bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Aspects of Double Refraction and Structure in Rubber
Authors: Rowland B. W.
Published: February 2011

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Heat Treatment and Polymorphism of Gutta-Percha and Balata
Authors: Dean J. N.
Published: February 2011

The hydrocarbon from balata or gutta-percha is polymorphic, and the modification in which it is usually known is the metastable variety, but it can be converted to the stable modification by one of a variety of comparatively simple heat-treatments. The α modification, to which it is converted by the heat-treatment, has somewhat different properties and these are compared. Some beneficial effects are reported which enable gutta-percha products to become the basis of a very superior variety of submarine cable insulation, which has been called K.-gutta. In writing this article the author is indebted to W. S. Smith and H. J. Garnett for criticism and advice and to F. Mattingley and H. F. Wilson and others of the laboratory staff for assistance and coöperation in carrying out this work. Thanks are also due to the Telegraph Construction and Maintenance Co., Ltd., for permission to publish these results.
Modifications of the Gutta-Percha Hydrocarbon. II
Authors: De Jong A. W. K.
Published: February 2011

It was proved by dilatometer experiments that the spongy product contracts between 61° and 64.5°, and that this contraction is not caused by an impurity or by oxidation. An experiment using a pycnometer showed that contraction was accompanied by fusion, and that during fusion with tension at 64.5° to 67° no contraction took place. The products obtained by grinding the spongy product in a mortar and by crystallizing it from a benzene solution in an ice-box showed no contraction; on the contrary after fusion they showed a slight expansion at ordinary temperature. A method is given for obtaining a pure hydrocarbon from sheet balata.
The Refractometry of Rubber and Gutta-Percha Hydrocarbons. I. The Influence of Depolymerization and Oxidation on the Refractive Exponents of These Hydrocarbons
Authors: Kirchhof F.
Published: February 2011

1. The acetone-extractable substances from different natural rubbers have an appreciable influence on the index of refraction of their hydrocarbons. This influence is different in the case of Hevea rubbers from that in the case of African rubbers, for example. 2. The indices of refraction of different kinds of raw rubber after extraction likewise differ appreciably. These differences may be attributed in part to the different quantities of benzene-insoluble non-rubber substances, in part to differences in the degree of polymerization of the different hydrocarbons. 3. A study of the influence of mastication, depolymerization by heat and oxidation on the magnitude of the light refractive exponents of rubber and gutta-percha shows that there are characteristic differences between the two kinds of hydrocarbons, at least as far as the initial stage of oxidation is concerned. 4. From the purely practical and laboratory-testing points of view, it is possible to detect quickly and easily differences in the same kinds of raw rubber which are originally present or result from mastication, and to follow the course of mastication. 5. Furthermore it appears possible to draw conclusions regarding the constitution of rubber and gutta-percha hydrocarbons from differences in their viscosimetric and osmotic behavior. Accordingly the refractometry of rubber and gutta-percha hydrocarbons may furnish a new way of gaining a deeper insight into the structure of these natural substances.
The Problem of Changes in Rubber Brought about by Atmospheric Oxygen
Authors: Dufraisse Charles
Published: February 2011

Returning now to an earlier subject, let us ask in what way the conversion of rubber to fatty substances differs from plasticization by milling. Both originate in the same way, i. e., by the action of oxygen, and both are similar in appearance and in effects. To distinguish the two phenomena, one must resort to an arbitrary point of view, viz., that one phenomenon is spontaneous, whereas the other is induced. One is harmful, the other is advantageous, but fundamentally, whether advantageous or disadvantageous, they are nothing more than one and the same change in the rubber. Whether the change is an advantage or a disadvantage depends upon when it happens and upon its extent. This will explain why milling is such a critical operation and is so difficult to control. Because plasticization is a conversion to fatty substances, which is stopped at the right time, the operations involved in practical milling are a delicate and dangerous process, a process the effects of which are attained not in years or even in months but in minutes. The least miscalculation, and disastrous results may be obtained. Without entering into detail, it may be asked how many irregularities hitherto unexplained are from this time on readily explainable. The success of mastication depends upon peroxides, neither the quantity nor the behavior of which have so far been controlled, and even the existence of which has not until recently been suspected. It is a surprising fact that everything has always taken place in the desired way, particularly since to add to the complexity of things, the formation of peroxides itself depends upon electricity, and worse still upon the most changeable or capricious form, static electricity. Without suspecting it, one requires of a mixing mill that it perform the function of a generator of static electricity. Mixing is then at the mercy of influences which hinder the output of static machines, and it depends to some extent upon all kinds of indefinite factors, such as the state of the atmosphere, the temperature, the humidity and surface effects, not to mention the mixing mill itself, where nothing has been planned in advance to promote the unforeseen action. Henceforth, with a knowledge of the mechanism of mastication, it is going to be possible to improve the various factors playing a part, and it does not require a great prophet to foresee within a short time a profound change in this century-old technique.
The Elastic Behavior of Vulcanized Rubber
Authors: Hencky H.
Published: February 2011

