bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low Temperature Flexing Apparatus
Authors: Martin S. M. 
Published: February 2011

Abstract
For the past ten months, Sub-Committee V of SAE-ASTM Technical Committee A on Automotive Rubber has been working on the standardization of synthetic rubber specifications. Insofar as possible, methods of tests have followed ASTM procedures. ASTM has no recommended procedure for measuring the low temperature flexibility of synthetic rubber. This committee, after careful consideration, has recommended the use of a modification of the Thiokol Corporation's freeze test. This method of testing for low temperature flexibility has been incorporated into a number of recent Aeronautical Material Standards Specifications covering synthetic rubber. The modified test uses the same apparatus as that used in the Thiokol Corporation's Laboratory, or slight modifications of this. Because of the interest in this apparatus, a short description of it is here given.
Ionic and Radical Mechanisms in Olefinic Systems, with Special Reference to Processes of Double-Bond Displacement, Vulcanization and Photogelling
Authors: Farmer Ernest Harold 
Published: February 2011

Abstract
The α-methylenic reactions discussed in the preceding two papers recall a series of interesting observations by Baker and Nathan, which indicate that a p-methyl substituent attached to the benzene nucleus can permit electron release to the nucleus in a manner that appears only in lesser degree in higher alkyl groups, and may be absent in some (e.g., Buγ). Thus in p-methylbenzyl bromide, the suggested function of the methyl group (dotted arrows in (I) permits (see PDF for diagram) additional electron release at the C—Br bond, and so facilitates the anionization of the bromine. Baker and Nathan suggest that the electrons of the duplet constituting the C—H bond of the methyl group are less localized than those in a similarly placed C—C bond, and hence that a methyl group attached to the necessary conjugated unsaturated system is capable of electron-release by a mechanism similar to the tautomeric effect:
Statistical Thermodynamics of Rubber. II
Authors: Wall Frederick T. 
Published: February 2011

Abstract
During recent years, considerable progress has been made in connection with theories of rubber elasticity. Two general types of theories have been advanced, one from a macroscopic point of view and the other from a molecular point of view. An example of the former is the theory of Mooney, who arrived at an equation which agrees well with observation. For molecular theories, the reader is referred to the work of Guth and Mark, Kuhn, and Pelzer, who carried through calculations of a statistical nature. More recently, the author extended the statistical theory along lines which avoided some of the earlier difficulties. In the present paper, the calculations will be carried still further, and the molecular theory will be related to the macroscopic theory of Mooney. It will also be shown theoretically that, although rubber does not obey Hooke's law for ordinary elongation, it should obey Hooke's law for shear. It will be supposed that individual rubber molecules are long chain hydrocarbons capable of assuming various lengths and shapes as a result of free rotation about carbon-to-carbon valence bonds. When a piece of rubber is under no stress, the rubber molecules have a certain distribution of shapes. When the rubber is subjected to a stress, however, the molecules assume another distribution of lower probability. The theory here advanced relates this probability to the entropy of strain, thus providing a means of arriving at the mechanical properties of rubber. Two postulates are made. (1) When a macroscopic piece of rubber is strained, the components of the lengths of the individual molecules (along some set of axes) change in the same ratio as does the corresponding dimension of the piece of rubber. (2) When a piece of rubber is elongated, no change in total volume takes place. The first assumption was made in the earlier paper of this series, whereas the second was not. Experimental support for the second postulate has been given by Holt and McPherson. Our first problem is to investigate the effect of this second assumption on the equation of state for rubber.
The Effect of Temperature and Solvent Type on the Intrinsic Viscosity of High-Polymer Solutions
Authors: Alfrey T. , Bartovics A. , Mark H. 
Published: February 2011

