bluuebunny/crossref_metadata_2025_split huggingface dataset:
Natural and Synthetic Rubber Fibers. Electron Microscope Studies
Authors: Hall C. E. , Hauser E. A. , leBeau D. S. , Schmitt F. O. , Talalay P. 
Published: February 2011

Abstract
Hevea rubber fibers suitable for observation in the electron microscope were prepared from thin films produced by spreading rubber solutions and dispersions on a water surface. Fibers of guayule, Cryptostegia, Neoprene, and Buna-S were prepared in a similar manner and studied with the electron microscope. Unvulcanized Hevea rubber was separated into sol and gel fractions. Electron micrographs of the sol fraction show fibers bearing many large nodules along their lengths. The spherical shape of many of the nodules is strongly suggestive of fluid properties. The gel fraction shows practically no nodules, but tends to form closely branched networks. The smallest fibers have a characteristically beaded appearance which may be related to the state of aggregation of the isoprene chains. When pale crepe or smoked sheet is worked on the mill, cross-linked networks of the gel fraction disappear, and the milled material takes on the appearance typical of the sol. Vulcanization of milled rubber in solution has the effect of producing cross-linked networks of fine fibers similar to those from the gel fraction. Unvulcanized and vulcanized compounds containing carbon black were examined. From the location and distribution of the carbon in rubber particles, films, and fibers, suggestions are offered concerning the nature of the reënforcement phenomena.
Factors Influencing the Plasticity and Recovery of GR-S
Authors: Neal Arthur M. , Ottenhoff Pieter 
Published: February 2011

Abstract
One of the vital problems connected with the successful conversion from natural rubber to GR-S is the availability of the industry to mill and otherwise process this elastomer. When the polymer was first introduced, reports indicated at least twice as much equipment would be required to handle GR-S as to handle an equal volume of natural rubber. As the production of GR-S has increased, the product has become more uniform and less difficult to handle; it is now estimated that the processing of GR-S will not require more than 10 per cent more equipment than natural rubber. In spite of this improvement the problem of processing GR-S is still important. One of the fundamental difficulties is due to the lack of correlation between laboratory tests and factory processability. Vila showed that there is no relation between the Mooney plasticity and tubing speed, regardless of whether the basis is the plasticity of the compounded stock or of the uncompounded polymer used in the stock. Sturgis and Vincent showed that there is no correlation between the milling characteristics of the raw polymer and plasticity, whether measured by Mooney plastometer, Williams parallel-plate plastometer, or the Williams pendulum plastometer. This apparent lack of correlation between plasticity and processability is difficult to understand. The present work was undertaken to determine whether a study of the changes which take place under various conditions of milling would give information that would explain this anomaly.
Processing Behavior of High Polymers. Correlation with Elastic-Plastic Properties
Authors: Zapp R. L. , Gessler A. M. 
Published: February 2011

Abstract
The difficulties in correlating the processing behavior of synthetic high polymers with results obtained by standard plasticity methods indicate that present methods do not completely evaluate polymer differences. A connecting knowledge between processing qualities and molecular structure would be of increasing value, not only as an aid to process control, but also as a possible guide to polymerization research. Observations on the elastic-plastic properties of high polymers seem to indicate some molecular differences that govern processing behavior. Williams stated that, if one grade of rubber is considered, elastic strain is a function of resistance to flow. When different types of rubber or other materials are considered, the relation between plasticity and elastic strain does not remain constant. The purpose of this paper is to present some of the factors involved in carrying on further study of the plasticity, processing, and molecular structure correlation.
Cellular Rubbers
Authors: Gould Louis P. 
Published: February 2011

Abstract
This paper has presented a report on the progress which has been made in the cellular rubber field during the past several years; now a few words about the future. It is said that Russia has seventeen kinds of Buna-S. At present the United States has only one kind, namely, GR-S. Of course, this country does have several types of Buna-N and several types of Neoprene. Possibly the day will come when there will be available one or more types of both solid and liquid synthetic rubbers made specifically for the manufacture of cellular rubber products. In the past, many production difficulties in this field have been due to variation in the plasticity and in the rate of cure of different lots of natural rubbers, and to variation in the stability and rate of cure of different shipments of natural rubber latices. These difficulties may well be overcome in the synthetic rubbers of tomorrow.
Physical Testing of Synthetic-Rubber Products
Authors: Cooper L. V. 
Published: February 2011

