bluuebunny/crossref_metadata_2025_split huggingface dataset:
Benzothiazyl Disulfide-Accelerated Vulcanization of Carbon Black Loaded Natural Rubber
Authors: Studebaker M. L. , Nabors L. G. 
Published: February 2011

Abstract
Sulfur group analyses of reinforced MBTS accelerated vulcanizates reveal chemical differences which can be related to the surface chemistry of the carbon blacks. The analytical procedure is based on the treatment of the vulcanizate with lithium aluminum hydride followed by potentiometric titration of sulfide and mercaptan sulfur. The polysulfide crosslink density and the values of x in the R—S—Sx—S—R polysulfides are dependent upon the quinone content of the carbon black. Both the quinone content and the surface area of a carbon black appear to determine its influence on the disappearance of free sulfur and the apparent crosslinking of the vulcanizate.
Ionic Crosslinking of Chlorosulfonated Polyethylenes
Authors: Maynard John T. , Johnson Paul R. 
Published: February 2011

Abstract
A new and simple technique for curing chlorosulfonated polyethylene elastomers has been found that offers an economical means of making white and light-colored vulcanizates that do not contain sulfur compounds. This kind of stock can therefore be used directly in contact with bare copper, as in wire coverings, or with lead, as in lead press cures of hose and cables. In applications where the presence of litharge is acceptable, excellent water resistance can be developed. Aging characteristics of vulcanizates are generally comparable to those employing other curing systems, although extensive data are not now available. Because crosslinking is achieved entirely through electrostatic bonding of ion pairs, compression set values of these compounds are high, and this should be recognized in considering the applicability of this technique.
Poly(1-Butene) Chain Flexibility from Sorption Data
Authors: Pavlyuchenko G. M. , Gatovskaya T. V. , Kargin V. A. 
Published: February 2011

Abstract
A previous investigation of the sorption properties of polyethylene over a wide range of temperatures, above and below the melting point, showed that this polymer, the simplest member of the polyolefin series, has chains of quite high flexibility, a factor which also governs its extent of crystallization. The present work is devoted to the study of the sorption properties of crystalline polybutene to obtain data on chain flexibility. This polymer is of considerable interest, since it exhibits elastomeric properties as well as crystalline structure. A polybutene sample with an intrinsic viscosity of 1.14 (determined in decalin at 90°) was used in the study. Observation in a polarization microscope showed that the sample melted in the temperature range 94.3° to 104.8°. Isotherms for sorption of n-octane by polybutene at 50°–115° (Figure 1) were obtained by means of a spring balance placed in a high temperature air thermostat. As Figure 1 shows, sorption increases regularly with temperature up to a relative adsorbate vapor pressure of 0.45, with the exception of the isotherm obtained at 50°, which lies above the isotherm at 60°. This somewhat unexpected result is possibly associated with the less dense packing of the chains at 50°, a factor which also results in higher sorption. At higher relative vapor pressures, when chain flexibility increases as a result of the plasticizing effect of the solvent, the density of molecular packing increases, and sorption becomes lower than at 60°.
Cyclization of Diene Polymers
Authors: Tutorskii I. A. , Markov V. V. , Fomina L. P. , Belyanin V. B. , Dogadkin B. A. 
Published: February 2011

Abstract
1. During the cyclization of natural rubber (unmasticized pale crepe) in phenol solution containing P2O5 as a catalyst, there is a drop in viscosity of the solutions—sharply at the beginning of the process and insignificantly after 5 hours cyclization time. 2. The speed of solution of rubber in phenol containing P2O5 is considerably greater than in pure phenol. This indicates that cyclization is started in the gel state and proceeds to full solution, and accelerates the breakdown of the gel fraction of the rubber. 3. Release of acetic acid, during oxidation of rubber for various periods of cyclization with chromic acid, diminishes in the course of the first four hours of the process, and then remains constant, whereas the viscosity continues to lessen. This serves to show that the process of breakdown goes forward even after the cyclization process is completed. 4. Unsaturation of cyclorubber, determined by the reaction with perbenzoic acid, amounts to approximately 25% of the original known unsaturation of rubber. 5. The presence in the ultraviolet spectrograph of cyclorubber of absorption bands at 275–280 mµ and in the infrared spectrograph of a series of absorption bands at 690 and 740−1, and again at 1500 to 1600 cm−1, indicates bound phenol in cyclorubber.
The Gel Phase in Natural Rubber
Authors: Allen P. W. , Bristow G. M. 
Published: February 2011