Abstract
1. The specific viscosity of a dilute solution of polystyrene or rubber is strongly dependent on the nature of the solvent; the specific viscosity is high in a good solvent, and low in a poor solvent or a solvent-nonsolvent mixture. This has been interpreted as being due to changes in mean molecular shape. The specific viscosities of cellulose acetate solutions are not so sensitive to the nature of the solvent. 2. The extrapolated specific viscosity at the limit of solubility is in the same range for several different solvent-nonsolvent systems. 3. The effect of a temperature increase is to lower the specific viscosity of rubber or polystyrene solutions in a good solvent, but to increase the specific viscosity in a mixture of solvent and nonsolvent. 4. The specific viscosity of a dilute polystyrene solution is more nearly linear with concentration in a toluene-methanol mixture than in pure methanol. The quadratic term b in the equation: (ηsp=ac+bc2), is reduced relatively more than the linear term a by the presence of the nonsolvent.
Further Studies of the Infrared Absorption of Rubber
Authors: Williams Dudley , Dale Brock 
Published: February 2011

Abstract
The transmission spectrum of natural rubber has been studied in the region between 1µ and 15 µ and the effects of linear and radial stretch have been observed. Linear extension greater than 400 per cent of the original length produces an increase in the C—C vibrational frequency. Both linear and radial stretch produce an increase in absorption coefficient and a decrease in reflection coefficient. The changes in absorption and reflection coefficients are greatest at short wave-lengths.
Properties of Hard Rubber. XIV. Influence of Some Ingredients on Surface Deterioration in Sunlight
Authors: Church H. F. , Cooper L. H. N. , Daynes H. A. 
Published: February 2011

Abstract
Experiments have been made to find to what extent ingredients capable of reacting with sulfuric acid to form insoluble sulfates can prevent the loss of insulating properties of hard rubber on exposure to daylight. Hard rubbers containing small and large percentages of calcium and barium carbonates and litharge have been tested, along with a comparable unloaded material and one containing an inert filler, barium sulfate. In no case was there a substantial improvement. Although the basic fillers gave better results than the inert filler, the samples containing them were inferior to the unloaded sample. The partial recovery of insulating properties on removal from light after a low surface resistivity has been reached has been investigated. Appreciable recovery took place in all cases, but this was most marked with the sample containing calcium carbonate. It was anticipated that the basic ingredients examined would to some extent prevent the undesirable effects of acid forma- tion in cases where the exposure to light was not continuous or so severe as bright north daylight. Further experiments on this point are recommended. The value of benzidine as an ingredient which forms an insoluble sulfate was tested by treating the surface of hard rubber with aqueous and benzene solutions of this material. Appreciable improvement was observed in each case. Attempts to prepare vulcanizates containing benzidine or derivatives of it having the same protective effect were unsuccessful.
Factors Affecting Results Obtained with the Mooney Viscometer
Authors: Taylor Rolla H. 
Published: February 2011

Abstract
Experience with the operation of the Mooney viscometer in 18 laboratories indicates the need for better reproducibility of results. A study of the available data from these laboratories along with numerous experiments made at the National Bureau of Standards have shown the factors that must be considered in improving the reproducibility. If uniformity in the values of Mooney viscosity on the same sample with different viscometers and in different laboratories is to be obtained, the methods of adjustment that must be followed and the precautions that must be taken are cleaning, mechanical calibration, dimensions of dies, die holders, and rotors, die closures, and preparation of testpieces. Each of these items and the errors which may result from maladjustments and lack of precautions in the use of this instrument are discussed.
The Hertzian Spectrum of Rubber and Its Micellar Constitution
Authors: Girard Pierre , Abadie Paul 
Published: February 2011