As a consequence of the work described the author arrives at the conclusion that in the deformation range from 0 to 270 per cent only one elastic constant is needed for a full mathematical description, and that this constant is the modulus of shear defined for infinitely small deformations. If models could be made of rubber at less expense, this material could be used for the integration of the equations of elasticity. The solutions could be easily corrected for the lack of compressibility and for the change in the common law of elasticity.
Heat Treatment of Vulcanized Rubber
Authors: Fujiwara Takeo , Namiki Toshio
Published: February 2011

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.
Plasticity Measurements in the Rubber Industry
Authors: Behre J.
Published: February 2011

With the growing realization of its importance in factory operations, the plasticity of raw rubber and rubber stocks is being studied more and more. As far as can be seen from the literature, four methods for measuring plasticity are known up to the present time. The most commonly used apparatus is probably that developed by Williams, which depends upon measuring the change in the thickness of rubber under a load. The same principle is followed in the recently published method of Karrer, except that in this case the elastic recovery is also measured. The other two methods, which were used first by Marzetti and by Griffith, depend on the other hand upon a wholly different principle. Here the rubber or the rubber mixture is extruded through a narrow opening under high pressure and the quantity extruded is measured. Griffith used a dead weight whereas Marzetti used compressed air to produce the pressure. For several years the author has worked with an apparatus constructed according to the Marzetti principle, and the present paper deals with experiments with this apparatus.
The Surface Properties of Rubber
Authors: Vellinger E.
Published: February 2011

It is known that the properties of rubber depend in large measure upon the nature of the ingredients which are compounded with it. Certain facts seem to show the enormous effect on the mechanical properties of rubber of surface forces which intervene between the rubber and the filler. In order to study the influence of this factor, the surface activity of the rubber was investigated in the present work. This activity was determined by measuring the lowering of the interfacial tension between a benzene solution of rubber and aqueous solutions of electrolytes by the tensiometer method of le Comte du Noüy, following a technique already described by the author and Weiss for measuring the interfacial tension of mineral oils.
Rubber Vibration Insulators. Some Characteristic Properties and Tests
Authors: Abbott Franz D.
Published: February 2011

Insulating of vibrating parts of engineering devices and structures is one of the vital problems of this age. The original purpose of carriage and automobile tires was, as indeed the major purpose of their use today still is, the suppression and elimination of shocks and vibrations during travel. This is true in spite of the importance of the “increased mileage” obtained by the use of rubber tires—a factor of no mean importance. This purpose is not so self-evident in the case of belting, hose, rubber-covered rolls, etc., where flexibility and/or elasticity are apparently prime requisites, but nevertheless the interception and safe-transmission of impulses or stresses with a minimum of vibration and noise are certainly of inestimable value. The use of rubber parts elsewhere in the automobile and general engineering field is unquestionably solely for the suppression or elimination of vibration. Recognition of the importance of rubber parts for such service came with the organization early in 1927, at the request of the Society of Automotive Engineers, of a committee to make a study of the most important characteristics of rubber necessary in such service and finally to set up standards of tests for these properties. This committee was formed by the American Society for Testing Materials and is composed of a number of the leading automotive engineers of the country and rubber technologists from the leading rubber companies. The S. A. E. also has an official representative. The scope of the work of this committee includes hardness testing, deflection under compression and compression-set (cold flow), resistance to cold, and dynamic fatigue, but to date its active efforts have been confined largely to the first two. The trend toward the use of rubber vibration insulators in railway work, both between ties and rails and in the cars themselves, is opening up a virgin field of enormous importance, and certainly shows the importance of these properties and the necessity for standardized tests. Of course, good aging qualities, resistance to abrasion, oil and heat, and relatively high tensile, shear, cutting and tearing strengths are important in the life of the part (but to varying degrees depending on the service intended). In addition, a standardized test for the adhesion of rubber to metal is now imperative. At present most specifications for motor supports in which rubber is bonded to metal require a direct pull, perpendicular to the metal-rubber interface, of 250 lbs. per sq. in. minimum, with actual values ranging up to over 1000 lbs. per sq. in.
Acetylene Polymers and Their Derivatives. V. The Polymerization of Bromoprene (Third Paper on New Synthetic Rubbers)
Authors: Carothers Wallace H. , Kirby James E. , Collins Arnold M.
Published: February 2011

