bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cis-Trans Isomerization of Natural Rubber under the Influence of Hydrogen Chloride or Ethylaluminum Dichloride
Authors: Boldyreva I. I. , Dolgoplosk B. A. , Kropacjeva E. N. , Nel'son K. V. 
Published: February 2011

Abstract
We have established earlier that organo-aluminum compounds, and titanium tetrachloride, bring about the isomerization of the cis-isoprene units in natural rubber into the trans. The isomerization process, as influenced by the above materials, proceeds at appreciable velocity even at room temperature. The present communication reports the results of investigating the cis-trans isomerism of natural rubber as influenced by hydrogen chloride and ethylaluminum dichloride. The isomerizing action of hydrogen chloride upon unsaturated acids and stilbene was dislosed earlier in a series of papers. We investigated the action of dry hydrogen chloride and ethylaluminum dichloride on benzene solutions of natural rubber under the conditions described earlier. Hydrogen chloride was introduced in the form of a saturated benzene solution. In investigating the hydrogen chloride activity, each polymer sample was examined for unsaturation, chlorine content of the polymer chains and microstructure. The latter was characterized with the aid of infrared absorption spectra. As in the previous report, quantitative determination of the cis and trans content was made in the 840 cm−1 region, where the intensity and contour are substantially dissimilar for natural rubber and guttapercha. Furthermore, an additional inspection was made qualitatively in other regions of the IR spectrum (1100–1150 cm−1 and 1300–1330 cm−1), the feasibility of utilizing the 1300–1330 cm−1 region having been reported in a recent publication by Golub, who investigated the isomerization of natural rubber and guttapercha under the influence of selenium at temperatures of 180–220°.
Crystallizability of SKI Vulcanizates by Adiabatic Stretching
Authors: Votinov M. P. , Subbotin S. A. , Samoletova V. V. , Konytovskaya S. P. , Kuvshinskiĭ E. V. 
Published: February 2011

Abstract
Lithium isoprene rubber (SKI) which is very similar to natural rubber (NK) in structure and properties has been synthesized at the S. V. Lebedev VNIISK. During the development of the method of preparation and the investigation of the properties of SKI the necessity of studying the crystallizability of different samples of this new type of rubber became apparent. With this object in view we studied the conversion of work into heat during the adiabatic deformation of rubbers. It was shown that the conditions of preparation and of vulcanization determine whether SKI rubbers will crystallize on stretching or remain amorphous. This paper presents some of our data on the crystallizability of SKI rubber.
Unpaired Electrons in Carbon Blacks
Authors: Collins R. L. , Bell M. D. , Kraus Gerard 
Published: February 2011

Abstract
Two types of unpaired electrons have been observed in a heat treated channel process carbon black. In the original black, and for this material heat treated up to 1400° C, the unpaired electrons are believed to consist of unpaired mobile π electrons stabilized by resonance energy in large condensed ring structures, many of which probably contain oxygen. These disappear with heat treatment above 1400° C and a new species of unpaired spins appear which have been assigned to localized σ electrons at defects in the graphitizing lattice. The unpaired electrons in most commercial carbon blacks are believed to be π electrons, similar in concentration and g value, but varying considerably in line width and oxygen sensitivity. The highly graphitic acetylene black may contain σ electrons also, for its line width is little affected by oxygen. A tentative explanation has been formulated for the origin of unpaired electrons in charred materials and carbon blacks.
The Formation of Urethan Foams
Authors: Saunders J. H. 
Published: February 2011

