Tobolsky and his coworkers. The changes which take place during aging in the physical properties of vulcanized rubber are the result of two independent phenomena which occur simultaneously: (1) chain scission, and (2) formation of intermolecular bonds. As far as the aging of vulcanizates of natural rubber under normal conditions, e.g., socalled natural aging, is concerned, the chief phenomenon involved is scission of the chain molecules. In principle, therefore, there are two methods for combatting the deterioration of rubber on aging: (1) to impede chain scission by obstructing the fixation of oxygen, and (2) to promote the progressive formation of intermolecular bonds which compensate for the effects of the scission process. The first of these processes is that in which antioxygenic agents play the active part; in the second process, deactivating agents play the active part. From this viewpoint, deactivating agents play a part analogous to that of accelerators, and they may be regarded as representing a special type of acceleration. This theory makes possible a better understanding of a number of facts which, a priori, seem surprising: (1) the relationships of both chemical structure and mode of action of accelerators and deactivating agents, and (2) the protective effect of litharge, peroxides, and nitro compounds, all of which are vulcanizing agents. With respect to the intimate mechanism of the deactivating effect, one question remains unanswered, viz., how are intermolecular bonds formed under the influence of deactivating agents? This question recalls the question of the function of vulcanization accelerators, which has been the subject of many investigations, but which still remains a mystery.

Determination of Total Sulfur in Vulcanized Rubber Mixtures

1952 ◽  
Vol 25 (2) ◽  
pp. 371-374 ◽  
Author(s):  
Horst Frey
Keyword(s):  
Iron Oxide ◽  
Ion Exchange ◽  
Barium Sulfate ◽  
Aqueous Sodium Hydroxide ◽  
Total Sulfur ◽  
Aqueous Sodium ◽  
Vulcanized Rubber ◽  
Exchange Agent ◽  
Volumetric Methods

Abstract A method is described, which, by means of a resin ion-exchange agent, makes possible the elimination of the disturbing effects of foreign cations, particularly iron and chromium, in the determination of the total sulfur in vulcanized rubber mixtures. By this procedure, rapid volumetric methods for determining sulfate, even in the analysis of mixtures containing iron oxide or chromium oxide pigments, can be utilized. The procedure involves precipitation of the sulfate by benzidine and determination by titration with aqueous sodium hydroxide. The method is more rapid and more reliable than ordinary gravimetric methods involving precipitation of barium sulfate.

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 strength of highly elastic materials

1967 ◽  
Vol 300 (1460) ◽  
pp. 108-119 ◽  
Keyword(s):  
Chemical Structure ◽  
Unit Area ◽  
Strength Properties ◽  
Polymer Chains ◽  
Chemical Bonds ◽  
Elastic Materials ◽  
Chemical Corrosion ◽  
Vulcanized Rubber ◽  
Theory And Experiment ◽  
Highly Elastic Materials

Under repeated stressing, cracks in a specimen of vulcanized rubber may propagate and lead to failure. It has been found, however, that below a critical severity of strain no propagation occurs in the absence of chemical corrosion. This severity defines a fatigue limit for repeated stressing below which the life can be virtually indefinite. It can be expressed as the energy per unit area required to produce new surface ( T 0 ), and is about 5 x 10 4 erg/cm 2 . In contrast with gross strength properties such as tear and tensile strength, T 0 does not correlate with the viscoelastic behaviour of the material and varies only relatively slightly with chemical structure. It is shown that T 0 can be calculated approximately by considering the energy required to rupture the polymer chains lying across the path of the crack. This energy is calculated from the strengths of the chemical bonds, secondary forces being ignored. Theory and experiment agree within a factor of 2. Reasons why T 0 and the gross strength properties are influenced by different aspects of the structure of the material are discussed.

Sign in / Sign up

Export Citation Format

Share Document