bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparing Crude Rubber Test-Specimens for Oxygen-Absorption Measurements
Authors: Gowans William J. 
Published: February 2011

Abstract
Recent investigations have shown the advantages of using a volumetric oxygen-absorption apparatus for accelerated aging tests on crude rubber. Current work in this laboratory has confirmed the advantages of this apparatus as a rapid means for determining the storage stability of a given crude rubber stock. Unfortunately, crude rubber test-specimens cannot be placed in the oxygen-absorption apparatus in the same manner as can test-specimens of vulcanizates. The tendency of crude rubber to flow, particularly during the more advanced stages of oxidation, may cause errors in oxygen-absorption measurements by limiting the diffusion of oxygen into the test-specimen. For this reason it was necessary to devise a method of preparing rubber test-specimens for oxygen-absorption measurements which is applicable to crude rubber. Test-specimens of crude rubber suitable for oxygen-absorption measurements can be readily prepared with the aid of an aluminum mold and a vulcanizing press. The method of pressing the crude rubber into a sheet from which the specimens are taken is a slight modification of that used by McPherson and Cummings in preparing samples for refractive-index measurements. Oxygen-absorption data were obtained in an apparatus similar to the one described by Shelton and Winn'. The results indicate several important advantages of the present hot-press method of sample preparation, compared with the test tube-film method used by Glazer and coworkers in preparing crude GR-S samples for oxygen-absorption studies.
Products of Oxidation of an Olefin Structurally Related to GR-S
Authors: Mitchell G. R. , Shelton J. Reid 
Published: February 2011

Abstract
The fields of rubber, plastics, surface coatings, and petroleum include a considerable portion of the industrial activity of the world, and in each of these industries oxidation is an important factor in product processing and in the properties of the final product. Information regarding the nature of the oxidation reactions observed in any of these fields can be applied in part to the others. Because of the complexity of the materials involved, it is frequently desirable to study pattern molecules of comparable structure and to seek to apply the knowledge obtained in this way to the more complex systems. This investigation is a part of a research program on the nature of the oxidation of natural and synthetic rubber and related materials. It is confined to the study of an olefin, 5-phenyl-2-pentene, which represents one of the possible repeating structural units of GR-S rubber. There is considerable information in the literature regarding the probable mechanism of oxidation of hydrocarbons, both saturated and unsaturated. The oxidation of olefins, for example, has been studied extensively by workers in the laboratory of the British Rubber Producers' Research Association and the following sequence of reactions for either thermal or photoxidation with molecular oxygen was proposed:
Polymerization and Copolymerization Reactions with Alfin Catalysts. In Relation to Masterbatch Preparation
Authors: Stewart R. A. , Williams H. Leverne 
Published: February 2011

Abstract
Alfin catalysts, as developed by Morton, have been used for a study of the polymerization reactions of butadiene-styrene, and other monomers. Catalyst activity was affected by minor variations in the method of preparation and increased during the first few days of storage of the catalyst. Water, alcohols, and ketones acted as catalyst poisons. Technical pentane and crude propylene streams can replace the normally pure materials used in the preparation of the catalyst. Copolymers of butadiene with styrene or α-methylstyrene were slightly richer in the styrene than the corresponding emulsion copolymers, except when Circosol-2XH was present in the medium. This resulted in polymers less rich in styrene. Attempts to induce cross-linking by incorporation of vinyl crotonate or divinylbenzene into the polymers did not result in a tighter gel. In the polymerization of butadiene, there is a threshold concentration of catalyst below which no reaction occurs and above which the final conversion obtained rises rapidly to 100 per cent with increased catalyst concentration. The lower the concentration of inert diluents in the reaction system, the lower the threshold value. The intrinsic viscosity of the polymer increases as reaction temperature is raised and decreases as conversion proceeds. Intrinsic viscosities over 20 can be otained. In contrast, butadiene-styrene copolymers increase in intrinsic viscosity as conversion is increased and have a lower gel content. The intrinsic viscosity of the copolymers is much lower than for the polybutadiene samples and the catalyst requirement is higher. Polymerization will occur in the presence of butanes and butylenes, hydrocarbon oils such as Circosol-2XH, carbon black, and stearic acid although the catalyst requirements are thereby increased. Incorporation of such materials before or immediately after polymerization markedly improves the processability of the polymers. Physical evaluation of resulting masterbatches has indicated retention of desirable properties.
Structure and Properties of Loaded Rubber Mixtures. VIII. Tensile Strength of Loaded Rubber Mixtures Prepared Directly from Latex
Authors: Uzina R. , Dostian M. 
Published: February 2011

