bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Resistance to Abrasive Wear. XI. Influence of the Type of Abrasive
Authors: Newton R. G. , Scott J. R. , Willott W. H. 
Published: February 2011

Abstract
Tests with the du Pont machine show that the practice of expressing abrasion test results as an abrasive index, i.e., abrasion-resistance relative to a standard rubber, does not enable different types of abrasive to be used indiscriminately because these are found to give widely different abrasive indices for the same rubber; thus, some abrasives may give four times as high an index as others. If attention is confined to abrasive papers, as distinct from bonded abrasive wheels, this variation is reduced, but is still large enough to be a serious factor in accurate work. It is clear that, even when this comparative method of testing is used, standardization of the abrasive paper is essential to reduce discrepancies between results obtained in different laboratories. Discrepancies will still exist, however, because abrasive paper is not uniform, and there is evidence that abrasive indices determined on different portions of the same paper may differ as much as those from different types of paper. To minimize the effect of this nonuniformity, two courses are open. (1) All the rubbers to be compared could be abraded on one and the same area of paper, preferably a large area to avoid wearing the surface, e.g., by giving each rubber a short run on each of the several paper discs used, instead of using a different disc for each rubber. (2) Different specimens could be tested on the two sides of the machine provided this has a pivotted arm. It is shown that this technique has several advantages. The factors that cause the abrasive index to vary from one abrasive to another are not known; it appears, however, that the degree of abrasiveness is not a determining factor. The two methods of calculating abrasion loss—as cc. per hr. and cc. per H.P.-hr.,—usually do not give the same abrasive index; in any standard test method it is therefore essential to state which is to be used. The variation of the abrasive index from one abrasive to another is the same whichever method of calculation is used.
Determination of Resistance to Abrasive Wear. XII. Comparison of Akron and Du Pont Abrasion Machines. Value of an Abrasive Index
Authors: Scott J. R. 
Published: February 2011

Abstract
Abrasion tests on several sole and heel rubbers have been made on the Akron and du Pont machines to determine whether the same abrasive index (abrasion-resistance relative to a standard rubber) is given by both methods. The following conclusions are drawn from the results. (1) The two methods do not give the same abrasive index for the same rubber; a study of published data shows that this is true of at least some other abrasion test methods. In using an abrasive index to specify or control the quality of manufactured articles it may, therefore, be necessary to establish a separate index figure for each type of machine used. (2) Broadly speaking, the higher the abrasive index of a rubber by any one method, the higher is its indices by other methods, so abrasive indices can be converted approximately from one method to another by using a suitable factor or conversion formula; a formula for interconverting Akron and du Pont results is given. (3) Such conversions from one method to another are only approximate, however, because indices determine by different methods are by no means exactly related. The magnitude of the errors involved is indicated and discussed; in the present experiments the average discrepancy between an index measured directly and that calculated by the formula from the index given by the other machine, is about 20 per cent; corresponding figures from published data range from about 6 to 40 per cent. (4) Errors similar to those just mentioned, occur in predicting the relative service wear of different rubbers from laboratory abrasion tests. Although these errors seem large, the chances of a rubber that gives a satisfactory test result proving really poor in service are small. (5) The adoption of any system that prevents unsatisfactory material being put on the market is a valuable means of saving rubber. On the basis of the present results with the Akron and du Pont machines, it can be shown that by the application of a laboratory abrasive index test the resultant saving of rubber is at least two-thirds of what would be saved if acceptance or rejection could be based on actual service wear results—an ideal but impracticable procedure. (6) There is evidence that among rubbers of similar composition, e.g., sole and heel rubbers made by any one manufacturer, abrasive indices obtained by different methods are more closely related than among rubbers in general. For control and development work within the factory, therefore, the abrasive index system should prove more satisfactory than when applied to a varied assortment of rubbers of unknown composition. (7) Abrasion methods may differ in their power of discriminating between rubbers; thus, in the present experiments, the Akron test shows wider differences in abrasive index than the du Pont test, although the latter has the higher power of discrimination.
Qualitative Detection of Titanium Dioxide in Rubber
Authors: Hammond G. L. 
Published: February 2011

