bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some Aspects of Double Refraction and Structure in Rubber
Authors: Rowland B. W. 
Published: February 2011

Abstract
Evidence has been presented to show that the micelle in distorted rubber is anisotropic, exhibiting a positive rodlet type of double refraction; that the micelle orients with its long axis in the direction of stretch; and that the micelle orients upon compression as a rodlike structure perpendicular to the direction of compression. It is proposed that stretch involves an intimate distribution of the soluble viscous hydrocarbon within the gel phase, tending toward an optical homogeneity of the mass and loss of distinction between the two phases. The double refraction of artificially polymerized isoprene is very similar to that of natural rubber. Photographs are presented to show the similarity of double refraction in rubber to that of a uniaxial crystal. EARLY measurements (1, 5) were made to discover a quantitative relationship between double refraction and deformation in rubber, while more recently de Visser (6) noted the difficulty of relating calender effect to double refraction, because the anisotropy was found to vanish during the swelling of the material for examination as an optically “mixed body.” De Visser believed the sign of the double refraction to be positive, a point of uncertainty in much of the earlier work. Kroger (4) examined the double refraction of a rubber film stretched equally in all directions and concluded that a negative-form double refraction resulted, characteristic of a lamellar structure, in accordance with the Wiener theory (7).
Water Absorption of Rubber Compounds
Authors: Winkelmann H. A. , Croakman E. G. 
Published: February 2011

Abstract
It seems advisable to await further experimental evidence before attempting a theoretical explanation of the results obtained. Further work should be done on the effect of softeners, accelerators, immersion at elevated temperatures, and source of pigment. Water absorption of the uncured compound is often important. Additional work will show whether the observations made here hold for different types of compounds containing combinations of pigments, reclaims, and accelerators. The fact that the control without pigment shows water absorption of about the same range as some of the pigments would indicate that water absorption when pigments are present is more or less independent of the tendency for these pigments to absorb moisture. Higher water absorption for the undercures may be due to porosity, the compound becoming denser with increasing time of cure; the increase in water absorption after the optimum cure may be due to a chemical change of the protein during vulcanization. A consideration of these problems will be helpful in the preparation of reclaims as well as rubber products subject to exposure to water and steam.
Observations on the Coagulation of Hevea Latex
Authors: Fullerton R. G. 
Published: February 2011

Abstract
1. The continuity of the course of coagulation of: (a) fresh field latex, (b) preserved latex, and (c) centrifuged latex, by the addition of acids has been studied, and the PH values defining the various zones in the irregular series determined by means of the quinhydrone electrode. 2. In the case of fresh latex diluted to a rubber content of less than 10 per cent the transition from the first liquid zone to the first coagulation zone is accompanied by a progressive series of changes in the state of the dispersion, and is also rather irregular, variations in the pH. values defining the transitional stages being found for latex harvested on different days. In most cases on examining the series in the direction of decreasing pH there is a gradual progression from a state of complete dispersion to complete coagulation, through regions of partial flocculation, complete flocculation, and incomplete coagulation in that order. Generally, the range covered by this transitional stage is from pH 5.30, at which point a separation of the rubber component from the dispersion is first visible at pH 4.87, which marks the beginning of complete coagulation. These values agree fairly closely with those obtained by van Harpen.
Technical Note on the Use of Certain Solvents in Solutions
Authors: Coulangeon H. 
Published: February 2011

Abstract
A general procedure for making two pieces of vulcanized rubber adhere consists of putting between them a thin layer of fresh, tacky rubber obtained from a solution of pure rubber in a solvent (such as benzene, toluene, etc.). The two surfaces to be joined are first cleaned, or even scraped, and coated with the solution. After suitable drying, the two surfaces are pressed firmly together for some minutes, or they are struck many times with the hammer and anvil so as to be certain of close contact. If the operations have been correctly carried out and the solution is of good quality, that is, prepared by a standard procedure and first tested in the laboratory, the adherence will usually be good. But it may happen to be poor or even very bad for the following reason: The volatile solvent brings about by its evaporation a very considerable local drop in the temperature; the layer of air with which it is in contact becomes cooled, and if the hygrometric state is raised its water vapor settles out (dew point). The quantity of this vapor is more or less great and the waste more or less serious. We shall discuss these various points and give rules which can be followed to suit the particular conditions involved.
Isoprene and Rubber. XXIV. The Reduction of Rubber with Hydriodic Acid
Authors: Staudinger H. , Senior James R. 
Published: February 2011

