bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Milling on Properties of Hevea and Buna Rubbers
Authors: Wiegand W. B. , Braendle H. A. 
Published: February 2011

Abstract
1. The superior cut-growth resistance of Hevea tread stock is partly ascribed to its pronounced relaxation or lengthening when subjected to repeated severe cyclic extensions. Under such conditions the breaking elongation increases from 700 to 900%. GR-S under similar treatment fails to develop any lengthening. 2. As a consequence of this failure to lengthen under repeated severe strains, such as those antecedent to cut-growth failure, GR-S exhibits higher modulus, i.e., at 500 or 600 per cent elongation, or higher retractive forces than does Hevea. This also promotes cut growth. 3. In Hevea, progressive milling (at normal temperature) of tread stocks tends to develop a tensile maximum. At this point of optimum milling, d.c. resistivity reaches a minimum. Overmilling, characterized by a decrease in tensile, shows a sharp rise in log R. 4. With Perbunan, highest tensiles and elongations are realized only after several remillings, at which point modulus and Shore hardness have already shown marked decline. 5. With Buna-S (GR-S), tensile and elongation reach their maxima at about one remilling (at normal temperatures). Milling beyond this point is reflected in sharp degradation of elongation. Log R provides no indication of optimum conditions, since it is rising at this point. 6. In Butyl B, tensile and modulus reach a simultaneous maximum between two and three remillings. Log R in this region is declining and reflects retardation due to the softness of Butyl stocks. 7. Hot milling of GR-S shortens and reduces heat and flex properties. Cold refining lengthens GR-S and improves these properties, but does not protect against subsequent damage from heat. GR-S shortened by heat cannot be restored by subsequent cold refining. The benefits of cold refining apply also to the completely formulated tread. 8. Extreme development of the cold-refining technique produces the following results (based on treatment of complete tread mixing) : Modulus declines continuously to less than 50 per cent of control. Elongation increases continuously to 125 per cent of control. Tensile strength increases to 110 per cent at 20 passes and then remains steady. Hot-iron life (thermal shortening) improves continuously to 310 per cent at 80 passes. Cut-growth resistance improves progressively to 370 per cent of control at 160 passes, and is still rising. 9. The fact that such striking all-round quality takes place at about fifty cold refinings with rolls at 80° F (stock at about 120° F) suggests the importance, in the fabrication of GR-S tires and other products subject to dynamic usage, of (a) avoidance of elevated temperatures at all stages, and (b) further study of the remedial effects of strenuous mastication of refining of GR-S tread type, carbon-reinforced stocks under low-temperature conditions. 10. Attempts to improve GR-S should be oriented in two opposite senses: to decrease its hysteresis at low extensions (under 100 per cent) but to increase its hysteresis, or capacity to relax, at the higher extensions antecedent to cut growth.
Low-Temperature Flexibility of Synthetic Elastomers Effect of Aviation Gasolines
Authors: Wilson G. J. , Chollar R. G. , Green B. K. 
Published: February 2011

Abstract
A tensiometer can be used to measure the stiffness of rubber stocks; accurate data are secured which lend themselves to a quantitative interpretation of the effect of low temperatures on any compound. Where changes in the sensitivity to flexing of thin rubber sections are important, such data, represented by curves of temperature vs. flexibility, seem more important than durometer changes and bend-brittle points. The compounding practice of high plasticizer does not in itself provide low-temperature flexibility where fuel immersion and ensuing plasticizer extraction are conditions of service. Tests designed to evaluate low-temperature flexibility and freeze resistance which utilize organic liquids as temperature conditioners must be double-checked to ensure that the cooling medium is not exerting its own specific effect on the stocks. Graphs indicate the influence of aviation fuels on low-temperature resistance; it has been experimentally proved by the same method that acetone has a similar effect. It is established that some synthetics are more resistant than others to prolonged low temperature. Service requirements and field conditions should be carefully considered in all cases where laboratory evaluation does not include every variable factor. The need for a thorough application analysis of functional stocks cannot be overemphasized.
The Molecular Weights of Rubber and Related Materials. V. The Interpretation of Molecular Weight Measurements on High Polymers
Authors: Gee Geoffrey 
Published: February 2011