Abstract
Titanium dioxide, either as such or in the form of the composite titanium whites, is now used to such an extent as a rubber pigment that a test for titanium is frequently necessary in the analysis of a compounded rubber. Owing to the insoluble nature of titanium dioxide, troublesome fusions are required to detect it by the normal qualitative tests in the ash remaining when a rubber is incinerated. The following method is offered as a quick and easy means of detecting titanium. A small portion (about 0.01 gram usually suffices) of the ash from the sample is placed in a clean glazed 15-cc. Porcelain crucible. One drop of concentrated sulfuric acid is then added, and the whole is heated on a hot plate for 30 seconds, i.e., until most of the acid is evaporated. The crucible is allowed to cool, and 2 drops of 6 N sulfuric acid added, followed by 1 drop of a 5 per cent aqueous solution of the sodium salt of chromotropic acid (1,8-dihydroxynaphthalene-3,6-disulfonic acid). A brownish red to purple coloration is obtained if titanium be present. In place of the chromotropic acid, 1 drop of 10-volume hydrogen peroxide is added in a second test, when the well-known golden yellow color is obtained.
Stresses and Birefringence in Rubber Subjected to General Homogeneous Strain
Authors: Treloar L. R. G. 
Published: February 2011

Abstract
The conclusion to be drawn from the preceding analysis of the stress-strain relations may be summarized in the following way. As a first approximation the equations derived from the statistical treatment of a molecular model provide a basis for the interpretation of the elastic properties of rubber. A closer approximation is obtained by including an additional term in the stored-energy function, i.e., by the use of Mooney's Equation (3). This appears to give an accurate representation of the properties of a swollen rubber, but is still inadequate when applied to a dry rubber, for which a third approximation, including at least one more general term, is likely to be required. It is necessary to emphasize that the use of the second or higher approximations does not in itself throw any light on the physical mechanism responsible for the behavior observed. It is, in fact, the 3-dimensional analog of simple curve-fitting. It must also be borne in mind that any physical model that might be postulated must necessarily lead to results which may be represented by some combination of the stored-energy functions discussed in the section on the theoretical interpretation of the data.
The Thermodynamics of a Strained Elastomer. I. General Analysis
Authors: Mooney M. 
Published: February 2011

Abstract
The thermodynamic functions of principal interest in a strained elastomer are the entropy and energy of deformation. The volume is of secondary importance, and it can be assumed, with sufficient accuracy for most purposes, that the volume is linear in the temperature and the mean pressure. The basic partial differential equations of thermodynamics can then be integrated, yielding expressions for the energy and entropy of deformation in terms of observable quantities. In the present analysis the volume effects caused by changes in mean pressure and crystallinity are taken into account, and the effects associated with change in shape are sharply separated from those associated with change in volume. It is shown that the superelastic functions of deformation previously published have a very general validity.
The Thermodynamics of a Strained Elastomer. II. Compressibility
Authors: Copeland L. E. 
Published: February 2011

Abstract
Adiabatic compressibility coefficients were measured on a series of cured polymers of commercial types under pressures up to 5000 pounds per square inch. In most eases, the second order as well as the first order coefficient could be determined from the data. The linear isothermal compressibility also was calculated from the measured linear adiabatic coefficient. Preliminary measurements of the thermal expansion of a stretched Hevea gum stock show that there is a slight decrease in expansion at the 200 per cent elongation, presumably due to partial crystallization.
The Thermodynamics of a Strained Elastomer. III. The Thermal Coefficient of Modulus and the Statistical Theory of Elasticity
Authors: Copeland L. E. , Mooney M. 
Published: February 2011

Abstract
Published thermoelasticity data are critically analyzed by means of thermodynamic equations developed in the first paper of this series. Equations known to be of the proper form are fitted by least squares to the experimental data, which were first corrected to allow for the changes in shape when tested under variable temperature and constant length. If the measurements are accepted as truly reversible, the data show that several different elastomers depart considerably in some respects from the predictions of the statistical theory of elasticity. Some thermoelasticity measurements in torsion are reported which seem to give the most reliable evidence that stress is proportional to absolute temperature.
The Formation and Structure of Vulcanizates
Authors: Bardwell J. , Winkler C. A. 
Published: February 2011

Abstract
The characteristic mechanical properties of vulcanized rubber are believed to result from a network structure made up of chainlike molecules bonded together by occasional cross-linkages. In relating the physical properties of the vulcanizate to the structure of the network, it is therefore necessary to consider the concentration of cross-linkages and the molecular-weight distribution of the rubber molecules before cross-linking. Various theories have been proposed for the dependence of elastic properties on these structural factors, but experimental proof of the suggested relations has been meager, largely because of the complexities met with in, vulcanization reactions. In the present investigation some of these difficulties have been overcome, and the quantitative relations between the elastic behavior of GR-S and its network structure have thereby been revealed.
The Unsaturation of Butadiene Rubbers. I
Authors: Vasil'ev A. A. 
Published: February 2011

