bluuebunny/crossref_metadata_2025_split huggingface dataset:
Absence of Free Radical Cracking of Stressed Rubber
Authors: Layer Robert W. 
Published: February 2011

Abstract
Crabtree has reported that free radicals formed on ultraviolet irradiation of certain organic compounds caused cracking of stressed rubber in the same manner as ozone. Although the types of free radicals used were mentioned, no comment was made concerning the amount of material used, the time of irradiation, the light source, nor the type of rubber used. In fact, experimental details were in general missing. Since this work is now generally being quoted, work was undertaken to determine if the reported free radical cracking of rubber actually occurred in the strict absence of oxygen, and if so, if it occurred under conditions mild enough to be considered important in the degradation of rubber materials. Initially diacetyl, which is well known to give acetyl radicals on ultraviolet irradiation, was used as a radical source. Samples of diacetyl weighing from 0.001 to 0.15 g were sealed in nitrogen-filled bulbed capillary tubes. The bulb and a bent loop vulcanized black natural rubber sample (NR 100, ZnO 5, stearic acid 2, HAP black 50, MBT 1, and S 3 parts vulcanized at 284° F for 60 minutes), 1 cm by 3 cm and 2 mm thick were placed in a 2-liter Pyrex flask. The flask was evacuated to 0.5 mm and filled with lamp grade nitrogen. This process was repeated four more times. The bulb was now broken by shaking the flask, and the flask was irradiated with a Hanovia SC ultraviolet lamp—type 16200—at a distance of 20 cm for 16 hours. The samples were examined under 27 power magnification and found to contain no cracks. Neoprene and SBR black vulcanizates, when exposed to similar treatment, showed no cracks. When compressed air was used instead of the nitrogen, ozone cracking was found to take place. As would be expected, air and diacetyl gave cracks much sooner than air alone. Other possible radical sources were tried but none caused cracking of the rubber sample on ultraviolet irradiation. These materials were di-tert-butyl peroxide, di-n-butyl disulfide, and butyl nitrite.
The Status of the Theory of Bond Strength in Multiply Articles
Authors: Slonimskiĭ G. L. 
Published: February 2011

Abstract
1. Ply separation of multiply specimens and articles, operating under conditions of repeated deformation, is a result of fatigue of the boundary layer. 2. The development of the process of fatigue is determined by the structure and composition of the fatigued material, and also by the pattern of action. 3. The difference of fatigue of the boundary layer from the fatigue of uniform masses of material is governed by their difference in composition and structure, and also by the difference in the patterns of deformations of the boundary layer and of the uniform materials. 4. The formulation, technological and physical chemical factors, which influence each other mutually, determine the structure and compositions of the boundary layer which is eventually formed in the process of contacting the surfaces and vulcanization. 5. The pattern of action of the mechanical forces upon the boundary layer is determined by the applied external forces or deformations, by the construction of the multiply specimen or article and by the ratio of the elastic characteristics of the material (Young's modulus and Poisson's coefficient). 6. The formation of principles of a theory of bond strength between the elements of multiply articles is possible only by ascertaining the mechanism of fatigue of the boundary layer. For this we require the investigation of the viscoelastic properties of the raw stocks, of the phenomena which take place at surfaces of uniform raw stocks and of pliedup raw stocks, and of the process of vulcanization in the boundary layer. All these questions must be investigated as a complex, i.e., with consideration of the internal bonds existing between the formulation, technological and physical chemical factors. In addition it is necessary to analyze the influence of the construction and the elastic properties of the materials upon the character of the stresses, which arise in the joint zone. 7. A further major task in the theory of bond strength is the theoretical consideration of the nature of the tackiness of raw stocks and of the mechanism of the action of bonding agents.
Derivatives of 2-Mercaptobenzothiazole as Accelerators
Authors: Feldshteĭn M. S. , Eĭtingon I. I. , Dogadkin B. A. 
Published: February 2011

