bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Determination of Free Sulfur in Soft Vulcanized Rubber by a Volumetric Method
Authors: Guppy W. D. 
Published: February 2011

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.
Natural and Synthetic Rubber. X. Constituents of the Rubber Hydrocarbon
Authors: Midgley Thomas , Henne Albert L. , Renoll Mary W. 
Published: February 2011

Abstract
1. Fractional precipitation has been used to determine and isolate the constituents of the rubber hydrocarbon. 2. A “standard precipitation point” has been devised and its use advanced as a physical constant of rubber. 3. The presence of a single component, amounting to more than 50% and characterized by a standard precipitation point of 35°, has been demonstrated. 4. The presence of highly soluble portions, of indeterminate s. p. p., has been shown.
Studies of Polymers and Polymerization. IV. Observations on the Polymerization of Isoprene and 2,3-Dimethylbutadiene-1,3
Authors: Whitby George Stafford , Crozier Robert Nelson 
Published: February 2011

Abstract
The polymerization of isoprene and dimethylbutadiene at temperatures ranging from 10° to 145° C. has been studied with reference to the nature of the dimeric products and the influence of the temperature and period of heating on the extent of polymerization, the ratio of oil to rubber and the molecular weight of the rubber and viscosity of its sols. There was no evidence of the formation from either diene of an open-chain dimer, polymerizable to rubber, such as the “β-myrcene” of Ostromislenski. The ratio of oil: rubber from a given diene is approximately constant in different periods of polymerization at a given temperature. The ratio increases with rise of temperature. Isoprene gives far more oily by-product than does dimethylbutadiene. As polymerization progresses, the molecular weight of the rubber and the viscosity of its sols rises. The higher the temperature of polymerization, the lower is the molecular weight ultimately attained. The polymerization is catalyzed by air. The viscosity of the sols of the synthetic rubbers is low and falls on keeping, owing to oxidation.
Isoprene and Rubber. Part 37. Homologous Polypranes
Authors: Staudinger H. , Leupold E. O. 
Published: February 2011

Abstract
According to investigations by Staudinger and Fritschi the hydrorubber obtained by the catalytic reduction of rubber at 270° is a high molecular paraffin hydrocarbon. Concurrently with this work, Pummerer and Burkard were occupied with the reduction of rubber. They describe hydrorubber as an autoöxidizable substance, an observation which has been shown to be incorrect. According to Pummerer and Koch, hydrorubber can be distilled in high vacuo without decomposition, and is a highly viscous oil having the composition (C5H10)10. The hydrorubber obtained in this way is, however, according to experiments by Staudinger and Schaal highly decomposed by cracking. Our concept of the constitution of hydrorubber and the products obtained from it by cracking is again confirmed by the preparation by Karrer, Stoll, and Stevens of two high molecular hydrocarbons with numerous methyl side chains. Like octomethyldotriacontane (G40H82) recently prepared by Karrer, hexahydrosqualene (C30H62)9 and tetramethylhexadecane (C20H42) prepared by Fischer, these new hydrocarbons are to be regarded as lower members of the series of paraffins with branched chains, whose end members are hydrorubbers. Accordingly, in this series of hydrocarbons (the polypranes), representatives from the lowest member, isopentane C5H12, to the highest member, a hydrobalata having the composition ((C5H10)700 and a molecular weight of about 50,000 are known.
The Vulcanization of Rubber in Concentrated Solution in the Presence of Ultra-Accelerators
Authors: Bourbon A. 
Published: February 2011

Abstract
The appearance of an article by Thiollet on the formation of jellies in rubber solutions containing rapid accelerators (Revue Générale du Caoutchouc, Vol. 9, No. 79, 5–9 (1932); Rubber Chemistry & Technology, 5, 296–300 (1932)) has suggested the publication of the present paper, which deals with experiments in the same field. In 1927 the author was occupied in studying the vulcanization of thick solutions of rubber containing ultra-accelerators. On account of lack of time this investigation was never carried as far as was desired, therefore the results may appear to be incomplete and the conclusions may seem a little bold because of a certain lack of precision. The object was to study the rate of vulcanization of these solutions as a function of their concentration. For this reason the effect of a series of solvents under the same conditions was studied, and in this respect the work resembles that of Thiollet. A similar investigation had been made earlier by Boiry (Caoutchouc & gutta-percha, 21, 12257–62, 12293–37, 12335–41, 12386–89, 12454–60 (1924); 22, 12507–509 (1925); India Rubber J., 68, 651–54, 687–89, 727–31, 771–73, 807–808 (1924)), but his work was concerned only with dilute solutions, containing at the most 5 grams of rubber for 100 cubic centimeters of toluene. The present work was under different conditions.
Effect of Overmilling on Compounded Rubber
Authors: Wiegand W. B. 
Published: February 2011

