bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Chemical Changes in the Rubber Hydrocarbon on Its Oxidizability
Authors: Le Bras Jean , de Merlier Jacqueline 
Published: February 2011

Abstract
The hydrocarbon of rubber, which contains one ethylene linkage or double bond per isoprene unit, has such a structure that it is very sensitive to the action of oxygen, and the investigations of Farmer have shown clearly the part played by the α-methylene carbon atom in the process of oxidation. Since the rubber hydrocarbon can be made to react with compounds which unite directly with it, an attempt was made to find out what influence any changes of this kind might have on the oxidiazbility of rubber. The reagents chosen were saligenol and maleic anhydride. According to Cunneen, Farmer, and Koch, saligenol attaches itself to double bonds, with formation of a chromanic nucleus (I), the nature of which the present authors have examined and confirmed by ultraviolet spectrography of the compounds prepared. In the case of maleic anhydride, Delalande has shown that this compound and also related compounds, such as maleic imide, can combine according to the substitutive addition mechanism described by Alder, with the formation of a molecule of type (II). The reactions were carried out with exclusion of air, in accordance with the technique of Moureu and Dufraisse on benzene solutions of purified crepe rubber, and in the absence of a catalyst.
Tetramethylthiuram Disulfide Vulcanization of Extracted Rubber. I. Introduction and Compounding
Authors: Craig David , Juve A. E. , Davidson W. L. 
Published: February 2011

Abstract
(1) Large dosages of TMTM inhibit TMTD vulcanization or vulcanization with sulfur. (2) The desirability of up to about 1.5 phr zinc oxide for TMTD vulcanization was confirmed. If an unusually large amount of TMTD (10 phr) is used, a well vulcanized stock may be obtained without zinc activation. (3) Palmitic acid displays only a mild activating effect on TMTD vulcanization. (4) Zinc dimethyldithiocarbamate, a main product of TMTD vulcanization, is not an activator for a TMTD-zinc oxide recipe. (5) Dimethylammonium dimethyldithiocarbamate does not activate TMTD-zinc oxide formulations. (6) Zinc sulfide is an effective activator for TMTD vulcanization.
Tetramethylthiuram Disulfide Vulcanization of Extracted Rubber. II. Structure of Radioactive Tetramethylthiuram Disulfide
Authors: Craig David , Davidson W. L. , Juve A. E. , Geib I. G. 
Published: February 2011

Abstract
Tetra-substituted thiuram polysulfides are notable because of their action as “accelerators” in rubber vulcanization and also because of their ability to vulcanize rubber without added sulfur, especially in the presence of zinc oxide, which leads to the formation of zinc dimethyldithiocarbamate (ZnDMDC) and other substances. A study of the structure of tetramethylthiuram disulfide (TMTD) is reported in this paper. This has involved the introduction of radioactive sulfur. A corollary has been the similar study of ZnDMDC, which is an “accelerator” but not a vulcanizing agent. The synthesis of radioactive TMTD (i.e., TMTD*) was accomplished by heating 4.16 grams (0.02 mole) of tetramethylthiuram monosulfide (TMTM) and 1.28 grams (0.04 atom) of radiosulfur (S*8) to 120° in a stream of nitrogen for 30 minutes. By extraction with hot alcohol and benzene, a series of crystalline fractions was secured which totaled 3.38 grams, a yield of 70 per cent. This material melted at 150–156° C, with decomposition. The excess S*8 was recovered in a second experiment. Pyrolysis of the TMTD* prepared in the above manner was carried out at 160–230° C in a modified Claisen flask. There were produced S8*, tetramethylthiourea*, and CS2* in nearly theoretical yield. The radioactivities of the thiuram disulfide and of the pyrolysis products (the CS2* being converted to phenylhydrazinium phenyldithiocarbazate* or to 1-phenylthiosemicarbazide* for study), which are recorded in Table I, show that the tracer sulfur atoms distributed themselves uniformly throughout the various molecules.
The Swelling of Cross-Linked Amorphous Polymers under Strain
Authors: Treloar L. R. G. 
Published: February 2011

