bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purified Rubber for Electrical Insulation
Authors: Kemp A. R. 
Published: February 2011

Abstract
THE water absorption and the dielectric stability of soft rubber insulating compounds under wet conditions is influenced by the kind of crude rubber employed. For most rubber-covered aerial and building wire where moisture conditions are not severe, the better grades of plantation rubber are satisfactory. However, for service involving immersion for long periods in fresh water, a need exists for rubber containing less nonhydrocarbon water-absorbing substances than the plantation product. This is particularly true when the insulating wall is thin and a high degree of electrical stability is required. Only recently has the preparation of such a type of purified rubber been given serious consideration on the plantations in the Far East. In the past, coöperation on such a problem with the plantation has been difficult, and for that and other reasons methods have been developed here for preparing this rubber in the factory. The purpose of this paper is to discuss the nature and role of protein and other substances found in Hevea rubber and to outline various methods for purifying rubber. Data are presented on the composition and properties of the resulting products.
Examination of Rubber Latex and Rubber Latex Compounds. I. Physical Testing Methods
Authors: Jordan H. F. , Brass P. D. , Roe C. P. 
Published: February 2011

Abstract
PRECISE control is essential to the successful operation of any commercial process, particularly of those processes involving the use of rubber latex. Latex is, of course, a complex natural product; it contains a variety of nonrubber constituents, such as proteins, soaps, and others which control or influence its colloidal properties. In order to ensure uniform behavior of latex in process, it is obviously desirable to test its uniformity as a raw product. It is furthermore important that such tests should be, wherever possible, fundamentally sound and free from the personal equation. Unless the results can be expressed in basic fundamental units, which are independent of the apparatus used and of the operator, confusion will result. It is the purpose of this paper to review critically the more important general physical tests and methods of analysis which can be applied to latex, particularly from the standpoint of accuracy and sources of error, and to recommend certain procedures on the basis of commercial experience in the authors' control laboratories. Some of the recommended methods have been developed in these laboratories, while others have been improved over procedures given in earlier works on latex (3, 6, 9). Part I is concerned with physical tests such as pH, surface tension, viscosity, and mechanical stability, while Part II is concerned with analytical methods.
The Preservation of Latex by Acids
Authors: Rhodes Edgar , Sekar K. C. 
Published: February 2011

Abstract
It is shown that by the application to field latex of amounts of formic acid of the order of 9 per cent by weight of the latex or 10 per cent by volume of the 90 per cent commercial acid, a product results which will retain its fluidity for long periods. It is, however, apparently micro-flocculated, and unstable. Because of their instability, it seems unlikely that acid latices of this kind will find technical applications. The findings are in no way contradictory to those of Fullerton, whose experiments on coagulation did not include trials with such large amounts of acid. It is regretted that fuller experimental data cannot be given because most of the relevant records were destroyed recently by fire at the Institute. It is probable that a further study will be made, from which additional experimental data together with a possible explanation of the empirical observations given here may emerge.
Contributions to the Analysis of Rubber. II. The Qualitative Determination of the Serum Components of Raw Rubber and of Vulcanized Rubber
Authors: Dekker P. 
Published: February 2011

Abstract
The use of latex in the rubber industry has been increasing to a considerable extent, and in many cases where formerly solutions of ordinary plantation rubber were used exclusively, e. g., for impregnating fibres, spreading and adhering textiles, and manufacturing dipped goods, latex mixtures are now employed. Then again there is increasing interest in rubber prepared by evaporation or spraying of latex, especially for the production of powdered rubber. Consequently the time has come, as is evident from recent publications, when it may be an important problem whether in the preparation of a rubber mixture it is best to use ordinary plantation rubber, latex, or, perhaps, evaporated latex. Now the peculiarity of a rubber mixture prepared from latex or from evaporated latex is its relatively high precentage of serum substances from the latex. In the first Communication on the present subject, which dealt with the “Determination of the Water-Soluble Components of Rubber,” a method was described for determining the serum substances in vulcanized rubber. In view of the fact that with technical rubber mixtures, and in the presence of zinc, calcium, and magnesium compounds, this method is complicated and tedious, the present experiments were carried out with an aim to developing a procedure for determining qualitatively the serum substances. A method of this kind must naturally be restricted to the identification of some substance which originates in the serum and not in the curvatives or other compounding ingredients. Among the various substances which are present in latex serum, 1-methylinositol is one of the most important, and rubber mixtures prepared from latex or from evaporated latex contain a notable quantity of this substance. Consequently proof of the existence of 1-methylinositol in a mixture should be evidence of the presence of serum substances. The investigation to be described was therefore confined to the development of a characteristic reaction of 1-methylinositol.
Studies in the Vulcanization of Rubber. VII. Unsaturation of Rubber Vulcanized with Nitro Compounds and Benzoyl Peroxide
Authors: Blake John T. , Bruce Phillip L. 
Published: February 2011