Abstract
An understanding of the formation of urethan foams involves consideration of the organic chemistry of the reactions leading to gas formation and molecular growth, the colloid chemistry of nucleation phenomena and bubble stability, and the rheology of the polymer system as it cures. Experimental data are not available to permit complete evaluation of all details of the foam formation and cure. Nevertheless enough information has been developed in the urethan and related fields to permit one to develop a fairly reasonable explanation of the process. This summary attempts to present such a picture, and is not concerned with the more familiar areas of foam production and foam properties. A distinction is made between experimentally observed data and reasonable speculation. One may naturally assume that future research will modify and extend the concepts presented here.
The Vulcanization of Elastomers. 13. The Vulcanization of Natural Rubber with Sulfur in the Presence of Mercaptobenzothiazole. II
Authors: Lorenz O. , Echte Elisabeth 
Published: February 2011

Abstract
The vulcanization of natural rubber with sulfur, using mercaptobenzothiazole as accelerator in the presence of zinc stearate, was investigated. The results were as follows: 1) When natural rubber is cured with sulfur in the presence of zinc oxide and mercaptobenzothiazole, as well as zinc stearate, one observes, with the first order diminution of sulfur concentration, an induction period that grows longer as the cure temperature falls. 2) For the disappearance of sulfur there is calculated, from the temperature dependence of the rate constants, an activation energy of 19.5 kcal/mole. This value is considerably smaller than that found for the mercaptobenzothiazole-accelerated sulfur cure when no zinc stearate is present. 3) The percentage loss in mercaptobenzothiazole during vulcanization is, in the presence of zinc stearate, independent of the temperature; there is a reaction, independent of the amount of stearate added of 5 molecules of S8 for each molecule of mercaptobenzothiazole. 4) The diminution in accelerator can also be explained as a first order reaction, and it becomes evident that disappearance of accelerator and sulfur are equivalent-rate processes. 5) The crosslinking, measured by the reciprocal equilibrium swelling, goes according to the first order, yet sulfur disappearance and the crosslinking reaction are not equal rate processes, which was always true in the absence of zinc stearate. In each case the crosslinking rate constants are greater than those for the decrease in sulfur. 6) For the activation energy of network formation, we calculated, from the temperature dependence of the rate constants of the reciprocal equilibrium swelling, 20.5 kcal/mole. 7) When the stearate content is constant, there is a linear relationship between kSI, the rate constant for sulfur diminution, and the given amount of mercaptobenzothiazole, up to an initial molar ratio of mercaptobenzothiazole: stearate = 4:1. Increases in accelerator proportion beyond this initial ratio cause no further rise in the rate constants. 8) The rate constants of the crosslinking reaction also increase with increasing proportion of mercaptobenzothiazole (stearate portion remaining constant), until the initial molar ratio of mercaptobenzothiazole:zinc stearate = 4:1 is reached. Nevertheless, the relationship is not linear. 9) There is a linear relationship between the amount of zinc stearate in the vulcanizate and the maximum sulfur-loss rate constants kSI (max). 10) The maximum rate constants of the network forming reaction kQI (max) are proportional to the square root of the stearate content. 11) The number of crosslinkage points formed is independent of the quantity of mercaptobenzothiazole, when the stearate content is constant. 12) The number of crosslinking points formed increases, however, along with increasing stearate content, and is proportional to the square root of the stearate content. The investigations will be continued.
The Thermal Vulcanization of Synthetic Rubber
Authors: Luttropp H. 
Published: February 2011

Abstract
It is shown that synthetic rubbers, in contrast to natural rubber, can be vulcanized to soft rubber by a simple thermal treatment without any previous admixture of sulfur or accelerators. This process has been designated as “Thermovulcanization” to distinguish it from the regular vulcanization procedure under heat with the addition of sulfur and accelerators. Various synthetic rubbers of Schkopau production have been investigated for their behavior in the process of thermovulcanization. Both butadiene-styrene and butadiene-acrylonitrile copolymers as well as the butadiene block polymerizate lend themselves to vulcanization by this thermal treatment. For the butadiene-styrene copolymer with higher styrene content, thermovulcanization leads to products which are not equivalent to the regular sulfur-accelerator vulcanizates. Natural rubber cannot be vulcanized to soft rubber by thermovulcanization. The investigation of the effect of temperature revealed that a temperature of 195° C, for example, was applicable for all the synthetic rubbers studied. The addition of active carbon was found to accelerate the thermovulcanization process and certain properties of the vulcanizates are improved. The results of some comparative studies are presented, and it is pointed out that thermovulcanizates and normal vulcanizates show agreement in some of their properties and vary in others. The thermovulcanizates, as compared with normal vulcanizates, show somewhat lower tensile strength and somewhat lower fatigue resistance. Also their resistance to swelling is lower. On the other hand they are better in abrasion, have somewhat improved elastic properties, and show improved resistance to aging including surface aging phenomena under static and dynamic stress.
Hydrogenation of Butadiene Rubber
Authors: Yakubchik A. I. , Gromova G. N. 
Published: February 2011