Abstract
Evidence is presented which suggests that the true gel phase in natural rubber is composed of small crosslinked latex particles (microgel), whose presence is revealed by light scattering and by electron microscopy. These are combined into a matrix with soluble rubber molecules, forming the apparent gel phase. The rate of solution (and hence the apparent gel content) of this phase varies with solvent and is governed by the diffusion rate of solvent into rubber. Prolonged extraction removes the soluble component. Since the redissolution of the soluble component is very rapid, it is inferred that it is initially bound to the microgel particles by specific forces which have to be overcome by the diffusing solvent. Mastication of crepe breaks up the matrix, leaving microgel particles whose presence can be detected in solution.
Radiochemical Investigation of Polymer Unsaturation. Reaction of Butyl Rubber with Radiochlorine
Authors: McNeill I. C. 
Published: February 2011

Abstract
The reaction between chlorine and butyl rubber is of interest for two reasons: because of the industrial importance of the reaction the mechanism of which has not been fully understood, and because of the possibility of using it as a method for the determination of unsaturation. By the use of (36Cl)-chlorine, it has been possible to study the reaction on a conveniently small scale, the radiochlorine being manipulated quantitatively by a vacuum line technique. It has been shown that the reaction with chlorine is freer from side effects than the iodine chloride reaction. Two atoms of chlorine are incorporated in the polymer for each double bond originally present. These are incorporated not by addition but by a substitution process which is probably not free-radical in nature. A mechanism is proposed for the reaction. Radiochlorine is demonstrated to be potentially a useful reagent for investigating very low unsaturations in polymers.
Mold Release Agents in the Rubber Industry
Authors: Bertram Hans-Herwig 
Published: February 2011

Abstract
The efficient production of high quality molded products in the rubber industry depends substantially on the use of suitable mold release agents and mold lubricants. Their function is to release even odd shaped articles from the molds. Since the mechanical strength of the stock at curing temperature is only a fraction of the room temperature value mold release agents play an important role in this operation. Effective mold release agents decrease the percentage of rejects and shorten the time between release and injection. A number of additional qualities are required of an “ideal” mold release agent. No decomposition residues should build up on the mold surface, since this would affect the product surface and would require cleaning of the mold after each use. The mold surface should be protected against corrosion, thus a mold release agent should be thermally stable and chemically inert. Furthermore, a mold release agent should produce a good appearance and a convenient finish while avoiding undesired side-effects detrimental to the color, the adhesive properties or the lacquer acceptance of the rubber. The mold release agent should affect neither the aging properties nor the odor and taste of the product and must be nontoxic. In addition, a virtually unlimited shelf life is expected. In view of the multitude of technical requirements it is not surprising that no single compound will combine all these qualities. Practically, a compromise is made and a few shortcomings have to be accepted. The following is an attempt to characterize the most important groups of mold release agents with respect to their technological properties.
The Chemistry of Thiazoles and Dithiocarbamates as Antioxidants
Authors: Brooks L. A. 
Published: February 2011

Abstract
Using a strictly qualitative approach, the present work suggests a possible explanation for the observed antioxidant action of dithiocarbamates. It has been shown that dithiocarbamates react with hydroperoxides to form a new oxidized intermediate which in most cases is stable. These have been identified as semisulfinates: (see PDF for diagram) With continued oxidation, a normal sulfinate is formed, the structure of which is probably best represented as follows where M is a divalent metal and R is, e.g., a simple alkyl group: (see PDF for diagram) The stability of the above compound will depend upon the metal M and the nature or size of the alkyl group. These compounds further decompose into a thiuram monosulfide and the corresponding metal sulfate. Particularly active or sensitive dithiocarbamates are oxidized directly to the metal sulfate and thiuram monosulfide. In these cases, the ephemeral formation of the semi-sulfinate and normal sulfinate as intermediates is probable. In the presence of excess hydroperoxide, the thiuram monosulfide undergoes further oxidation to form a carbamyl thiocarbamyl disulfide: (see PDF for diagram) Compounds of this structure are moisture sensitive and readily undergo hydrolysis. In the presence of zinc oxide and water such as would be found on the surface of a conventional rubber stock, it is suggested that a further reaction occurs to form a zinc dithiocarbamate which will then undergo the sequence of reactions described above until the dithiocarbamate is completely consumed. It is suggested that these reactions account for the antioxidant behavior of dithiocarbamates in a hydrocarbon system such as rubbers and petroleum products where the oxidizing agent is a hydroperoxide or some peroxygen compound which, if not destroyed, would in turn degrade the product to one of no utility.
Sulfur Vulcanizable Ethylene-Propylene Rubbers
Authors: Natta Giulio , Mazzanti Giorgio , Crespi Giovanni , Valvassori Alberto , Sartori Guido 
Published: February 2011