Abstract
RUBBER is primarily an unsaturated hydrocarbon. Sulfur adds to its double bonds during vulcanization to form soft and hard vulcanizates. In the formation of soft vulcanized rubber, unsaturation is reduced several per cent by the chemical addition of sulfur. Spence and Scott (10) showed that the proportion of combined sulfur corresponds exactly to the decrease in unsaturation, and therefore that sulfur combination consists entirely of addition to the double bonds of rubber. The studies of one of the authors (1) on the vulcanization of rubber with nitro compounds indicate that these substances or their decomposition products combine with rubber. Van Rossem (8) also showed that vulcanization with benzoyl peroxide is accompanied by a decrease in extractable material, indicating that either the reagent or its decomposition products combine chemically with the rubber. The natural expectation would be that addition to the double bonds occurs and that the unsaturation decreases correspondingly. Van Rossem's proposed mechanism for the vulcanization with benzoyl peroxide would involve no change in unsaturation. Fisher and Gray (2) applied Kemp's method (4) in determining the iodine numbers of a single vulcanizate of each of four compounds. The vulcanizing agents involved were m-dinitrobenzene, trinitrotoluene, and benzoyl peroxide. Their unsaturation values agreed closely with calculated values for the unvulcanized compounds. They concluded from their results that “Ordinary vulcanization is an unknown or undetermined type of change in the hydrocarbon involving no change in the unsaturation and that chemical union of sulfur is a secondary reaction.” If true, this evidence is a serious blow to the chemical theory of vulcanization which postulates that a chemical reaction is essential for the process. The present paper offers evidence that the vulcanization of rubber with these reagents does involve change in its unsaturation.
Natural and Synthetic Rubber. VIII. Products of the Destructive Distillation of Sodium Rubber
Authors: Midgley Thomas , Henne A. L. , Shepard A. F. 
Published: February 2011

Abstract
The pyrolysis products of sodium rubber have been compared with those of natural rubber. They indicate that sodium rubber is isomeric with natural rubber in the positioning of its methyl groups, and that the double bond of sodium rubber differs from the true ethylenic bond of natural rubber. In the latter respect sodium rubber closely resembles overvulcanized rubber.
Crystalline Rubber Hydrocarbon
Authors: Washburn E. W. 
Published: February 2011

Abstract
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 this character is systematic crystallization, and a laboratory technic for applying this method to “rubber hydrocarbon” has recently been developed at this Bureau. The conditions which must be met in order to induce crystallization in such a typically colloidal material as rubber can be predicted. These conditions have been met and are embodied in the following procedure.
Isoprene and Rubber. Part 30. Hydromethylrubber
Authors: Staudinger H. , Brunner M. , Geiger E. 
Published: February 2011

Abstract
When rubber is reduced at 270° under high pressure, a hemi-colloidal hydrorubber is obtained, and it was proved by Geiger and Huber that the product has a higher molecular weight and is less cyclicized if a good catalyst is used in large quantity (for example, active nickel produced by the method of Kelber), while according to the original experiments of Fritschi, who carried out the hydrogenation in the presence of very little platinum, a more degraded and somewhat cyclicized hydrorubber is obtained. The saturated hydrorubber is much more stable than the unsaturated rubber since the loosening action of the double bonds is lacking. A hydrorubber of the average molecular weight of 10,000 is still relatively stable at 270°, while a hemi-colloidal rubber with this molecular weight will he cracked to still smaller fragments at this temperature, and these fragments are then changed by cyclicization. This behavior can be clearly seen in methylrubber. The following reduction proves that it is even more easily decomposed than rubber itself. With nickel as catalyst, Geiger obtained from methylrubber by reduction at 270° and 100 atmospheres a hemi-colloidal hydromethylrubber which had an average molecular weight of 1600 and therefore had a degree of polymerization of about 20. If rubber is reduced under the same conditions a higher molecular product is obtained with an average molecular weight of 3000 to 10,000. Judged by reduction experiments, the chain of butadiene rubber is still more stable, since the hydrobutadiene rubber prepared under the same conditions had the highest average molecular weight. The cleavage of the chains, as in the following formula, is therefore favored by the methyl groups:
Temperature Coefficient of Vulcanization. Determination for Mixes Accelerated with Mercaptobenzothiazole and a Crotonaldehyde-Aniline Condensation Product
Authors: Park C. R. , Maxwell R. B. 
Published: February 2011

