bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adsorption of Elastomers on Carbon Black
Authors: Kraus Gerard , Dugone Joseph 
Published: February 2011

Abstract
During the past three years considerable progress has been made in the study of adsorption of high polymers on the surfaces of solids from solution. A number of experimental investigations have established that linear polymers are adsorbed at a number of segments along the molecular chain and that an apparent saturation value of the adsorption is reached with increasing concentration, leading to isotherms that exhibit considerable similarity with the classical Langmuir isotherm. Kolthoff and others have shown that poor solvents favor adsorption and that fractions of high molecular weight are adsorbed preferentially. Polymer of low molecular weight is adsorbed more rapidly, but is eventually replaced by fractions of higher molecular weight. Kolthoff and Gutmacher also observed some evidence of adsorption hysteresis in rubber-carbon black systems. Preferential adsorption effects have also been described by Goldfinger and others, who, in addition, furnished an estimate of the thickness of the adsorbed layer. Theoretical explanation for many of these effects has recently come from a detailed statistical mechanical treatment of polymer adsorption by Frisch, Simha, and Eirich.
Studies of the Vulcanization of High Elastic Polymers. II. Vulcanization of Natural Rubber with Thiuram Disulfides. Part 2
Authors: Scheele Walter , Lorenz Otto , Dummer Wilhelm 
Published: February 2011

Abstract
This paper gives some insight into the kinetics of thiuram vulcanization. The following results were obtained. 1. The decrease of concentration of thiuram disulfides during vulcanization is a first-order reaction in the range of short vulcanization times. At longer reaction times, departures occur. The process then takes place more slowly. 2. The departures from the course of a first-order reaction are displaced with decreasing temperature toward the range of longer vulcanization times. 3. At 87° C, the reaction of tetramethylthiuram disulfide is of the first order over the whole range of vulcanization temperatures chosen, and at this temperature no deviations whatever are observed. 4. The same relationships are found in the kinetic study of dithiocarbamate formation. 5. From the combined results, it is concluded that, besides the two reactions occurring independently of each other during vulcanization, the diffusion of the reaction partners also has some influence on the kinetics. 6. The limiting value of dithiocarbamate formation is correlated with the macromolecular structure of the polyisoprene, and it is shown to be probable that this limit is not determined fundamentally by the chemistry of the vulcanization reaction.
Constant Power Principle in Abrasion Testing
Authors: Powell E. F. , Gough S. W. 
Published: February 2011

Abstract
This paper has been mainly concerned with presenting the case for power control in abrasion testing, and the implications of the better understanding of the mechanism of abrading. It is not claimed that the test machines described are perfect in their ability to assess resistance to wear action. There is still much to be done to remove anomalies that can still occur in results. One underlying principle, that of constant rate of energy dissipation at the abrading surface, is proposed as a criterion for comparison of the validity of test design for the many different types of laboratory test in regular use for assessment of wear resistance. Modification of the Lambourn constant-slip machine to make it conform with the constant-power principle is described, and the degree of correlation with service data on tires given. The effects of several major variables on the abrasion loss of rubber tread compounds, when tested with the modified Lambourn machine, are reported, including work on combating stickiness. Experiments with the Du Pont and U. S. Bureau of Standards abraders, modified to conform to constant-power principles, are also reported in this paper. The relations between work done in mechanically grinding rubber and the energy associated with the bonds ruptured in the grinding action are considered. It is suggested that a correlation may exist between abrasion and high-temperature flexibility properties of rubber.
Cut Growth and Flex Testing of Natural Rubbers and Synthetic Elastomers
Authors: Kaiser Rudolf 
Published: February 2011

Abstract
In the last decades, numerous studies have appeared concerning the behavior of tears in natural rubber and synthetic elastomers. In the United States' and England there are even standardized test methods. It can be seen from all the investigations and test instructions that the results are very poorly reproducible and only rarely agree with practical experience. In investigations on the behavior of tears, the two stages—the beginning of the tear and the growth of the tear (tear propagation)—must be differentiated. The following factors must be given primary consideration in starting the tear: external damage, the action of ozone and oxygen, frequently changing tensile or compression stresses. Here oxygen plays a role similar to that in the corrosion of metals. Fatiguing mechanical stress undoubtedly leads to the appearance of tears. But it can be assumed that the beginning of a tear observed in the area of maximum stress takes place at a preferred point on the surface. Such preferred points are always present. As is well known, the surface of a material— even on a high polymer—must not be regarded as completely “smooth”. In place of this supposed smoothness, there appears under microscopic or electron-microscopic observation a kind of “mountain system”. Observed under sufficient magnification, the “valleys” or cuts in the mountains are comparable to tears. Under mechanical stress, such cuts will then continue to grow particularly rapidly (nick effect). Now it is largely dependent on the kind of observation and the observer as to whether a small irregularity in the surface is called a tear. The beginning of the tear cannot, therefore, be defined clearly. The case is quite different with tear growth. The initial conditions—the tear present at the beginning of measurement—are given and only the growth of the tear has to be followed by measurement. The growth of the tear therefore seems to us to be well suited for detailed investigation.
Experimental Examination of the Statistical Theory of Rubber Elasticity. Low Extension Studies
Authors: Baldwin F. P. , Ivory J. E. , Anthony R. L. 
Published: February 2011

