bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Molecular Weight, Shape of the Molecule, and Presence of Polar Groups on the Autohesion of High Polymers. III
Authors: Voyutskiĭ S. S. , Shtarkh B. V. 
Published: February 2011

Abstract
1. It is shown for polyisobutylenes of different molecular weight that increase in the size of the chain molecule retards autohesion, but increases the limiting value to which the work of autohesion tends with increasing contact time. 2. Investigation of the temperature dependence of autohesion of polyisobutylenes showed that the activation energy does not depend on the molecular weight of the polyisobutylene. 3. It is shown for polybutadienes with varying contents of 1,4- and 1,2-structures that autohesion decreases with increase in the number of short side groups in the molecule, which apparently hinder diffusion by purely steric causes. 4. Investigation of the temperature dependence of autohesion of butadienenitrile copolymers with different contents of acrylonitrile in the molecule showed that the activation energy of autohesion increases with increase of polar nitrile groups in the polymer. 5. It is shown for the vulcanization of natural rubber that the formation of a spatial structure results in complete disappearance of autohesion in high polymers. It is shown that the kinetics of changes of autohesion during vulcanization can effectively characterize the structural changes which take place in the polymer during the process.
Theoretical Model for the Elastic Behavior of Filler-Reinforced Vulcanized Rubbers
Authors: Mullins L. , Tobin N. R. 
Published: February 2011

Abstract
One of the more important advances in rubber science during the past twenty years has been the development of quantitative theories describing the elastic properties of pure-gum vulcanized rubbers. As a result it is now possible to account for their equilibrium stress-strain behavior with considerable success. There is, however, no adequate theory to describe the elastic properties of filler-reinforced rubber vulcanizates and the work described herein is an attempt to provide a basis for such a theory. When a reinforcing filler is added to rubber it produces a large increase in the stiffness of the vulcanizate. This increase is reduced and may be substantially destroyed by deformation. Numerous attempts have been made to describe the increase of stiffness resulting from the introduction of fillers and relationships describing the dependence of the modulus on the concentration and particle shape of the filler have been developed. However, these do not take into account the softening which results from previous deformation and thus have limited applicability. Recently Blanchard and Parkinson have attempted to develop empirical relationships to describe the elastic properties in simple extension of reinforced rubber vulcanizates after they have been previously deformed. They started with the appropriate stress-strain relationships from the classical kinetic theory and introduced two curve-fitting parameters to describe stress-strain data obtained in conventional tensile tests on a Goodbrand machine. In this way they were able to fit the course of the stress-strain data obtained after previous extension at extensions less than those previously applied and to describe the dependence of the parameters on previous deformation. Unfortunately, the significance of the parameters is obscure.
Changes of Electrical Resistance of Rubbers Loaded with Carbon Black
Authors: Marshall D. G. 
Published: February 2011

Abstract
Many workers have studied the changes in resistivity that occur on deforming rubbers loaded with carbon black. This paper describes three types of experimental investigation that do not seem to have received detailed study previously, and also a theory that explains the results qualitatively in terms of variations of contact resistances between carbon black particles. Firstly, the changes of resistance of vulcanized natural rubber, Butyl rubber, Neoprene, and Thiokol FA loaded with carbon black have been studied during cyclic deformations. Secondly, the initial increase of resistance during stretching testpieces of vulcanized natural rubber containing several loadings of different carbon blacks has been investigated. Finally, the changes of resistance with time that occur after stretching and releasing samples of electrically conducting rubber have been studied. The ingredients and preparation of the compounds used in experiments discussed in this paper are listed in the Appendix. The testpieces used in the following experiments were approximately 0.7 cm. wide, 0.1 cm. thick, and 7.0 cm. long. Electrical contact was established by means of brass strips bonded by molding into the ends of the samples, so that the direction of current flow was along the length of the pieces, and in the same direction as the extensions.
Lignin as a Compounding Ingredient for Natural Rubber
Authors: Sagajllo I. 
Published: February 2011