The polymerization of bromoprene is closely analogous to that of chloroprene, but somewhat more rapid. Spontaneous polymerization yields as the final product μ-polybromoprene, which resembles vulcanized rubber but is more dense than rubber or μ-polychloroprene. A plastic (α) polybromoprene is readily isolated from partially polymerized bromoprene, and it is converted to the μ-product by the action of heat. At elevated temperatures in the presence of inhibitors a volatile liquid (β) polymer is formed. ω-Polybromoprene, a granular, insoluble, rubber-like mass, is produced under conditions that lead to very slow polymerization.
The Preparation and Crystallization of Pure Ether-Soluble Rubber Hydrocarbon: Composition, Melting Point, and Optical Properties
Authors: Smith W. H. , Saylor Charles Proffer , Wing Henry J.
Published: February 2011

Substantially all of the chemical and physical evidence concerning the nature of rubber is consistent with the chemical formula (C5H8)x, and this is the generally accepted formula for “rubber hydrocarbon.” An examination of the evidence discloses, however, that the above formula is not the only one which is consistent with this evidence. The difficulty of establishing beyond question the chemical composition of rubber hydrocarbon has been due largely to the lack of efficient physical methods for fractionating the hydrocarbon, of proving that the final fractions are one-component systems, and of chemically identifying these fractions. If, as seems not improbable, rubber hydrocarbon is a mixture of closely related hydrocarbons not all of which can be represented by the formula (C5H8)x, no single method of fractionation can be relied upon to separate this mixture into its constituents. The only methods heretofore available for this purpose have been those based upon extraction with different liquids and fractional precipitation. One of the most powerful methods for fractionating a mixture of hydrocarbons is systematic crystallization, and the purpose of this investigation was to develop a technic for applying this method to rubber.
A Method for Measuring Quantitatively the Swelling of Vulcanized Rubber in Organic Liquids by Means of a Voluminometer
Authors: van Wijk D. J.
Published: February 2011

1. A voluminometer for the study of the swelling of rubber is described, which may also be used for other substances, e. g., wood, gelatin, artificial silk, and similar materials. 2. The advantages of this apparatus are: (a) Swelling determinations with satisfactory precision can be carried out over longer periods of time than is the case with ordinary methods. (b) The accuracy of the apparatus is greater than with the direct weighing method or with direct dimensional measurements. (c) The procedure is extremely simple and rapid. 3. Typical results of practical swelling determinations at 20° C. and 30° C. are shown. The swelling curves derived from the data obtained agree with the investigations by Scott.
Reactions during Vulcanization. III. The Multiple-Accelerator Effect
Authors: Jones H. C.
Published: February 2011

Diphenylguanidine functions as an activator for mercaptobenzothiazole when the two accelerators are compounded in a stock deficient in fatty acids. Diphenylguanidine functions as an accelerator when compounded with mercaptobenzothiazole in a stock with a normal fatty acid content. Butyraldehyde aniline in conjunction with mercaptobenzothiazole behaves in the same manner as diphenylguanidine. Within the limits investigated, the amount of soluble zinc available for reaction has a direct bearing on the ultimate tensile strength of diphenylguanidine and mercaptobenzothiazole stocks.
Determination of Rubber in Rubber-Bearing Plants
Authors: Spence D. , Caldwell M. L.
Published: February 2011

THE determination of the true rubber content of both raw and manufactured rubber has been the subject of extensive investigation. Search has failed to reveal any corresponding record covering studies applicable to rubber-bearing plants. The authors' investigations, covering such methods as have been published, demonstrate their inaccuracy and inadequacy for practical use. There has never been published, as far as the authors have been able to determine, any thorough, systematic study of the factors which determine the value and accuracy of any method for the quantitative determination of the pure caoutchouc contained in a given specimen of plant tissue. The work embodied in the present communication was undertaken as an essential step towards the solution of some of the complex problems in the production of rubber from the guayule shrub. Without some method for determining with completeness and accuracy in terms of pure caoutchouc the value of any given sample it would have been fruitless to proceed to studies of the metabolism of the plant. The equally important problems in the control of commercial operations, both in field and factory, hinged at the outset on the development of an accurate means to determine the rubber content of the plant.
New Machine for Laboratory Evaluation of Fatigue of Rubber Compounds Flexed under Compression
Authors: Cooper Leslie V.
Published: February 2011