Abstract
1. The average temperature coefficient of mercaptobenzothiazole accelerated mixes, based upon physical data, was found to be 1.91 per 10° C. For crotonaldehyde-aniline, the value was 2.32 per 10° C. 2. Based upon combined sulfur data, the value was 2.30 (average) per 10° C., and for crotonaldehyde-aniline 2.67 per 10° C. 3. The values obtained from physical data are to be preferred for all practical purposes.
Measurement of Average Particle Size of Fine Pigments
Authors: Gehman S. D. , Morris T. C. 
Published: February 2011

Abstract
A method of obtaining excellently dispersed suspensions of rubber pigments of accurate concentration is described in which the pigment is milled into rubber and the stock then dissolved in a solvent. The average particle sizes of carbon blacks measured by the Zsigmondy count method were found to range from 0.061μ for rubber gas black to 2.22μ for the coarsest one measured. The zinc oxide pigments had average particle sizes from 0.076μ to 0.57μ.. Measurements on several other pigments of interest are included. Because of the high visibility in the ultra-microscope, this method gives smaller values for average particle size than the photomicrographic methods. The results have been used to calibrate a microturbidimeter of the extinction type for use in measuring average particle size. Curves are included showing how the turbidities of suspensions of zinc oxide and carbon black vary with the average particle size, concentration, and wave length of light used.
Vulcanization with Benzoyl Peroxide. I. Contribution to the Knowledge of the Vulcanization Process
Authors: van Rossem A. , Dekker P. , Prawirodipoero R. S. 
Published: February 2011

Abstract
Three-quarters of a century have passed since the discovery of the vulcanization process by Charles Goodyear, Thomas Hancock, and Alexander Parks without the discovery of an essentially new process of vulcanization. In 1915 Ostromislenski reported the discovery of two new methods of vulcanization, namely, vulcanization with nitrocompounds and vulcanization with peroxides and peracids like benzoyl peroxide. Ostromislenski was of the opinion that vulcanization is a process which can be divided into two distinct phases, “Thus we arrive at the conclusion that the vulcanization of caoutchouc is divided sharply into two fundamental phases: 1, a chemical reaction affecting only an insignificant part of the caoutchouc and, 2, adsorption or swelling of the unchanged caoutchouc into the product of this chemical reaction.” a concept which was developed by van Iterson, Jr., in somewhat different form as a working hypothesis for the vulcanization process. It is noteworthy that only in 1929 did Ostromislenski publish a second communication on vulcanization with benzoyl peroxide, even then without offering any new theoretical points.
The Cause of Variability in the Plasticity of Plantation Rubber after Storage
Authors: Martin G. , Elliott L. E. 
Published: February 2011

Abstract
There are two reasons why a study of the plasticity of rubber is of importance to the planter, viz.: (1) the variable plasticity of plantation rubber leads to many difficulties in manufacturing operations; and (2) first-grade plantation rubber is so hard that it is frequently mixed with inferior grades and other materials to enable it to pass more easily through the different processes. The results of the investigations recorded in this report suggest a definite reason for the hardness and variability of first-grade rubber. Tests carried out by De Vries in Java showed: (1) that freshly prepared plantation rubber is uniform in plasticity, but that many samples gradually become hard or soft on keeping and so develop differences; and (2) that rubber containing more serum substances than usual becomes hard, and that containing less than usual becomes soft. On the other hand, tests carried out by the Scheme on a large number of samples for over three years show that in most cases rubber becomes harder on keeping for six months at 15° C. The hardening of the rubber at European temperatures has been confirmed by Griffiths of the Dunlop Rubber Co., Ltd., who stated that large-scale experiments on rubber from different estates showed that in all cases, after storage for three years, it was necessary to increase the time of milling by about 30 per cent in order to obtain the required plasticity.
The State of Rubber in Solutions, Based on the Surface Properties of the Solutions
Authors: Dogadkin B. , Pantschenkow G. 
Published: February 2011