Abstract
The equilibrium swelling of vulcanized natural rubber in benzene and heptane was investigated experimentally as a function of the state of strain. Three types of strain were examined, i.e., simple elongation, 2-dimensional extension, and unidirectional compression. The swelling ratios were determined either from measurements of linear dimensions, or by weighing, precautions being taken to ensure uniformity of the strain over the measured region. Measurements of swelling ratios were reproducible to about 1 per cent and the swelling process was completely reversible (with respect to strain variations). Changes in swelling ratios of up to 50 per cent were observed, the swelling increasing under tensile stresses and falling under compressive stresses. The results were accurately accounted for by the author's extension of the Flory-Rehner statistical theory, using two independent parameters—one the μ-value in the Flory-Huggins equation for the free energy of mixing, which was obtained from vapor pressure data; the other, the degree of cross-linking, which was determined from the swelling of the unstrained rubber. It is concluded that, for good swelling agents, this theory is applicable to a homogeneous strain of the most general type.
Power Factor and Vulcanization
Authors: Waring J. R. S. 
Published: February 2011

Abstract
Over a wide range of curing systems electrical power factor was found to increase as combination with sulfur proceeded. The main experimental results were obtained at nine megacycles frequency and laboratory temperature, using a Q-meter for the electrical measurements. Some experiments were also carried out through frequency and temperature range. Analysis of the data shows that no simple conversion factor can change electrical power factor into combined sulfur, indicating that the electrical losses are affected by the type of combination with sulfur. The omission of zinc oxide causes a marked increase in the rate of change of power factor with combined sulfur. Dipole moments have been calculated from the slopes of these correlation curves, assuming monosulfide —S— when zinc oxide was not included in the mix and disulfide —S—S— when zinc oxide was present. Reasonable agreement has been obtained with experimental data on simpler compounds, e.g., dilauryl mono- and disulfides. The experimental technique has provided an analytical tool with possible applications both to problems of factory control of cure and to checking theories of vulcanization.
Thermoelastic Properties of Noncrystallizing Rubber
Authors: Bartenev G. M. 
Published: February 2011

Abstract
1. A method of measuring and obtaining the equilibrium isotherms of strain for vulcanized butadiene-styrene rubber is described. 2. It is shown that the component of the elastic force of the rubber which depends on the internal energy has a value of several per cent. 3. Calculation shows that the change in the volume of uncrystallizable rubber, at 300 per cent strain, has a value less than 0.1 per cent. 4. A comparison of the results obtained with the thermodynamic equations shows that the deformation of the rubber investigated can be considered strictly high elastic and entropic. 5. A comparison of the experimental data with the theory of high elastic deformation confirms the accuracy of the conclusions from the theory.
The Role of Intermolecular Forces in the Mechanism of High-Elastic Deformation. I. The Molecular Mechanism and an Equation for the Kinetics of High Elastic Deformation
Authors: Dogadkin B. A. , Bartenev G. M. , Reznikovskii˘ M. M. 
Published: February 2011

Abstract
1. The molecular mechanism of the relaxation of deformation of high-elastic polymers has been studied. 2. It is shown that the slow relaxation, which is typical of high-elastic polymers, may be best explained as a restoration process, which either partial or complete (depending on the degree of development of side chains in the molecular structure formed by the main valence chains) of the balanced configurations of the molecular chains. 3. It is shown that the rate of the relaxation process in this case is determined by the molecular activity of the particular polymer. 4. An approximate equation for the kinetics of high-elastic deformation which expresses qualitatively the mechanical properties of high-elastic polymers is proposed. 5. Hypotheses concerning the relation between the time of relaxation and the unbalanced stress are advanced. Equation (2) is derived as characteristic of this relation. 6. It is shown that the joint application of Equations (1) and (2) makes it possible to describe qualitatively the relaxation of stress at constant deformation.
Crystallization and Second-Order Transitions in Silicone Rubbers
Authors: Weir C. E. , Leser W. H. , Wood L. A. 
Published: February 2011