Abstract
The spectra which were studied lie within the region of hertzian frequencies, and can be represented either by dispersion curves showing the dielectric constant of the substance as a function of the frequency (or wave length λ), or by absorption curves showing the loss angle as a function of this frequency. These two types of curves represent the same phenomenon, i.e., orientation of the dipolar molecules in the alternating electric field, in accordance with the theory of Debye. The spectra and their interpretation depend chiefly on whether the molecules are crystalloid with relatively small and similar dimensions, or are colloidal, with large and unequal dimensions. In the first case, the spectra gives evidence chiefly on the form of the molecules and their structural features. Dilution in a nonpolar solvent shows for certain dipolar compounds, e.g., alcohol, considerable deformations, which differ according to the solvent. In the case of colloids, e.g., rubber, which has a permanent moment, the spectra and the meaning of these spectra are far different. In this case the spectra indicate that the absorption and dispersion values in the hertzian region are closely related to the micellar constitution, i.e., to the different types of micelles, to their size, and to the proportion of each type.
Applications of Infrared Methods in the Structural Examination of Synthetic Rubber
Authors: Field J. E. , Woodford D. E. , Gehman S. D. 
Published: February 2011

Abstract
Infrared absorption spectra have been long recognized as a convenient means for studying the structure of organic molecules. The interpretations of the spectra are based on the energy interactions of the molecule and the radiations which arise from the vibration of the constituent atoms and molecular rotations. For simple or highly symmetrical molecules, the determination of the normal modes of vibration and the calculation of the absorbing frequencies are relatively simple and straightforward. For more complicated organic molecules, this becomes increasingly difficult because with each additional atom, the number of degrees of freedom is increased by three and the determination of the normal modes of vibration becomes practically impossible. However, interpretations can be made to a useful extent through empirical comparisons with the absorption spectra of simpler known structures. The data that have been accumulated by investigators in this field have made it possible to assign rather definite absorption frequencies to some of the chemical linkages and functional groups. These correlations which have appeared in numerous places in the literature are partially reproduced in Table I. Organic compounds generally have strong absorption bands below 1300 cm−1, to which few definite assignments can be made with certainty because the vibrations of many of the atoms of the molecule may be involved rather than a specific part of it. It is clear that such empirical relationships must be relied upon in studying the structural variations of the long chain, complex molecules which occur in butadiene and isoprene polymers and copolymers and other synthetic rubbers. This procedure has been applied to determine the effects of oxidation and of variations in monomers and polymerizing conditions on the structure of synthetic rubber. It is practically certain that physical deficiencies of synthetic rubber are due principally to the structure of the long chain molecules rather than to the chemical nature of the monomers used.
Crystallization of Unvulcanized Rubber at Different Temperatures
Authors: Wood Lawrence A. , Bekkedahl Norman 
Published: February 2011

Abstract
Crystals may be formed in natural rubber under varied experimental conditions. Different combinations of stretching and cooling have been used to induce crystallization in unvulcanized and in vulcanized rubber. The appearance and disappearance of crystals have been studied by observations of the volume, heat capacity, light absorption, birefringence, x-ray diffraction, hardness, and other mechanical properties. There has, however, been no comprehensive study of the effect of temperature on the crystallization. The present investigation was undertaken to explore this field. In the work reported here it has been the aim to study crystallization at different temperatures under the simplest possible conditions. The main features of the crystallization of vulcanized rubber have been shown to be similar to those of the crystallization of unvulcanized rubber, vulcanization decreasing the rate of crystallization. Consequently unvulcanized rubber was selected for study. Stretching obviously complicates the experimental conditions, and so was not employed. Of the different methods of measuring crystallization, it seems that change of volume is the simplest and best adapted to yielding quantitative data on the course of the crystallization or fusion. The present work is, therefore, concerned with a general study of the volume changes in unvulcanized rubber at different temperatures.
Optical and Dimensional Changes Which Accompany the Freezing and Melting of Hevea Rubber
Authors: Smith W. Harold , Saylor Charles Proffer 
Published: February 2011