Abstract
Unless an ultracentrifuge is available, absolute molecular weight determinations must be based ultimately on osmotic data. Viscosity measurements furnish a convenient method of interpolation, and give reliable results for homogeneous linear polymers. The viscosity molecular-weight of a typical unfractionated polymer would not be very seriously in error unless the polymer were extensively branched. No reliable conclusions about molecular-weight distribution can be drawn from molecular-weight data alone without carrying out a fractionation, although a useful guide to the homogeneity of a polymer known to be of linear structure is furnished by the ratio of the viscosity and osmotic molecular weights.
Staining Rubber in Ground or Milled Plant Tissues
Authors: Haasis Ferdinand W. 
Published: February 2011

Abstract
Accessory to a comprehensive study of guayule production now under way by the United States Department of Agriculture is an analysis of the rubber content of plants of various strains and ages grown under diverse environmental conditions. This analysis is currently made by chemical extraction of the rubber from finely ground tissues by a method based on that described by Spence and Caldwell. This method consists of a number of distinct steps, and it is part of the program to test possible variants of these steps. As a check on the effectiveness of such tentative modifications, the ground samples are examined microscopically, especially the spent charges remaining after extraction.
The X-Ray Diagram of a Buna-S Vulcanizate
Authors: Morris Ross E. , Jordan Charles B. 
Published: February 2011

Abstract
Sebrell and Dinsmore (India Rubber World 103, 37 (1944); Rubber Chem. Tech. 16, 857 (1943)) found that the x-ray diffraction pattern of Buna-S consists of a broad halo similar to that obtained with liquids. This type of pattern was obtained whether the Buna-S was unstretched or stretched. Unstretched natural rubber gives a similar pattern, but stretched natural rubber gives a characteristic fiber pattern. This fiber pattern demonstrates the existence of three-dimensional crystallites. Buna-S would not be expected to yield a fiber diagram while stretched because the molecules of this synthetic rubber are probably not constructed in a regular fashion. The styrene residues are presumably distributed at random along the length of the molecule, and there may be side-chains which branch off the main chain. However, when considerably stretched, a Buna-S vulcanizate would be expected to exhibit some indication in its x-ray diagram that alignment of the molecules has occurred.
Two Modes of Action of Antioxidants in Rubber
Authors: Le Bras Jean 
Published: February 2011

Abstract
It is a commonly accepted belief that antioxidants protect oxidizable products from the harmful effects of oxygen by retarding the rate at which these oxidizable products combine with oxygen. Consequently, if the oxidizability of a rubber mixture containing no antioxidant and the oxidizability of the same mixture to which such an agent has been added are measured under the same conditions, the absorption of oxygen would be expected to be distinctly less rapid in the second case. This has, in fact, been proved to be true in general, not only for rubber, but also for other substances which are protected by antioxidants. In a systematic study of a series of antioxidants of differing chemical compositions, various observations were made which gave indications that these products react in two different ways. In these experiments a rubber mixture of chosen composition was prepared as a blank or control, and was compared with other mixtures of the same base composition to which various antioxidants selected for study had been added in the same proportion in all cases.
Damping, Heat Development and the Length of Life of Vulcanizates
Authors: Springer A. 
Published: February 2011

