bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress-Strain Isotherm for Polymer Networks
Authors: Ciferri A. , Flory P. J. 
Published: February 2011

Abstract
According to the molecular theory of rubber elasticity, the stress τ is related to the relative length a in simple extension according to τ=kT(ν/V)〈α〉2(α−1/α2), where (ν/V)〈α〉2 is a parameter of the network structure. Improved agreement with experiment has been claimed through use of the relation τ=(2C1+2C2/α)(α−1/α2) which contains the additional parameter C2. In order to explore factors affecting this theoretically inexplicable term, stress-elongation measurements were performed on networks prepared from natural rubber, Butyl rubber, poly-(dimethylsiloxane), poly-(ethyl acrylate), and poly(methyl methacrylate) under a wide range of experimental conditions. Results may be summarized as follows: (1) the C2 term offers improved agreement over the extension phase of an elongation cycle, but not for the subsequent retraction phase; (2) apparent values of C2 (determined on extension) vary widely from one polymer to another, increasing with hysteresis and with proximity to the glass transition temperature; (3) they are insensitive to the degree of crosslinking; (4) C2 is markedly reduced by permanently swelling the network with a diluent, or by swelling and deswelling the sample at each tension ; (5) incorporation of diluent prior to establishing a network by crosslinking with gamma radiation likewise lowers C2, the value characteristic of the unswollen polymer being restored upon removal of the diluent. The results demonstrate that the controversial C2 term arises from the difficulty of attaining elastic equilibrium; under ideal experimental conditions the value of this parameter becomes negligible. An alleged limitation of the theory of rubber elasticity is thus refuted.
Determination of Relative Damping at Various Prestresses
Authors: Kempermann Th , Clamroth R. 
Published: February 2011

Abstract
After a short review of the history of the development of the concept of damping, the definitions—one in words, the other in the form of an equation—given in DIN 53513 are discussed, and their usefulness for measurements at various values of prestress is investigated. It is evident that the mathematical definition given in the Standard applies only in the special case when prestress and alternating stress are equal. For the complete range of prestress, the phase angle δ or some simple function of δ, such as the loss factor, tan δ, should be measured. If it is desired not to relinquish the percentage statement of the energy loss, then a new definition for the relative damping is proposed which is independent of the prestress, just as is tan δ. The dependence upon the prestress of the damping values under discussion is demonstrated in an experimental section, for various types of elastomers.
Reinforcement of Rubber by Fillers Tear Resistance
Authors: Mullins L. 
Published: February 2011

Abstract
The results of experimental studies on 1) the effect of reinforcing fillers on tear strength and on the roughness of the resultant torn surfaces, 2) the relative adhesion of rubber to fillers and 3) the effect of hysteresis on tear strength are critically examined. They show that the maximum reinforcing effect of fillers is only exhibited if sufficient time is allowed for their strengthening role to develop during tearing, and that under these conditions the tip of the growing tear is broader and the torn surface rougher. They also confirm that the surface or immediate environment of filler particles provide a region of relative weakness, and that failure takes place at the interfaces ahead of the advancing tear, the rupture path wandering from one internal flaw to another. In addition they show that the more reinforcing fillers adhere more strongly to the rubber. Further, for gum vulcanizates, it appears that there is a simple relationship between tearing energy and hysteresis and that rubbers with higher hysteresis possess higher tear strength. A synthesis of the results of these three investigations provides a qualitative picture of the role of reinforcing fillers in increasing the strength of rubbers. It appears that a process giving rise to sufficiently rapid relaxation of stress ahead of the tip of a growing tear can in principle result in broadening of the tip of the tear and lead to increased strength. It is considered that this type of process plays an important and sometimes dominant role in the reinforcement of rubbers by fillers or by crystallization, and provides a consistent and coherent mechanism which indicates a source of the roughening of rupture surfaces of filler reinforced rubbers and of their possible branching and knotty tearing.
Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I
Authors: Scheele Walter , Hillmer Karl-Heinz 
Published: February 2011

Abstract
As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.
Investigation of Radical and Polar Mechanisms in Vulcanization Reactions
Authors: Shelton J. Reid , McDonel E. T. 
Published: February 2011