Abstract
In the course of an investigation to determine which rubbers might be suitable for use at low temperatures, interferometric measurements of the length-temperature relationships of silicone rubbers have been made. Crystallization was found between −60° and −67° C in Dow-Corning Silastic X-6160 and in General Electric 9979G silicone rubber, the latter of which contains no filler. Crystallization between −75° and −85° C was found in Silastic 250. Melting occurred over a range of temperature above the temperature of crystallization. The volume change on crystallization varied from 2.0 to 7.8 per cent. No crystallization or melting phenomena were observed in Silastic X-6073 between −180° and +100° C. All types of silicone rubber exhibited a second-order transition at about −123° C, the lowest temperature at which such a transition has been observed in a polymer. The coefficient of linear thermal expansion of silicone rubbers containing no filler was found to be about 40×10−5/degree C between −35° and 0° C.
Simple Method for Determining the Dynamic Coefficient of Friction of Vulcanized Rubber
Authors: Boonstra B. B. S. T. 
Published: February 2011

Abstract
A method for measuring the coefficient of friction at low speeds by means of a normal dynamometer for rubber testing is described. To this end a couple of molded rubber wheels are pulled over a piece of roadlike surface. At the same time the wheels are forced to rotate with a speed nonconcordant with the linear speed on the surface, so that a certain amount of friction occurs. The force necessary to turn the wheels over the surface is recorded on the dynamometer; the average is proportional to the average coefficient of friction. Preliminary experiments were carried out to prove the usefulness of the apparatus. A number of compounds of natural rubber, GR-S, and “cold” rubber were tested on four surfaces: asphalt, asphalt with rubber, concrete, and ground glass. Although the apparatus allows variation of load and of speed, the experiments were carried out at a speed of 100 cm. per minute and only with a load of 4 kilograms. On dry surfaces, the highest coefficient of friction was found with a natural-rubber compound on an asphalt material in which rubber powder had been dispersed. With most rubbers this surface showed a somewhat higher coefficient of friction than did the asphalt without rubber-powder, which in turn was better than the other two surfaces. On the average there was little difference between the various rubber compounds, though natural rubber seemed to yield the highest values. Natural-rubber pure gum compound did not show higher values than the carbon black mixes, but a vulcanizate with cyclorubber instead of carbon black was definitely better.
Failures of Rubber Insulation Caused by Soil Microörganisms
Authors: Blake John T. , Kitchin Donald W. , Pratt Orison S. 
Published: February 2011

Abstract
The failure of rubber insulation brought about by soil microörganisms can best be detected by a decrease of several decades in the insulation resistance. To study the mechanism of attack and the physical structure that makes rubber insulation vulnerable to such attack, it is necessary to have means of locating and marking the failed spots. Several methods of doing this have been described. The electrodeposition of copper in the micropores created by microbes affords the best insight into the physical structure of the faults. Two distinct modes of attack have been shown. The simpler one, which is characteristic of natural rubber, is a progressive eating away of the bulk insulation. The second, a more obscure type, creates micropores through the wall, but without visible surface erosion. This mode is typical of the synthetics, in which the base hydrocarbon or polymer, if freed of extraneous microbe food, does not support microbe growth. The imperfections consist of streaks of microbe food scattered in a random manner through otherwise inert material. Their distribution is affected by physical processing. These streaks are not hygroscopic and do not lead to failure in prolonged immersion in either hot or cold water. They do, however, tend to lower the d-c breakdown of samples after several days soaking in hot water. Thus with a given susceptible compound it is possible to predict which processing will produce the greatest stability in soil by breakdown tests on samples not exposed to soil. The breakdown tests relate to physical structure. To test the inherent resistance of a material to soil exposure, the simple visual fungus test is very convenient. The validity of this test as a criterion of stability has so far been confirmed by the routine resistance tests after accelerated laboratory soil exposure. It is not safe to predict the stability of a complete compound from the results of visual tests on the base material. The vulcanized insulation must be tested. Insulating compounds shown to be promising by the visual test should be given a thorough soil exposure test. The testing of preventives is a field in itself. It is not simple. Materials which are strongly antiseptic in water may not be so when mixed in a rubber compound. Many of them would be completely unsuitable in rubber insulation. Some preventives are effective in a compound before it is vulcanized but not afterwards. Some are completely inactivated by certain other necessary or desirable ingredients. Others may leach out in time and cease to protect the material. Oxidation inactivates some preventives. A nicely balanced compound is required to produce insulation with sufficient stability in soil, proper physical characteristics, and high electrical quality.
Optical Examinations of Anisotropy in Vulcanizates
Authors: Oberto Stefano 
Published: February 2011