Abstract
Evaluation that will predict with a high degree of accuracy the suitability for service of any product is the object of all physical testing. Over a comparatively short period of about twenty-five years, rubber technologists have evolved a series of tests which have evaluated natural rubber compounds reasonably well. When it became necessary to evaluate rubber substitutes, it was only natural that the same tests would be applied. The results obtained convinced everyone that these materials were definitely not equivalent substitutes, and to use them involved more than just replacement. Although the background is not so extensive as might be desired, the A.S.T.M. Committee D-11 on Rubber Products has learned enough about these materials to be able to present certain facts and recommendations to industry in general with regard to specifications covering synthetic rubbers and products made from them. The entire field of physical testing is quite extensive, as it covers not only finished products but the component raw materials from the time they are received until they emerge as final products ready to be put into service. Also, in this large field, not everyone is interested in the same phase of testing synthetic rubber products. Tire development engineers are not interested in load deflection figures, which are so essential to automobile design engineers, and the latter have no concern with adhesion to fabric which must be considered by the pneumatic tire technologists and those concerned with hose and belting. This paper is intended to deal primarily with some of the physical properties which affect the service of finished products.
Cure of GR-S in Thick Articles
Authors: Morris Ross E. , Hollister Joseph W. , Mallard Paul A. 
Published: February 2011

Abstract
Information on the relative rates of cure of GR-S stocks and similar Hevea stocks in thick sections is of interest to many rubber manufacturers. Since curing conditions for thick articles from Hevea stocks have been established, they would like to know how these conditions must be altered when GR-S stocks are used in the same applications. They could develop a GR-S stock with the same rate of cure as the Hevea stock which it replaces according to laboratory tests on comparatively thin sheets, but this agreement does not mean necessarily that thick sections cure at the same rate. The respective rates of heat flow through the rubbers must be considered. Only if the rates of heat flow as well as the curing rates of thin sections are in agreement, will the curing rates of the thick sections be equal. Juve and Garvey found that GR-S tread stocks cure faster in the center of thick sections than similar Hevea tread stocks. They were unable to explain this behavior because, according to their measurements, the thermal conductivity of the GR-S tread stock was less, and its specific heat greater than, the corresponding values for the Hevea tread stock. They concluded that the difference mav be due to an exothermic reaction.
The Du Pont Modified Williams Plastometer
Authors: Keen W. Newlin 
Published: February 2011

Abstract
Webster defines plasticity as “the ability to retain a shape attained by pressure deformation”. Plasticity measurements are made by rubber technologists for one or more of the following reasons: (1) to measure the workability of rubber or synthetic elastomers; (2) to determine the effect of natural or accelerated aging on the processability of compounded rubber or synthetic elastomers; (3) to determine to what extent softeners or compounding ingredients may have affected the workability of rubber or synthetic elastomers; (4) to serve as a control test in the manufacture of synthetic elastomers. The Williams Plastometer has been widely used in the rubber industry for a number of years. Since its introduction in 1924 by Williams it has undergone a number of refinements which have improved its mechanical efficiency and simplified its operation. However, the fundamental operating principles of this machine have been retained. This article discusses the modifications that have been incorporated into the instrument now in use at the du Pont rubber laboratories.
The Thermodynamics of Rubber at Small Extensions
Authors: Elliott D. R. , Lippmann S. A. 
Published: February 2011

Abstract
On analyzing their own data, Meyer and Ferri have concluded that, at small extensions, rubber is an ideal elastomer according to the definition that (∂E/∂L)P,T=0. Further analysis of Meyer and Ferri's data does not sustain their conclusion. If, however, (∂E/∂L)V,T=0 is taken as a new criterion for an ideal elastomer, Meyer and Ferri's data do indicate that rubber is ideal, at least for extensions up to 166 per cent. The new criterion implies that the valence angles do not store an appreciable amount of energy when the rubber is stretched. However, both the molecular orientation and the interatomic displacements do influence the energy required for extension.
Photo Vulcanization. A Study of the Products of the Action of Light on Rubber Under Conditions Precluding or Restricting Oxidative Degradation
Authors: Stevens Henry P. 
Published: February 2011

Abstract
Milled sheeted rubber in evacuated sealed tubes or tubes filled with inert gas becomes vulcanized on exposure to sunlight or ultraviolet radiation. Stress-strain curves and also swelling and solubility data are given in confirmation. The vulcanizing effect is enhanced by treating the surface, preferably the under-surface, of the rubber with sensitizers, which may be regarded as photovulcanizing agents. These usually are also photogelling agents, and comprise aldehydes, ketones, quinones and chlorinated quinones. Sulfur is also active, and to a lesser extent other substances, including some thermalvulcanization accelerators, although these latter do not act as photovuleanization accelerators. Some photovulcanizing agents protect rubber from oxidation during insolation, so with them a vulcanizing effect is obtainable in the presence of air. The nature of the photovulcanizing effect and its relation to modern theories of vulcanization are discussed.
Molecular Requirements for Synthetic Rubbers
Authors: Baker W. O. 
Published: February 2011