Abstract
Although it is still not possible to calculate or to predict the behavior and length of life of different types of rubber products under service conditions, it is nevertheless of value to make clear the relations involved, and to trace back the many already known phenomena to their physico-chemical causes. The present work deals with the following aspects of the subject. A relation between damping, shape of test-specimen, heat conductivity, frequency and heat development is derived, with the aid of which both the rise in temperature and the maximum temperature, and in precise measurements the temperature factor as well, can be calculated. With certain assumptions for the sake of simplicity, the energy loss can be calculated from the stress and elastic constant. It appears that the behavior of vulcanized rubber mixtures when they are tested under constant stress is different from that when they are tested at constant deformation. The destructive action brought about by prolonged repeated stressing is ascribed to chemical reactions, and on the basis of this assumption it is shown that the length of life depends on the temperature. Attention is called to the possibility of evaluating Wöhler curves on a mathematical basis. The equations which are formulated are verified by a large amount of experimental data, and a few characteristic diagrams are given by way of illustration.
Stiffening Effect of Pigments in Rubber
Authors: Gehman S. D. 
Published: February 2011

Abstract
The use of reinforcing pigments in rubber, especially in synthetic rubber, is important in securing desirable physical properties. The earlier literature on the subject has been reviewed by Shepard, Street, and Park. Several theories were advanced to explain the effectiveness of reinforcing pigments in rubber. Some of these emphasized the importance of particle size and shape: others, the chemical composition and surface activity. The electron microscope has now furnished more reliable information on the particle size and shape of pigments, especially of carbon blacks, than was available in the earlier work2. The carbon blacks used in rubber compounding are essentially spherical; the mean diameter varies from 28 to 274 mµ for different types. Systematic studies have been carried out to show the influence of particle size and surface area on various physical testing indices used to evaluate rubber compounds. The x-ray structure of rubber stocks containing carbon black has been investigated. Several articles dealing with the theory of pigment reinforcement have appeared. This additional work has not clarified the original concepts advanced to explain filler reinforcement, but the research of Wiegand shows beyond doubt that particle size is the predominating factor in explaining differences in the properties of rubber compounded with various blacks. The present paper will attempt to explain some of the effects of pigment reinforcement of rubber, particularly increased stiffness, by simple mechanical considerations which may be regarded as extensions or extrapolations of the results of measurements on rubber in compression.
Molecular Processes during Deformation of Rubberlike Elastic Bodies
Authors: Meter Kurt H. , Van Der Wyk A. J. A. 
Published: February 2011

Abstract
It has been demonstrated that the elastic force of a moderately vulcanized rubber kept at a constant stress is proportional to the absolute temperature, T, in the region of medium elongations. In this respect, rubber behaves somewhat like an ideal gas, the pressure of which at constant volume is also proportional to T. By applying the first and second laws of thermodynamics, it can be shown that the internal energy of isothermally stretched rubber changes as little as that of an ideal gas if its volume is increased or decreased isothermally. In both cases, however, the entropy of the system changes. Meyer, Susich, and Valkó, Karrer, and Busse explain this behavior in the following way. All rubberlike substances consist of long, flexible, chain molecules whose links are thermally mobile. In the undeformed amorphous rubber, the molecules represent randomly coiled chains ; as a result of the deformation their shape is changed, e.g., partly stretched by elongation. Thus a thermo-dynamically less probable shape is forced on them ; the thermal agitation tends to eliminate it ; because of the reciprocal felting and intertwining of the molecules, a return to the thermodynamically more probable state is possible only if the deformation can be reversed. The thermally mobile chain links are referred to as kinetic units or chain segments. In the present paper, we shall discuss the molecular processes taking place in the course of deformation, in particular such questions as: “How is the deforming force transferred to an individual chain molecule and its segment?” “How does the molecule react to this force?” After having discussed these questions, we shall examine how far the requirements are complied with for a quantitative theory such as the derivation of an equation to calculate the modulus of elasticity from structural data. We shall also discuss the attempts known to have been made in this direction so far.
A Study of the Various Molecular Fractions of Rubber and Their Behavior during Vulcanization
Authors: Hauser E. A. , Le Beau D. S. , Shen Yen 
Published: February 2011