Abstract
In the past, the reduction of rubber has been of special interest since Harries was of the opinion, based on his ideas on the constitution of rubber, that hydrorubber might possibly be distilled without decomposition in vacua, and therefore that its preparation would be of importance in explaining the constitution of rubber. Staudinger and Fritschi obtained a hydrorubber by catalytic reduction, which they considered to be a high molecular paraffin hydrocarbon; in the distillation it cracked and yielded low molecular cleavage products. It was concluded from this that rubber must also be a high molecular hydrocarbon. Contrary to this opinion, there was the evidence that the hydrorubber had the same appearance as rubber and dissolved readily in solvents like ether, and therefore showed essential differences from high molecular paraffins of known constitution as, for example, dimyricyl. Since hydrorubber has a branched chain, it might be thought that it differed from dimyricyl on this account. It was surprising, however, that in the reduction of butadiene rubber the hydrogenation product obtained likewise does not possess the physical properties of a high molecular paraffin hydrocarbon, although here properties similar to those of high molecular paraffins are to be expected, since a normal paraffin chain should result from the reduction of butadiene rubber. These problems were sufficient inducement for preparing hydrorubber in still another way. Berthelot had already many years ago converted rubber with hydriodic acid at an elevated temperature into paraffin hydrocarbons, which distilled above 350° without decomposition. One might assume, therefore, that there is perhaps in this substance the true hydrogenation product of rubber which was sought by Harries, whereas in catalytic hydrogenation the rubber micelle assumed by Harries is not completely split up.
Rubber. Part XIV. The Behavior of Rubber with Iodine Chloride and with Dithiocyanogen
Authors: Pummerer Rudolf , Stärk Herman 
Published: February 2011

Abstract
1. The Determination of the Iodine Number of Rubber The investigation of carotinoids has shown us that a large excess of iodine chloride must be employed if conjugated systems of double bonds are to be completely attacked. If, for example, with isoprene 150% of the calculated quantity of iodine chloride is used, then the reaction reaches after one day and after one week only 1.77 and 1.80 double bonds, respectively. 200% of iodine chloride must be used in order to obtain the correct number of double bonds. A still greater excess of iodine chloride does not then change the results any further. Such isoprene systems, which have added a halogen atom on every carbon atom in the chain, are obviously stable to substitution by iodine chloride. The frequently discussed question of whether in rubber a pair of conjugated double bonds is present as a terminal group, therefore a true isoprene system, has been proved by Pummerer and Mann by means of iodine chloride. At that time, however, the results did not apply to isoprene. For that reason it was necessary again to titrate the rubber with a great excess of iodine chloride. In this way it was shown that trustworthy results were obtained only by using 110–120% of iodine chloride (100% = 1 mol. of iodine chloride per C5H8 group), accordingly with an excess of from 10–20% iodine chloride. Within this range the results of the titration did not vary. Also only very few (often none at all) acids appeared with the titration, and these could be disregarded. On the contrary, if a greater excess of iodine chloride is used, the iodine numbers and acid values are essentially higher, which, as is well known, indicate substitution. Thus with 200% iodine chloride a value of 147 was obtained. The same phenomenon is true of gutta-percha. The earlier titrations of rubber were accidentally carried out within the favorable range of excess iodine chloride, so that the values for sol-rubber have undergone scarcely any correction. We have now carried out iodine chloride titrations with six fractions of crepe sol-rubber extracted with cold acetone, then fractionally dissolved in cold ether, and in this way we have found, as for sol-rubber, values for alkali-purified latex. They are very close to 100 (Fraction I: 100.1; II: 100.3; III: 99.9, IV: 99.6; V: 100.0; VI: 99.9). No difference in the titre was established by the various fractions.
Effect on Vulcanized Rubber Compounds of Immersion in Boiling Water
Authors: Soule K. J. 
Published: February 2011