Abstract
Rubbery substances consist basically of long chains of atoms to which other atoms may be attached in small groups that occur repeatedly, and often regularly, like the links along a chain. There are hundreds of atoms in one of these “macro” molecules. It is the particular arrangement and the active forces between these molecules that are responsible for the elastic properties of many substances. The structure of the molecules of most synthetic rubbers as well as that of natural rubber is so complex, however, that efforts to determine, by direct study of the commercial products, what produces their rubbery characteristics have yielded results that are difficult to interpret. Progress in solving the puzzle has recently been made by starting with simple chain compounds and forming from them, by known chemical modifications, substances which have some of the properties that are found in natural rubber. Studies of these “model” chain compounds indicate that the long-chain molecules of rubbery substances must have forces between atomic groups which are small enough to permit twisting and kinking of the chains. There must also be lateral forces to hold adjacent molecules together, like a bundle of sticks, especially when the substance is stretched. Moreover, the molecules must have side groups to avoid the close packing, when unstretched, that is characteristic of crystals.
The Structure of Polyisoprenes. III. Ultraviolet Absorption Spectra
Authors: Bateman L. , Koch H. P. 
Published: February 2011

Abstract
The quartz ultraviolet absorption spectra of highly purified polyisoprenes correspond closely to those of simple ethylenes having the same degree of alkyl substitution at the double bond. This is also true of geranylamine hydrochloride, which shows no obvious characteristic that can be identified with the structural anomaly revealed by x-ray crystal analysis. The extent to which spectral variations are a measure of the electronic properties of groups and molecules of this type is therefore discussed—with the conclusion that for formally saturated substituents the correlation is still obscure. Evidence is presented to show that inductive influence is slight, and that interpretations hitherto advanced on the basis of hyperconjugation are unsound.
Inverse Correlation between Rubber Hydrocarbon and a Crystalline Fraction Isolated from Latex of Cryptostegia Grandiflora
Authors: Stewart William S. , Hummer Richard W. 
Published: February 2011

Abstract
1. Analysis of 157 samples of dried latex from above-ground portions of Cryptostegia grandiflora indicated a linear inverse correlation between the percentage of rubber hydrocarbons and the insolubles. 2. By extraction of the latex “insolubles” with absolute ethanol and fractional precipitation of the extract, an unidentified crystalline fraction was obtained which was inversely correlated with rubber hydrocarbons. It is possible that this crystalline fraction is the only one in the insolubles and latex inversely correlated with the rubber hydrocarbons.
Recent Advances in the Physics and Chemistry of Rubber. II. The Kinetic Theory of Rubber Elasticity
Authors: Treloar L. R. G. 
Published: February 2011

Abstract
In Part I, the nature of the rubber molecule was discussed, and it was shown to consist essentially of a single chain of relatively very great length. Many of the characteristics of rubber, such as the high viscosity of rubber solutions, the high elasticity, and the capacity for swelling in solvents, are directly connected with this fundamental molecular structure. The present Part II is concerned with the elasticity of rubber, and discusses the origin of the remarkable difference between the elastic properties of rubber and ordinary hard solids. The typical solid, e.g., a rock salt crystal, is represented by a structure in which each atom is held in an equilibrium position by strong forces. The application of a deforming force disturbs the equilibrium positions of the atoms very slightly, in such a way that internal stresses which balance the externally applied force are brought into play. The value of Young's modulus for a crystal is of the order 1011, and the maximum extension before breakage occurs is generally about 1 per cent. Rubbers on the other hand can be deformed by 700 per cent or more by comparatively small forces, corresponding to Young's moduli of the order 107. These enormous differences point to a different elastic mechanism in the two cases. When we look at the range of materials which show rubberlike elasticity, we find in all cases the same fundamental pattern of molecular structure. The atomic constituents of the molecule may vary, but the molecule invariably takes the form of a very long chain, generally, but not necessarily of carbon atoms. It is this basic similarity which provides the clue to the understanding of the phenomenon of high elasticity.
The Chemical Constitution of Butadiene Rubbers, Based on the Formic Acid and Formaldehyde in the Decomposition Products of Their Ozonides
Authors: Yakubchik A. I. , Vasiliev A. A. , Zhabina V. M. 
Published: February 2011

Abstract
A rapid method has been developed, with the aid of several types of synthetic rubber, for determining the characteristic chemical structure of butadiene rubbers by means of the formic acid and formaldehyde recovered when their ozonides are decomposed.
The Interaction of Plasticizers and Polymers
Authors: Frith Elizabeth M. 
Published: February 2011