THE failure of rubber compounds to resist fatigue when subjected to flexing under compression, or their tendency to “blow-out,” has always been a serious problem, and is becoming an even greater limiting factor in all phases of rubber technology. A new machine has been developed recently in the laboratories of The Firestone Tire and Rubber Company for the measurement of fatigue resistance of rubber compounds. Previous machines of this type have usually been large wheels or drums on which whole tires have been run to destruction; The laboratory machines have not been very numerous or very successful. The Schopper detrition tester (2) is a laboratory machine for testing the fatigue and abrasion resistance of rubber stocks in the shape of small balls. Abbott (1) obtained blow-outs in his laboratory work on testing rubber used to absorb vibration. Many suggestions have been advanced as to how correct laboratory evaluation of fatigue resistance might be accomplished. The design finally adopted (Figure 1) was made up by Raymond W. Allen, of the Firestone engineering staff, in whose name the patent application on this Flexometer has been made.
The Problem Whether Litharge Is an Antioxygen or a Proöxygen toward Rubber. The Practical Consequences
Authors: Dufraisse Charles , Drisch Nicolas , Pradier-Gibello Denise
Published: February 2011

In work which was the subject of an address before the second International Congress of Rubber Technologists we were surprised to find that the oxidation of rubber is accelerated by litharge, in view of the fact that this product has the reputation of protecting rubber against attack by atmospheric oxygen, at least during vulcanization, where in its presence it is possible to operate in hot air. Comments made to us at that time by several technologists, as well as our own ideas, led us to undertake a more detailed study of this phenomenon. Later systematic experiments were undertaken, and these were the subject of two brief communications. The present paper covers the complete series of researches.
Investigation of the Aging Processes of Rubber. II. The Gold Reaction of Products of the Initial State of Oxidation
Authors: Dogadkin B. , Balandina W.
Published: February 2011

1. Aqueous extracts of pale crepe, which were exposed to the radiation of a quartz lamp or which were masticated for a short time on cold mills, reduce slightly alkaline gold chloride solution with the formation of colloidal gold. 2. The maximum intensity of the gold reaction under the experimental conditions described lay within the limits of 20–30 minutes' exposure to radiation. 3. The maximum intensity for smoked sheets lies within the same range; however even before irradiation this rubber yields an extract which reduces gold chloride. 4. The electric conductivity of aqueous extracts increases continuously, and under the experimental conditions described began after 30 minutes of irradiation of the rubber. 5. The character of the variations in the intensity of the gold reaction and the electric conductivity of the extracts must be explained on the basis of corresponding concepts of the chemistry of changes in rubber during aging.
Estate Practice and Its Relation to Factory Requirements
Authors: Jones F. B.
Published: February 2011

In spite of continuous investigation of the problem of the variation in supplies of raw rubber, a completely satisfactory method of dealing with the matter has yet to be devised. Before discussing estate practice it is necessary to agree what the desirable properties of raw rubber should be. It is perhaps a surprising fact that rubber manufacturers are not in complete agreement. There seem to be two schools of thought. One school considers quick-vulcanizing and high-tensile rubbers to be preferred, while the other favors a slow-vulcanizing and easily worked raw material. The most desirable properties in raw rubber from the factory point of view are uniformity, ease in handling, and a high level of quality in the finished product. Uniformity must come first. If the properties of raw rubber are known to be consistent, a standard manufacturing process can be confidently adopted and followed. Nowadays the ability to repeat operations exactly is so important from a factory efficiency point of view that variability in raw material is much more important than the actual properties of that material, assuming of course a reasonable level of quality.
The Antioxidants of Rubber Latex. I.
Authors: Bondy H. F. , Lauer G. G.
Published: February 2011

Various authors have observed that raw rubber from which the acetone-soluble portions have been removed deteriorates much more easily than does crude raw rubber itself. It is certain that this deterioration is associated with an autoöxidation of the rubber. In this laboratory it has been proved in different ways that sheets of crude rubber may lie in the air for years without any change. On the contrary, rubber which has been purified according to Pummerer's method is extraordinarily sensitive to oxygen. If such a purified rubber lies in the air for a couple of days it loses its elasticity, becomes tacky and short, and finally becomes completely fluid. Accordingly there must be a substance in natural rubber which prevents the autoöxidation of the hydrocarbon, or at least retards it greatly. The object of the present work was to identify this substance, to isolate it, and to explain its constitution and its mode of action if possible.
Molecular Weight and Chain-Length of Natural and Synthetic Rubber
Authors: Wildschut A. J.
Published: February 2011

The determination of the chain-length of high molecular substances, as, e.g., rubber and gutta-percha, has lately been the subject of many investigations, though as yet the problem has not been definitely solved. The ordinary methods—measurements of the raising of the boiling point and of the depression of the freezing point—can be used only for molecular weights of some thousands, and there always remains a large gap between these compounds and the far greater natural ones. To bridge over this gap Staudinger has developed a supposition according to which it is possible to determine very high molecular weights by means of a viscosimetric method. This method depends on the known fact that for dilute solutions, in which the molecules do not hinder each other (so-called sol-solutions), the specific viscosity is proportional to the length of the molecule. For homologs we have: