bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flex-Cracking and Crack Growth Tests Some Important Factors
Authors: Buist J. M. 
Published: February 2011

Abstract
Flex-cracking has been a major cause of failure in rubber articles for many years and since the early 1930's various test methods have been suggested. The whole subject of the mechanism of flex-cracking and flex-cracking tests was reviewed recently, and in 1950 Committee ISO/TC/45 agreed that only the De Mattia machine should be considered for international standardization and that the question of crack growth should be tackled before flex-cracking. Cooperative tests, following the suggested crack-growth procedure, are being carried out in nine laboratories, four laboratories in the United Kingdom, one in Austria, one in France, one in Holland, one in Italy, and one in the United States. Preliminary results show that agreement between laboratories is not good and support the view that the greatest possible care and attention must be given to experimental details if reproducible and comparable results are to be obtained in different laboratories. In the earlier paper referred to above, three important aspects of accuracy of testing are defined as: (a) the accuracy of the measurement of flex-cracking and crack-growth resistance of any one sample; (b) the degree of reproducibility of the test conditions; (c) the degree of reproducibility of the test-specimens.
Self-Closing Grips for Rubber
Authors: Stubbs A. J. 
Published: February 2011

Abstract
The provision of satisfactory grips for holding dumb-bell specimens in tensile testing machines has always presented a number of difficulties. Several styles of self-closing grips are available, but none has been regarded as entirely satisfactory. Thus, the cam type is clumsy and often fails to hold the test-piece at very high extension or when the surface of the rubber is covered with a wax bloom, as sometimes happens. Another type, the bar grip, illustrated in Figure 1, has very much better holding power, but requires the specimen to have undersirably long end tabs.
Colorimetric Determination of 2-Mercapto-Benzothiazole in Compounded Rubber
Authors: Bauminger B. B. , Poulton F. C. J. 
Published: February 2011

Abstract
A method for the determination of 2-mercaptobenzothizaole (MBT) in compounded rubber is based on the formation and evaluation of the red-brown color obtained by reacting the alkaline salt with nickel ion. Application of the method to a variety of compounded rubbers has shown that MBT can be determined with a reasonable degree of certainty in only the simplest rubber mixings. In general, the more complex in composition and the more processing the mixing has undergone, the further will the figure for MBT recovery deviate from the amount originally incorporated. The effect of the other compounding ingredients, notably antioxidants, other accelerators, and softeners, from which considerable interference was anticipated, is in fact negligibly small. Among common accelerators the reagent can be regarded as specific, but the decomposition of those accelerators which yield MBT will naturally be reflected in the final results. High mixing temperatures and longer vulcanizing times favor the transformation of MBT to the disulfide (which, however, can be estimated by reconversion to MBT), and to simpler breakdown products.
Crystal Violet, an Electronic Model Substance for Rubber and Related Olefins
Authors: van Veersen G. J. 
Published: February 2011

Abstract
It is shown that triphenylmethyl dyes like crystal violet can be used as model substances for rubber and related olefins. Arguments are given in support of the assumption that agents which react with rubber and related olefins in a polar manner cause a reversible shift in color from blue to yellow with crystal violet, whereas a fading of the blue color of crystal violet (if alkaline or reducing agents are excluded) points to a radical reaction. Since the electronic structures of donor olefins and crystal violet are considered and not the molecular structure, as usually is done in the choice of a model substance, these dyes have been named electronic model substances. Though crystal violet, as an electronic model substance cannot be used for the study of the overall reactions, information can often be obtained concerning the first step in a reaction of rubber with a certain chemical agent by means of a simple test-tube reaction with crystal violet. It was pointed out that the π-electron availability at the non-methylated carbon atom of the double bond in rubber and at the nitrogen atoms in crystal violet is probably of the same order. As an application of crystal violet as an electronic model substance for rubber, a polar reaction between sulfur and rubber is suggested as the first step in vulcanization.
Partially Chlorinated Derivatives of Rubber
Authors: Woods D. E. 
Published: February 2011