Abstract
1. Solutions of butadiene rubber were hydrogenated at atmospheric pressure and room temperature on the following catalysts: palladium on calcium carbonate; palladium on nickel, platinum black from platinum dioxide, platinized carbon activated with doses of chloroplatinous acid, and Raney nickel. 2. It was established that when butadiene rubber is hydrogenated on these catal sts the activity of the catalyst decreases, evidently owing to its surface being obstructed with products of hydrogenation. It was consequently impossible to study the behavior of the double bonds in butadiene rubber on the basis of the curves of the rate of hydrogenation. 3. Specimens of butadiene rubber were prepared at various degrees of hydrogenation on all these catalysts and the following quantities were measured : total unsaturation, proportion of external and internal double bonds, index of refraction, relative viscosity of 0.08 per cent benzene solutions, and vitrification temperature. 4. It was established that when butadiene rubber is hydrogenated on the catalysts studied the external double bonds of the rubber are hydrogenated more rapidly than are the internal bonds. 5. It was established that an increase in the degree of hydrogenation of butadiene rubber leads to a decrease in the index of refraction, relative viscosity of benzene solutions, and vitrification temperature. 6. The decrease in the index of refraction of rubber during hydrogenation shows the absence of cyclization and can be explained by the disappearance of the double bonds of the rubber molecule. 7. It was shown that the decrease in viscosity of benzene solutions of butadiene rubber with increase in the degree of hydrogenation is due to changes in the shape of the rubber molecule during hydrogenation.
The Wear of Passenger Car Tires
Authors: Geesink H. A. O. W. , Prat P. 
Published: February 2011

Abstract
One can thus say that in the course of tire tests, all of the experimental conditions, whether they affect more particularly the wear by test period or by wheel position, influence the wear results. Notwithstanding the complexity of these influences and of their interactions it has been possible to verify that a relation existed between the tests on special cars and those made on private cars commonly used by everyday users, and to establish a correlation between the normal road tests and accelerated tests on the track. These studies have shown the importance of the severity of the tests for the estimation of the relative value of the mixtures and it has been possible to evaluate the influence of a certain number of factors on this severity which is, in reality, the resultant of the effects of all the experimental conditions on the wear of pneumatic tires. The variations in relative wear of the mixtures as a function of the severity have led to the thought that a correlation might exist between the practical tests on the road or on the track and the experiments made in the laboratory with the aid of abrasion machines. The existence of such a correlation is very important for it will permit an effective selection of the mixtures, destined for the manufacture of treads, in the research investigations. However, one must still look for a suitable adjustment of laboratory tests in order to obtain an estimation which is directly transposable to the complex domain of the pneumatic tire. This simplification, however, will not bring about the disappearance of road tests for it will, after all, be necessary to make a few practical verifications, be it only for studying the road behavior of the experimental mixtures or their resistance to cracking. This study has been made within the framework of the research programs of the Rubber-Stichting and of the French Rubber Institute, the study being in turn a part of the entirety of the investigations pursued under the protection of the International Rubber Research Board.
The Ultimate Properties of Simple Elastomers
Authors: Bueche A. M. 
Published: February 2011