Abstract
At suitable, low temperatures, unvulcanized rubber loses its elasticity and becomes hard and opaque. Similar changes frequently occur in baled rubber which has been tightly compressed before shipment. It is said to be frozen or “boardy.” The phenomenon has been studied by many investigators who have determined changes of volume, softening temperatures, the effects of increasing time of storage at low temperatures, the influence of pressure during freezing, and changes in heat capacity and entropy. These effects have generally been ascribed to a form of crystallization, and x-ray diffraction powder patterns indicate that crystals are present in frozen rubber. When total rubber is stretched, there are changes of volume and of heat content such as attend crystallization. With x-rays a crystal fiber pattern is obtained. It and the powder pattern obtained with frozen, compact rubber have been shown to indicate similar spacings and are assumed to be caused by the same type of crystal, the differences being ascribed to conditions of orientation. Dilute solutions of rubber hydrocarbon in ethyl ether yield small crystals of the hydrocarbon when they are subjected to temperatures between −35° and − 60° C. for several hours. The optical properties and melting points of these crystals and their x-ray diffraction patterns indicate their identity with the crystals in stretched and frozen rubber. Under the best conditions the crystals appear in spherulitic groupings, the individual needles in each spherulite having optical properties that closely approach those of a uniaxial crystal with negative elongation. The crystals of sol rubber which we obtained, melted between 9.5° and 11.0° C. Crystals of gel rubber melted between −2° and 14° C., but the melting ranges within this interval were not the same for all samples. Numerous observations have repeatedly confirmed the data. About 90 per cent of the rubber in solution may be obtained as birefringent material at −65° C. Temperatures between −40° and −50° C. have been preferred, however, because better crystals are obtained in that range.
The Problem of Making Uniform Crude Rubber and Its Standardization
Authors: Bocquet M. 
Published: February 2011

Abstract
The problem of attaining uniformity in crude rubber and of standardizing its properties has become of the greatest concern to planters, and at the present time two facts are evident: 1. In evaluating the product which the planter has furnished him, the rubber broker has based his judgment solely on the superficial appearance of the rubber, which frequently has nothing in common with its intrinsic quality. 2. The manufacturer has found frequent cause of complaint in the variability of different lots of rubber which he has purchased and which it has been impossible for him to distinguish by superficial examination. for these reasons the planters, in agreement with the manufacturers, should welcome the classification of crude rubber into a small number of types based on the physical and chemical properties of the product. However, considering the variability of rubber at the present time, crude rubber must obviously be uniform before any attempt is made to draw up specifications. As is shown by M. Bocquet in the following discussion, the production of uniform rubber should not require any great efforts on the part of the planters, and if the planters prefer not to change their methods at the present time, it is because their methods are adjusted to the output of commercial sheet rubber, the only kind salable on the open market.
An X-Ray Study of Rubber Hydrochloride
Authors: Gehman S. D. , Field J. E. , Dinsmore R. P. 
Published: February 2011

Abstract
The x-ray diagram of rubber hydrochloride is a worthy addition to those of other natural high polymers and derivatives, and its study is a fruitful field for investigating the internal structure of such materials. Various peculiarities have been pointed out which have raised a question as to whether the properties of rubber hydrochloride can be explained on the basis of a chemical structure consisting of long, chlorinated, paraffin chains. These disturbing facts are (1) the effect on the x-ray diagram of the first addition of hydrogen chloride; (2) the failure to secure the theoretical chlorine content; (3) the possibility of vulcanization; (4) the amorphous diagram of balata hydrochloride, and (5) the shortening of the chains compared to normal paraffin chains. A partial departure from the strict formula may, in turn, lead to a colloidal structure which may be essential for such properties as the elasticity shown at higher temperatures and the ability to rack. The interpretation of the x-ray diagram seems to be possible on the basis of such long chains if some deformation from the zig-zag form is permitted to shorten them about 10%.
Mechanism of Oxidation of Rubber and Its Bearing on Accelerated Aging Tests Parts I And II
Authors: Morgan L. B. , Naunton W. J. S. 
Published: February 2011