Abstract
Further work is very desirable on the effect of different accelerators, antioxidants, and fluxes. It is possible that their study will throw more light on the mechanism of the swelling phenomena, and also help to explain the anomalous behavior of some of the fillers tested. It would also seem to be worth while to study the action of a few selected stocks in water, at several temperatures between room temperature and 100° C., to determine if the water absorption and swelling merely increase with rising temperatures, or whether there might be an actual change in behavior at different temperatures.
Further X-Ray Studies of Gutta-Percha and Balata
Authors: Stillwell Charles W. , Clark George L. 
Published: February 2011

Abstract
New x-ray diffraction data for gutta-percha and balata are given and considered in the light of von Susich's recent conclusion that these substances are identical and exist in two crystalline forms. The data also support the assumption that gutta-percha is a mixture of balata and another crystalline constituent, an assumption that is in some respects preferable to that of von Susich. Although the relation between gutta-percha and balata has been established and there may be no ultimate difference between them, it is pointed out that the majority of specimens examined of material classified commercially as balata produce a diffraction pattern different from that of gutta-percha, a fact of practical significance. THERE has been considerable disagreement as to the significance of x-ray diffraction data for gutta-percha and balata as reported by different investigators. The main point at issue has been the fundamental difference between gutta-percha and balata. Clark (1) and Hauser (2) have obtained different diffraction patterns for the two when unstretched, while Hauser has found them to be the same when stretched. Von Susich (3) has recently done much to clarify the problem. He reaches the conclusion, as a result of x-ray diffraction data, that gutta-percha and balata are identical, and that the substance exists in two different crystalline modifications, the alpha form being stable below about 60° C. and changing to the beta form when heated above this temperature. Of course, this at once explains Hauser's results, since the specimens were doubtless heated above 60° C. when stretched and would then show the beta pattern.
Some Fundamental Rubber Problems
Authors: Whitby G. Stafford 
Published: February 2011

Abstract
In a famous phrase Kipling once declared: “What do they know of England who only England know!” If I may take the liberty of paraphrasing this, I would ask: What do they know of rubber who only rubber know? I believe that it is a mistake, particularly in regard to the more fundamental problems presented by rubber, to direct attention too exclusively to rubber itself, and that it is highly desirable and indeed almost essential to consider other materials which display in some degree the behavior and properties of rubber. By drawing analogies from the study of simpler and more tractable systems, we may hope to obtain an insight into the more complicated and difficult case of natural rubber itself. It is my intention to offer some considerations regarding the chemical constitution of rubber, approaching the question from a consideration of the mechanism of polymerization in general; regarding the physical structure of rubber, approaching the question from a consideration of the behavior of artificial elastic colloids; regarding the nature of vulcanization, approaching the question from a consideration of the vulcanization, not of rubber, but of fatty oils.
The Appearance of Atmospheric Cracks in Stretched Rubber
Authors: Van Rossem A. , Talen H. W. 
Published: February 2011