Abstract
The problem of the constitution of rubber and especially of its state in solutions has recently again become the subject of active discussion. Based on a series of investigations, Staudinger reached the conclusion that dilute solutions contain free colloidal rubber molecules which are composed of closed chains of an unusually large number of isoprene residues. Pummerer considers the molecular weight of rubber to be much less than does Staudinger. (According to Staudinger the molecular weight of rubber is 50,000 to 170,000; according to Pummerer it is 1200 to 1600.) Meyer and Mark assume for the primary valence chain of rubber a molecular weight of about 5000. These latter investigators are of the opinion that there are secondary aggregates of rubber molecules in a rubber solution and that the high values which were found by a number of investigators (Caspari, Kroepelin, and others) do not represent the molecular weight but the average micellar weight of rubber. In deciding the question of the state of rubber in solution the majority of investigators make use of the classic cryoscopic and osmotic methods of investigation. Staudinger has used viscosimetric measurements in an original way in his experiments. In the present work we have turned to a study of the surface properties of rubber solutions, assuming that data along this line might explain some peculiarities in the structure of these solutions.
Rubber Solutions
Authors: Stamberger Paul 
Published: February 2011

Abstract
In my earlier publications the hypothesis was suggested that rubber is a homogeneous substance and not a mixture of homologous polymers. This hypothesis has been criticized from many sides. My conclusions were based on the fact that the diminution of the vapor pressure and of the osmotic pressure of rubber solutions is independent of the origin of the rubber and of the treatment it receives. With regard to the discussion of the objections which have been made, I have obtained evidence that this hypothesis is also supported by other quantitative measurements of the state of equilibrium, e. g., the specific heat. In the course of this discussion, Bary questioned the basic theory by which I arrived at this conclusion when the incompatibility of the Raoult law has been established. Kroepelin calls attention to the fact that, in concentrated swollen substances, molecular groups and not molecules are united with the solvent. In the case of rubber these have double bonds. I do not know any reason that can justify this conclusion of Kroepelin. The investigations which I have undertaken on more dilute solutions do not support such a theory. A little later I shall go into more detail about Bary's comment.
The Reënforcement of Rubber
Authors: Antonoff G. 
Published: February 2011

Abstract
It is a well-known fact that, when mixed in rubber, certain powders reënforce the latter to a considerable extent, whereas others have no effect or only a relatively slight one. Since the nature of the phenomena which take place under these conditions in rubber is far from well established in the present state of knowledge, I have carried out certain experiments of a very simple kind which will by analogy throw some light on the subject. I have found that very important information can be obtained from the study of some physical properties of mixtures of different powders in organic liquids. For a beginning, ordinary paints were tested, but the presence of drying oils complicated matters and it was found advantageous to replace the linseed oil with a non-oxidizing oil, as for example, peanut oil. In this way, pastes of different concentrations were prepared, and the resistance to rupture of the films of these pastes was measured by a method often used to determine the surface tension of liquids. A convenient method of operation is as follows: two thin rods are wet with the paste and are made to adhere to one another. The upper rod A is fastened permanently in a way not shown in Fig. 1. From rod B hangs a pan for small weights which, added in convenient quantity, will finally bring about rupture of the film and separation of the two rods.
Experiments on the Autoöxidation of Rubber and the Catalytic Phenomena Which Are Associated with It
Authors: Dufraisse Charles , Drisch Nicolas 
Published: February 2011

Abstract
This first series of experiments was aimed to establish the value of the method of study which is described, and to indicate its applications. Furthermore, we were less interested in going deeply into the various problems considered than to show by the various examples the convenience and the precision of our method. There still remains the problem of determining the relation between autcöxidation observed in this way and true aging by ordinary methods. This will be a task for the future. However, as far as we have gone in this work, a satisfactory parallelism has often been found between our data and that already obtained by the usual methods. Although we have not made a detailed study of some of the results, we have been led to a certain number of concrete conclusions in the course of the study. Two of them are worthy of being mentioned. One concerns the variation of the action of every catalyst of autoöxidation, the other the future of methods of protection. Moureu and Dufraisse have already emphasized the sensitivity of autoöxidation catalysts to the slightest influences, and this is again confirmed in the case of rubber. Consequently, a catalyst, whatever may be its properties, should not be classified as a good antioxygen in general. It should receive this qualification only for precise conditions where its efficacy has been effectively controlled, because its influence is subject to variations which may extend as far as a change in the sign, oxidation then being accelerated instead of retarded. In regard to the future of the protection of rubber, it is easy to predict from what has been found for other oxidizable substances. Remarkable progress has already been made in the industrial use of antioxygens. Instead of continuing to evaluate them by certain units, the coefficient of protection should be calculated by powers of 10, as with so many other substances. In that case, rubber, at last really stabilized, would find vast markets opened up in which it cannot be used at present on account of its instability.