Abstract
The ultimate properties of polymers are very poorly understood. A large mass of practical data is available but at present there seem to be no molecular theories for its correlation or for use as a guide in obtaining new data. In the following pages a theoretical approach to the ultimate properties of simple crosslinked elastomers will be described. The treatment will be limited to the tensile strength and ultimate elongation at temperatures high enough so that crystallinity and the viscous work during extension are negligible. The theory can be extended to cover compressive or shear strength with relatively little effort. The incorporation of the effects of viscosity and crystallinity will require somewhat more work. (After the completion of the major part of this work I learned that Prof. F. Bueche, University of Wyoming, has developed a somewhat similar theory for the tensile strength of viscous elastomers.)
Influence of Molecular Shape on the Tensile Strength of Vulcanizates
Authors: Novikov A. S. , Dorokhina T. V. , Zubov P. I. 
Published: February 2011

Abstract
A study of the mechanism of the formation of albuminous gels has shown that the mechanical strength of films depends on the shape of the chain molecules. Films prepared from globular casein have a lower tensile strength than those prepared from fibrillar casein. It would be natural to assume that the mechanical properties of rubberlike polymers and vulcanizates depend on the shape of the molecular chains. In order to verify this hypothesis, vulcanized films prepared from solutions of butyl rubber in various solvents were examined, assuming that the degree of twisting depends on the nature of the solvent. Benzene and carbon tetrachloride, in which the degree of twisting of the butyl rubber chains is quite different, were chosen as solvents. The tensile strengths given in Table I are the mean statistical data from 25 specimens. Data of the change in relative viscosity of solutions of butyl rubber in benzene and in carbon tetrachloride as functions of the temperature and concentration are shown in Figure 1. It is seen that the relative viscosity of benzene solutions is lower than that of carbon tetrachloride solutions of equal concentration. An increase in the relative viscosity of benzene solutions of butyl rubber is observed with an increase in temperature, while a decrease is observed in carbon tetrachloride solutions. These changes of relative viscosity with an increase in temperature are less pronounced in solutions with concentrations up to 0.3 g per 100 cc, where the polymer forms true molecular solutions, and are more pronounced in concentrated solutions.
The Mutual Solubility of Polymers. I. Physicomechanical Properties of Stocks Prepared from a Mixture of Polymers
Authors: Komskaya N. F. , Slonimskiĭ G. L. 
Published: February 2011

Abstract
1. The mixing of rubbers (or of any amorphous polymers) may be considered as a mutual solution of two liquid phases, conforming to thermodynamic laws. 2. The stocks studied, which were prepared from a base of a combination of different rubbers, fall into two groups as regards the nature of the relation between their mechanical properties and the proportions of the mixed rubbers. The opinion was expressed that the anomalies observed in the properties of combined stocks prepared from a mixture of SKS-30 and SKB are due to the micrononhomogeneous two-phase structure of such stocks. 3. It was shown that the properties of combined stocks are governed primarily by the behavior of the mixed rubbers themselves, and not by the ingredients incorporated into the stocks. 4. The compatibility of two polymers should be considered from two points of view. A macroscopic compatibility can almost always be achieved, provided that the polymer can be converted to the fluid state. However, compatibility in microregions, i.e., the mutual solubility of polymers, is determined by their thermodynamic properties and may not coincide with macrocompatibility. The reason for the discrepancy between macro- and microcompatibility is the chain structure of the polymer molecules, and the resulting large viscosity of polymers which have a high mobility of small segments of the flexible chain molecules.
Mastication. V. Separation and Structural Investigation of Natural Rubber-Polymethyl Methacrylate Interpolymers Formed by Mastication
Authors: Angier D. J. , Watson W. F. 
Published: February 2011