Abstract
1. The data on the unsaturation of butadiene rubbers previously obtained by using the method based on the reaction with iodine bromide have been checked and confirmed with the aid of the reactions with pyridine sulfate dibromide and with iodine chloride. 2. The influence of various factors on the unsaturation of butadiene rubbers has been checked, and the possibility of estimating changes in unsaturation with the aid of the reaction with iodine bromide has been established. 3. The present investigation shows that, during the reaction between butadiene rubbers and halogens, it is impossible to attain a degree of saturation exceeding 85–90 per cent of the theoretical values. This is apparently due to the existence of intramolecular cyclization, to the presence of intermolecular connecting bridges, and possibly to the presence of double bonds resistant to halogenation or of conjugated double bonds in the molecules of these rubbers. The reaction with halogens offers no possibility of confirming these suppositions experimentally.
The Abnormal Melting of Raw Rubber
Authors: Isihara Akira 
Published: February 2011

Abstract
The experimental results on the abnormal melting of crystallized raw rubber by Wood and Bekkedahl are studied theoretically. The effect can be explained by the fact that the relaxation time for the thermal expansion of crystalline particles differs from that of amorphous particles. At the point where the melting begins, the time interval of observation becomes comparable to the relaxation time of amorphous particles. The point becomes higher as the time rate of heating increases, and also as the relaxation time itself becomes larger. The point at which fusion is complete is determined by the relaxation times of the amorphous and crystallized states, heating rate, and previous history. This effect becomes large at a suitable heating rate, and is larger in natural rubber than in vulcanized rubber.
Structural Changes in Rubber Brought about by Molecular Oxygen. III. Properties of Disintegrated Vulcanized Natural Rubber
Authors: Dogadkin B. , Tarasova Z. , Pasynskii A. 
Published: February 2011

Abstract
1. The product of destructive solution of vulcanizate contains 50 mg. of oxygen per gram of substance; of this quantity, 3.77 mg. falls to the share of oxygen contained in free carboxyl groups. 2. The disintegrated vulcanizate is soluble in ordinary rubber solvents, as well as in binary mixtures of associated and unassociated liquids. 3. The viscosity and light diffusion of a broad range (up to 6 per cent) of disintegrated vulcanizate solutions are linear functions of the concentration. 4. The average molecular weight of the disintegration product of a vulcanizate, as determined from the coefficient of diffusion, is 3600; according to the viscometric and optical data, the molecules represent very large, elongated entities with an axial ratio of 1:24. The distribution curve of diffusion coefficients has a sevenfold dispersion. 5. The mechanical strength and elasticity of films prepared from a disintegrated vulcanizate are very much lower than those of films made of vulcanized rubber.
Flow Phenomena in Rubber. I. Flow Curves for Natural Rubber
Authors: Saundeks D. W. , Treloar L. R. G. 
Published: February 2011

Abstract
From the flow curves, the readings to be expected in the standard (shearing-disc) Mooney viscometer were calculated. These differ from the observed figures by about 15 per cent. The temperature dependence of the rate of flow is accounted for on the basis of the simple Eyring formula, and a value of 8.1 k. calorie per mole was obtained for the energy of activation involved in the flow process.
Polymerization. VIII. The Action of Metalating Reagents on Rubber
Authors: Morton Avery A. , Ramsden Hugh E. 
Published: February 2011

Abstract
When metalating agents act on natural or Alfin rubber, gel is formed. The amount of gel increases with the activity of the metalating agent and the severity of the conditions under which it is used. Metallic sodium or potassium does not cause gel to form in natural rubber. Under very severe conditions these metals metalate the highly active hydrocarbons, fluorene, triphenylmethane and diphenylmethane, in fair to poor amounts, depending on the hydrocarbon, but they metalate toluene only slightly, even under highly favorable conditions.
The Reaction of Sulfur and Sulfur Compounds with Olefinic Substances. IV. The Thermal Decomposition of Organic Polysulfides, and Its Contribution to the Sulfur Olefin-Reaction
Authors: Bloomfield George F. 
Published: February 2011

Abstract
At temperatures in the region of 140°, organic polysulfides undergo disproportionation resulting from thermal fission of S—S bonds and recombination of the fission products. In the presence of olefins a considerable proportion of the fission products become attached to ethylenic centers of the olefin, forming mixed mono- and polysulfides. The major part of the monosulfide product is fully saturated, hydrogen capture occurring during, or subsequent to the formation of adducts from the olefin and sulfurated fragments; unsaturation, however, appears in the polysulfide portion. The polysulfides are capable of producing monothio cross-links between the original olefinic molecules only in so far as they are able to yield up elementary sulfur to the olefin, and when the original olefin is a polyisoprene, the tendency towards the formation of a high proportion of intramolecular cyclic sulfide still further reduces the opportunity for formation of intermolecular sulfur-cross-linked products.
X-Ray Studies of Low-Temperature Polybutadiene and Butadiene-Styrene Copolymers
Authors: Beu Karl E. , Reynolds W. B. , Fryling C. F. , McMurry H. L. 
Published: February 2011