Abstract
The results obtained with free radical traps in a variety of curing systems for SBR rubber give evidence for both polar and free radical mechanisms. There is apparently no one mechanism even for sulfur vulcanization and the relative free radical or polar character of the crosslinking reaction varies over a broad range including situations in which both types occur in the same formulation. This may be due to competing reactions which function independently, or it may be the result of a combination of polar and free radical reactions in a single complex mechanism. For example, certain accelerators may initiate the reaction by dissociation to free radicals which attack the S8 molecule and form polysulfides which then decompose by a polar mechanism to initiate the propagation stage of the reaction. Based on the information obtained in this study and other supporting evidences, it is possible to group the familiar curing systems according to the apparent polar or free radical character of the reaction as observed in SBR. It is interesting to note that the accelerated sulfur curing systems which most closely approximate a polar mechanism either involve an amine (DPG) or a compound which is either present as a zinc salt (dithiocarbamate) or can easily form zinc salts at the curing temperature (thiuram disulfide and mercaptobenzothiazole systems). All curing systems studied which include free sulfur appear to involve a polar mechanism.
Synthesis of Polysulfides Containing Polar Linkages
Authors: Iwakura Y. , Hori T. , Suzuki K. , Wakasugi T. , Kobayashi G. 
Published: February 2011

Abstract
Polysulfide polymers are usually prepared from dihalogen compounds and sodium polysulfide and are used as synthetic rubbers. Also, polyamides or polyurethanes, such as Nylon 66, Perlon U (Igamid U) or Vulcollan, are used because of certain good properties. Therefore, if new polysulfide polymers could be produced when sodium polysulfide reacts with a dihalide having a polar linkage such as an amide group, we might expect excellent properties in the new materials because they might contain urethane, urea or amide linkages. We now show that dichloro compounds, which contain urethane linkages, can be prepared by the reaction between a chlorohydrin (ethylene chlorohydrin or 4-chlorobutanol-l) and polymethylene diisocyanate (where n=3, 4, 6 and 8 in (CH2)n).
Cis-Trans Isomerization in Natural Polyisoprenes
Authors: Cunneen J. I. 
Published: February 2011

Abstract
The cis and trans isomers of many simple olefins and conjugated polyolefins can be interconverted by the action of heat, light, and various catalysts, and in many such systems the changes in geometric configuration can be readily followed and the isomers separated and identified. Previous attempts to isomerize natural rubber and gutta-percha by treatment with ultraviolet light and various chemicals gave no detectable cis-trans isomerization, and in general configurational changes in unconjugated polyolefins have been unknown until recently when Golub converted the cis-1,4 units in polybutadiene into the corresponding trans units. This isomerization was achieved by irradiation of the cis-polymer with ultraviolet light in the presence of various organic bromides and sulfur compounds, but apparently this method did not isomerize natural rubber. In attempts to retard the rate of crystallization of natural rubber at moderately low temperatures—i.e., −10° to −40° C—by the attachment of side groups which would interfere with the molecular packing, it was observed that very small amounts of thiol acids were remarkably effective. This suggested that structural changes other than simply the attachment of side groups were occurring in the polyisoprene molecule. Recently it was found that thiol acids could interconvert the cis and trans forms of a simple trialkyl ethylene—e.g., 3-methylpent-2-ene—and subsequently, the isomerization of natural rubber and gutta-percha by these reagents was also observed. Following this, natural rubber, gutta-percha, squalene and cis and trans forms of 3-methylpent-2-ene have also been isomerized by treatment with sulfur dioxide and allied compounds; this work, including an investigation of the physical properties of the vulcanizates obtained from some of the isomerized polyisoprenes, is described in the present paper.
The Mutual Solubility of Polymers. V. Mechanochemical Blending
Authors: Slonimskiĭ G. L. , Reztsova E. V. 
Published: February 2011

Abstract
1. In the mixing of two polymers with intermixing of molecules, which, depending on the mutual solubility or insolubility, may lead to homogeneous or to mieroheterogeneous systems, there takes place also a mechanochemical mixing consisting of the formation of graft and block copolymers. 2. The proportion of these processes of mixing is determined by the intensity of and duration of the mechanical action in the process of mixing, and also by the concentration of additives capable of inhibiting the free radicals formed in the mixing. Of particular importance are special stabilizers, antioxidants and other such additives to the raw rubbers, and also oxygen. 3. The anomalies previously observed in the dependences of the mechanical properties of the vulcanized rubbers based on a combination of two mutually insoluble raw rubbers may be reduced by increasing the part played by the mechanochemical mixing. This opens up ways of producing high quality mixtures of mutually insoluble polymers.
A Study of Macroradicals in Processes of Polymerization and Degradation. I
Authors: Bresler S. E. , Kazbekov E. N. , Saminskiĭ E. M. 
Published: February 2011

Abstract
The use of a sensitive electronic paramagentic spectrometer permits one to obtain a number of new quantitative and qualitative data regarding the kinetics of polymerization and behavior of macroradicals with large polymerization depths. In particular, it is shown that in the photopolymerization of methyl methacrylate in a block of considerable number of sequestered macroradicals accumulates in the final stages. On the basis of an investigation of the change of the spectra in the heating of the polymer some assumptions are made concerning the secondary reactions of the radicals and concerning the influence of low-molecular impurities on the velocity of these reactions.
The Mechanism of Radiation Damage to Elastomers. I. Chain Scission and Antirad Action
Authors: Bauman Richard G. , Born John W. 
Published: February 2011

