bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Chemistry of the Active Molecules Formed in the Mechanical Degradation of Polymers
Authors: Berlin A. A. 
Published: February 2011

Abstract
At the present time there is a multitude of data indicating that when polystyrene, natural rubber, polyvinyl acetate, cellulose, starch, proteins and other high molecular weight compounds are mechanically ground up, a degradation of the polymeric chains is observed. The mechanical scission of macromolecules during grinding in a colloid or ball mill, or when they are broken down on mill rolls, proceeds most rapidly at temperatures below the range of the viscous-fluid state, since under these conditions the forces of intermolecular interaction are considerably greater than the strength of the covalent bond. However, the mechanical destruction of macromolecules is also possible through certain mechanical effects acting on solutions of polymers. Thus, for instance, the force of friction generated in the flow of a 0.05% solution of polystyrene (Mcp=6×105) in tetralin through a platinum capillary is due to the scission of macromolecules, which brings about a 30% decrease in the specific viscosity. The significant gradients in the rate and in the forces of friction and cavitation developed in polymer solution through the action of ultrasonic waves with frequencies of the order of 200–300 kilocycles/sec. are due to the mechanical scission of macromolecules of polystyrene, rubber, polyvinyl acetate, cellulose and a number of other high molecular weight compounds.
Quantitative Determination of Antioxidants after Chromatographic Separation on Completely Acetylated Filter Paper. I. Determination of Phenyl-1-Naphthylamine and of Phenyl-2-Naphthylamine
Authors: Zijp J. W. H. 
Published: February 2011

Abstract
In this paper a general method for the quantitative determination of antioxidants is described. After isolation from the rubber compound the antioxidants are separated by partition chromatography, using completely acetylated Whatman paper No. 1. A detailed procedure is given for the quantitative determination of phenyl-1-naphthylamine and of phenyl-2-naphthylamine. These antioxidants are coupled with diazotized sulfanilic acid and determined colorimetrically.
A Spectrophotometric Method for Residual Styrene in SBR Latex
Authors: Hilton C. L. 
Published: February 2011

Abstract
The spectrophotometric method of analysis for residual styrene monomer in SBR latex has several advantages. No standardization of reagents is required. The method is rapid, accurate, and precise. The direct ultraviolet absorption method is applicable only in absence of interferences. The alternate distillation-ultraviolet method is applicable even in the presence of most interferences.
The Reactions of Amines and Sulfur with Olefins. II. The Reaction of Diethlamine and Sulfur with Trialkylethylenes
Authors: Moore C. G. , Saville R. W. 
Published: February 2011

Abstract
The reaction of diethyl and sulfur with trialkylethylenes, R⋅CMe:CHR′, at 140° C yields tert.-alkanethiols and di-tert.-alkyl disulfides as major products, with only minor amounts of the corresponding polysulfides and sulfurated polymers containing three or more olefin units linked by sulfur bridges. The degree of sulfuration is much lower than with the corresponding sym-dialkylethylene, cyclohexene, and monosulfide formation is negligible. Both observations indicate that steric influences govern the nature and the yield of the sulfurated products.
The Reactions of Amines and Sulfur with Olefins. III. The Reaction of Diethylamine and Sulfur with 1,5-Diolefins
Authors: Glazebrook R. W. , Saville R. W. 
Published: February 2011

Abstract
2,6-Dimethylocta-2,6-diene (I) with the sulfur-diethylamine combination at 140° C yields mainly saturated cross-linked sulfides, R⋅Sx⋅R, where R contains thiacyclopentane groups adjacent to the sulfide cross-link (x=1 or 2), together with the cyclic sulfides (II) and (VI), (VII), and (VIII), formed by the intramolecular sulfuration of (I). Infrared spectroscopic evidence suggests the occurrence of similar cyclic structures in squalene polysulfide and in ebonite.
Mechanism of Vulcanization of Polysulfide Rubbers
Authors: Fettes E. M. , Jorczak J. S. , Panek J. R. 
Published: February 2011