Abstract
The conviction seems more and more prevalent that the full reinforcing capabilities of fine pigments such as carbon black have not as yet been fully developed. A great deal of thought is therefore being devoted to the study of improved means of dispersion of such ingredients in rubber. The various conditions of grinding and the effect of dispersing agents are examples of the lines along which the modern study of this problem is progressing. This naturally leads to the question of what is happening to the rubber phase during the dispersion process. In other words, what damage, if any, will over-mastication do to the rubber quality? What influence do these conditions exert on aging behavior? What is the effect of mill opening during such mastication?
An Investigation of the Visco-elastic Properties of Rubber
Authors: Eccles J. C. , Thompson J. H. C. 
Published: February 2011

Abstract
An account is given of an investigation of the visco-elastic properties of rubber by means of observations on the damping of forced longitudinal vibrations. An attempt is made to determine the visco-elastic limits for rubber, as well as the normal visco-elastic constant τ and the coefficient of normal viscosity E′. The analysis of the experiment predicts the form of the photographic record of the damped vibrations, and gives an expression for τ in terms of the period of vibration and the logarithmic decrement of the amplitude per vibration. Two series of experiments are described in detail. In the first series, where catapult elastic was used, the experimental results are susceptible of detailed analysis. They agree with those predicted by the theory of visco-elasticity when the rate of strain does not exceed 0.1 per second. This is the upper visco-elastic limit. The lower visco-elastic limit for the rate of strain was not reached, so it must be less than 0.017 per second. The value obtained for τ is 28.7×10−4 seconds, and the corresponding value of E′ is 3.42×104 in c.g.s. units. In the second series of experiments pure black rubber was used, and a wider range of frequency of vibration and rate of strain was obtained. Also experiments were carried out at different mean tensions. The experimental results show signs of some unknown disturbance and are difficult to analyze. They suggest 6×10−4 seconds as a probable value Ä , and 0.78×104, for pure black rubber, with a rate of strain 0.1 per second as a probable upper visco-elastic limit (at a mean tension of 150 grams weight). The value of Ä at 300 grams mean tension does not differ significantly from that at 150 grams.
Photoelastic Properties of Soft, Vulcanized Rubber
Authors: Thibodeau Wilfred E. , McPherson Archibald T. 
Published: February 2011

Abstract
This paper describes an exploratory study of the photoelastic properties of transparent, soft, vulcanized rubber. The work was originally undertaken to obtain data on rubber samples that were used in an investigation of stresses in models by the photoelastic method, and was extended to provide general information on the relation of the photoelastic properties to the composition of rubber. Measurements of the photoelastic behavior of rubber have been made by several previous investigators, whose work points to a functional relation between double-refraction and stress. Bjerken made measurements on rubber of unspecified composition at stresses from 5 to 69 bars, which corresponded to elongations from 66 to 434 per cent. Rossi observed the behavior of three types of rubber compositions, (1) crude rubber, (2) the same mixed with oil and wax, and (3) rubber vulcanized with 15 per cent of sulfur and subsequently extracted with benzene. Rossi's measurements extended only to stresses of 5 to 7 bars, which corresponded to elongations of 50 to 100 per cent. The measurements of the coefficient of relative retardation by both Bjerken and Rossi, when plotted as functions of stress, give smooth curves which are either linear or nearly so. Van Geel and Eymers, however, working with sheets of rubber made by the evaporation of latex, obtained a discontinuous relation between relative retardation and stress. Other investigators have studied the double-refraction of rubber in relation to the structure. This latter work is summarized in a recent paper by Rowland.
Ether-Insoluble or Gel Rubber Hydrocarbon, Its Solution, Crystallization, and Properties
Authors: Smith W. Harold , Saylor Charles Proffer 
Published: February 2011

Abstract
A method of purifying and crystallizing ether-soluble rubber hydrocarbon was described in an earlier paper in this journal. The same procedure for purifying the hydrocarbon and separating it into two fractions was followed in the preparation of the insoluble or gel fraction, the properties of which are the subject of this paper. The method of purification was not merely another procedure for removing the impurities from rubber hydrocarbon, but, as stated in the earlier paper, it also “sought to maintain unchanged the structure of rubber hydrocarbon and to permit a sharp separation of the ether-soluble and insoluble fractions.” The latex which has been used was, in part, obtained from H. L. Fisher of the United States Rubber Co. Through the courtesy of the U. S. Department of Agriculture, latex has also been obtained direct from the plantation on the north shore of Haiti. Before the trees were tapped, the area surrounding the intended incision was carefully cleaned. After tapping commenced, the trees were tapped once each day, the latex from the first two tappings was rejected, and that obtained on the third day was put into clean glass bottles, which were filled completely after the addition of a little ammonia as stabilizer. The latex was immediately shipped to this Bureau and stored at a temperature maintained between 0° and 2° C.
The Restraining of Vulcanization in Rubber Manufacture
Authors: Twiss D. F. , Jones F. A. 
Published: February 2011