Abstract
Chlorinated rubbers containing from 1 to 17 per cent of chlorine were prepared by direct chlorination, at ordinary temperature, of crepe rubber dissolved in carbon tetrachloride. These products retain, to a greater or lesser degree, rubberlike properties, and are capable of hot or cold vulcanization with or without the addition of vulcanizing agents. The resulting vulcanizates are considerably more resistant to the swelling action of solvents, and also to the action of chlorine, than corresponding products prepared from crepe rubber. The resistance to swelling agents increased with increase in combined chlorine content; tensile strength and elasticity, however, decreased with increasing chlorine content. As expected, hardness increased with increase of chlorine content, and vulcanizates from derivatives containing more than 10 per cent combined chlorine were not sufficiently rubberlike to warrant many experiments. Fully chlorinated rubber was compatible with partially chlorinated rubber, and addition of the former was necessary for vulcanizates to pass the Post Office flame test for cables.
Polar Rubbers and Their Application as Ion Exchangers
Authors: Mastagli Pierre , Austerweil Geza , Zafiriadis Azfiri 
Published: February 2011

Abstract
Most of the ion exchangers in current use are prepared in the form of synthetic resins by the condensation of aldehydes or of ketones with amines or substituted phenols and polymerization these condensation products. However, resins prepared in this way have certain disadvantages, e.g., their solubility, instability, and tendency to swell. As early as 1938, one of the present authors was able to show that it is possible to obtain ion exchangers by avoiding the condensation phase of the process through the introduction of polar groups directly into the macromolecules, which are, and which remain, insoluble even after the introduction of polar groups (wool, aminopolystyrene, azotized rubber, etc.). By eliminating the condensation phase, the —RCH(R′)OH groups and consequently any steric hindrance are avoided; hence, the stability and effectiveness of the products as ion exchangers are enhanced.
Light Stiffening of Rubber
Authors: Newton R. G. , Wake W. C. 
Published: February 2011

Abstract
The form of deterioration which we have designated light stiffening can be detected only when the rubber is in the form of a thin film, as it is, for example, in light-weight single-texture proofings. The implications of this work, however, extend far wider than its immediate application to thin proofings, important though this is, and we have no reason to suppose that the surface crazing seen on articles of rubber exposed to sunlight is not essentially the same thing. It is convenient, for reasons which appear later, to distinguish these two forms of deterioration of rubber, even though chemically and energetically they may have the same fundamental basis. Light stiffening is the noticeable increase in the bending modulus of thin sheets of rubber which occurs with exposure to light and air. This increase is easily observed by handling proofed fabrics so exposed, and in normal speech we refer to a “stiffening” of the article. It is an effect greater at the surface and decreasing with penetration into the bulk rubber, and for this reason is subjectively evident only where the “surface layers” form an appreciable proportion of the total thickness of the rubber. This deterioration becomes essentially a defect confined to thin proofings and other articles, the rubber parts of which form a sheet or layer a few thousandths of an inch in thickness.
Organic Sulfides as Vulcanizing Agents of Rubber
Authors: Sibley R. L. 
Published: February 2011

Abstract
1. It has been demonstrated that a number of organic sulfides possess the property of breaking down under vulcanizing conditions in a rubber compound to produce a cure. 2. Although several scores of sulfur-containing organic compounds other than those discussed in this paper or described in other papers have been tested, as yet there appear possible no generalizations to serve as a guide to further exploratory studies. 3. Organic sulfur compounds which are unstable under temperature conditions higher than normal do not liberate all of their sulfur in all cases. 4. Organic sulfur compounds employed alone as vulcanizing agents usually produce slower-curing rubber stocks than does sulfur, and at the same time lessen greatly the tendency of the stock to scorch. 5. Stocks of satisfactory physical properties, superior aging characteristics, and outstanding freedom from scorchiness are obtained by the use of a fractional part of the normal sulfur requirement together with a sulfur liberator. 6. Morpholine disulfide is a good example of a sulfur liberator, and exhibits its greatest effects in conjunction with a mercaptobenzothiazole type accelerator. 7. Morpholine disulfide gives satisfactory cures when used in place of sulfur in natural rubber, GR-S rubber, and Hycar-OR, but gives slow cures in GR-I rubber.
Alfin Catalysts and the Polymerization of Butadiene
Authors: Morton Avery A. 
Published: February 2011

