bluuebunny/crossref_metadata_2025_split huggingface dataset:
Milling Procedure Its Effect on Physical Properties
Authors: Martin B. J. A. , Parkinson D. 
Published: February 2011

Abstract
The experiments described roughly represent the three main stages in the preparation of a rubber compound before molding, viz., mastication, mixing, and reworking. At each stage, variations in the process affect, in varying degrees, processability at subsequent stages and the ultimate physical properties. In general, the effects in isolation at any one stage are small when considered against the background of economic processing. Whether uncontrolled or deliberately applied, process variations are, in the main, independent at each stage. Consequently, the magnitude and direction of the effects they produce may also be independent. In any considerable period of time, therefore, the properties of a compound may vary between two extremes which represent the adding together of all the effects at the separate stages. On the evidence presented here it is considered that process changes which might in normal practice be applied for expediency or economy, or such as might occur, between different production units of one company could, by this additive effect, produce total variations of practical significance. The properties likely to be affected most are plasticity, scorch, tear resistance, and electrical resistivity.
Vulcanization of Crepe Rubber by Sulfur Monochloride. I. The Gelation Method
Authors: Glazer J. , Schulman J. H. 
Published: February 2011

Abstract
When a dispersion of rubber (4 per cent) in benzene is treated with sulfur monochloride (1 per cent) at room temperature, the solution becomes opaque and gelation occurs in a few minutes. With a more dilute dispersion of rubber (1 per cent), Meyer and Mark obtained a weak gel, which could be broken up by stirring to give, after one hour, a pale yellow precipitate, corresponding to the formula C10H16SCl2. By analogy with the reaction of ethylene and sulfur monochloride, these workers proposed the following reaction process: (see PDF for diagram) The so-called cold-vulcanization process, which is essentially the above reaction, thus appears to correspond to the cross-linking of adjacent isoprene units by means of thioether-bond formation. This result contrasts with the hot sulfur vulcanization process, where the reaction does not involve the sulfurization of any appreciable number of olefinic groups. The mechanism of the cold vulcanization process is unknown. However, it is known that certain commercial sulfur vulcanization accelerators speed up the above gelation process to a remarkable extent. The present work describes an attempt to investigate the kinetics of the reaction between rubber and sulfur monochloride, with the eventual view of establishing the mechanism of the process. In general, two main methods have been developed for assessing reaction velocities. They are the dilatometric method and a more arbitrary time-of-gelation method. While the former method is of importance in studying the more detailed quantitative features of the reaction, the latter method is of help as a powerful auxiliary. Although it is not yet possible to propose a clear-cut mechanism for the vulcanization process, certain kinetic features have been established, and indications of the most fruitful lines of attack are presented.
Load-Carrying Capacity of Latex Foam Rubber
Authors: Talalay Joseph A. 
Published: February 2011

Abstract
Specifications for latex foam rubber usually include a required hardness, which is measured by the force necessary to compress the material to 75 per cent of its original height. While the hardness of a slab of foam rubber depends primarily on its foam density, it also depends on the type of latex, the curing system, compounding materials, and moisture content. It is likewise affected by cell size (larger cells being more favorable) and cell shape (spherical cells being more efficient than flattened cells). for slab material of any given composition and cell structure, the hardness can be related to density by a simple equation. For cored material, hardness and density can be related by integrating deflections of small increments of height over the entire height of the article. This procedure can be reduced to a few simple equations for most shapes of core pins. With these equations, the effect of mold configuration on the weight of a given foam article has been investigated. for any specified hardness, the required weight of a foam rubber article can be reduced by increasing core-pin diameter, decreasing pin spacing, and reducing the thickness of uncored top stock, or in effect increasing the cored-out volume. Intrinsically this is made possible by the fact that hardness of homogeneous (slab) foam material increases approximately with the square of its density. These design variables have been subjected to both theoretical and experimental study. Their effect and their practical limitations are discussed. The experimental data are primarily based on foam rubber produced by the so-called Talalay process. However, the general relationships presented in this paper are believed to apply equally to latex foam made by the Dunlop method.
Representation of the Mechanical Properties of High Polymers by the Model Method
Authors: Bartenev G. M. 
Published: February 2011