Abstract
Delayed-Action Accelerators During the past few years, considerable advance has been made in the ordinary method of compounding technic with respect to scorching. The advances fall essentially into two well-marked divisions, viz., the development of “delayed-action accelerators” and the addition of “vulcanization restrainers,” “inhibitors of prevulcanization,” or “antiscorch agents.” With a true delayed-action accelerator vulcanization should not occur until a certain period of time has elapsed, after which rapid vulcanization takes place. The existence of this “time lag” can be explained on the basis that the reputed accelerators are inactive, but on heating are decomposed into other substances which constitute the real accelerators. Some organic accelerators give a temperature lag, and though comparatively safe from prevulcanization in processing, they vulcanize only above a certain critical temperature. Hence, when the rubber mixture is heated, vulcanization does not take place until this temperature is attained. Such accelerators are not delayed-action accelerators in the narrower sense. In all organic accelerators the activity can be associated with a particular grouping, and in the simplest form of accelerator generally with a particular hydrogen atom. Most if not all delayed-action accelerators can be regarded as chemical derivatives of known powerful accelerators in which the place of the active hydrogen atom is occupied by a more or less easily displaceable organic grouping; the delayed-action accelerator is consequently often a compound, e. g., of the thio-ester or thio-ether (or even “thio-anhydride”) type, which itself strictly is not a vulcanization accelerator, but is capable of undergoing decomposition (e. g., “hydrolysis” or fission) with formation of one.
The Tensile Properties of Latex Products
Authors: Barron Harry 
Published: February 2011

Abstract
The rubber manufacturer of today is brought up in the tradition of facts and figures. The one without the other is useless. There can be no doubt that much of the present prosperity of the rubber industry is due to widespread benefits conferred by the publication of research work on rubber, and the standardization of production. The major discoveries in the recent history of rubber, such as the discovery of accelerators, the discovery of reinforcing action, and more recently the rediscovery of latex, have invariably followed a similar trend. The first activities in each case have been purely of a qualitative nature. After the frenzied rush to patent discoveries has subsided, everybody has settled down to find out the quantitative effects of the respective products when incorporated into rubber, subjected to the various rigorous processes normally employed. Careful research work has brought its reward, in so far as the scope of the respective products has widened, quality has improved, and costs have been very much reduced. In every case progress has been made on all sides, physical, chemical, and technical. In this respect latex is lopsided. It is a remarkable fact that at the present time, when latex appears to be more and more widely employed, manufacturers are not at all enthusiastic about it. They certainly are not falling over themselves to apply it. This is a matter that warrants investigation.
A Water Bath Having Submerged Individual Sample-Containers for the Accelerated Aging of Rubber in Air
Authors: Holt William L. , McPherson Archibald T. 
Published: February 2011

Abstract
Improved equipment for conducting the familiar Geer aging test on rubber has recently been installed at the National Bureau of Standards. This equipment consists of thermostatically controlled water baths in which small air ovens are submerged. Each oven serves for the accelerated aging of samples of a single composition, and thus avoids the possibility of contamination, which may be an important factor when samples of different compositions are aged in the same oven. The apparatus differs from that described recently by Milligan and Shaw in that individual sample containers are employed and air circulation is obtained by convection.
Manganese Salts in Plantation Rubber
Authors: Sackett G. A. 
Published: February 2011

Abstract
1. Abnormal amounts of manganese in crude rubber compounded in a gum type stock using mercaptobenzothiazole or diphenylguanidine result in lowered modulus and poorer age resistance. 2. The effects of abnormal amounts of manganese are not as evident in a rubber-sulfur stock as in stocks using an organic accelerator. 3. High-manganese rubber in a mercaptobenzothiazole tread stock gives lower modulus and the age resistance is poorer, but the effect is not as marked as in a gum stock. 4. Phenyl-β-naphthylamine in a gum or tread stock greatly improves the age resistance of a high-manganese rubber stock. 5. Rubber containing abnormally high percentages of manganese cannot always be detected by appearance; in order to avoid the bad effects of manganese in the vulcanized stocks, analysis of the crude rubber is necessary. 6. Because there is apparently no benefit to the crude rubber manufacturer through the use of manganese in any form, and because of the very bad effects on vulcanized stocks, every care should be exercised by the rubber producer to see that manganese salts are not introduced at any step in the process. 7. Rubber containing abnormally high percentages of manganese should not be used in high-quality stocks; when used, they should be blended with large proportions of normal rubber and used in a highly loaded stock containing an antioxidant.
The Elasticity of Rubber
Authors: Meyer Kurt H. , Ferri Cesare 
Published: February 2011