Abstract
The wide use in industry of new types of synthetic rubbers calls for the creation of a variety of vulcanization systems of specific action. The quest for such vulcanization systems and, in particular, for vulcanization accelerators with given properties is of course made more difficult by the fact that up to the present time no one has cleared up the question of the influence of the chemical structure of the accelerators upon their vulcanizing activity. As a result of this the provision of experimental data revealing the connection between the chemical structure and the action of vulcanization accelerators is of immediate theoretical and practical value.
The Interaction of Tetramethylthiuram Disulfide with Rubber and with Compounds Containing a Labile Hydrogen Atom
Authors: Dogadkin B. A. , Shershnev V. A. 
Published: February 2011

Abstract
In the interaction of TMTD with rubber, sulfur and nitrogen from the TMTD add to the rubber, a maximum being exhibited on the rate curve for sulfur addition. At the same time dimethyldithiocarbamic acid is formed which, in mixtures containing zinc oxide, becomes bound in the form of Zn-DDC but which decomposes to carbon disulfide and dimethylamine in mixtures containing magnesium and calcium oxides and in the absence of metallic oxides. In the absence of oxides or in the presence of CaO or MgO a less dense three dimensional network is formed and reversion takes place which is accelerated by carbon disulfide and dimethylamine. The degree of crosslinking increases with increase in content of 1,4 structural units while the amount of combined sulfur and the rate of accumulation of zinc dithiocarbamate diminish. Dithiocarbamic acid also forms in the interaction of TMTD with geraniol and isopropylbenzene. The thermal decomposition of TMTD to thiuram monosulfide, sulfur, tetramethylthiourea and carbon disulfide takes place in the absence of compounds with a labile hydrogen atom. The reaction proceeds through the stage of rupture of the S—S and C—;S bonds of TMTD to form free radicals. The radical mechanism of the reaction is confirmed by electronic paramagnetic resonance specta.
Stress Relaxation during the Thermal Oxidation of Vulcanized Natural Rubber
Authors: Dunn J. R. , Scanlan J. , Watson W. F. 
Published: February 2011

Abstract
The photoinitiated oxidative aging of peroxide vulcanized natural rubber (which contains only carbon-carbon cross-links) was found by stress relaxation measurements to be autocatalytic and to be sensitive to the presence of free radical retarders and catalysts. Similar behavior would be expected in thermal aging. However, earlier work in these laboratories indicated that the thermal aging of peroxide vulcanizates was not autocatalytic. Because of this discrepancy the stress relaxation of peroxide vulcanizates at elevated temperatures has now been reinvestigated and the study has been extended to include also the aging of the other types of networks which are produced on vulcanization by tetramethylthiuram disulfide in the absence of sulfur, by sulfenamide-sulfur, and by sulfur alone.
Influence of Accelerator Residues on Age Resistance of Vulcanizates
Authors: Ossefort Z. T. 
Published: February 2011

Abstract
It has been shown that the age resistance of elastomeric vulcanizates is influenced to a very marked degree by residues formed in situ in the vulcanizate during the curing process. By a dual process of removal of these residues and incorporation of selected ingredients subsequent to vulcanization, it has been shown that age resistance (as measured by accelerated oven-aging tests at 212° F) in rubbers cured by sulfur and/or sulfur bearing accelerators, is a prime function of these residues and nearly independent of the stability of the network structure. An extremely active inhibitor is formed in situ during vulcanization of SBR and natural rubber using thiuram accelerators. This inhibitor can be used to “reinhibit” acetone-extracted accelerator-cured rubber. When added to sulfur/accelerator, peroxide, or radiation-cured vulcanizates, it improves their age resistance, but only in the case of the sulfur/accelerator cured rubber is this improvement better than with conventional inhibitors. This leads to the conclusion that the efficiency with which an inhibitor protects a vulcanizate varies widely, and conversely it appears that certain types of network structures are more readily protected or that certain inhibitors can function more efficiently in the protection of certain structures than others. In the case of natural rubber cured with TMTD (zinc oxide present), the bulk of the accelerator residue is ZnDMDC, and this residue has been shown to function as a very efficient antioxidant when incorporated into acetone-extracted, accelerator-cured vulcanizate. It is no more effective than conventional inhibitors, however, when incorporated into an acetone-extracted, sulfur/accelerator-cured vulcanizate. Finally, it has been shown that acetone extraction of the various vulcanizates may lead to improvement or worsening of their age resistance, depending upon the nature of the residues resulting from the curing process.
Important Stability Factors for Styrene-Butadiene Rubber
Authors: Hunter B. A. , Nawakowski A. C. , Barnhart R. R. , Campbell E. M. , Hansen E. B. 
Published: February 2011