Abstract
1. Simple models are described which are based on physical concepts and which represent the mechanical properties of high polymers having a spatial network (class 1) and having no spatial network (class 2). 2. The physical concept of characteristic mechanical properties of high polymers and their relation to the structural properties of the high polymers were studied. 3. The particular models which represent the three physical states of high polymers are discussed, and the corresponding equations of deformation are indicated.
The Interaction of Polymerizing Systems with Rubber and Its Homologs. II. Interaction of Rubber in the Polymerization of Methyl Methacrylate and of Styrene
Authors: Mebrett F. M. 
Published: February 2011

Abstract
In Part I of this investigation, the effect of dihydromyrcene on four vinyl polymerizing systems was studied, and it was found that this compound reduces both the molecular weight of the polymer formed and the rate of polymerization. With rubber, the results are more complicated. A method for separating the simple polymers from the graft (compound) polymers is developed. This method is based on the peculiar colloidal properties of the graft polymers. These separations show that interaction between the natural and synthetic polymers depends on the catalyst used for initiating the polymerization and, therefore, that more than simple transfer is involved. Thus, with benzoyl peroxide, numerous very short side chains are combined with the rubber, while the free vinyl polymer chain grows to approximately the length predicted from known data. With azoisobutyronitrile, on the other hand, there is little or no reaction between the rubber and vinyl component. It is suggested that the formation of these very short grafted chains in place of the expected long ones may be a general feature of rubber-polymer systems of this type.
Structure and Properties of Loaded Rubber Mditures. XII. Dielectric Properties of Natural Rubber-Carbon Black Mditures
Authors: Lukomskaya A. I. , Dogadkin B. A. 
Published: February 2011

Abstract
1. The temperature and frequency curves of dielectric constant ε′ and coefficient of dielectric loss ε″ of unvulcanized natural rubber and simple rubber-carbon black mixtures, and also vulcanizates of natural rubber containing various proportions of thermal black or channel black, were studied in the frequency range from 50 to 2.5×107 cycles per second at 20° C, and in the temperature range from −75° to 152° C at frequencies of 103 to 4×104 cycles per second. 2. As in the case of sodium-butadiene mixtures, the addition of carbon black to the rubber leads to three kinds of dielectric losses, viz., a loss due to the nonuniformity of the dielectric, a loss due to the passage of a direct current (conductivity), and a loss due to structure formation. Vulcanization of rubber leads to the appearance of dipolar dielectric losses, which can be explained by the orientation of the sulfur dipoles in the electric field. Loading of vulcanizates causes a change of the dipolar dielectric properties, which depend both on the content and type of filler and on the type of vulcanized rubber. 3. For all the types of vulcanizates, the dependence of the dielectric properties (a measure of the orientation processes in the rubber phase) on the form factor ( a measure of the structure-forming capacity of the carbon black) corresponds to the dependence of the physical-mechanical properties on the carbon black content.
Inhibited Oxidation of Elastomers
Authors: Kuzminskii˘ A. S. , Lezhnev N. N. 
Published: February 2011