Abstract
This investigation was carried out to discover the terminal group present in polysulfide rubbers of the kind represented by Thiokol Type FA and the chemical reactions involved in the standard vulcanization recipe. Hydroxyl groups were found to be present as terminals on these polysulfide rubbers. The effects on vulcanization of omitting the compounding ingredients normally used, of varying the amounts of zinc oxide, substituting other metallic atoms for zinc, and of using diisocyanates were studied, and the mechanism was deduced. Knowledge of the end groups present in the polymer chain is helpful in planning supplementary experiments to try to discover the chemical reaction involved in the cure with zinc oxide. It also makes it possible to look intelligently for improved vulcanizing agents for these polysulfide polymers.
Vulcanization of Rubber by Organic Peroxides
Authors: Braden M. , Fletcher W. P. , McSweeney G. P. 
Published: February 2011

Abstract
Comparatively few organic peroxides meet the rather exacting requirements of the ideal peroxidic curing agent for rubber. Only di-tertiary butyl peroxide has yet been found to give satisfactory vulcanization in black stocks. Pure gum vulcanizates of a high degree of transparency and good color have been obtained with two commercially-available non-hazardous peroxides which have also been used successfully with some non-black fillers. The incorporation of resorcinol overcomes a tendency to surface tackiness in peroxide cures and has a beneficial influence on tensile strength.
Infrared Analysis of Some Chlorinated Natural Rubbers
Authors: Salomon G. , van der Schee A. Chr 
Published: February 2011

Abstract
In an earlier paper spectra of polyisoprenes were discussed. In this communication effects due to the introduction of 1 to 4 chlorine atoms per C5H8 unit are reported. Since an unlimited number of polymers with such empirical compositions derived from isomeric monomer units is conceivable, it seems convenient first to compare some prototypes, then to report in more detail our experience, which is a continuation of earlier work in this field.
Behavior of Reclaiming Agents in Sulfur and Nonsulfur GR-S Vulcanizates
Authors: Amberlang J. C. , Smith G. E. P. 
Published: February 2011

Abstract
1. Di-tert-butyl-m-cresol sulfide was found to be less active in reclaiming p-benzoquinone dioxime-cured GR-S than in reclaiming sulfur-cured GR-S. It appeared to have no effect on p-benzoquione dioxime cures activated with red lead, though the presence of litharge or red lead in sulfur cures did not seem to retard reclaiming by the same agent. 2. N,N-di-n-butyl-m-toluidine sulfide had no reclaiming action under alkaline conditions on p-benzoquinone dioxime cured GR-S. Under these conditions the same sulfide reclaiming agent actively catalyzed the reclaiming of sulfur cures either in the presence or absence of litharge activation. 3. Di-tert-butyl-m-cresol sulfide did not affect the reclaiming of GR-S cured with dinitrobenzene and litharge. 4. Di-tert-butyl-m-cresol sulfide had a strong reclaiming action on a non-elemental sulfur cure (diisopropylxanthic disulfide) activated with litharge. 5. n-Octadecylamine was a reclaiming agent for sulfur-cured and benzoquinone dioxime-cured GR-S but less active than 4,6-di-tert-butyl-m-cresol sulfide. For benzoquinone dioxime-red lead and for dinitrobenzene-litharge cures it was an active reclaiming agent; it had no reclaiming effect on a diisopropylxanthic disulfide cure. 6. Oxygen absorption measurements failed to show any simple relation between the rate of oxygen absorption of vulcanizates and their behavior in the reclaiming process. 7. Direct oxygen determinations on vulcanizates before and after reclaiming showed that 4,6-di-tert-butyl-m-cresol sulfide is an oxidation catalyst for GR-S cured with sulfur, unactivated benzoquinone dioxime or diisopropylxanthic disulfide, the same vulcanizates for which it was a reclaiming agent. Octadecylamine appeared not to be an oxidation catalyst for the GR-S vulcanizates under the reclaiming conditions studied. 8. Zinc sulfide determinations on the vulcanizates before and after reclaiming showed an increase as a result of the experimental conditions, but no correlation with reclaiming effects. 9. Low-temperature GR-S (X-611) polymer, softened by the addition of furfural phenylhydrazone or o,o′-dibenzoylaminodiphenyl disulfide, showed slightly lower oxygen content than the control.
The Reactions of Amines and Sulfur with Olefins. I. The Reaction of Diethylamine and Sulfur with Cyclohexene
Authors: Moore C. G. , Saville R. W. 
Published: February 2011