Abstract
Hevea prime ribbed smoked sheets were subjected to diffusion fractionation. The rubber recovered from the separate fractions was compounded and vulcanized. The physical and chemical properties of the vulcanizates showed pronounced differences. A tentative explanation for these results is offered on the basis of the molecular and colloidal structure of the rubber hydrocarbon.
The Mechanism of Reinforcement. II
Authors: Goldfinger George 
Published: February 2011

Abstract
Further experimental evidence is given which indicates that, when a dilute solution of GR-S is mixed with carbon black, certain fractions of the rubber are preferentially adsorbed by the black. After removal of the carbon black and the adsorbed fractions by centrifuging, the “treated” GR-S is obtained by precipitation from the solution. Samples compounded as GR-S gum stock show increasing modulus with increasing amounts of carbon black used for adsorption treatment. However, when the GR-S thus treated is compounded with carbon black, then the effect is reversed. The more black used in the treatment and the higher the modulus of the gum stock, the lower the modulus of loaded stock.
Specific Heats of Hevea, GR-S, and GR-I Stocks
Authors: Hamill W. H. , Mrowca B. A. , Anthony R. L. 
Published: February 2011

Abstract
1. A calorimeter, suitable for determining the specific heats of various rubber compounds (with a precision of 1 per cent or better), is described. Although the results reported are for room temperature (actually 26–27° C), the calorimeter could be operated with minor changes at other temperatures. 2. Employing values of the specific heat at room temperature as given by the National Bureau of Standards for various raw rubbers, it is shown by direct measurement on various gum and loaded stocks that the specific heats of these materials can be calculated from a knowledge of the specific heats of the ingredients. 3. A 5 per cent deviation from linearity in the stress-temperature curves at constant length can cause a total variation in cL of only about 0.00014 calorie per cc. per 1° C over an elongation range of 0 to 200 per cent. This result holds, provided an equation of state exists and provided the region of temperature and elongation considered is one in which phase changes do not occur. Subject to these restrictions, we may neglect variations in cL with elongation and may interpret cL (in calories per gram per ° C) as being identical with cp (in calories per gram per ° C) at the same temperature. 4. Accurate knowledge of cL is needed for the correlation of the reversible heat developed when rubber is stretched rapidly with the entropy component of the stress-strain curve. It is also needed to correlate calculated energy losses with rise in temperature in flexometer experiments.
The Photogelation of Rubber Sols in the Absence of Accelerators
Authors: Buckingham R. , Planer G. V. 
Published: February 2011

Abstract
Irradiation of rubber sols with ultraviolet light in the absence of oxygen results in gelation under certain conditions. From a study of the reaction curves the mechanism of this reaction was shown by the authors in a previous paper to consist mainly of a three-dimensional polymerization. The curves were derived by following the reaction by means of viscosity measurements, in the presence of an accelerator, benzophenone, with carbon tetrachloride as solvent. It was deemed of interest to compare these curves with those obtained without the use of benzophenone, and the experimental work described in the following deals with the study of the reaction in the absence of accelerators. The products obtained on removing the solvent from photogels differ markedly for various solvents, but are in all cases insoluble and show elastic properties similar to those of lightly vulcanized rubber. The solvents used are of two types, active and inactive. In the case of the active ones, such as carbon tetrachloride, the solvent molecules condense with the rubber, and on removal of the solvent from the resulting photogels, the products are often considerably heavier than the original rubber samples. When carbon tetrachloride is used, the reaction product has been shown to contain appreciable amounts of combined chlorine. With inactive solvents like benzene, ligroin, etc., no increases in weight are observed and gels are generally formed less readily.
Nonsulfur Vulcanization. II. An Experimental Study
Authors: Alfrey Turner , Hendricks J. G. , Hershey Robert M. , Mark Hermann 
Published: February 2011