Abstract
It was established that two factors are necessary for the formation of cracks: (1) stretching of rubber; (2) the action of ozone. Experiments at night proved without doubt that light is not necessary for the formation of cracks, in fact it often has a negative influence as a result of the formation of a surface skin. The formation of cracks begins at about 8 per cent elongation and reaches its maximum, i. e., the formation of largest cracks, which thickly cover the whole surface, at about 10 to 20 per cent elongation, above which degree of elongation the cracks become gradually smaller. Artificially ozonized air causes the same cracks as the open air, only much more rapidly. Nitrogen oxides, sulfur dioxide, and chlorine form no cracks. Moreover, no cracks were formed in unstretched rubber subjected to the highest concentrations of ozone. The influence of sunlight or the light from a mercury quartz lamp is not necessary to the formation of cracks; in fact, an oxidized skin may be formed by the light, and this skin may even prevent the formation of cracks. Chemical factors, too, which promote the oxidation of rubber (iron and copper compounds) have no influence on the formation of cracks. The influence of the degree of vulcanization on the formation of cracks is to be attributed solely to the mechanical properties, and indeed to the modulus of vulcanized rubber. The smaller the modulus the larger are the cracks.
Studies on the Thermochemistry of Rubber. I. Heat of Vulcanization of Rubber
Authors: Hada Kyoichi , Fukaya Koichi , Nakajima Takeji 
Published: February 2011

Abstract
1. The heat of vulcanization of the system: pure rubber-sulfur is determinated. 2. The absolute value of the experimental data is in doubt, however, since the results were widely different from those of Blake. 3. The experimental results are discussed. 4. The results of Blake are discussed. 5. The difference from the results of Blake is attributed to the difference in the content of resinous substances in the sample.
The Problem of the Action of Selenium in Rubber Mixtures
Authors: Rimpel H. 
Published: February 2011

Abstract
When in 1926 Boggs and Follansbee published their interesting studies on selenium, the discovery that selenium has an extraordinarily favorable effect on the resistance to abrasion of vulcanizates was of the greatest interest to rubber technologists, for the resistance to abrasion of rubber vulcanizates such as rubber tires and other products is of vital importance. It is not to be wondered at, therefore, that the question was immediately raised whether the enormous quantities of selenium which the rubber industry would probably require would be obtainable for all. Several years have passed since that time without a shortage of selenium. As a matter of fact, up to now selenium has been used in the rubber industry only in relatively small quantities. In 1929 only 50,000 kilograms of selenium were used by the rubber industry, which represents only about one-fifth of the world production. The actual reason for this lack of consumption has not been generally understood until now. The writer, too, has from the first attempted to make use of selenium in order to obtain a greater resistance to abrasion. It was soon evident that something was wrong, and that in all events the addition of selenium to correctly vulcanized mixtures did not produce a greater resistance to abrasion. In order to settle this problem conclusively, a series of systematic experiments was begun. In this Connection the method of measuring the resistance to abrasion was of decisive importance. Boggs and Follansbee carried out their experiments on abrasion with all the apparatus known at that time, and they obtained values which agreed very well.
Natural and Synthetic Rubber. VII. Fractional Precipitation of Natural Rubber
Authors: Midgley Thomas , Henne Albert L. , Renoll Mary W. 
Published: February 2011

Abstract
Temperature—concentration diagrams are given of the systems natural rubber—alcohol—benzene, pure rubber—alcohol—benzene and synthetic rubber—alcohol—benzene. A method based on these diagrams is given for the separation of nitrogen-free rubber hydrocarbon by fractional precipitation of natural rubber from a mixture of alcohol and benzene.
Scorching, and Other Plasticity Changes in Rubber Compounds on Heating
Authors: Dieterich E. O. , Davies J. M. 
Published: February 2011

Abstract
A method is described which employs the Goodrich plastometer for detecting the initial stages of vulcanization of uncured rubber compounds. Reduction in plasticity, at standard room temperature, of test pieces previously heated for various intervals at selected temperatures is used to determine the degree of cure and thus to estimate safe operating temperatures and periods. Examples of the application of the method to a variety of compounds are presented. Other temperature effects, such as heat stiffening and softening, which have not previously been reported, are illustrated.
Influence of Oxygen on the Degradation of Rubber Solutions
Authors: Bary Paul , Fleurent Émile 
Published: February 2011