Abstract
Our research directed to obtaining new rubbers based on the copolymerization of ethylene with propylene started some years ago. We soon succeeded in establishing that it was possible to prepare copolymers of these two monomers showing interesting elastomeric properties. From the beginning, the problem arose of how to vulcanize these copolymers: while certain interesting methods for direct vulcanization were investigated and identified, we also investigated the possibility of terpolymers containing unsaturation and therefore vulcanizable with the ingredients normally employed in the rubber industry, particularly for the low unsaturated rubbers. The problem involved some difficulties, due to the following three reasons. (1) In order to maintain the peculiar characteristics of resistance to aging and chemicals, typical of ethylene-propylene copolymers, it was necessary to obtain terpolymers in which the unsaturation was present in a very small amount. (2) To obtain valuable properties in the vulcanizates, the unsaturation had to be well distributed in all the macromolecules. (3) In order to avoid branching or crosslinks, the residual double bond of the diene entering the polymer chain must not be able to react further during polymerization. Our research led to a number of monomers which may copolymerize with ethylene and propylene and which, under suitable conditions, gave terpolymers having a sufficiently homogeneous composition. Investigation of the behavior, in anionic coordinated polymerization of hydrocarbons containing internal double bonds led to an interesting solution to the problem of producing terpolymers.
Microscopy of Pigment-Elastomer Systems
Authors: Hess W. M. , Ford F. P. 
Published: February 2011

Abstract
Rubber technologists have always been fascinated by the remarkable effects produced in rubber by carbon black. Many people have contributed to an understanding of these phenomena. We have referred to some, but by no means all of such individuals' efforts in this review. In retrospect, it may not be inappropriate to recall some observations made 40 years ago by Ellwood Spear. In a remarkably perceptive paper on carbon black reinforcement, published in 1923, he said: “It is believed that the rubber is adsorbed on the surface of the carbon particles and that adsorption … is the real cause of the effect of carbon black in rubber”. And further: “The distinction between mere fillers … and those substances which reinforce rubber to an appreciable degree, lies in the hypothesis that the latter adsorb rubber strongly, whereas the former form a very weak union with it”. There are perhaps few chemists, physicists, rubber compounders, or microscopists who will disagree with these observations. But the measure of their success in unravelling the mysteries of carbon reinforcement of rubber will be the real facts they are able to find in support of such speculations. We hope that the present review will be helpful to others in their search for such facts. If we have succeeded in answering a few questions as well as in evoking some new ones, then perhaps our efforts will have been worthwhile.
Electrical Properties of Elastomers and Related Polymers
Authors: McPherson Archibald T. 
Published: February 2011

Abstract
Interest in the electrical behavior of elastomers stems from several widely different sources. From the theoretical standpoint electrical measurements provide a valuable tool for the study of the molecular structure of elastomers and other polymers and the relation of structure to properties. From a practical point of view an understanding of the electrical behavior enables the manufacturer of wire and cable to produce insulation that will better withstand the severe conditions of space flight, or that will meet price competition and show a profit. The present day applications of elastomers are so many and varied that nearly any type of compound is likely to be employed for some practical purpose. A cable for x-ray equipment, for example, may be made wholly from elastomers with conductor, insulation, and jacket each from a different compound. At one time when almost the only electrical use of rubber was to provide the highest practical degree of electrical insulation it was correct to speak of “good” and “poor” electrical properties. Now, however, an elastomer that is a poor insulator may be excellent in an antistatic application. Communication cables require an insulation of the lowest practical dielectric constant, but for power cables a layer of insulation of high dielectric constant next to the conductor may be essential to prevent excessive electrical stresses. Modern technology not only calls for a wide diversity of electrical properties but it often requires further that elastomers having these properties be available in a wide range of mechanical properties. For example, the insulation on a cable for use in an airplane must be as thin and light as possible to save weight while an unarmored cable for laying in shallow water must have insulation that is thick and tough for mechanical protection and of high specific gravity to prevent the cable's being moved by waves or tide. Thus, the diversity of present and possible future applications is such that no one in the industry is likely to escape for long some contact with an application involving an electrical property. Accordingly, this review has been prepared to acquaint the rubber chemist and technologist with current information in the field. In the 25 years that have elapsed since an earlier review was prepared by the same author a great deal of work has been done on the relation between the properties of polymers and their molecular composition and structure. It is now possible to predict the properties of some polymers from their structural formulas, and a beginning has been made in relating the properties of simple elastomeric compounds to the properties of the different ingredients. However, knowledge in the field is still far from the state at which it would be possible to compile a table of functions such that the electrical properties of a multi-ingredient insulating compound could be computed from the properties of the individual ingredients.
Some Stereoregular Polymerizations of Conjugated Dienes
Authors: Lehr Marvin H. 
Published: February 2011