Abstract
The anisotropic behavior of vulcanizates is revealed by differences in modulus, breaking load, and tear, swelling in solvents, and electrical properties, according to the direction of test. Anisotropy is attributed both to a state of tension in the rubber phase alone and to a preferential orientation of the elongated particles of certain fillers. It bas recently been recognized that anisotropy due to movement of the stock in the mold during the first phase of vulcanization is of very great importance. By submitting overflow slaba, sheets, and test-pieces to examination under transmitted polarized light, it is relatively easy to obtain optical evidence of the presence of anisotropy caused by movements during molding operations. The localization of the movements may make it desirable to examine with a microscope at low magnification microtome sections of the vulcanizates 50 microns thick. A transparent gum compound can be used, but more details can be seen if 1 per cent of carbon black is added. The transparent compound may be used under polarized light for the direct examination of samples a few millimeters thick or of sections of equal thickness taken from products of different dimensions. In injection-molded products, it is possible to tell from variations of double refraction when molding conditions favor scorching before the rubber has come to rest. If talc or some other ingredient with elongated strong double-refractive particles is introduced into the transparent compound, it is possible to observe the orientation of the particles cauaed by the processing or molding flow. In a calendered sheet, the talc particles lie almost parallel to each other, but toward the center of the sheet the orientation may be less marked or may occur along slightly different directions. In injection molding the tale clearly reveals flow direction and anisotropy. Under optical observation, in restricted areas, the difficulty of obtaining entirely isotropic rubber products is confirmed. Almost pure-gum compounds have been examined, but the anisotropy found will probably assume even greater importance in loaded mixings, especially those loaded with carbon black.
The Destructive Dissolution of Vulcanized Rubbers
Authors: Dogadkin B. , Tarasova Z. 
Published: February 2011

Abstract
In previous work the process of destructive dissolution of vulcanized natural rubber was described, and it was shown that, in the strict absence of oxygen, a vulcanizate cannot be dissolved in a hydrocarbon medium at temperatures up to 140° C. Only in the presence of molecular oxygen does heating bring about dissolution of vulcanized rubber in the solvent, under which conditions the process proceeds along this pattern: union of oxygen with the double bonds → disintegration of the molecular chains where oxygen has combined → dissolution. if the surface area of the vulcanizate remains constant, the process takes place at a constant rate which depends on the temperature and the partial pressure of the oxygen in solution. In the following, experiments are described, the results of which show that vulcanized synthetic polymers also undergo destructive solution. The experimental method was the same as that described previously. The vulcanizates were prepared from recipes adapted to the particular synthetic rubbers. As was expected, the rate of destructive solution depends on the molecular structure of the rubbers (see Figure 1).
Primary Creep and Stiffness of Vulcanized Rubbers
Authors: Cooper D. H. 
Published: February 2011