Abstract
1. The change of physical properties of loaded films of natural latex with the degree of loading is related to a change of distribution of the filler; when the filler content is small a loose structure is formed, which possesses a lower density and strength. 2. Mastication destroys the loose structure which forms in the range of small loadings, and leads to a disappearance of the minima on the corresponding concentration-strength and concentration-density curves. In synthetic-latex mixtures, there is no minimum strength or density for a particular degree of loading, since no loose structure is formed. This is still true after mastication. 4. In natural latex, bentonite clay is an active filler; channel carbon black hardly reinforces such latex mixtures. In synthetic latex (Igetex S-3), channel carbon black shows significant reinforcing properties. 5. Mastication of dried latex mixtures does not change the action of fillers. 6. Mastication of coagulated natural-latex mixtures causes channel carbon black to become an active filler; the behavior of fillers in synthetic latex mixtures is not changed by mastication. 7. The above mentioned phenomena are the result of the action of surface-active substances present in latex and adsorbed on the surface of its globules.
Characterization of Cord Fatigue in Tires
Authors: Williams K. R. , Hannell J. W. , Swanson J. M. 
Published: February 2011

Abstract
Fatigue in tire cords causes a linear loss of cord tensile strength with mileage and an increased fiber torsional stiffness. The loss in cord strength is centered mainly in the flex zone. The loss of cord strength stems from broken filaments and from a small loss of fiber strength throughout the tire. The lowered fiber strength is attributed to a lowered D.P., and does not appear to be connected with the broken filaments observed in the flex zone. The cause of the broken filaments has not been resolved. However, studies show that it is not due to abrasion or heat degradation. It was found possible to duplicate tire fatigue characteristics in the laboratory by causing cords to go through an extension-compression cycle approximately equivalent to the one in tires. Under these conditions, the Goodrich disk-type tester showed the same relative rate of strength loss for rayon and cotton cords as was found in a passenger tire fleet test.
Effect of Severity of Service on the Relative Abrasion Resistance of Natural Rubber, GR-S-10, and GR-S-100
Authors: Biard C. C. , Svetlik J. F. 
Published: February 2011

Abstract
The data in this report show that the rate of wear is affected very greatly by the severity of the test. Both laboratory and actual road wear performance data show that synthetic rubber and natural rubber are fairly similar in rate of wear under mild conditions of testing, but in severe service the synthetic polymers are vastly superior to natural rubber. It therefore becomes evident that, in order to correlate laboratory data with road test results, the severity of service must be known, and a laboratory test conducted under one set of conditions would not necessarily be expected to correlate with all road test results.
Thermal Decomposition of Vulcanized Structures of Deformed Vulcanizates Containing Various Accelerators
Authors: Dogadkin B. , Tarasova Z. 
Published: February 2011