Abstract
Although it is now generally recognized that the temperature of polymerization affects profoundly the properties of emulsion elastomers, there is very little evidence available pertaining to the cause of the variations of properties. It is felt by some that the improved properties of low-temperature elastomers can be related to variations in molecular weight and molecular-weight distribution. In this laboratory, however, the opinion has prevailed that the lower emulsion polymerization temperatures appreciably alter the fine structure of the molecules with an increase in the regularity of the polymer chains. If there were actually less branching and cross-linking in low-temperature polymers, and less 1,2-addition to monomer components, the increased order should be evident from x-ray diffraction patterns. To provide information on the above questions, x-ray studies were made with four purposes in view: (1) to determine the effect of polymerization temperature on the crystallization properties of unstretched and stretched polybutadienes; (2) to determine the influence of styrene content on the crystallization of butadiene-styrene copolymers; (3) to study some effects of compounding and vulcanization on crystallizable polybutadiene; and (4) to use the preferred orientation patterns obtained from some of these polymers for structural evaluations. To accomplish these objectives, x-ray patterns were obtained at several temperatures of some unstretched and stretched polybutadiene polymers, butadiene-styrene copolymers, and a vulcanized and compounded polybutadiene. The polybutadienes were prepared by emulsion polymerizations at 55°, 40°, 30°, 20°, 5°, −10° and −20° C. Since the −20° C polybutadiene showed the most marked crystallization patterns, the effects of compounding and of styrene addition were studied, using polymers prepared at this temperature for comparison. Three butadiene-styrene copolymers containing, respectively, 10, 20, and 30 per cent styrene in the monomer charge and one vulcanized polybutadiene compounded with Wyex carbon black were studied.
Influence of Structure on Polymer-Liquid Interaction. III. Swelling and Mechanical Properties of Some Partly Crystallized Polymers
Authors: Salomon G. 
Published: February 2011

Abstract
We have shown in the first part of this work the influence of association on liquid-polymer equilibrium, while a study of nitrile copolymers revealed that mechanical properties are much more sensitive to certain changes in polymer structure (such as the introduction of methyl groups) than are swelling equilibria. In partly crystallized polymers, however, a close correlation between liquid-polymer interaction and mechanical properties exists, as is seen from the present paper.
Reaction Kinetics of Adiabatic Systems
Authors: Gordon M. 
Published: February 2011

Abstract
Conventional kinetic measurements, based on isothermal reaction runs, have hitherto been used to evaluate the reaction parameters required for the description of a chemical rate process. These parameters are the order n of the reaction, its activation energy E, and its frequency factor X. A new technique is here proposed in which adiabatic reaction runs are employed. The temperature change is used to follow the reaction progress. The theory of the heat-effect of adiabatic reactions is deduced, and the mathematical working-up of adiabatic time-temperature data for the evaluation of n, E and X is set out on the basis of stated assumptions. A critical discussion of the method follows, and shows that it is of particular value in polymer chemistry and wherever viscous rubbery or solid reaction media are encountered. The difficulties of heat exchange associated with isothermal measurements are avoided. To what extent the proposed method may be complementary to the conventional in general appears as yet a matter of speculation.
Adiabatic Reaction Kinetics of Buna-S Vulcanization
Authors: Gordon M. 
Published: February 2011

Abstract
In a previous paper a technique for making kinetic measurements adiabatically instead of isothermally was discussed, and the possible advantages of this technique in reactions involving polymers was indicated. In the present communication, the theory is supported by an analysis of published data relating to the vulcanization of butadiene-styrene copolymer. There are considerable gaps in our knowledge of the overall chemical changes concerned in the vulcanization of various rubbers, quite apart from the kinetic interpretation of rate measurements and the postulation of elementary steps. Because of the difficulties involved, isothermal rate measurements have not yet given much insight into the kinetics or the chemistry of the time-honored sulfur vulcanization discovered over a hundred years ago. The difficulty of maintaining the temperature constant against the considerable heat of reaction is only one of the obstacles ; that of finding a convenient and accurate measure of the progress of vulcanization considered as a chemical reaction is perhaps even greater. The difficulties of the adiabatic technique are essentially different in nature.