Abstract
Alfin catalysts are special combinations of sodium salts which cause the rapid catalytic polymerization of butadiene to polymers of unusually high molecular weight. These polymerizations show characteristics which are common to all reactions of organosodium compounds, namely, the tendency to undergo multiple reactions. The reagents are also insoluble aggregates of ions whose behavior is affected by the ions in the aggregate. The history of the discovery is reviewed. The catalytic polymerization shows no property in common with the conventional sodium process for polymerizing butadiene. The present problems center in the elimination of secondary reactions that are known to occur. The theory by which all the reactions occur, including polymerizations induced by organosodium compounds, is discussed. Progress toward the practical use of the alfin polymers is being made.
The Structure of Elastomers and Their Reactivity
Authors: Kuz'minskii A. S. , Lezhnev N. N. 
Published: February 2011

Abstract
It has not yet been ascertained what constituent parts within the structure of various elastomers have the greatest influence on the reactivity of the elastomers. There are indications that the side chains, the presence of methyl groups acting as substitutes, and differences in spatial configurations, etc., all have definite effects. The present authors have investigated the oxidation of several different elastomers at different temperatures. The experiments were carried out both in the presence and in the absence of an inhibitor (phenyl-β-naphthylamine). The elastomers and the inhibitor were first carefully purified. The kinetics of autoxidations were studied volumetrically by means of an apparatus already described by one of the authors. A chainless molecular introduction of oxygen into the double bonds of the elastomer in the presence of the inhibitor was studied with the aid of our own previously described inhibitor methods. The study included the oxidation of butadiene elastomers containing different distributions of double bonds in the main and side chains, divinylstyrene rubber, and the hydrocarbons of natural rubber and gutta-percha. These products are distinguished by their different degrees of unsaturation, the number of side chains, the number of double bonds in both their main and side chains, the length of their molecular chains (the mean molecular weight), and their spatial configurations.
Effect of Fillers on Plasticity of Unvulcanized Rubber
Authors: Mullins L. , Whorlow R. W. 
Published: February 2011

Abstract
An investigation into the effect of fillers on the flow properties of rubber stocks is described. It is shown that rubber stocks containing fillers soften on working and stiffen on standing, and these changes are associated with the breaking down and formation of some internal structure. The amount of this structure which can be broken down or built up in this way depends on the nature of the filler; it is most evident in stocks containing fine reinforcing carbon blacks, but the ability of the filler to form structure can be modified by addition of small quantities of surface-active materials. The measured value of the plasticity of compounded rubber stocks is thus not a definite value characteristic of the stock, but depends on the whole past history of the sample, and a wide range of plasticity values may be obtained, depending on the history and the conditions of test. The practical significance of these results is discussed, and proposals which would assist the revision of ideas on plasticity tests are put forward.
The Mechanical Activation of Rubbers (Oxidation under Mechanical Stress)
Authors: Kuz'minskii˘ A. S. , Maizels M. G. , Lezhnev N. N. 
Published: February 2011