Abstract
The general problem of plasticizer compatibility is discussed, and it is suggested that a comparative measure of compatibility can be obtained from experiments which measure polymer-plasticizer interactions (w). Experiments are described which measure the viscosity of dilute polymer solutions in suitable mixed solvents containing the plasticizer in question. The slope of the ηsp/c−c curve is shown to be related to the equilibrium extent of swelling of the polymer in the pure plasticizer and, in general, the slope of the curve is a good comparative measure of the plasticizer's compatibility. The effects of temperature and composition of the mixed solvent are also discussed. The experiments are considered in the light of a previous theory of the effect of solvent on the ηsp/c ratio: the results do not support the suggested view that the slope of the ηsp/c−c curve is a simple linear function of w/kT.
Rubber Photogelling Agents
Authors: Stevens Henry P. 
Published: February 2011

Abstract
This paper details an evaluation of a number of rubber photogelling agents or activators under insolation, particularly oxygen and sulfur. Contrary to previous statements, both elements are shown to be activators, and sulfur combines with rubber as in thermal vulcanization. Molecular oxygen, after allowing for degradative oxidation, is an extremely powerful gelling agent, comparable with quinonic or peroxidic oxygen.
Coagulation Studies of the Latex of Cryptostegia Grandiflora, R. Br. A Wartime Source of Vegetable Rubber. I
Authors: Siddiqui Rafat Husain , Warsi S. A. , Sastri V. V. K. 
Published: February 2011

Abstract
1. Coagulation can be brought about by methods which are physical and chemical in nature. The chemical methods are suitable for the coagulation of latex on a large scale. 2. The latex coagulates at a pH range of 4.2–7.5. 3. The range toward pH 4.2 is reached by acids and acid salts. 4. Coagulation when effected by chemical reagents, by autocoagulation or by passage of an electric current is always accompanied by a change in the hydrogen-ion concentration of the latex. 5. Dilute solutions of alkalies, acids and of some salts give very good results. 6. If the quantity of the coagulant exceeds the minimum amount required for the coagulation of latex, no coagulation occurs, and the latex passes into a second phase or zone. 7. When coagulation is effected by shaking, centrifuging, the application of dry heat, or adding alcohol and acetone, the pH value of the latex remains unchanged. 8. Coagulation is brought about also by reagents used for hydration and dehydration and for precipitating proteins, and by microörganisms and enzymes.
Carbon Blacks in GR-S
Authors: Parkinson D. 
Published: February 2011

Abstract
The importance of different types of colloidal carbon as reinforcing agents for the butadiene-styrene copolymer, GR-S, has been stressed in recent papers. It has been shown that, to a first approximation, the effect of carbon blacks in this type of synthetic rubber is similar to that in natural rubber, but it has been shown also that the extremely low tensile strength and poor tearing properties of uncompounded vulcanized GR-S necessitates the addition of some form of carbon black to almost all types of compounds. The present paper considers the influence of carbon blacks in vulcanized GR-S compounds. Earlier papers have discussed the effect of carbon blacks in natural rubber.
The Structure of Polyisoprenes. IV. Double-Bond Interaction in Certain Carbalkoxy-Substituted 1,5-Dienes
Authors: Bateman L. , Jeffrey G. A. 
Published: February 2011

Abstract
A peculiar lack of olefinic reactivity, combined with a facility for cyclization of methyl and ethyl Δ1,5-hexadiene-1, 1, 3, 3, 4, 4, 6, 6-octacarboxylates, has been attributed by Ingold, Parekh, and Shoppee to ring-chain mesomerism. A reinvestigation of these and related compounds has now been made by using x-ray methods, and it is shown that the crystal structure of the methyl ester is incompatible with the cis-configuration required for such interspatial double-bond saturation. A radical disruption of a mesomeric system by crystallization from solution is improbable and, an earlier formulation incorporating a bicyclobutane nucleus being rejected on chemical grounds, it is necessary to seek a new interpretation of the anomalous reactivity. We suggest that the determinative condition is hyperconjugation throughout the carbon framework of the molecule, and discuss this in relation to 1,5-dienes generally.
The Cold-Compression sets of Natural and Synthetic Vulcanizates
Authors: Morris Ross E. , Hollister Joseph W. , Mallard Paul A. 
Published: February 2011

Abstract
The behavior of certain large synthetic rubber gaskets on naval vessels during the past winter points to the necessity for a cold compression-set test in the specifications for these gaskets. It has been found, for example, that Neoprene gaskets on large valves, which perform satisfactorily at temperatures of 60° F and above, are not usable at temperatures of 40° F and below. They take a cold compression-set, while the valves are closed, so that when the valves are opened and then again closed, the leading edge or surface of the valve does not seat properly. This cold compression-set is not permanent; when the gaskets which exhibit cold compression-set are removed to a warm atmosphere (about 80° F), they slowly regain their original shape. A survey of the literature dealing with the effects of low temperatures on rubber compounds yielded no information on cold compression set. The set test proposed by Morris, James, and Evans in connection with their low temperature stiffness test is not directly applicable to the present problem because it is conducted in tension. Therefore to investigate cold compression-set, it was necessary to devise a new testing procedure.