Abstract
1. The oxidation of elastomers in the presence of true inhibitors, of which secondary aromatic amines are an important class, is for practical purposes an initiation reaction and primary oxidation of the chains is possible only to a slight degree. 2. Inhibited oxidation (initiation) is fundamentally distinct from autocatalytic oxidation. 3. The method of study of inhibited oxidation (initiation) consists in the study of the consumption of inhibitor, while the rate of this process is equal to either the proportional rate of initiation or the constancy of the concentration of dissolved oxygen in the entire mass of the rubber film or specimen studied. 4. In the inhibited oxidation of different types of rubber, the rate of initiation is practically constant for each temperature. The activation energy of the reaction is equal to 22.6 kcal. per mole, and is independent of the nature of the polymer in the absence of electrically negative substituents in the polymer. 5. In the case of strongly activated nitration, the diffusion of oxygen in the rubber may have a retarding influence. Then the concentration of dissolved molecular oxygen [O2] differs at different depths below the surface. The relation of the rate of consumption of inhibitor wi to the concentration of oxygen is a straight-line function, i.e., wi=A[O2]n; at 120° C, n=0.5. 6. The reactivity of rubber hydrocarbons with respect to molecular oxygen and certain other chemically active agents is determined principally by the content of double bonds in the main chains of the molecules of the polymers. Marked structural differences, such as degree of polymerization, spatial configuration, presence of aromatic rings, etc., have practically no influence on the rate of inhibited oxidation. 7. The absorption of oxygen by the double bonds of the side chains of butadiene rubbers has a much higher activation barrier (27–28 kcal. per mole); consequently, the double bonds are practically inactive during the inhibited oxidation of elastomers. 8. The oxidation of polyisobutylene in the presence of phenyl-2-naphthylamine is characterized by the presence of a temperature threshold, below which initiation does not take place. The directly related change of molecular weight and consumption of inhibitor indicate that destruction of the polymer continues until a constant molecular weight is reached. 9. The inhibited oxidation of Butyl rubber is characterized by the simultaneous progress of two rates of oxidation. The first is the rate of oxidation of the chains, which do not reach a constant weight; the second is the rate of absorption of oxygen at the double bonds. In both polyisobutylene and Butyl rubber, the ordinary bonds of the long chains are considerably weakened. Since the concentration of ordinary bonds in Butyl rubber is much higher than the concentration of double bonds, the rate of oxidation of the former is greater than the rate of oxidation of the latter.
Smearing of Vulcanized Rubber
Authors: Gehman S. D. , Wilkinson C. S. , Daniels R. D. 
Published: February 2011

Abstract
The surface heating which occurs at the interface of rubber sliding under a load may be part of the mechanism of abrasion, especially under severe conditions. Removal of rubber by thermal degradation and a smearing process occurs if the rubber attains sufficiently high localized temperatures. A procedure, using a melting point bar, was developed for measuring the temperature at which smearing occurred for rubber vulcanizates. Smear points reproducible to about ±2° F were measured. The effect of compounding variables on the smear point was investigated. The most important variable in this category was the vulcanization system, probably inasmuch as it determined the type of cross-linking. The presence of free sulfur within the rubber also tended to increase the smear temperature. Highest smear points were obtained with mercaptobenzothiazole-tetramethylthiuram disulfide mixtures, and for a non-sulfur compound using p-quinone-dioxime as the curing agent. The highest smear point observed for natural rubber was 475° F, obtained with this system. GR-S tread compounds showed no smearing even at 560° F, which was as high as could be obtained with the apparatus used. The resistance to smearing of GR-S may be an important factor in explaining its superiority in road wear under severe conditions. Laboratory abrasion experiments were performed to illustrate the effect of smearing on the relative abrasion loss of GR-S and natural-rubber tread compounds.
Formation of Rubber Films from Solutions and Aqueous Dispersions
Authors: Sandomirskii˘ D. M. , Gagina K. 
Published: February 2011

Abstract
1. The mechanical properties, shrinkage, and swelling in water vapor of rubber films prepared from various latexes and rubber solutions, were studied. 2. It is shown that the behavior of films varies with the method of preparation. 3. An explanation of the difference in properties of rubber films prepared from solutions and from latex mixtures is suggested, based on the presence in films from latex of a network of nonrubber substances.
Low-Temperature Properties of Plasticized Butadiene-Styrene Copolymers
Authors: Henderson D. A. , McLeod L. A. 
Published: February 2011