Abstract
The results of this study may be summarized as follows : (1) The agreement observed between theory and experiment is remarkably good in this region of low extensions—almost to within the estimated experimental errors. (2) The predicted nonlinear dependence of stress on temperature is confirmed by the experimental data. (3) In agreement with the Guth-James theory, the thermoelastic inversion extension is found to be a function of temperature, and is observed to increase with increasing temperature. (4) Small deviations from the predicted dependence of the stress on temperature are observed. These appear to increase in magnitude with decreasing temperature, and are strongest for the Paracril rubber at low extensions and temperatures. It seems probable that these deviations are the result of intermolecular forces not specifically included in the theory. That the deviations should be stronger for the Paracril-35 rubber is not at all surprising in view of the highly polar nature of the nitrile groups. At the higher temperatures employed in the experiment, such forces may be neglected to a first approximation, because of the greater average distances between molecular groups and the greater thermal kinetic energies. At lower temperatures, however, these forces are no longer negligible, and the molecules exhibit an increasing tendency to “lock-up” as the glassy region is approached. (5) Finally, an inspection of Figures 6 and 7 reveals a tendency for the theoretical stress-strain curve to lie above the experimental curve at the higher extensions. Recent studies indicate that this is a real deviation, and that it increases rapidly with increasing extension. Similar deviations at somewhat higher extensions have been noted by Treloar and by Gumbrell, Mullins, and Rivlin.
A Comparison of the Flow of High Polymers in the Cavity of a Mooney Plastometer
Authors: Fensom D. S. 
Published: February 2011

Abstract
From idealized Mooney plasticity-time curves for Butyl and GR-S synthetic rubber, the distinctive features of the various parts of the shearing curve are pointed out. Actual experimental curves are given for Butyl, GR-S, “cold rubber”, polyisobutylene, polybutadiene, polystyrene, and some natural-rubber gum stocks. For polymers which were produced in emulsion, the degree of branching as indicated by the Huggins k′ value seemed to be loosely correlated with the time to reach the primary peak in the Mooney flow curve. Cross-linking and entanglement in structure as indicated by high gel content seemed to be correlated with secondary rise in shearing force shown during a long test. An hypothesis of flow in the cavity of the Mooney machine is advanced to explain these phenomena, supported by drawings of cross-sections of samples run in the machine. According to this hypothesis, some high polymers shear in a streamline fashion, others shear along certain slip planes and may even exhibit a mixing of parts which seems to be similar to turbulence in fluids.
Chlorination of Rubber and Some Products of Its Partial Chlorination
Authors: Troussier Maurice 
Published: February 2011

Abstract
A study of the chlorination of rubber, and of products of its partial chlorination, by physical and chemical methods has made it possible to suggest a mechanism of chlorination. This mechanism, which is in good accord with the analytical results of Bloomfield, involves cyclization reactions, and thus confirms the cyclized structure of chlorinated rubber which has been attributed by some authors to completely chlorinated rubbers.
Abrasion of Butyl Rubber
Authors: Zapp R. L. 
Published: February 2011

Abstract
By using the Lambourn abrader, a concept of abrasion has been proposed that fits the performance of a wide variety of compounds. The ability of this type of machine to give varying degrees of slip and braking forces has aided in the selection of the proper conditions for abrasion studies. By using a small tread pattern on the sample wheel, laboratory results are brought into closer agreement with actual road wear tests. The work of Schallamach and the analysis of abrasion by a needle abrader have been extended to an abrasive surface. To the considerations of compound strength and surface friction or traction has been added the consideration of dynamic hardness. The abrasion of rubber has then been related to a ratio of dynamic modulus over rupture energy. Thus if a compound is made dynamically softer or more conformable without a sacrifice of its resistance to rupture, a superior abrading tread will result. In simple terms, what is needed for best abrasion resistance is the softest toughest material. Butyl owes its comparable or superior abrasion resistance (compared to other rubbers) to the fact that its vulcanizates are dynamically softer. The heat treatment of Butyl carbon black mixtures produces vulcanizates that are still softer in relation to their rupture energy. This is the sole advantage of such a mixing procedure. Other polymer and compounding variables that tend to decrease the ratio of dynamic hardness to rupture energy improve abrasion resistance. These changes include increasing the molecular weight of the polymer and reducing somewhat the unsaturation. A certain quantity of plasticizer to increase softness and a reduction of the state of cure have been shown to be beneficial. The latter change produced by a reduction of the amount of sulfur in the compound, which limits the extent of cross-linking, has resulted in distinctly superior tire treads.
Power Transmission—Slippage-Abrasion. An Investigation of the Abrasion of Tread Compounds
Authors: Viehmann Walter 
Published: February 2011