Abstract
In order to explain the elasticity of rubber, several authors assume that long chain molecules have a tendency to form spirals, and that when an external force displaces them from this state of equilibrium, they tend to return to it. These concepts lead in turn to two different points of view. 1. It may be assumed that there are forces of attraction between the different parts of a single molecule, for example, between the double bonds. Upon stretching, these forces of attraction are overcome. The free energy of the stretched thread thus consists of the potential energy of the molecular parts which have been separated from one another. 2. On the other hand, the molecule may be said to have a certain rigidity which, in its final analysis, depends upon the rigidity of the tetrahedric valences of carbon. In this case it is to be assumed that stretching brings about a deformation of the angles between these vectors. The first hypothesis has been developed by several authors. Recently Mack has assumed that there are forces of attraction between the hydrogen atoms in the rubber chains. He attributes the phenomena of elasticity to a mechanism of “evaporation and condensation of hydrogen.” None of these hypotheses explains the elastic properties which are found in substances such as elastic ligaments, and especially in elastic sulfur, which have a wholly different structure from that of rubber. Moreover these two hypotheses, which involve a change in the total potential energy, are incompatible with the fact that the tension of substances such as rubber, which are stretched and held at a constant length, increases with the temperature. Now a rise of temperature ought to diminish the work necessary to overcome on the one hand the forces of attraction and on the other hand the forces which keep the atoms in a position of established equilibrium. The result would be that the tension of a stretched rubber thread would diminish with an increase in temperature.
The Oxidation of Rubber by Hydrogen Peroxide
Authors: Kagan B. , Sukhareva N. 
Published: February 2011

Abstract
It was noticed long ago that rubber changes during storage, and that it loses its valuable qualities. Many authors have tried to explain this phenomenon as a union of oxygen with rubber molecules. The most interesting work on this subject was the early work of Herbst (Ber., 39, 523 (1906)). Herbst blew air for 140 hours through benzene solutions of rubber and obtained two products, C10H16O3, as a main product, and C10H16O, as a very small admixture. Later Peachey and Leon (J. Soc. Chem. Ind., 31, 1103 (1912); 37, 55 (1918)) subjected rubber films to the action of oxygen and found that for each group of C10H16, four atoms of oxygen were added and one atom of carbon was liberated. These workers succeeded in separating several compounds with different degrees of oxidation, viz., C10H16O; C10H16O 4; C6H9O 2. Herbst thought that he had obtained an addition product of oxygen and rubber hydrocarbon, but Peachey considered that the compounds were the result of a splitting and depolymerization of the rubber molecules. Boswell (India-Rubber J., 54, 981, 987 (1922)) and his students investigated the phenomenon of oxidation of rubber and obtained different oxidation products for each oxidizing agent. A solution of rubber in carbon tetrachloride oxidized by means of potassium permanganate in the absence of air (in carbon dioxide) gave a product of the formula, C25H40O, which in turn was readily oxidized in air to C30H48O2. Using 3% hydrogen peroxide as an oxidizing agent, Boswell obtained a product with the formula, C30H48O, which in turn was easily oxidized to C25H40O2.
The Mastication of Rubber
Authors: Behre J. 
Published: February 2011

Abstract
Probably from the beginning of the rubber industry no process has changed so little as that for softening raw rubber, its socalled mastication. Although Hancock's machine, the masticator (1826), consisted of an internal rotating roll and a stationary shell, and modern machines have two rotating rolls, the same principle has always held true, viz., a compression and consequent stretching of the rubber by means of great friction. Even enclosed mixers are essentially only a development of the Hancock principle, the value of which naturally will not be discussed here. In spite of such long experience, the process of mastication is not clearly understood, and it is remarkable that there has apparently been little interest in this problem until recently. Only within the last few years has it received somewhat more attention, and attention should be called to the work of Cotton, in which there is a compilation of the literature. As a result of this lack of knowledge, the conditions under which the most rational processes of mastication can be carried out have not been established, and even today the manufacturers of machines produce for the most part mills which have the most widely varying constants, without any satisfactory reasons for the particular constructions. The following discussion aims therefore to contribute toward the establishment of these conditions, and at the same time to view critically the various theories of the process of mastication. In this discussion plasticity values obtained by the method of Marzetti have been used as a measure of the degree of mastication since, as I have been able to show earlier and has recently been confirmed by others, these plasticity values approach most nearly to practical conditions.