Abstract
In the practical application of rubber products, their fatigue characteristics, i.e., the rate of deterioration under repeated mechanical deformation, are frequently of wide importance. Work by several authors has established the fact that the fatigue effect increases significantly under the influence of oxygen, e.g., the fatigue resistance of rubber in an atmosphere of oxygen is many times lower than in an inert medium. It was found also that in the fatigue process, as in the thermal oxidation of rubber, the inhibitor is consumed. The cause of the more rapid deterioration of rubber with fatigue is the subject of discussion of the present work. Until now the effect of mechanical stresses on the oxidation processes has not been accurately determined. The present authors have investigated the effect of repeated deformations on the rate of oxidation of vulcanized butadiene-styrene rubber in different kinetic periods of the reaction (induction period, autocatalysis). In these experiments, particular attention was devoted to the microkinetics (kinetics of inhibited oxidation) of the inhibition method which was employed. The latter was used in the investigations of the kinetics of the consumption of the inhibitor (phenyl-β-naphthylamine) in the oxidation of rubber. Since in thermal oxidation, this process follows a linear law, the kinetic curve with respect to the time axis gives the rate of reaction. The latter approximates the rate of the initial reaction between the oxygen and the rubber, that is, the rate of initiation of oxidation (Wi) if all the original active centers are eliminated by the inhibitor.
Tetramethylthiuram Disulfide Vulcanization of Extracted Rubber. IV. Behavior of Rubber as an Acid
Authors: Craig David , Juve A. E. , Davidson W. L. 
Published: February 2011

Abstract
The retarding effect of organic acids on vulcanization as well as the activating effect of certain acids on certain accelerators is well recognized. The activating and accelerating effects of bases and metallic oxides is also well recognized. In this connection, the mild activating effect of palmitic acid on vulcanization with TMTD in the presence of zinc oxide was described in the first paper of the present series. With the behavior of acids and bases during vulcanization as a background, the study of rubber itself as an acid has been undertaken. This paper sets forth a description of two reactions investigated during the study. These are the reaction of rubber with zinc palmitate and of TMTD with acids.
Dielectric Relaxation of Natural Rubber Vulcanizates
Authors: Schallamach A. 
Published: February 2011

Abstract
The dielectric loss tangent of different types of vulcanizates of natural rubber has been measured as function of the frequency. Comparisons of the losses in different vulcanizates containing the same amount of combined sulfur show that they decrease with increasing modulus, and it is suggested that the dielectric loss is mostly due to sulfur which has been combined in forms other than cross-links. The dielectric relaxation time is approximately an exponential function of the percentage of combined sulfur. It has been found that moisture increases the audiofrequency losses in rubber more than the radiofrequency losses.
The Role of Intermolecular Forces in the Mechanism of High Elastic Deformation. III. Effect of Swelling on the Mechanical Properties of Vulcanized Rubber
Authors: Dogadkin B. A. , Gul V. 
Published: February 2011

Abstract
1. The construction of an apparatus (elastometer) for the mechanical investigation of high elastic substances is described. This apparatus makes it possible to draw deformation curves and curves of the relaxation of stress atconstant temperature and in different gaseous media, and also to investigate the life at multiple deformations. The sensitivity of the apparatus is: ΔP=0.01 g., Δl=0.01 cm. 2. The molecular weight of the segments of the chains between the bonds of the spatial network of the vulcanizate, calculated by means of Flory's equation, increases with swelling, and approaches a certain maximum value. This is evidence of the rupture of the local intermolecular bonds on swelling. 3. The maximum time of relaxation, calculated according to the equation of Dogadkin, Bartenev, and Reznikovskil, as a consequence of swelling, generally does not change uniformly; it decreases with swelling of natural rubbers in benzene and chloroform in the initial stages, then increases, and finally decreases again in the last stages of swelling. 4. An increase of temperature displaces the minimum times of relaxation to lower degrees of swelling. 5. The increase of the maximum time of relaxation as a result of swelling causes a decrease of the life of the vulcanizate; a decrease of this factor is accompanied, at least within certain limits, by an increase of life. 6. Swelling causes a decrease of tensile strength and of the relative elongation of vulcanizates. 7. The changes recorded above in the equilibrium and kinetic characteristics of high elastic deformation are explained by the presence in the vulcanizate of different intermolecular bonds.
Application of X-Ray Diffraction Methods to the Identification of Natural and Synthetic Rubbers
Authors: Goldspiel S. , Bernstein F. 
Published: February 2011