Abstract
In Part I the literature on nonsulfur vulcanization was reviewed, with particular emphasis on the reaction mechanisms involved. The present paper reports a series of experiments conducted in this laboratory. The first part deals with a chemical investigation of dinitrobenzene vulcanization ; the second part deals with the physical properties of nonsulfur vulcanizates, and includes some results reported in the literature as well as those experimentally established here.
Oxidation of GR-S Vulcanizates
Authors: Shelton J. Reid , Winn Hugh 
Published: February 2011

Abstract
Oxygen absorption studies on a tread type GR-S vulcanizate show: 1. There are three stages involved in the oxidation: (1) an initial rapid absorption, of apparent first order at constant pressure, which is of short duration and appears to involve a limited number of especially reactive centers in the vulcanizate ; (2) a constant-rate reaction, of apparent zero order at constant oxygen pressure, which would extend over most of the useful life of the vulcanizate in service ; (3) an autocatalytic reaction, beginning after a given stock has absorbed a definite amount of oxygen that is independent of the temperature at which the absorption takes place. 2. The rate of oxygen absorption increases with temperature. The temperature coefficient for the constant rate reaction is 2.6 for a 10° C change in temperature over the range 80° to 120° C. 3. Diffusion is not rate controlling, provided the specimen thickness does not exceed 0.080 inch at 100° C or 0.040 inch at 120° C. 4. The effect of cure on the rate of oxygen absorption by GR-S vulcanizates is slight, and consequently, the technique is particularly useful for studying the effect of changes in compounding upon aging resistance. 5. Oxygen absorption data can be satisfactorily correlated with changes in physical properties during aging. While the fundamental nature of the mechanism of the oxidation of GR-S is still unknown, considerable information has been obtained with respect to some of the factors involved, and the general nature of the reaction has been established. This information, together with the work still in progress, should be of value in pointing the way toward possible methods of improving the resistance of GR-S to aging.
Recent Advances in Rubber Analysis
Authors: Wake W. C. 
Published: February 2011

Abstract
There is considerable overlap between the various methods reviewed above, some of which are completely self-contained, whereas others have to be grouped together to provide a complete analytical scheme. There are, consequently, several ways of building up a comprehensive system, and which way is preferred in practice depends on the amount of information already in the possession of the analyst, and his purpose in carrying out the analysis. In the case of an unknown vulcanized sample requiring full investigation, the following order of procedure will be found helpful. (1) Sufficient of the rubber for the tests required is acetone-extracted and dried. (2) Preparations for determining swelling ratios should be made. Unless the modified micro-method is used this result will not be available for a week. However, it is definitely worth starting as the preparations take only the time required for weighing and although the rest of the analysis will be completed, confirmation of such work arriving after a few days will be valuable as in independant check and an insurance against error or accident. (3) The systematic scheme for qualitative analysis given in U.9 should be used, starting with the sodium fusion for elements. Even if elements characteristic of certain types are present, it must be assumed that hydrocarbon polymer is present also and that part of the scheme given for cases where characteristic elements are absent should be used. It may, however, be abbreviated by limiting it to the use of color tests for natural rubber and GR-S, although there is danger of missing the presence of alkali reclaimed natural rubber if this is done. (4) From the qualitative composition such rubbers, as are indicated present, are determined quantitatively. (5) It is useful to make certain that the results obtained are in agreement with any physical properties that can readily be noted, e.g., freeze resistance and specific gravity.
Rubber Plastometer with Uniform Rate of Shear—Shearing-Cone Plastometer
Authors: Piper G. H. , Scott J. R. 
Published: February 2011

Abstract
A new shearing-cone plastometer, suitable for investigating the plastic-flow relations of highly viscous materials over a wide range of stress, is described. A mushroom-shaped rotor, having upper and lower surfaces of conical type, is rotated in the plastic material contained in a cylindrical mould. With this type of shearing surface the rate of shear is uniform throughout the material, except for a small edge zone, thus overcoming some disadvantages of previous plastometers. The mechanical design is based on the Mooney shearing-disk plastometer except that provision is made for a wide range of speeds of rotation.