Abstract
According to the hypotheses developed by the authors, vulcanized rubber is a system in which the molecular chains are united by local molecular and chemical bonds of varying intensity. The concentration, distribution, and strength of these bonds determine the principal physical and mechanical properties of the vulcanizates. Consequently the study of the structure of the vulcanizate is of primary practical value. The explanation of the nature of the bonds in a vulcanizate by chemical methods is very difficult, mainly because of the impossibility of distinguishing the specific chemical groups which enter into the composition of the different molecular chains from those bonds between the chains which are responsible for the development of spatial structures. From this view point, the thermo-mechanical method described below, which is based on the study of stress relaxation at different temperatures, is of great significance. As was shown by Dogadkin and Reznikovskii˘, the delayed stress relaxation in a vulcanizate at temperatures up to 70° C is caused by rupture of the local intermolecular bonds and the regrouping of the structural elements of the polymeric chains without destruction of the chemical bonds between them. Accordingly, after some time at these temperatures, a practically balanced stress is established, which depends on the number of the stronger bonds remaining. At temperatures above 70° C, rupture of the chemical bonds between the chains takes place; its speed increases with decrease of the energy activating the rupture of the given type of bond. Particularly in the case of sulfur vulcanizates, we can assume that the following types of bonds exist between the chains of the rubber: (1) —C—C—, which develop as a result of the polymerizationprocesses; (2) —C—S—C— monosulfide; (3) —C—S—S—C— disulfide, and (4) —C—Sn—C— polysulfide, formed as a result of the direct participation of the vulcanizing agent, sulfur, in the process of joining of the molecular chains. The energy of these chains can be estimated as 62.7 kcal, per mole for C—C, 54.5 kcal. per mole for C—S, and 27.5 kcal. per mole for the —S—S bond. Naturally, the heat stability of a vulcanizate will depend on which of the indicated types of bonds predominates.
Rapid Plastometry
Authors: Scott J. R. 
Published: February 2011

Abstract
The uses of plasticity tests, especially rapid simple tests, are discussed, with particular reference to the limitations imposed by the complex plastic behavior of unvulcanized rubbers and stocks, leading to the conclusion that simple tests are likely to be of use only for routine control of repeat, nominally identical batches. A summary is given of information collected from the industry to show under what conditions a plasticity test is required to be used in factory control. The efficiency of a plasticity test is defined, and a discussion given on how the type of instrument (rotation, extrusion or compression) and the conditions of a compression test affect both efficiency and rapidity, thus showing what conditions furnish the best form of test. It is concluded that the parallel-plate compression test is the most suitable, provided the test-piece is precompressed to a small thickness so that it can be quickly heated to the test temperature before applying the load; other factors considered are the size of compression plates and of test-piece, use of release medium (e.g., thin paper), degree of precompression, preheat period, load, compression period, and temperature. Existing rapid plastometers are described, including full details of the new Wallace modification of the Hoekstra instrument, which embodies the recommended conditions of test.
Influence of Structure of Elastomers on Their Permeability to Gases
Authors: Van Amerongen G. J. 
Published: February 2011

Abstract
It is a known fact that rubber membranes are permeable to gases and that the rate of permeation is a specific function of a given gas and rubber. We may picture this permeation of gas through rubber as a process in which gas molecules dissolve on one side of the membrane, then diffuse through the rubber to the other side, and there evaporate out of the membrane. Thus the process of permeation is divided into several independent processes, those of solution and evaporation being governed by Henry's law and that of diffusion by the diffusion equation (Fick's law). The problem to be considered is why a given rubber should possess a given permeability to a given gas. It will at once be evident from what has just been stated that, while studying the problem, the process of solution (or evaporation) and that of diffusion must be dealt with separately. It was shown in earlier investigations on a series of rubber varieties and gases how the chemical structure of the rubber molecules affects the rate at which the gas passes through, and, notably, that the introduction of methyl and polar groups in the polymer molecules and crystallization reduce this rate of diffusion. It was also found that a gas diffuses more slowly as its molecules are larger. The solubility of the gas in the rubber is determined by its tendency to condense and by the interaction between the rubber and the gas molecules. These views will now be put to the test with reference to another series of rubbers and gases. We shall also see that knowledge of the necessary conditions for low permeability may help to evolve new kinds of rubber of low permeability.
Ultra-Speed Tensile of Rubber and Synthetic Elastomers
Authors: Villars D. S. 
Published: February 2011