Abstract
In this paper, x-ray diffraction patterns and data for rubber compounding ingredients are presented and applied to the identification of major crystalline ingredients in several basic rubber stock types. Methods for the identification of natural and synthetic elastomers by low temperature aging and (or) stretching, using film techniques, are described. The extension of such methods to the Geiger counter x-ray spectrometer is presented and discussed.
Plastic Yield of Butadiene-Styrene and Isoprene-Styrene Ebonites
Authors: Scott J. R. 
Published: February 2011

Abstract
In unloaded ebonites made from butadiene-styrene copolymers, the resistance to plastic deformation at elevated temperatures is better the higher the styrene content of the copolymer, at least up to 46 per cent. An isoprene-styrene copolymer ebonite has poorer plastic-yield resistance than a corresponding butadiene-styrene ebonite. All the styrene-containing copolymers, however give ebonites more heat-resistant than natural rubber ebonite, the best giving yield temperatures 30° C above the latter. To attain the best plastic-yield resistance in butadiene-styrene ebonites, the amount of sulfur added should correspond to more than 1 atom (e.g., 1.2 or even 1.4 atoms) per butadiene molecule.
Determination of Unsaturation of Butyl Rubbers and Certain Branched Olefins. Iodine Monochloride Method
Authors: Lee T. S. , Kolthoff I. M. , Johnson Ethel 
Published: February 2011

Abstract
The reaction of iodine monochloride with highly branched olefins and polymers is abnormal in that the addition products formed possess steric strain and tend to decompose. The products of decomposition react further with iodine monochloride, generally leading to high results in the determination of unsaturation. Based upon the fact that the addition of iodine monochloride to the decomposition product is not so rapid as the addition of iodine monochloride to the original olefin or polymer, new procedures have been developed for the determination of unsaturation of highly branched ethylenic substances. The procedures have been shown to give reliable results for olefins such as the diisobutylenes and for copolymers, such as isoprene Butyl rubber and butadiene Butyl rubber.
Chlorination of Natural Rubber. II. Preparation and Properties of Rubber Dichloride
Authors: van Amerongen G. J. , Koningsberger C. 
Published: February 2011

Abstract
As we have seen in Part I, the chlorination of rubber with chlorine under the most varied conditions leads to products in which the chlorine is initially attached fairly loosely to an allylic carbon atom. Consequently, chlorinated rubbers of low chlorine content have rather poor properties. We shall now proceed to describe two methods by means of which, with saturation of the double bond, chlorine is introduced into rubber and the formation of products with allylic chlorine is avoided. In this way chlorinated rubbers of comparatively low chlorine content can be obtained, and these are considerably more stable than the products of the same chlorine content resulting from the direct chlorination of rubber. One of these methods depends on a catalytic additive chlorination of rubber with sulfuryl chloride; the principle of the other is the addition of HC1 onto rubber followed by normal chlorination. The aniline test described in Part I (in which the chlorinated rubber is heated with aniline for 17 hours to 100° C) was again employed to establish the nature of the chlorine bond in chlorinated rubber. Under the conditions of this test, allylic and tertiary combined chlorine reacts quantitatively. Chlorine attached by addition to the double bond of the rubber reacts to the extent of only about 4 per cent. We are therefore in a position to mark off clearly allylic and tertiary chlorine from addition chlorine. This reactive tertiary chlorine is introduced into rubber by the addition of HC1, with the formation of rubber hydrochloride. In the chlorination of rubber we are mainly concerned with allylic and addition chlorine, between which the aniline test distinguishes unmistakably. Moreover, the splitting off of the chlorine from chlorinated rubber with aniline gives us a good idea of its chemical stability.