Abstract
The effect of antirads on chain scission as measured by stress relaxation is one of inhibition both in the presence of air and to a lesser extent in its absence. This can be explained by assuming a reactivity of the antirads with RO2⋅ radicals yielding stable products, and a somewhat decreased reactivity with R⋅ radicals. A greater tendency of RO2⋅ radicals to lead to chain scission than R⋅ radicals seems to be indicated.
Factors Influencing the Stability of SBR Latex
Authors: Sliemers F. A. , Bennett Bailey , Stickney P. B. , Heiligmann R. G. , deDecker H. K. J. 
Published: February 2011

Abstract
The theory is proposed as a result of this work that under “static” conditions, latex destabilization proceeds through a time-dependent localized polymer-particle dehydration. This dehydration apparently occurs in two stages. In the initial stage more or less reversible aggregates are formed. This creaming is accompanied by a perceptible increase in viscosity. In the second stage the aggregates are further dehydrated and coalescence occurs. This latter process is irreversible. Evidence is presented to support the argument that the prime requirement for the dehydration and, consequently, for the destabilization of high-stability latex is the presence of a static latex surface in contact with an unsaturated gas phase. Three factors involved here are (1) surface area, (2) surface agitation, and (3) the degree of saturation of the gas phase in contact with the surface. In addition, it is shown that particle growth precedes the destabilization and that stability is influenced by a number of other factors, including (1) temperature, (2) polymer concentration, and (3) polymer-particle size, which contribute, either directly or indirectly, to the dehydration process.
Physical Chemical Factors in Bond Strength in Multiply Vulcanized Articles
Authors: Dogadkin B. A. 
Published: February 2011

Abstract
Bond strength between the components of multiply articles in the vulcanized state depends on many factors which make themselves evident in the various stages of manufacture of the articles as well as under service conditions. In the present paper we shall give a description of the main physical chemical factors which were revealed in the course of experimental work in the physics and chemistry divisions of the Tire Research Institute, mainly in 1951 to 1953.
Determination of Static and Dynamic Bond Strength between Vulcanizates
Authors: Reznikowskiĭ M. M. 
Published: February 2011

Abstract
Methods employed for the determination of bond strength between vulcanizates may be classified as static or dynamic. Each of these groups has its own advantages and shortcomings. One undoubted advantage of the majority of static methods is that the tests are carried out under conditions where the stresses and deformations which determine ply separation may be measured directly. It is at the same time easy to determine the temperature since the specimens undergoing ply separation may be thermostatically conditioned. Nevertheless the practical value of the results obtained in static tests is very limited. In the first place, the character of the stresses governing ply separation in no way reproduces the true picture of the service life of multiply vulcanized rubber articles (in particular, tires), and, secondly, the resistance to ply separation for a single loading, for a number of reasons, may not indicate the endurance of the articles under repeated deformation. In dynamic tests we use the endurance under repeated deformations as a criterion of bond strength, presuming that the dynamic pattern of testing in some way reproduces the pattern of service of the material in the article. Unfortunately, the index of service life of any test specimens depends, in a complex manner which we do not in general understand, not only upon the bond strength between the vulcanizates, but also upon the stresses, deformations and also temperatures developed in the boundary layer. These parameters (stress, deformation and temperature) depend in their turn upon the elastic and relaxation properties of the vulcanizates from which the test specimen is made up. If the testing of the specimens is carried out in a dynamic pattern essentially different from that of service, then the results may be quite contrary to the behavior of the materials in an article. The selection of a rational method of dynamic testing applicable to tire compounds is particularly complicated on account of inadequate knowledge of the dynamic pattern of the operation of the component parts of the tire. Summarizing, we see that in investigations and tests of bond strength between vulcanizates we are obliged to use both static and dynamic methods. The static methods, allowing a quantitative interpretation of the results, must be considered more reliable for investigations in the fields of adhesion and covulcanization, particularly in cases where we are studying the effect of factors which essentially alter the properties (above all, the elastic and hysteresis properties) of pliedup vulcanizates.
Determination of Isoprene Unit Structures in Polyisoprene Rubbers
Authors: Kasatkina N. G. 
Published: February 2011

Abstract
Conditions were selected for simple and rapid determination of the percentage of 1,4, 3,4 and 1,2 units in synthetic isoprene rubbers from the curves of the rate of their oxidation by benzoyl hydroperoxide. The content of 1,4, 3,4 and 1,2 units in synthetic isoprene rubbers was determined by comparing the curves of the rate of their oxidation by benzoyl hydroperoxide with the curves of oxidation of model compounds, i.e. limonene and gutta percha.
The Butyllithium-Initiated Polymerization of 1,3-Butadiene
Authors: Kuntz Irving , Gerber Arthur 
Published: February 2011