Abstract
(1) Styrene-butadiene rubber (SBR) is very susceptible to oxidative degradation unless an effective stabilizing agent is incorporated in the polymer during manufacture. (2) Degradation of SBR appears as discoloration or resinification during drying of the polymer or during storage. Changes in the polymer may appear as variation in Mooney viscosity or as an increase in gel content. (3) Deterioration of inadequately stabilized SBR may also show up during processing operations when the polymer is subjected to heat—as in the Banbury or on a hot mill. (4) Deterioration of SBR polymer will appear as degraded physical properties in the cured vulcanizate. (5) The rubber goods manufacturer will benefit from the use of a really effective SBR stabilizer incorporated in the polymer during manufacture or by adding additional stabilizer to provide more protection against heat degradation in his operations. (6) Tris(nonylated aryl) phosphite exhibits unusual effectiveness as a stabilizer for SBR. (7) The presently widely used method of salt-acid coagulation of SBR polymer leaves room for improvement as far as polymer stability is concerned. (8) The more effective SBR stabilizers exhibit benefits in the aging of SBR vulcanizates.
The Sorption of Antioxidant from Solution
Authors: Novikova E. N. 
Published: February 2011

Abstract
The sorption of amines, hydroxy amines, and naphthols from water and ethyl alcohol by synthetic rubbers was studied with the help of an interferometer and a SF-4 spectrophotometer. It was shown that: 1. SBR (SKS-30) sorbs a large amount of 1-naphthylamine, less of the 1- and 2-naphthols and m-toluidine and m-hydroxydiphenylamine to an insignificant degree. 2. The degree of sorption of 1- and 2-naphthols from water is inversely proportional to their dipole moments and correlates with their activity as antioxidants. 3. The polar rubber (SKN-40) absorbs from ethyl alcohol the amines the best, the hydroxy amines poorly, and an insignificant amount of 2-naphthol. 4. The amines in a decreasing magnitude of sorption on SKN-40 from alcohol fall in a series (phenyl-2-naphtholamine &gt; 2-naphthylamine &gt; diphenylamine) which correlates with their activity as antioxidants. 5. The electronegative OH group, sticking out of the body of the molecule, exerts an influence on the degree of sorption of m-hydroxyphenyl-2-naphthylamine, m-hydroxydiphenylamine and naphthol from polar solvents.
Factors Affecting Bond Strength between the Elements of Tires
Authors: Buĭko G. N. , Arenzon N. M. , Tumanova A. I. , Zinchenko N. P. , Pruzhanskaya N. A. , Pakomova E. A. , Kolomytseva A. I. , Bugrova E. G. 
Published: February 2011

Abstract
1. Ply separation of tires is one of the essential factors reducing their mileage, particularly under difficult service conditions. Enhancement of the dynamic bond strength between elements of the tires is a most important line of study for increasing the mileage of tires based on synthetic rubber. 2. An analysis of defects in tires failing as a result of separation shows that for a given level of technical proficiency in handling synthetic rubber the adhesion type of separation between pliedup compounds or between rubber and cord (of viscose filament) is predominant. This form of failure is particularly characteristic of tires with vulcanizates based on butadiene/styrene rubber in all the main parts. 3. In investigations concerning separation phenomena in tires, decisive importance attaches to methods of determination of bond strength under conditions of dynamic loading of pliedup vulcanizates and rubber cord systems. We still do not have methods which could be regarded as fully satisfying the requirements proposed. However a series of methods have been provided which make it possible to assess, with an accuracy suitable for practical purposes, the effect of this or that factor upon the bond strength and to show the advantages and inadequacies of pliedup systems from the point of view of the operation of tires under actual service conditions. 4. The experimental results obtained show that the dynamic bond strength in pliedup systems, as also the endurance of the tires in relation to separation resistance, is determined by a complex body of physico-chemical and technological factors, by the construction of the articles, and also by the pattern of loading under repeated deformations. The general theoretical ideas developed in articles by some investigators, that the highest bond strength is to be achieved where full adhesion of the raw pliedup stocks takes place, as shown by the disappearance of boundaries between them, and that in all cases the factors which enhance the flowability of the stock enhance also the bond strength between them, were not confirmed experimentally.
The Catalytic Polymerization of Isoprene with Butyllithium
Authors: Korotkov A. S. , Chesnokova N. N. , Truchmanova L. B. 
Published: February 2011