Abstract
The abrasion behavior of vulcanizates of the tire-tread type have been studied by the method of constant energy, with a test apparatus operating on the principle of the Dunlop-Lambourn machine. As a result of this work, the following facts were established. Up to a critical slippage, the value of which is characteristic of every individual vulcanizate, the abrasion, i.e., the amount of rubber worn off per unit of time, increases with the square of the slippage. The slippage increases linearly with the power transmitted. To this quadratic relation between the power transmitted and the slippage corresponds a linear dependence of the abrasion power, i.e., it is possible to assign a specific abrasion energy to every individual vulcanizate. The specific abrasion energy is inversely proportional to the temperature and also inversely proportional to the mean particle size of the abrasive material. A comparison of the measured specific abrasion energy with the corresponding value to be expected by theoretical calculation shows that the experimental value is too high by a factor of 106. From this, one is led to the conclusion that the abrasion power is practically completely consumed as heat in the abrasion boundary layer, an idea which is supported by measurements of the temperature of abrasion and a comparison of this with the calculated values. Above the critical slippage value, the simple linear dependence of the abrasive wear on the abrasion power no longer holds true, and a specific abrasion energy cannot be defined. In addition, the abrasion patterns described by Schallamach then appear, and any correlation between laboratory tests and road wear tests is lost.
Effect of the Temperature of Polymerization on the Structure of Butadiene-Styrene Copolymers
Authors: Sheĭnker A. P. , Medvedev S. S. 
Published: February 2011

Abstract
The addition of monomer molecules to the growing polymer chain during the polymerization of dienes may take place in several ways. In the polymerization of butadiene, the addition takes place in the 1,2- and 1,4-positions. In the latter case polymer chains are obtained with structural variations, e.g., the position of CH2 groups at the double bonds is cis or trans. The resulting polymer chains vary in configuration. It is of interest to determine how the configuration is affected by different conditions of polymerization. Several papers related to the subject are to be found in the literature. In this work, we studied with an infrared spectrometer the compositions of butadiene-styrene copolymers prepared at different temperatures. Also determined was the content of the various configurations of butadiene links in the polymer chains. The samples were prepared by polymerizing emulsions by the dilatometric method in the absence of oxygen. A satisfactory emulsion was obtained with a magnetic stirrer inserted into the dilatometer (Figure 1 ). The rotation of the stirrer (activated by a magnet attached to the axis of a motor under the thermostat) sucked the upper part of the liquid through the upper opening (1) and expelled it through the side opening (2); this assured emulsification.
Some Features of the Kinetics of Catalytic Copolymerization. Copolymerization in the Butadiene-Isoprene and Butadiene-Styrene Systems
Authors: Gantmakher A. R. , Medvedev S. S. 
Published: February 2011

Abstract
In the course of research into carbon-chain polymerization under the influence of the acid-type catalysts, aluminum chloride, boron fluoride, stannic chloride, and others, a series of investigations have established the fundamental mechanisms of these chain processes, indicating that they have an ionic character. On the basis of this research, it was suggested that the active center in carbon-chain polymerization is a compound with a tervalent positive carbon atom at the end. The kinetics of catalytic copolymerization had not been studied until the present. There has been only a little work published in connection with determining the composition of copolymers and calculating the copolymerization constants for the systems in question. We initiated some research into the dependence of the speed of catalytic copolymerization on the composition of the original mixture, in conjunction with a determination of the speeds of separate polymerization of the monomers involved, since a comparison of data on the kinetics of copolymerization with that of separate polymerization gives a more complete representation of the mechanism of the process. A study was made of the speed of copolymerization of the systems : isoprene-butadiene and styrene-butadiene, and also of the kinetics of separate polymerization of these monomers. Polymerization was carried out in ethyl chloride with stannic chloride as the catalyst, at 0° C, by the dilatometric method.
Influence of Crystallization on the Sorption of Hydrocarbons by Natural Rubber and Gutta-Percha
Authors: Kargin V. A. , Gatovskaya T. V. 
Published: February 2011