Abstract
The reaction of diethylamine and sulfur with cyclohexene at 140° yields dicyclohexyl monosulfide and disulfide and also saturated polymeric products, C6H11⋅Sx⋅(C6H10)⋅Sx⋅C6H11, containing cyclohexane units linked by sulfur, where x is 1 or 2. N-Ethylthioacetamide (IV) is formed as a major product; minor products include N,N-diethylthioacetamide (V) and diethylammonium hydrogen sulfide (VI), IV, V, and VI are formed also by the reaction of diethylamine with sulfur at 140°. The mechanisms of the olefin-sulfuration processes are discussed.
Test of the Applicability of Dielectric Loss Measurements to the Study of the Aging of Pure-Gum Rubber Mixtures
Authors: Henri-Robert P. 
Published: February 2011

Abstract
The measurement of the dielectric properties at radioelectric frequencies requires a technique and apparatus which are too delicate to serve at the present time as a practical test of the aging of vulcanized rubber. On the other hand, from the viewpoint of research, the dielectric method should furnish valuable data on the way in which oxygen tends to combine with rubber according to the particular conditions of aging. Thus, it has been found in aging tests of three different types of vulcanizates containing no protective agent that there is an increase of polarity, which is in some cases great, an increase of the dielectric viscosity, and a broad distribution of polar groups, formed by oxidation, between the different types of structures. The dielectric absorption leads in particular to the same classification of vulcanizates as do the classic methods of measuring oxidizability and decrease of tensile strength. Finally, in addition, measurement of the dielectric absorption makes possible the estimation at a high level of sensitivity of the degree of polarity of oxidation products.
Mechanical Activation of the Initiation of Oxidation of Elastomers
Authors: Kuzminskii˘ A. S. , Maizels M. G. , Lezhnev N. N. 
Published: February 2011

Abstract
1. This is the first study of the relation of uninhibited oxidation to the conditions of mechanical stress of vulcanized and unvulcanized rubber. Inhibited oxidation is confined to the initiation process. 2. At the end of the inhibition period and in the earliest stages of autocatalysis, the physical-mechanical properties of vulcanizates change sharply, and lose much of their technical value. In practice, one is nearly always concerned with inhibited oxidation, and, consequently, the study of this process is very important. 3. The rate of initiation of fatigued vulcanizates and plasticized rubber is determined by studying the kinetics of consumption of the inhibitor, which in the present work was phenyl-2-naphthylamine. 4. The uniform concentration of initial active centers is directly proportional to the rate of initiation (wi) and inversely proportional to the concentration of inhibitor dissolved in the rubber. The probability of chemical rupture of the hydrocarbon chains increases with increase of wi. 5. An increase of the rate of initiation or decrease of the concentration of inhibitor leads to an increase of the probability of oxidative rupture of the hydrocarbon chains. There is an increase of wi when the temperature is increased, when oxidation catalysts are added, or when the hydrocarbon chain is subjected to mechanical stresses. 6. Repeated stretching or plasticization leads to a decrease of the activation barrier of the initiation reaction, since the mechanical forces conteract the forces of chemical combination. Owing to the relaxation character of deformation, an increase of severity of the conditions of stressing causes an increase of wi. 7. Both the mechanically activated chemical reaction and the direct action of mechanical stresses can lead to rupture of test-specimens. In the case of fatigue, the probability of purely mechanical ruptures is small; during plasticization it is much larger. 8. With an increase of intensity of the mechanical reactions, and a large decrease of the activating energy of initiation, there is a simultaneous abrupt decrease of the pre-exponential factor. The decrease of Ea is functionally related to the decrease of ln A. 9. The decrease of the pre-exponential factor when mechanical stresses are applied is evidently due to a decrease of mobility of the stressed chains. The total number of contacts decreases, while the proportion of effective contacts increases.
Crystallization in Natural Rubber. III. Filled Compounds
Authors: Gent A. N. 
Published: February 2011

Abstract
Measurements are described of the changes of volume accompanying crystallization in filled vulcanized natural rubber, and of the corresponding relaxation of stress in extended test-pieces. The observed changes in the rate of crystallization and relaxation of stress are attributed to the reduction in mobility of the rubber molecules in the neighborhood of foreign particles and to the effective higher orientation of some elements of the rubber matrix when the filled vulcanizate is subjected to simple extension.
The Rheological Unit in Raw Elastomers
Authors: Mooney M. , Wolstenholme W. E. 
Published: February 2011