Abstract
Important claims have been made in recent years regarding the capacity of lignin to reinforce natural and synthetic rubber. In 1949 Dawson reviewed the literature on the use of lignin in rubber and drew particular attention to the work of Keilen and Pollak who had shown that in certain circumstances lignin could be considered to rival EPC black in its ability to yield strong GR-S vulcanizates with high resistance to tear. Raff and his coworkers subsequently showed that the reinforcement of GR-S by lignin is enhanced if the lignin, before coprecipitation with the latex, is subjected to oxidation; other workers studied the application of lignin to the reinforcement of different elastomers, the influence of coprecipitation conditions on the properties of the product, and the problem of overcoming the delaying effect of lignin on vulcanization of lignin-natural rubber coprecipitates. Keilen and Pollak in their experiments incorporated lignin into rubber by coprecipitation at the latex stage, but they indicated that similar results could be obtained if lignin “in the gelled state” was added to rubber by milling. No reinforcement was observed however when lignin was added to rubber as a dry powder. Lignin is potentially an abundant and cheap material which according to the above claims should extend the range of useful compounds available to rubber manufacturers. The present paper describes work undertaken to gain firsthand knowledge of the technique of coprecipitating lignin with natural rubber from preserved latex, to learn something about the properties of natural rubber compounds prepared from lignin coprecipitates, and to study possible ways of incorporating lignin into rubber by means other than coprecipitation. It also records test results for masterbatches prepared by the Rubber Research Institute of Malaya from fresh latex on a pilot plant scale.
Carboxylic Rubbers from Scrap Vulcanized Rubber
Authors: Green Joseph , Sverdrup E. F. 
Published: February 2011

Abstract
Scrap vulcanized rubber has been used principally for the manufacture of reclaimed rubber, which exhibits properties inherent in the original polymers of the scrap. Little has been found in the literature on the utilization of scrap vulcanized rubber as a low-cost starting material for controlled polymer synthesis. In the present investigation scraps containing natural and Type S synthetic rubbers have been modified to produce chemically different polymers possessing properties not usually associated with the initial elastomers. The authors believe that reactions with vulcanized rubber are not usually the same as reactions with the raw polymers and in this work the physical means of accomplishing the reaction are different. In 1938 Bacon and Farmer reported that when masticated raw natural rubber and maleic anhydride were dissolved in a solvent and the solution was heated in the presence of benzoyl peroxide, the ingredients reacted, yielding a variety of tough, fibrous, or resinous products. When vulcanized natural and Type S synthetic rubber scraps were reclaimed in a Reclaimator (a specially designed extruder type plasticator, made by the U. S. Rubber Reclaiming Co., Inc.) in the presence of a critical concentration of certain activated unsaturated compounds, a reaction occurred between the unsaturated compound and the scrap vulcanized rubber. With maleic anhydride, the resulting product was a carboxylated and replasticized rubber. This elastomer exhibited vulcanizing versatility via the carboxyl groups—i.e., curing with bivalent metallic oxides, diamines, glycols, epoxy resins, and diisocyanates. The polarity imparted by the carboxyl groups and the degree of crosslinking of the polymer appear responsible for its oil resistance, a property not normally present in a tire reclaim. The blocking of the double bonds, either by reaction at the double bond or by steric hindrance, added to the good aging properties anticipated with nonsulfur vulcanizates.
Application of Paper Chromatography to the Identification of Accelerators and Antioxidants
Authors: Zijp J. W. H. 
Published: February 2011

Abstract
Various difficulties in the identification of accelerators and antioxidants in rubber compounds are reviewed. A detailed procedure for the detection of four guanidine derivatives by paper chromatography is mentioned. The identification of diphenyl thiourea and diorthotolyl thiourea is also described. A detailed procedure is given for the paper-chromatographic separation and identification of some mercapto-substituted heterocyclic compounds. The detection of these accelerators in rubber mixes and vulcanizates is also described. A detailed procedure is given for paper Chromatographic separation and identification of dithiocarbamates, which are used as ultra-accelerators in the rubber industry. These dithiocarbamates decompose in acid medium into secondary amines. The salts of these amines are better soluble in water than the dithiocarbamates, and are therefore more suitable for a paper-chromatographic separation. A method for the simultaneous detection of dithiocarbamates and thiuram sulfides is also described. The paper-chromatographic separation and identification of various antioxidants is described. Because only few antioxidants can be separated by paper chromatography after coupling with diazotized arylaminosulfonic acids, it is preferable to separate these compounds, which are generally insoluble in water, by means of acetylated filter paper. The identification of antioxidants using acetylated filter paper is described. A detailed procedure is given for the identification of accelerators and antioxidants in rubber mixes and vulcanizates of unknown composition.
Analytical Methods for Calculating Temperatures inside Rubber Articles during Vulcanization
Authors: Fogel V. O. 
Published: February 2011