Abstract
1. The kinetics for the polymerization of isoprene with butyllithium in a solution of saturated hydrocarbons were determined. 2. The reaction has the mechanism of a chain catalytic reaction, in which active centers appear that are involved complexes formed from metallorganic compounds and monomer-polymer molecules. 3. Deactivation of growing chains takes place as a result of the reaction of active centers with each other or with metallorganic compounds. With this there are formed new metallorganic compounds of high molecular weight capable of becoming new polymerization centers. 4. The polymer possesses a narrow range of molecular fractions, closely approximating the Gaussion distribution, but the value of the average molecular weight of the polymer after completion of polymerization is inversely proportional to the catalyst concentration. 5. The polymerization temperature, and also the concentrations of the monomer and catalyst, do not affect the microstructure of the polymer (content of 1,2 and 3,4 isoprene units).
The Copolymerization of Isoprene and 1,3-Butadiene by Butyllithium
Authors: Rakova G. V. , Korotkov A. A. 
Published: February 2011

Abstract
Up to now catalytic copolymerization with alkali catalysts has hardly been studied. Only a few papers have been published which give quantitative data. Judging by the values of the copolymerization constants, monomers differ very considerably in their reactivities. Monomers in which the double bond of the vinyl group is conjugated with the multiple bond of a nitrile or a carboxyl group have the greatest activity. The copolymerization of diene hydrocarbons under the action of basic catalysts has not been investigated as yet. It is known that in free radical (emulsion) polymerization these hydrocarbons have relatively similar activities. It seemed interesting to establish the relative reactivity of the diene hydrocarbons, isoprene and 1,3-butadiene, which differ by only a methyl group, in alkali-catalyzed copolymerization. Labeled atoms were used for determining the composition of the copolymers. For this we synthesized isoprene containing radioactive carbon, C14 (from acetylene-C14, prepared from BaC14O3) by a modification of Favorskii˘'s method. Copolymerization and separate polymerizations of isoprene and 1,3-butadiene were carried out in hexane solution with butyllithium at 50°, with a total monomer concentration of 2 moles/liter and a catalyst concentration of 0.0025 mole/liter. Butyllithium was synthesized by the known method. The butyllithium solution was analyzed by the usual method with a double titration. Thoroughly purified and dried monomers and solvent were used for the polymerization. All operations of measuring out the products into the reaction ampules were carried out in a current of dry nitrogen and in a vacuum apparatus having a distributing comb (manifold). The reaction ampules consisted of two sections, separated by a wall and connected with a graduate tube. The solvent and monomers were placed in one section and the catalyst, a solution of butyllithium in hexane, in the other.
Isoprene Polymerization by Organometallic Compounds. II
Authors: Tobolsky Arthur V. , Rogers Charles E. 
Published: February 2011