Abstract
The second-order transition temperatures of plasticized butadiene-styrene copolymers have been measured by dilatometric techniques. In a series of ester plasticizers, the ability of a given plasticizer to depress the second-order transition temperature of the polymer is related to the swelling effect of the plasticizer on the polymer. The special case of a crystallizing plasticizer (dibutyl sebacate) has been discussed. Common petroleum plasticizers do not appear to behave in a similar manner. The change of coefficient of expansion of the ester-plasticized copolymers is related to the measured transition temperature of the blend.
Aging Stability of Neoprene Latex. Relation between Cross-Linking and Hydrolysis of Allylic Chlorine
Authors: Andersen D. E. , Kovacic Peter 
Published: February 2011

Abstract
Neoprene polymer chains are cross-linked between active chlorine sites on the chains. There are two types of active sites of different reactivity. It is necessary to use more vigorous curing conditions to actuate the less reactive chlorine. The polymer develops cross-links while aging as a latex as well as during cure, and the decline of tensile strength with latex age may be inversely correlated with the amount of cross-linking during aging. The decline of tensile strength can be prevented by compounding with bis (diethylthiocarbamyl) disulfide. The calculations of the swelling data are not so complete as might be desired, primarily because of difficulty of measuring and interpreting the molecular weight of high-conversion polymers and to some uncertainty in determining μ. It is felt that the qualitative observations are justified, and that they serve to define both the technically important effect of film structure on tensile strength and the mechanism of cure.
Mechanism of Formation of Cream in GR-S Latex
Authors: Howland L. H. , Nisonoff Alfred 
Published: February 2011

Abstract
The formation of cream, which occurred in many of the early cold, high-solids GR-S latexes, is undesirable because it results in nonuniformity of the latex and is injurious to the properties of latex films. On the other hand, it is dispersible and, hence, much more tolerable than coagulum. The mechanism of its formation is, therefore, of interest. A cold high-solids latex activated by ferrous sulfide was used as the basis for the study. The giant particles constituting cream begin forming between 18 and 35 per cent conversion in latex stabilized only with the soap present initially, and increase in quantity until the end of polymerization. Their formation can be prevented by the timely addition of sufficient stabilizing soap, or by the use of a soap which initiates a small enough number of particles in relation to its stabilizing capacity. The formation of coagulum, rather than large particles, is favored by decreasing the amount of electrolyte or increasing the amount of water charged, and by the presence of cross-linking in the polymer. The effect of increasing the water level or introducing cross-linking is to increase the size rather than the amount of agglomerates. Methods are suggested for controlling the formation of very large particles.
Infrared Study of the Oxidation of Elastomers
Authors: Field J. E. , Woodford D. E. , Gehman S. D. 
Published: February 2011

Abstract
It is a matter of considerable interest that polymers can combine with the large amounts of oxygen shown in these experiments, with so little evidence of this combination in the infrared spectrum. Either the oxygen must be distributed in a wide variety of types of compounds or it occurs in a type of linkage having low infrared absorption. In accordance with a previous discussion, it is reasonable to believe that a large proportion of these are ether linkages. If, as has been postulated, the initial step in the autoxidation of hydrocarbons is the formation of hydroperoxides, it is not detected in the infrared spectrum. In order to conform to current theories on autoxidation, it must be assumed that the hydroperoxides formed in the initial oxidation reactions are decomposed at a rate about equal to their formation, so that their net concentration is always below the sensitivity of infrared observation. This does not appear to be an unreasonable assumption. Therefore, only the structures of the terminal products of the secondary reactions are believed to be observed in the infrared spectrum.
The Protection of Rubbers against Ozone Cracking
Authors: Zuev Y. S. 
Published: February 2011

Abstract
The paper describes a study of the aging of natural rubber and synthetic rubbers by the action of ozone. Ozone promotes the development of cracks under tension. The cracking does not occur under compressive stress, a fact which suggests a means of protection, namely, precompression. Another suggestion is the formation of a resistant surface layer that is insensitive to the action of ozone, such as Neoprene. Experiments based on these recommendations are described. A practical method of obtaining precompression is to distend the surface of the rubber with suitable swelling agents, such as triethanolamine. The effect is analogous to the shot-blasting treatment used for prestressing metals to protect them from fatigue cracking.
A Study of Permeability to Gases. Mixtures of Natural Rubber and Other Elastomers
Authors: Barbier Jean 
Published: February 2011