Abstract
Polymerization of methyl methacrylate admixed with natural rubber occurs on rupture of rubber molecules to free radicals by applied shearing forces. The polymeric products after different conditions and extents of reaction have been separated into uncombincd rubber, two interpolymer fractions, and uncombined polymethyl methacrylate by fractional precipitation and extraction methods. The structure of the interpolymers has been investigated by measurement of composition and osmotic molecular weight, ozonolysis to degrade the rubber segments and isolation of the polymethyl methacrylate fragments, autoxidation of the rubber segments, and viscosity measurements on the uncombined rubber. The interpolymer is a linear block polymer containing one polymethyl methacrylate segment and of the order of one or two rubber segments per molecule. The Trommsdorff gel effect has a profound influence on the rate of formation, composition, and structure of the interpolymer.
Mastication of Rubber. VI. Viscosity and Molecular Weight Relationships for Natural Rubber after Cold Mastication
Authors: Angier D. J. , Chambers W. T. , Watson W. F. 
Published: February 2011

Abstract
Values of limiting viscosity number, Huggins' interaction constant, k′, osmostic molecular weight and Flory-Huggins' constant, μ, of masticated and unmasticated rubber have been compared. A calibration of limiting viscosity against molecular weight has been obtained for masticated rubber, but one is not available for unmasticated rubber due to the occurrence of different extents of branching. A mechanism is advanced of rupture during mastication of molecules above a critical molecular weight.
End Groups of Oxidized Rubber
Authors: Bevilacqua E. M. 
Published: February 2011

Abstract
Chain scission during the oxidation of polymeric 1,5-dirnethyl-l,5-dienes occurs nearly quantitatively through the scission of an unusual peroxidic intermediate, followed ultimately by evolution of a group of fragments of low molecular weight at each scission. The composition of this group depends on the reaction conditions. The first known stable intermediates to be formed subsequent to scission are levulinaldehyde and formaldehyde: Bolland's kinetic and analytic studies combined with the requirements of the observed stoichiometry of scission form the basis on which it is possible to write a detailed mechanism for the transformation represented by Equation 1. Nothing is known in detail of the sequence of reactions resulting in Equation 2. It has been suggested that scission is associated with propagation rather than initiation—that is, with decomposition of a peroxy radical rather than of a hydroperoxide as is indicated in this scheme. This is still a moot point. It is now known, for example, that overall scission efficiency is strongly determined by temperature and that benzothiazolethione and o,o′-dibenzamidodiphenyldisulfide both accelerate oxygen consumption as well as scission, in contrast to earlier belief.
Adhesion of High Polymers. 2. A Method for Determination of the Mutual Adhesion of High Polymers
Authors: Shapovalova A. I. , Voyutskiĭ S. S. , Pisarenko A. P. 
Published: February 2011

Abstract
1. A simple and fairly accurate method for determination of adhesion between two high polymers has been developed, based on separation of the joints by a peeling method. 2. It was found, in agreement with data available in the literature, that the manner of separation of the joints changes with variations of the speed of separation. At low speeds, separation of polymer-polymer joints is cohesive in character, at moderate speeds it is mixed, and at high speeds it is purely adhesive. No increase of the work of adhesion with increasing speed of separation was found. 3. It is shown that the width of the joint does not affect the results of the adhesion determinations. 4. It was found that in the limits studied (from 150 to 55µ) the thickness of the polymeric adhesive layer does not affect the value of the specific work of adhesion. 5. It is shown that if the layer of high molecular adhesive on the substrate is formed from solution, the pressure to which the joint is subjected after it is made does not affect the adhesion. 6. It was found that heat treatment of the joints considerably increases adhesion. 7. It is shown that adhesion increases and tends to a definite limit with increasing time of contact between a high molecular adhesive and a high molecular substrate. 8. It is suggested that the increase of adhesion by heat treatment and by increased contact time is caused by diffusion of molecules of the adhesive into the substrate and vice versa, which leads to disappearance of the interphase boundary and to formation of a stronger adhesive joint.