Abstract
The publications of Staudinger, of Dufraisse and Drisch, and of other authors have called attention to the pronounced effect of oxygen on the rigidity of rubber and on the viscosity of its solutions. In our preceding papers, we have shown that the degradation of rubber solutions in different solvents at different temperatures and concentrations, in all cases in the presence of oxygen—even in very small proportions, approaches a limiting viscosity of the same order of magnitude as that of the solvent used. We have now carried out a new series of experiments on several solutions of different concentrations of plantation rubber (in the form of smoked crepe) in xylene. The work was done in tubes sealed after prolonged evacuation. Ten sealed tubes were prepared for each concentration and for each temperature, and were placed together in the oven at a temperature of 44° and also at 92° C. After varied periods of heating, one tube from each series was taken, was allowed to cool to 20° C., and the rate of flow through a capillary tube was then determined. The ratio of the time of flow of the solution to that of the pure solvent was considered to be the relative viscosity.
Homologs of Chloroprene and Their Polymers (Second Paper on New Synthetic Rubbers)
Authors: Carothers Wallace H. , Coffman Donald D. 
Published: February 2011

Abstract
Three substituted vinylacetylenes were treated with hydrogen chloride and thus converted to the corresponding chlorobutadienes. Chloro-2-methyl-3-butadiene-1,3 polymerized very rapidly and yielded a rubber-like polymer, which alter vulcanization was less extensible than the corresponding product obtained from chloroprene (chloro-2-butadiene-1,3). Chloro-2-dimethyl-3,4-butadiene-1,3 polymerized very slowly and the product, even alter vulcanization, was soft and lacking in nerve. Chloro-2-tetramethylene-3,4-butadiene-1,3 also polymerized very slowly and the product was very soft, plastic and sticky. The structures of the three new chlorobutadienes were established through their reaction with α-naphthoquinone to form crystalline addition products, which were oxidized to the corresponding anthraquinones.
The Measurement of Water Absorption by Rubber
Authors: Daynes H. A. 
Published: February 2011

Abstract
The absorption of water by rubber has occupied a prominent place in recent literature, especially in connection with cable and other insulating materials, since it is well known that their electrical properties are adversely affected by absorbed moisture. Many other classes of rubber goods and materials also are subject to water absorption, e. g., rubber soling, tires, washers, packings, hose, tank and grinding mill linings, hot-water bottles, and surgical goods. Apart from the performance, of such articles in service, moisture absorption is important in relation to factory operations, such as drying and vulcanizing, and to storage and mechanical testing. This paper deals with the selection of a method for measuring the amount of water absorbed by rubber when saturation has been reached. In the work for which the method was developed, the rate of absorption was of no interest; but it was necessary to correlate the water absorbed by the vulcanized product with that absorbed by the raw material, so that a method was required which could be applied equally well to raw rubber, vulcanized rubber, and ebonite. It is not proposed to discuss in detail the mechanism of absorption. The literature has already been briefly reviewed by Lowry and Kohman (J. Phys. Chem., 31, 23 (1927)), who have been largely responsible for present ideas on the subject. It will be sufficient to recall that the process is a reversible one, and that the amount absorbed at any temperature depends on the humidity of the surrounding gas and the nature of the rubber.
Studies on the Thermochemistry of the Vulcanization of Rubber. VII. Heating Curves for the Vulcanization of the System: Raw Rubber—Sulfur (2)
Authors: Hada Kyoichi , Nakajima Tokeji 
Published: February 2011

Abstract
1. Vulcanization of raw rubber by sulfur is preceded by an endothermic reaction from fusion of the sulfur. 2. Vulcanization of raw rubber is always accompanied by an exothermic reaction. 3. There is a definite time interval between the endothermic and exothermic reactions. 4. The exothermic reaction increases proportionally to the amounts of sulfur used in compounding until the point of theoretical saturation is reached. 5. The time of starting of the exothermic reaction is not influenced by the proportion of sulfur but is uniformly the same. 6. There is no endothermic reaction after the vulcanization reaction has begun, and there is but one exothermic reaction during the vulcanization. The reaction does not proceed in steps.