Abstract
The addition of two compounded blacks renders induction concerning the mechanism of either black uncertain. Generally speaking, however, the black in a specimen of given size may be thought of as replacing its volume of rubber, so, when under a particular load, the rubber remaining is more highly stressed. Because the rubber is highly stressed, the relative creep is increased, but because there is less of it, the actual creep is diminished. for a given shape of specimen, all soft compounds and gum stocks have the same curve of load-area vs. strain up to 20 per cent compression, 40 per cent tension, and 40 per cent shear; the same applies to medium hard stocks. The stiffness of any such specimen can be expressed in terms of a convenient reference level, such as the load-area at 10 per cent shear 1-minute strain. Over a wide range of conditions in which polymer, compound, cure, and geometry of loading have been varied, 10-minute creep remains proportional to 1-minute deflection for each particular geometry of loading, but in tension the ratio of 10-minute creep to 1-minute deflection is greater than in shear, in compression less—an effect which is generally more marked in soft than in hard compounds. Measurements of creep on specimens in which the ratio of diameter to height is greater than 1.6 were, mainly on account of the small deflections involved, not sufficiently accurate to be included. It is reasonable to assume, however, that creep is proportional to strain under other conditions than those considered here, such as in specimens of other shapes and specimens loaded in bending and torsion.
The Chemical Structure Responsible for the Deactivating Effect of Compounds Which Protect Rubber from Deterioration by Oxygen
Authors: Le Bras Jean , Le Foll Jacques 
Published: February 2011

Abstract
One of the present authors has already offered evidence which indicates the existence of a deactivating effect, whereby vulcanized rubber is protected against deterioration by oxygen. This effect is evident with such compounds as mercaptobenzimidazole (I), mercaptobenzoxazole, and ethylene-bis (N,N′-phenylthiourea) (II), and the phenomenon seems to be connected in some way with the presence in the molecule of a thiol group united to a nitrogen atom under such conditions that the possible tautomerism between the thion and thiol forms (III) is probably displaced toward the thiol form. We have completed these earlier experiments by a more systematic study, which has included an examination of the influence of cyclization, the nature of the ring, and hetero atoms.
The Chemical Constitution of Chlorinated Rubber
Authors: Allirot René 
Published: February 2011

Abstract
The results of the work described in the present paper indicate that, by the prolonged action of chlorine on polyisoprenes, chlorinated compounds corresponding to the composition (C10HxCl7)n are formed, irrespective of the molecular weight. The exact hydrogen content of these products can be calculated from determinations of the hydrogen chloride evolved in the reaction, and measurements to this end are in progress. Furthermore, determinations of the osmotic pressure and intrinsic viscosity, which have already been undertaken, should make it possible to determine with certainty the mean degree of polymerization of each fraction.
Polysulfide Liquid Polymers
Authors: Jorczak J. S. , Fettes E. M. 
Published: February 2011

Abstract
Polysulfide liquid polymers are a comparatively recent development conceived at the Thiokol Laboratories in 1943. The development was initiated by the problem of finding methods to reduce the molecular weight of a polysulfide rubber which was too tough to process on conventional rubber milling equipment. The problem was solved by reduction of a few of the disulfide links present in the polymer chain. It was soon found that the method was applicable to the preparation of polymers low enough in molecular weight to be liquids. The method produces dithiols of high purity which are extremely active in a wide variety of chemical reactions. Some formulations have been developed which depend on conversion from the liquid to rubber state at temperatures as low as 50° F in about 30 minutes. Most of the converting agents function through oxidation with hydrogen removal from the thiol and a linkage of sulfurs to reform the disulfide group. The converted polymers have the general properties of polysulfide polymers: good solvent resistance to a wide range of solvents, low diffusion rate of gases, good resistance to oxidation, ozone, and weathering, and a service temperature range from −65° to +250° F. (Some compounds can withstand intermittent temperatures as high as +350° F.) The low temperature properties are inherent in the polymer and do not depend on special compounding techniques.
Wax Blooming and Exposure Cracking
Authors: Best L. L. , Moakes R. C. W. 
Published: February 2011

Abstract
A brief résumé is given of the types of deterioration which cause cracking and similar forms of deterioration in vulcanized rubber and the possible remedies. A study has been made of the development of wax bloom on rubber and some of the factors which affect this development. The waxes constituting the blooms have been examined, as has the wax in the bulk of the rubber. The protection afforded by these wax blooms against ozone attack on various base mixes with both natural and synthetic rubber has been determined, using a standard technique for the ozone exposure.