Abstract
A high speed stress-strain machine has been developed which is capable of recording the stress-strain curve of elastomers at elongation rates up to 270 per cent/msec. Data are reported on two series of gum and tread stocks of Hevea and of the synthetic elastomers, GR-S, Hycar-OR, Butyl, Perbunan, and Neoprene-GN. The second (elastomer) series was also run at 150° C. In general, stress-strain curves fall into two classes. Stocks of elastomers which are known to crystallize on stretching tend to show tensile strengths which decrease with increasing speed up to about 10 per cent/msec, pass through a minimum, and rise more or less drastically to values 100 per cent (or more) greater than the Scott tensile strength. Elastomers which do not crystallize on stretching tend to show a steady rise in tensile strength with increasing speed. Elongation at break curves show a maximum with crystallizing stocks and no maximum with noncrystallizing stocks. The shape of the modulus vs. speed curves is accounted for on the hypothesis of different types of slipping bonds with different characteristic relaxation times. The shift of curves for tread stocks with temperature allows the estimation of a heat of activation of slippage. This comes out to be of the order of 3 kg.-cal.
Stress-Strain Properties of Natural Rubber under Biaxial Strain
Authors: Boonstra B. B. S. T. 
Published: February 2011

Abstract
(1) The stress-strain curves of vulcanized rubber held at definite tangential elongations during stretching differ more from the simple unidirectional-extension-stress curve than the theory predicts. The differences are larger at higher tangential elongations. (2) The relaxation constant determined at 600 per cent elongation is practically unaffected by tangential elongations up to 300 per cent.
Tetramethylthiuram Disulfide Vulcanization of Extracted Rubber. V. Low Molecular Products and the Mechanism of Zinc Oxide Activation
Authors: Craig David , Davidson W. L. , Juve A. E. 
Published: February 2011

Abstract
The essential features of TMTD vulcanization, as revealed by compounding tudies, were discussed in Part I of this series. Thus, TMTM, a product of TMTD vulcanization, and an active accelerator of sulfur vulcanization, was found to be an inhibitor, and ZnDMDC, a main product of TMTD vulcanization, in the presence of ZnO was found to be devoid of activating properties. As a replacement of ZnO, which is a potent activator, ZnDMDC displayed only mild activating effects. Zinc palmitate was even more potent than ZnO. Zinc sulfide was somewhat less active than ZnO. Palmitic acid and DMADC had little or no effect on the cure. The second paper reported that TMTD could be prepared in good yield by the reaction of TMTM with sulfur and also, as a result of radiosulfur techniques, that the four sulfur atoms in the TMTD molecule are chemically identical. Part II also reported that ZnO reacted with TMTD to form sulfur and ZnDMDC in good yield. Other reactions of TMTD were discussed. Part III, in presenting a short-path distillation technique for studying vulcanizates, reported that the nearly complete removal of zinc from the TMTD vulcanizate is not accompanied by devulcanization. Part IV reported on the behavior of rubber as an acid. This behavior results in the liberation of palmitic acid from zinc palmitate. From the comparison of the reaction of TMTD with acids and the reaction of rubber with TMTD, it was inferred that rubber is an OH-containing acid. Acids in the work reported were found to react rather slowly with TMTD to form dimethylamides and sulfur in good yield. The acidic nature of rubber did not seem to be great enough to contribute in any fundamental way to the vulcanization process. The present paper describes further studies of the TMTD vulcanization problem.
Comment on “Relationship between Gough-Joule Coefficients and Moduli of Vulcanized Rubbers”
Authors: Mooney M. 
Published: February 2011

Abstract
In an article of the title quoted above Conant, Hall, and Thurman were interested in establishing by experiment the theoretical equality between the tangent shearing modulus of a rubber and the ratio of the temperature coefficient of shearing stress to the negative temperature coefficient of shearing strain. Their published data can be used also for calculating the value of an important property, the relative temperature coefficient of relative stress, σ, at constant strain, γ, or T/σ(∂σ/∂T)γ. The value of this coefficient is unity if there is entropy change but no energy change in an isothermal strain, as is postulated in the kinetic theory of elasticity. The values of the coefficient can be calculated from the data given by Conant, Hall, and Thurman for σ/γ, 1/γ(∂σ/∂T)γ, and T, the reference temperature. The calculations yield the results:
Chlorination of Natural Rubber. I. Preparation and Properties of Chlorinated Rubber
Authors: van Amerongen G. J. , Koningsberger C. , Salomon G. 
Published: February 2011