Abstract
1. An apparatus is described for the measurement of the rate of oxidation of rubber at either constant pressure or constant volume. Provision is made for further additions of oxygen during the oxidation. 2. It was confirmed that the rate of oxidation of rubber is independent of the oxygen pressure. 3. The zero order reaction rate of oxidation varies with temperature according to the Arrhenius equation. 4. The depth of oxygen penetration decreases exponentially with temperature, and is reduced by low oxygen pressure, low oxygen permeability or by a fast rate of oxidation. 5. If the dimensions of the rubber sample are too large, or the temperature is too high, it is probable that only the outside layers of the rubber will undergo oxidation, and the low rate of oxidation observed will depend on the depth of oxygen penetration. 6. On exposure to light the propensity of the rubber for oxidation gradually increases, and the data suggest the slow attainment of a photostationary state between two opposing reactions, involving the formation of peroxide by light and disappearance by a dark reaction. 7. On removing light-activated rubber into the dark, the enhanced oxidation rate persists for a considerable time. 8. All specifications for accelerated aging tests should specify the importance of not exposing the samples to a bright light before submitting them to the aging operation. 9. The peroxide formed by the action of light can be destroyed by the action of heat in vacuo.
High-Speed Apparatus for Determination of Plasticity in Rubber Works and Some Results
Authors: Hoekstra J. 
Published: February 2011

Abstract
Since the day that Hancock invented his wooden masticator, plasticizing has been one of the outstanding features of the rubber industry. Although the application of rubber in the form of latex, thus avoiding the process of mechanical softening, is increasing, this does not imply that the use of heavy machinery for plasticizing coagulated rubber is lessening. It is now commonly accepted that plasticizing or mastication of rubber is a chemical process, occurring under combined mechanical and chemical (oxygen) influences and resulting in a diminishing of the length of the hydrocarbon molecules. This breakdown of rubber is of great technical importance, because the plasticity of rubber stock determines its workability. The degree of plasticizing or breakdown, especially when mastication has been prolonged, has also some effect on mechanical and aging properties after the plasticizing has been counterbalanced by the action of vulcanization. It follows from the foregoing that control of plasticity during fabrication is of great interest from a technological standpoint. From the standpoint of works economy the problem is not less urgent, because energy used by internal mixers and mixing rollers as well as extra costs resulting from wrong plasticity in calendering and moulding are of importance in total production costs.
The T-50 Test for State of Vulcanization. II
Authors: Gibbons W. A. , Gerke R. H. , Cuthbertson G. R. 
Published: February 2011

Abstract
The uses and applications of the T-50 test for state of vulcanization have been listed. New combined sulfur data corrected for sulfur combined as zinc sulfide have been presented. The T-50 values for vulcanizates which contain no zinc oxide, but which are widely different in composition, give identical curves when plotted against the total combined sulfur. The T-50 values for vulcanizates which contain zinc oxide and which are widely different in composition do not give identical curves when plotted against either the total or the corrected combined sulfur.
The Influence of Vulcanization on the Oxidizability of Rubber. Vulcanizing Agents Other Than Sulfur
Authors: Dufraisse Charles , Le Bras Jean 
Published: February 2011

Abstract
In a previous publication the influence of vulcanization by sulfur and sulfur compounds on the oxidizability of rubber was shown. The most important conclusion was that, in principle, the higher the proportion of combined sulfur, the greater is the oxidizability. However, with very high proportions, the activity of the sulfur changes, i.e., above a certain upper limiting range, the oxidizability tends towards a plateau, whereas below a lower limiting range the oxidation curve passes through a minimum. After having obtained these results, it seemed to be of interest to complete the investigation by studying the effects of vulcanization by agents other than sulfur on oxidizability. In the present work we have examined vulcanization by nitro compounds and peroxides, taking as examples m-dinitrobenzene, trinitrobenzene and benzoyl peroxide. This domain of rubber chemistry has been relatively little explored and certain points either have not received final confirmation or have even led to contrary conclusions. Accordingly it seemed useful to review from a purely objective point of view what has been done on this subject.