Abstract
The organolithium polymerization of isoprene (2-methyl-1,3-butadiene) has been studied in some detail. Hsieh and Tobolsky have reported that the polymer prepared in benzene or heptane had more than 90% cis-1,4-structure. Polyisoprenes prepared in ethers showed a change in stereochemistry to 3,4-, 1,2-, and trans-1,4-microstructures. Other research further studied the sensitivity of polymer stereochemistry to solvent and the specific organometallic initiator. Although it was observed long ago that organolithium compounds cause the polymerization of butadiene, the stereochemistry of the polymer has been reported much less completely. The patent literature contains references in this area, and Russian researchers have studied the butyllithium-initiated polymerization of butadiene in the presence of ethers, oxygen, alcohols, and thio ethers. This communication describes the polymerization of butadiene by butyllithium in n-heptane; it discusses the stereochemistry of the polymer obtained and the effect of catalyst and monomer concentration, polymerization temperature, and the presence of ethers on the details of polymer structure. The results obtained are compared with the reported data for the alkyllithium-initiated polymerization of isoprene.
Complex Formation and Chain Structure in the Polymerization of Divinyl with Butyllithium
Authors: Kropachev V. A. , Dolgoplosk B. A. , Nikolaev N. I. 
Published: February 2011

Abstract
It has been established by a number of studies that the chain structure in the catalytic polymerization of monoolefins and dienes is determined to a large degree by the nature of the catalytic complex, participating in the polymerization process. Also it was shown that the initial catalytic complex bears a direct relationship to each elementary act of the chain growth. The isolation of organolithium compounds in the pure state is associated with great experimental difficulties. Together with the formation of the organometal compounds the possibility of a complex mixture of their oxidation products being formed is not excluded. To elucidate the influence of the indicated oxidation products on the chain structure in the polymerization of butadiene it seemed expedient to investigate the influence of oxygen. As the result of the investigation made by us it was established that in the polymerization of 1,3-butadiene with organolithium compounds the introduction of comparatively small amounts of oxygen into the system leads to a substantial increase in the number of 1,2 units in the polybutadiene at the expense of a reduction in the number of 1,4 units. The addition of either alcohol or phenol exerts a similar influence on the structure of the polymeric chain (Table 1).
Molecular Weight Distribution in Polymers. Polymerization of Isoprene and Butadiene with Metal Organic Compounds
Authors: Bresler S. E. , Korotkov A. A. , Mosevitskiĭ M. I. , Poddubnyĭ I. Ya 
Published: February 2011

Abstract
Problems connected with the calculation and analysis of molecular weight distributions of polymers obtained by catalytic polymerization were examined. An approximate method of calculation was proposed which is unique in its simplicity and which gives good approximations in the majority of cases of practical interest. Experimental data from a study of samples of polybutadiene and polyisoprene prepared by polymerization in solution by means of butyllithium were considered. The low degree of polydispersity for these polymers was noted in particular.
The Crystallization of Modified Cis-Polybutadiene
Authors: Trick G. S. 
Published: February 2011

Abstract
From a sample of polybutadiene of high cis-1,4 content, the microstructure is modified by cis-trans isomerization or by crosslinking. Measurements of rates of crystallization and melting point are made on the modified samples. An increase in irons content or crosslink density markedly decreases the rate of crystallization at a fixed temperature. It is found, however, that this retardation in rate may usually be accounted for by the depressed melting point of the modified samples.
Effect of Redox Systems on Thermal Oxidative Plasticizing of Butadiene-Acrylonitrile Rubber
Authors: Devirts E. Ya , Novikov A. S. 
Published: February 2011

Abstract
1. By using a redox system consisting of iron salts plus dimethylphenyl-paracresol, the rate of breakdown was considerably increased and structure-formation suppressed. This enables thermal oxidative plasticization to be used in industry for butadiene-acrylonitrile rubbers. 2. As the number of nitrile groups in the polymer increases, the rate of breakdown during thermal oxidative plasticization decreases and structure- formation occurs more rapidly. Butadiene-acrylonitrile (82:18) rubber has the greatest rate of breakdown, and the (60:40) copolymer the highest rate of structure-formation. 3. Vulcanizates of stocks based on thermally softened experimental butadiene-acrylonitrile rubbers are slightly inferior as regards strength and elasticity to similar vulcanizates of mechanically softened rubber. Their properties are, however, sufficiently high to enable thermal oxidative plasticization to be applied industrially.