Abstract
It has been known that the mechanical properties and structure of amorphous and of crystalline polymers differ from one another sharply. However, the influence of the phase state of polymers on their thermodynamic properties has not been made clear. Hence it has been of interest to evaluate the effect of polymer crystallization on the polymer's sorption properties. For this purpose it was essential to compare the sorption properties of a polymer which can exist in either the amorphous or the crystalline state at the very same temperature. The most suitable material is natural rubber, which is capable of crystallizing either during prolonged aging or under stress and, therefore, may be obtained at the same temperature in both the amorphous and the crystalline states. With the aid of a McBain balance in a high vacuum and under isothermal conditions, curves for the sorption of n-hexane by amorphous and crystalline samples of natural rubber at 0° and 25° C were obtained. In the experiment at 0°, the sorbent consisted of strips of natural rubber, some of which had been aged 8 months at 0° (the crystallized sample), and others aged for the same period at room temperature (the amorphous sample).
A Thermochemical Study of High Molecular Weight Compounds
Authors: Khokhlovkin M. A. 
Published: February 2011

Abstract
Among the classical methods which have found application in research on high-molecular compounds, the method of Calorimetry is noteworthy. It is sufficient to mention the investigations into heat capacity, which, along with other measurements, helped to establish the second-order transition points, as well as the influence of crystallization temperature on the liquefaction of high polymers. The determination of the heat capacity of isoprene and of natural rubber, in combination with data on their heats of combustion, permitted a calculation of the change of free energy of formation of natural rubber. According to the data of Hock and Schmidt, the heat of swelling of natural rubber in various solvents ranges from +1.36 to −3.0 cal./gram. These data agree with those obtained from osmotic measurements. Thus the change of free energy when natural rubber goes into solution is approximately determined by the entropy term; i.e., ΔF=−TΔS. Bearing in mind that the heats of solution of rubber are of the same order of magnitude as the heats of mixing for two liquids, and are considerably lower than the heats of solution of solid bodies in liquids, we may conclude that the rubberlike state has more in common with liquid than with solid substances as regards solubility.
The Comparative Determination of the Molecular Weight of Rubber by the Methods of Light-Scattering and Osmometry
Authors: Dogadkin B. , Soboleva I. , Arkhangelskaya M. 
Published: February 2011

Abstract
1. An account is given of experiments to determine the molecular weight of natural rubber and other high molecular-weight compounds by light-scattering and osmometry. 2. A new design of osmometer for determining molecular weight is described. 3. It is shown that the light-scattering method gives molecular weight values which agree satisfactorily with those given by the osmotic method.
Dynamic Fatigue of Rubber and the Mechanism of Failure by Repeated Deformations
Authors: Bartenev G. M. , Galil-Ogly F. A. 
Published: February 2011

Abstract
Dynamic fatigue is thn reduction of the maximum tensile strength of a material by repeated periodic loads or deformations. The dynamic fatigue of vulcanized rubber is basically the result of chemical oxidation processes, destruction during repeated deformations taking place by rupture of the chains throughout the rubber as a result of mechanically activated chemical processes. Physical factors also influence dynamic fatigue. However, the question of the nature and mechanism of dynamic fatigue of vulcanized rubber has not yet been explained ; nor has the relation between fatigue and tensile strength of rubbers been clarified. The results of studies which make it possible to establish the fundamental laws of dynamic fatigue of rubbers and the destruction mechanism during repeated deformations are presented below. Two widely used sinusoidal systems of repeated deformation were studied: (1) constant (maximum) elongations or deformations, ε = const.; (2) constant (maximum) loads or conventional stress, f = const. The number N of cycles before failure and the time before breaking, or the life of a specimen, were determined in these tests. In the first system, the breaking load, fixed by the apparatus, was less than the initial maximum load, owing to the process of “dynamic relaxation“, and in the second system they were equal. The breaking load divided by the initial cross-section and the cross-section at break gives, respectively, the conventional f and the true dynamic tensile strength σ of the specimen.
Application of Radioactive Sulfur to the Study and Control of the Vulcanization Process
Authors: Tarasova Z. N. , Kaplunov M. Ya , Dogadkin B. A. 
Published: February 2011

Abstract
Ordinarily the kinetics of the vulcanization process is controlled by the proportion of combined sulfur, which is determined by the method of oxidation with nitric acid and bromine, the method of fusion with metallic potassium and magnesium, and other methods. A considerable increase of the rapidity and accuracy of the determinations may be achieved if labeled sulfur, containing the isotope S35, is used as the vulcanizing agent. The half-life of this isotope is 87.5 days, and the energy of the β-particles amounts to 0.17 Mev. The combined sulfur content is determined from the intensity of theβ-radiation. The method which we developed can be described as follows. A rubber stock, containing labeled sulfur of known radioactivity, is mixed on a laboratory mill. A sheet of this rubber stock, wrapped in cellophane, is vulcanized in a press at a given temperature and pressure. The thickness of the sheets should not be less than the maximum length of the path of β-particles in the rubber. for a soft rubber, this thickness amounts to 0.3 mm.