Abstract
An investigation of the permeability to nitrogen of various mixtures of natural rubber and synthetic elastomers has brought to light one highly important fact. The lower permeability obtained by the addition of a synthetic elastomer does not depend solely on the permeability coefficient itself of the particular synthetic elastomer. Rather, it depends in addition on another factor, which, in all probability, is a function of the internal structure of the mixture of natural rubber and synthetic elastomer. A study of this structure is not a simple problem, and mention is made only of the fact that, after having attempted unsuccessfully to analyze the structure by classic methods of microscopy, very encouraging results have been obtained with mixtures of natural rubber and Paracril-26 by measuring, at radio frequencies, the loss factor. The results indicate that, at least with natural rubber-Paracril-26 mixtures, milling brings about a certain degree of mutual diffusion of the two elastomers on a molecular scale. However, the vulcanizates give indications of a two-phase colloidal structure, one phase relatively rich in Paracril, the other phase relatively rich in natural rubber. Such a structure would be in harmony, at least qualitatively, with the conclusions drawn in the present investigation on the permeability to gases of mixtures of elastomers.
The Effect of Fillers on the Permeability of Rubber to Gases
Authors: Van Amerongen G. J. 
Published: February 2011

Abstract
The purpose of the investigation was to study the effects of fillers, especially various types of carbon black and new light-colored reinforcing fillers. In the discussion of the problem, it is shown that permeability to gases is related to the rate of diffusion, and to the solubility of the gas in rubber, and it is also shown how these properties were measured. The effect of carbon black on the permeability of rubber to gases is relatively small. Independent of the type of carbon black, the permeability is reduced only about 30 per cent by the addition of 50 parts by weight of carbon black per 100 parts of rubber. The permeability of a rubber mixture to a gas is increased considerably, however, by the presence of fine types of carbon blacks, while the rate of diffusion of the gas is decreased. This fact can be explained by assuming that gas is adsorbed by carbon black in rubber and thereby rendered inactive. The high oxygen adsorption of the finer types of carbon blacks in rubber mixtures explains the high rate of oxidation of such mixtures. A whole series of inorganic fillers, among them some light-colored reinforc- ing agents, have no noteworthy effect on permeability. With 20 parts by volume of such fillers per 100 parts of rubber, the permeability is decreased only about 25 per cent, irrespective of the particular filler. A considerable decrease of permeability, i.e., about 75 per cent, is observed, however, with lamellar fillers, such as powdered aluminum and powdered mica. A rubber mixture containing powdered mica shows, at 100° C, the same permeability to hydrogen and nitrogen that Butyl rubber does. The relation of permeability to the temperature of rubber containing fillers is practically the same as that for an unloaded rubber mixture. The decreases of permeability to gases which are observed, are, therefore, not related to energy factors, but are of a purely mechanical nature.
Mooney Viscosity Changes in Freshly Prepared Raw Natural Rubber
Authors: Wood R. I. 
Published: February 2011

Abstract
In the course of investigations carried out in connection with the technical classification of natural rubber, large permanent increases of Mooney viscosity of the order of 30 to 40 units have been observed when freshly prepared raw or masticated rubber is stored under conditions of low relative humidity. The rate of change and the extent of the increase are both affected by the relative humidity of storage, and the effects are most pronounced in the region below about 30 per cent relative humidity. The rate of change in dry air increases with decreasing thickness of the sample and with rise of temperature, although these effects are masked somewhat by oxidative breakdown on prolonged storage at temperatures higher than about 30° C. Mooney values continue to increase long after the rubber has reached constant weight on drying; the removal of acetone-soluble and nitrogeneous nonrubber components and of oxygen does not prevent the changes from taking place. The effects are only partially reversed by subsequent storage at high relative humidity, and there is evidence to suggest that the hardening is associated with the development of a cross-linked benzene-insoluble gel structure throughout the rubber.