Abstract
Reasons are adduced for suspecting that, in a raw elastomer subjected to continuous shear, there exist groups of molecules which are held together by entanglement or by thixotropic attachments and move and rotate essentially as elastic solid bodies. Such coherent molecular groups are called rheological units. If an elastomer in continuous shear consists essentially of closely-packed rheological units, such units, rolling on each other, will transfer a rubber-soluble dye across the shear planes as the ink rollers transfer ink in a printing press. This predicted phenomenon has been observed with a Mooney viscometer fitted with a smooth rotor, the face of which is covered with a thin film of dried cement containing a dye in high concentration. From the velocity of the color front, a rough value can be computed for the mean diameter of the rheological units. The diameters for a series of different elastomers lie in the range from 1 to 35 microns.
Effect of Molecular Interaction on the Light Scattering of Rubber Solutions
Authors: Gul V. E. , Klitenik G. S. 
Published: February 2011

Abstract
1. The molecular light scattering of rubber solutions which differ in the polarity of the dissolved high polymer and the polarity of the solvent was investigated. 2. The relation of the angular coefficient of the concentration curves of light scattering to molecular interaction and other factors is discussed theoretically. 3. A relation is proposed which may simplify the procedure of experimentally characterizing polymers by means of the numerical mean and average molecular weights. 4. A method of determining the specific cohesion energy of high polymers according to the data of molecular light scattering in their solutions is offered.
Breakage of Rubber-Filler Linkages and Energy Dissipation in Stressed Rubber
Authors: Blanchard A. F. 
Published: February 2011

Abstract
The marked softening of reinforced rubber by applied stress can be interpreted in terms of a range of strengths of secondary linkages formed by rubber-filler attachments, and this can be described by one common distribution parameter K for several grades and types of filler in natural rubber, and also for at least one type of carbon black in Krylene (GR-S) synthetic rubber. Linkages of this type are of little significance in reinforcement, judged by tensile strength or abrasion resistance. The fact that the filler particle diameter had no influence in these experiments on the energy dissipated in breaking secondary linkages, or their number as reflected by their stiffening action, may be considered a serious objection to the presumption that specific surface or interfacial area determines linkage formation in rubber and, hence (supposedly), the reinforcement. There is evidence of primary (strong) linkages introduced by carbon blacks, and these are likely to have a more important role in determin- ing the breaking, tearing, and abrasion of rubber.
Vulcanizing Variability of Natural Rubber in Pure-Gum and Carbon Black Compounds
Authors: Baker H. C. 
Published: February 2011

Abstract
The history of the ACS 1 compound and its use by natural-rubber producers to assess the variability of plantation sheet and crepe is described. Using modulus at a fixed cure as a criterion of vulcanizing properties, the large variation found in the ACS 1 compound is greatly reduced by the addition of carbon black, but there is good correlation between moduli in the presence and in the absence of black. Detailed results of tests for a range of properties are presented for Red, Yellow, and Blue technically classified rubber in compounds loaded with MPC, HAF, and SRF blacks, and with different accelerators. Some of these properties show a wider range of variation than modulus, and they also indicate that technical classification based on modulus in the ACS 1 compound is justified by the behavior of the black-loaded compounds, both in regard to the level of vulcanizate properties, curing times, and scorch characteristics.
Free-Radical Activity of Reinforcing Rubber Fillers
Authors: Garten V. A. 
Published: February 2011

Abstract
In our studies of the mechanism of rubber reinforcement, we were led to assume that primary valency bonds are likely to form between an “active” filler and the rubber-matrix via free-radical intermediates. The hypothesis was based on the following considerations. (1) Although a strong school of thought still maintains that the strength of bonding depends mainly on van der Waals forces, and therefore on particle size, a number of individual observations suggest the presence of “reactive sites” and formation of strong bonds of a chemical nature between filler and rubber. Foremost among these is the phenomenon that the incorporation of active pigments such as carbon blacks, silicas and the like into rubber results in the insolubilization of a part of the rubber. This part is conveniently called “bound rubber” or “carbon-gel”. (2) Farmer and his school have shown that the vulcanization process is based on a free-radical mechanism, wherein a number of the rubber double-bonds and α-methylene groups, sulfur and accelerator are involved, resulting in the formation of three-dimensional giant networks. The mechanism of mastication is also known to consist of the production of free radicals in the presence of suitable ‘radical acceptors’, such as oxygen. (3) There are some common features in both reinforcement and vulcanization, such as crystallization effects. (4) Little or no reinforcing action of otherwise active pigments is observed with saturated polymers, for example, polyisobutylene.
A Simple Objective Method for Estimating Low Concentrations of Ozone in Air
Authors: Beatty J. R. , Juve A. E. 
Published: February 2011