Abstract
Heating conditions for the vulcanization of rubber articles have been chosen in a purely experimental way up to the present time. Thus, in one tire plant, research on the question of the most efficient heating conditions for tire vulcanization has consisted of making dozens of experiments on the several variables of heat conductors, and then using the experimental temperature curves for further development. However, such experiments under industrial conditions not only require considerable time and material, but yield results which inevitably deviate from the true heating conditions in many cases. These deviations are due to fluctuations in the steam pressure and water temperature in the course of vulcanization, nonhomogeneity of material in the group of rubber articles being tested, etc. All these sources of error confuse the results of comparative experiments to a large extent, often making it impossible to reach any general conclusions. Undoubtedly the most accurate method of determining the ideal heating conditions for vulcanization is a combination of the calculation and experimental methods. In the vulcanization of rubber articles, as in some other branches of industry, heating conditions can be chosen satisfactorily through a preliminary calculation of the temperatures inside the articles, i.e., by a theoretical projection of the heating conditions, followed by a final experimental verification of the calculated results.
Infrared Spectroscopic Analysis of Elastomers
Authors: Davison W. H. T. , Bates G. R. 
Published: February 2011

Abstract
Infrared absorption spectroscopy is the most generally applicable technique available for the analysis of elastomers and other polymers encountered in the rubber industry. The emphasis of this paper is on the general identification and estimation of a wide range of elastomers, rather than the accurate quantitative analysis of particular copolymers and mixtures. The theoretical basis of spectra, particularly of polymers, is described. The additivity of absorbances is the basis of quantitative analyses, for which the procedures are outlined. Although theoretically some interaction between repeating units is to be expected, most repeating units have the same spectra whether in homopolymers or copolymers. Experimental techniques are described for preparing samples for spectroscopic examination from both uncured and cured materials. The latter, particularly when reinforced with carbon black, often give difficulty since they transmit insufficient energy for direct examination. As an alternative to solution or pyrolysis, a reflecting microscope may be used to increase the amount of energy available for measurement of the spectrum. Spectra of a large number of homopolymers, copolymers, and mixtures are reported from 650 to 3600 cm.−1, mostly in simplified line form. Polymers covered include polydienes, polyvinyl and tsopropenyl compounds (including polyketones and acrylates), polyesters, polyurethans, modified polyethylenes, and silicones. A summary of absorptions characteristic of particular polymer structures is given in the form of a correlation chart. The limitations of the technique are discussed, and probable future developments are suggested, i.e., extension of the spectral range below 650 cm.−1, improved techniques of sample preparation, and combinations of spectroscopy with chemical procedures such as pyrolysis.
Shear Dependence of Viscosity of Natural Rubber Solutions
Authors: Golub Morton A. 
Published: February 2011

Abstract
In an earlier paper viscosity measurements on dilute Alfin polyisoprene solutions at quite low shear rates were reported. It was shown that the limiting slope of the intrinsic viscosity vs. rate of shear plot at low shear rates, (Δ[η]/ΔD)D→0, is proportional to the square of the zero shear intrinsic viscosity [η]02. This relationship suggested the possibility of using the slope of the (Δ[η]/ΔD)D→0 vs. [η]02 plot as a molecular weight-independent parameter expressing the magnitude of the shear dependence of intrinsic viscosity, and thus as a possible means for studying polymer microstructure. It was thought that polymers having different structures would give rise to linear plots of the latter type, but with different slopes. To test this view, it was deemed desirable to extend viscosity measurements to another polyisoprene system, namely, natural rubber. This note describes the results obtained from viscosity measurements on Hevea fractions, and shows the comparative shear effects for both the natural as and the predominantly trans Alfin polyisoprenes.
The Role of Diffusion of Polymer Chains in the Mechanism of Adhesion and Autohesion of Rubbers
Authors: Deryagin B. V. , Zherebkov S. K. , Medvedeva A. M. 
Published: February 2011

Abstract
1. The researches so far published on the autohesion of polymers do not make it possible to isolate the influence of the mechanical properties of rubbers, which determine the true area of contact, from the influence of polymer chain diffusion. 2. Studies of the autohesion of thin films of rubber applied by the drain-off method to quartz threads, in relation to the film thickness and contact time, show that for films less than 3.10−5 cm. thick the adhesion force is small and varies very little with contact time. This proves, on the one hand, that in this instance the contact area is small (which is obvious) and does not increase with time, and on the other hand, that diffusion processes play no part in the autohesion of films of this thickness. 3. The effects which depend on mechanical properties and on the specific interaction (per unit area of true contact) between specimens may be separated if the measured values of adhesion between all possible combinations of pairs of rubbers are compared both with their compatibilities, and with their autohesion. 4. The measurements of the adhesional shearing strength of combinations of different pairs of polymers, carried out for this purpose, showed that the results for Butyl rubber may be interpreted on the assumption that diffusion processes do not play any appreciable role and that the adhesion strength is determined both by the true contact area, which depends on the mechanical properties of the corresponding polymer specimens, and also by the influence of forces associated with the electric double layer. 5. For the other rubbers the results may be interpreted only on the assumption that diffusion processes play a significant part. For similar polarities, T12/T11&gt;1 and for dissimilar polarities, T12/T11&lt;1. 6. General conclusion : autohesion and mutual adhesion of rubbers is determined both by mechanical properties, which determine the true contact area, and by diffusional properties. The latter are by no means always decisive. The electric double layer also probably influences the adhesional shearing strength in some instances. It is even more likely to play a role in some cases in measurements of the work of separation of two layers.
The Tensile Strength of Elastomers
Authors: Taylor G. R. , Darin S. R. 
Published: February 2011