Abstract
From the above results it would certainly appear that the ionic character of the growing ion pair (polymer−M+) is a very important factor in governing the structure of isoprene homopolymers. Another factor which may be sufficient or necessary for the formation of the unique cis-1,4-eonfiguration is the presence of an orienting surface or complex. It is well known that organolithium compounds are associated in hydrocarbon media, whereas they are probably monomolecularly dispersed in ethers and amines. It is apparent, then, that in hydrocarbon solutions the carbon-lithium chain end may be associated with other carbon-lithium pairs from unreacted initiator molecules or even with other chain ends or, in some cases, it may be associated with the lithium atoms on the surface of lithium particles. The fact that greater than 90 per cent cis-1,4-structure is obtained in hydrocarbons by use of either an apparently clear solution of filtered n-butyllithium or a heterogeneous system of lithium dispersion suggests that the massive surface of the lithium particle is not a necessary factor for the stereospecificity of the reaction. Whether we should consider the butyllithium or the lithium-initiated polymerizations as homogeneous solution reactions or heterogeneous surface reactions depends on the definition of a surface, since an associated complex or micelle may also conceivably serve as an orienting specie in the same way as a surface does. We emphasize this since so many stereospecific polymerizations such as the Ziegler system and the Phillips system appear to occur under heterogeneous conditions, presumably on an orienting surface of rather gross dimensions.
The Mechanism of Isoprene Polymerization Initiated with Ticl4-Trialkylaluminum. Molecular Weight Distribution of the Polymer
Authors: Bresler S. E. , Mosevitskiĭ M. I. , Poddubnyĭ I. Ya , Chesnokova N. N. 
Published: February 2011

Abstract
The molecular weight distribution of polyisoprene obtained by polymerization under the influence of complexes of titanium tetrachloride with tri-isobutylaluminum has been found within broad limits to be independent of the degree of conversion. On the basis of this finding an hypothesis is offered to explain the limitation of polymer chain length according to which chain scission is assumed to increase with the size of the chain.
Kinetics of Isoprenepolymerization Initiated with TiCl4—Trialkyl Aluminum
Authors: Bresler S. E. , Mosevitskiĭ M. I. 
Published: February 2011

Abstract
For the study of the mechanism of polymerization by means of complexes of aluminum organic compounds with titanium chlorides, data on the kinetics of polymerization is of great interest. Up to the present time, the rate of polymerization of propylene has been studied but the interpretation of the kinetic data is difficult because the polymer, which is practically insoluble in the reaction medium, entraps the catalyst resulting in a rate of reaction which is dependent on the diffusion of monomer through the polymer to the active sites. In this work the polymerization of isoprene, which yields polymers soluble in the monomer, in saturated hydrocarbons and in benzene, was studied. The rate of the polymerization reaction was measured by the thermal effect in a calorimeter consisting of a 3.5 1. Dewar flask, with a lid, immersed in a thermostated air bath maintained at approximately the temperature of the reaction. Low viscosity spindle oil, heated to the temperature of the reaction (about 32°), served as the calorimeter fluid. The ampoule holder extended outside of the calorimeter and was connected to a shaking apparatus. The ampoule was divided by a thin partition into two sections each holding 45–50 cc. Into one section previously purified monomers and solvent were distilled. The other section was filled with catalyst components from a Shlenk container. The change in temperature of the calorimeter was determined with a Beckman thermometer with an accuracy of 0.01 °. When the temperature of the calorimeter containing the ampoule remained constant to within 0.01–0.02° for 30–40 minutes, the shaking apparatus was connected and the partition was broken with a striker. Intensive shaking was continued during the entire experiment resulting in mixing of the reaction mixture and of the calorimeter fluid. The rate of reaction was determined by the rate of heat evolution ; in other words, by the temperature rise in the calorimeter. For a rise of 0.1–0.5° the reaction conditions remained practically isothermal. This rise permits the kinetics of the reaction to be observed with sufficient accuracy. Adiabaticity of the calorimeter and the effect of mechanical heat were controlled in separate experiments.
The Diffusion Theory of Adhesion
Authors: Voyutskiĭ S. S. 
Published: February 2011

Abstract
A theory of adhesion of polymers to each other is suggested ; according to it adhesion of dissimilar polymers as well as auto-adhesion is explained by the diffusion of chainlike molecules segmentally or otherwise. Starting with this theory, the effects of various factors on the adhesion of polymers to each other are discussed. The factors considered are: duration of contact between adhesive and substrate, temperature, molecular weight of adhesive, molecular shape and polarity.