Abstract
The chlorination of rubber has been the subject of extensive investigations, the rubber being commonly treated in solution with gaseous chlorine at a given temperature and pressure. The properties of the products of rubber thus treated vary in close dependence on the chlorine content, which may be as much as 70 per cent. The drawback to a low chlorine content is that, as a rule, the chlorine is loosely bound, with the result that, when exposed to heat or light, it splits off as HC1, with formation of discolored and cyclized products and serious deterioration of the mechanical properties. But the higher the chlorine content, the more stable are these chlorinated rubbers. The stability of chlorinated products of natural rubber containing approximately 65 per cent of chlorine is such that they are used commercially as a component of anticorrosive paint. The instability of chlorinated rubber of low chlorine content is closely connected with its chemical constitution and the mechanism of reaction. The current opinion ten years ago was that chlorine first adds to the double bond of the rubber, and that this primary product, while splitting off HC1, enters into further reaction with chlorine ; but reexamination of this reaction in the laboratory of our affiliated English organization and independently in our own laboratory has led to very different views. It was realized that rubber dichloride (the addition product of chlorine and rubber) is far too stable to act as an unstable intermediate product during the chlorinating reaction. Bloomfield argued that, during the primary reaction, the chlorine is attached by substitution to an α-methylenic carbon atom of the rubber molecule and that there is a considerable amount of cyclization. It was not our sole concern to study the mechanism of reaction; we were also bent on following the chlorination of rubber under the most diverse conditions, starting from dry rubber, rubber in solution, and rubber in latex, and with highly diversified sources of chlorine such as from liquid chlorine, gaseous chlorine, hypochlorites, and sulfuryl chloride. The normal course of reaction, involving the formation of unstable intermediate products, is discussed in Part I of this series; methods of producing comparatively stable rubber chlorides by adding chlorine onto the double bond are considered in Part II.
Determination of Copper in Rubber Latex
Authors: Poulton F. C. J. , Tunnicliffe M. E. 
Published: February 2011

Abstract
Small amounts of copper in rubber latex can be determined by following a dry-ashing procedure for removal of organic matter and concluding with a colorimetric determination of the copper in the ash. Provided the ignition is not undubly prolonged, the ashing temperature can safely rise to 800° C, and recovery of the copper is complete from the ash when a mixture of nitric and hydrochloric acids is used. Results are slightly higher than those obtained by the wet oxidation process. Assay of the copper can be carried out on the solution of the ash, either in aqueous medium or in carbon tetrachloride solution, depending on the extent of interference anticipated from iron and insoluble ingredients, such as clay, and on the degree of accuracy required. Visual color matching in aqueous solution is simpler and quicker, but insoluble material may give rise to considerable personal error. In aqueous solution, the copper equivalent of ferric iron is about 1/100, i.e., the coloration is about 100 times more intense for copper than for iron. for more accurate work, measurement of the color of a carbon tetrachloride solution of the copper diethyldithiocarbamate complex by means of a suitable colorimeter is recommended. The tendency of the complex to fade is overcome by replacing the sodium diethyldithiocarbamate by the zinc salt dissolved in carbon tetrachloride. In such a solution the copper equivalent of ferric iron is about 1/1000, but actual experimental conditions can vary this figure between wide limits. A more satisfactory procedure is, therefore, to measure the total color developed in carbon tetrachloride, and then bleach out the color due to copper with potassium cyanide. The residual (interfering) colors can thus be estimated, and the difference between the readings gives a direct measure of the concentrations of copper in the test solution.