Abstract
The theory of strength proposed above appears to describe satisfactorily the effect of crosslinking on the strength of amorphous elastomers, and to apply semiquantitatively to crystallizable elastomers. Further work, involving the effect of primary molecular weight, constitution, swelling, and additives is required to substantiate the general applicability of the theory. The mechanism of rupture, in particular, is poorly understood.
The Mechanism of Accelerator Action
Authors: Krebs Heinz 
Published: February 2011

Abstract
In the year 1839, Goodyear discovered that, on treatment with sulfur at elevated temperatures, natural rubber loses its plasticity and becomes elastic. Around the time of World War I, it was discovered that the reaction of the sulfur with the unsaturated rubber hydrocarbons could be promoted by the action of so-called vulcanization accelerators. The reaction then takes place not only faster and at lower temperatures but, in addition, one also needs less sulfur and the vulcanizates acquire considerably better technical properties. Accordingly a tremendous number of compounds have been examined as accelerators of vulcanization and much effort has been applied to develop accelerators with the most satisfactory properties. Today, accelerators are known which permit vulcanization at room temperature. In the past, the mechanism of accelerator action has been studied mostly with the methods of organic and physical chemistry. In the following, an attempt will be made to consider the problem from the viewpoint of the inorganic chemist. One can attempt to interpret the catalysis from two points of view. Either the reactivity of the unsaturated natural rubber hydrocarbon is enhanced, or the sulfur will be converted into a more reactive form. Twiss concluded from his investigations that the latter possibility is the more likely. Subsequently, this assumption has been supported by further observations. In particular, the discovery of Peachey pointed in this direction, since natural rubber is vulcanizable at room temperature if it is treated successively with hydrogen sulfide and sulfur dioxide gases. The sulfur which is formed by this reaction is in the nascent state and is very reactive.
Evaluating High Polymer Cable Insulations on the Basis of Loss Factor Profile
Authors: Hahne K. H. 
Published: February 2011

Abstract
If we desire to gage the difficulties encountered in judging and testing polymeric insulation, we should remember that, generally speaking, the poorer the electric characteristics of these materials, the better will be their mechanical and thermal qualities. Perhaps this has not been so noticeable in the case of the classic insulating materials, such as rubber and fibers. However, reduction in insulating resistance is the deciding factor with soft PVC where, as is well known, addition of softener will bring about a corresponding ability to withstand cold and bending. It is therefore necessary in this case to select the type and content of softener so that adequate thermal and mechanical characteristics are attained without loss of electric dependability. Also with other polymers, the additives used to improve mechanical and thermal qualities are unfavorable electrically. The test methods used in evaluating cable insulations must make possible the stipulation of optimum compounds. Therefore numerous individual tests must be made, so as to arrive at reliable conclusions in every respect. Table I gives a tabulation of the tests prescribed in Germany for cables with plastic insulation and cover. If special requirements must be met such as, for instance, resistance to chemicals or to ozone, additional tests may be prescribed. Test requirements in other countries are even more comprehensive than in Germany. Such extensive tests render more difficult any evaluation of polymeric cable insulations. They require much time and effort, especially when series of tests are involved in the case of newly developed materials. Inasmuch as each test brings out only a small part of the pertinent characteristics of the material and none can be ignored, it follows that the overall evaluation becomes difficult. It should be in order, therefore, to ask whether it is possible, by means of one single measuring method, to obtain at least a comparative survey of all determining characteristics of such high polymer insulating materials. Potthoff has mentioned, among other things, that too little use is made of the fact that carrying out simple and nondestructive measurements of the frequency and temperature dependent dielectric loss factor permits a deep insight into the characteristics of insulating materials. Actually, this measurement affords the means of grasping the most interesting influences involved with the least effort.
Frictional Temperature Rises on Rubber
Authors: Schallamach A. 
Published: February 2011

Abstract
Frictional temperature rises and frictional forces on rubber at velocities up to about 400 cm/sec and under various normal loads have been determined by employing a thermojunction as slider. In the experimental velocity range, the frictional temperature rises increase approximately proportional to the square root of the sliding velocity. The finite heat conductivity of the slider has been found not at affect the results materially. The temperature rises when plotted against the dissipated frictional energy lie on closely grouped curves. Coefficients of friction as function of load and velocity are given.