Abstract
A simple, accurate, and objective method for the estimation of ozone concentrations in air has been developed. It is based on the well known reaction of ozone on rubber subjected to strain, namely, the formation of cracks. The differential creep of a natural rubber thread, one-half of which is subjected to the ozone-containing atmosphere, the other half protected from ozone, is a sensitive measure of the severity of ozone attack or cracking. This differential creep or deflection is essentially linear with time at a given ozone concentration, and the rate of deflection is directly proportional to the ozone concentration. The variables of specimen, machine, temperature, thread elongation, humidity, and sunlight were investigated. The instrument, the B. F. Goodrich Ozonometer, is a small, self-contained unit, which may be operated in the horizontal or vertical position. Two areas of usefulness for this method and machine exist. 1. Tests for ozone concentration in locations inaccessible to ordinary chemical methods by virtue of the equipment and services required. 2. Comparisons of the resistance of rubber compounds to ozone attack under conditions of controlled ozone concentration.
Electron Microscopic Study of the Locus of Latex Reaction
Authors: Crampsey Edward , Gordon Manfred , Sharpe John W. 
Published: February 2011

Abstract
The outstanding example of the study of reaction loci in an emulsion system is Harkins's work in the field of emulsion polymerization. A simpler case presents itself for study when chemical reactions are carried out with preformed polymer emulsions (latexes), as in the hydrochlorination of polyisoprene latex. Here the reaction consists in the progressive conversion of the individual unsaturated isoprene units to their hydrochlorinated form: (see PDF for diagram) the polymer particles preserving their identity throughout the reaction. The hydrochloric acid arrives at the site of reaction by a series of diffusion processes from the vapor phase and through the continuous aqueous phase. In principle there are still two loci at which the isoprene units may react with this reagent: in the bulk of the particle and at (or near) the interphase between the aqueous acid and the polymer particle. We were led by kinetic experiments to conclude that the two loci do react at different rates and by different mechanisms, and it is the purpose of this report to provide quantitative evidence for this conclusion. At the same time we wish to put on record some observations connected with the electron microscopic technique used in the investigation.
Water-Soluble Acids of the Latex of Hevea Brasiliensis
Authors: Bevilacqua E. M. 
Published: February 2011

Abstract
Malic, citric, and succinic acids have been identified as components of the serum of Hevea brasiliensis latex preserved with ammonia. It has been confirmed that the plant acids are present in low concentrations in fresh latex but form a large fraction of the water-soluble serum solids.
The Role of Oxygen in the Vulcanization of Natural Rubber
Authors: Kuzminskii˘ A. S. , Cheetkova V. F. 
Published: February 2011

Abstract
A three-dimensional structure is formed during the vulcanization of rubber. The complex processes of formation, rupture, and regrouping of bonds during vulcanization lead finally to union of the long chain molecules into a compact network. The density of the network formed during vulcanization and the distribution and degree of sulfide formation by the bonds govern to a large degree the work-capacity of vulcanizates. Structure formation in vulcanizates is manifest by the change of their tensile strength, elasticity, swelling, and solubility. During the vulcanization of natural rubber, an optimum is observed in the change of tensile strength and other technically important properties of the material. The decrease of tensile strength of vulcanizates by overvulcanization is usually ascribed to the oxidative destruction of the molecular chains of the rubber. The strong influence which has been observed of oxygen on the tensile strength of natural rubber and its vulcanizates is the basic argument in favor of oxidative destruction. This influence, however, only appears when the rubber is in direct contact with oxygen or air. When, in the rubber industry, vulcanization is carried out in presses, the surface of the rubber mixture is isolated from atmospheric oxygen, and, consequently, destruction in this case can be caused only by the oxygen dissolved in the rubber mixture.