Abstract
After nearly a decade since man discovered how to carry out stereoregular polymerizations of dienes, his understanding of the reactions is disappointing in spite of the many studies that have been made. Part of the difficulty lies with patent disclosures as discussed by Natta in his forward to Gaylord and Mark's book. But most of the difficulty in this reviewer's opinion lies in the reporting of experimental work in the published literature. Too little attention is paid to those details needed for critical evaluation, and too much space is devoted to interpretation and speculation. In view of the many variables in preparing Ziegler catalysts, it would seem obvious to include, for example, such information as the order of addition and purity of reagents. Likewise, in view of the uncertainties, it would seem prudent to consider more carefully the merits of alternate interpretations. The author believes that progress in a field is often achieved by following an interpretation to its logical end. However, in preparing this review he found himself frequently frustrated because of insufficient experimental details. If the reporting continues as it has been, he feels that our knowledge will continue to remain in a rudimentary state in comparison to the effort expended.
Practical Parameters for Mixing
Authors: Van Buskirk P. R. , Turetzky S. B. , Gunberg P. F. 
Published: February 2011

Abstract
(1) Compounds mixed under high-shear conditions in a laboratory Brabender Plastograph or in larger Banbury mixers can be quantitatively compared on the basis of work input per unit volume. This quantity, unit work Wu, is proposed as a useful parameter for characterizing the effects of polymer, filler, and other ingredient on mixing performance. (2) This work supports the principle that, independent of the size and speed of a mixer, there is a unique relationship between unit work and such in-process properties of the compound as Mooney viscosity, die swell, etc. It has been shown that this relationship extends to other high-shear mixers, such as the Shaw Intermix and a cam-head type Brabender Plasticorder. (3) Practical unit work ranges for passenger tire-tread mixing found typical of factory operations are: first stage, 300–800 MJ/m3; second stage, 150–400 MJ/m3; final mix, 2000–4500 MJ/m3. Mixing to these unit-work levels in the laboratory achieved mixing quality that closely duplicated large-scale high-shear mixing. (4) Process profiles (the changes of certain in-process properties such as Mooney viscosity and die swell as functions of unit work) yield additional behavior indices that are characteristic of each individual rubber—filler mixture: The viscosity-work index (VWI), for instance, reflects the rate of change in the compound viscosity with increasing unit work, while the position of the maximum in the die swell vs. unit work curve is a good indicator of the minimum unit work required to obtain low levels of undispersed carbon black. (5) A second scaling parameter, based on an expanded concept of the total shear-strain performance for Banbury-type mixers, is proposed. It offers an alternative approach to scaled mixing when the actual measurement of unit work is not convenient. The total shear-strain parameter, as derived, is a dimensionless number Γ defined as Γ = [(shear rate) (time) (volumetric throughput ratio) (land-length ratio)]. Its use implies ideal viscous flow during mixing plus an accurate knowledge of mixer rotor and chamber dimensions.
Application of an Equivalent Strain at Equal Stress Principle to the Dynamic Hysteresis of Carbon-Black-Loaded and Oil-Extended SBR
Authors: Ulmer J. D. , Chirico V. E. , Dizon E. S. 
Published: February 2011

Abstract
A principle of equivalent strain at equal stress has been applied to dynamic measurements of hysteresis. At 24°C and 25% ptp dynamic strain, the relation of hysteresis to strain amplitude and the equivalence principle lead to an expression which describes the measured hysteresis of SBR-1712 filled with a wide variety of carbon black types and loadings to within about ±25%. At 105°C and 25% strain, the experimental results are much larger than the theory predicts, but are better described by the theory if an empirically determined exponent n is introduced in the equivalence principle. At strain amplitudes below 10%, the experimentally determined hysteresis is much lower than the theory predicts, but this deviation is described by the change in elastic modulus with strain amplitude at both 24° and 105°C. The deviations of the results from the theoretical predictions which are not described by the rate of change of elastic modulus with strain amplitude appear to be a function of carbon black surface area, structure, and loading.
Identification of Elastomers in Tire Sections by Total Thermal Analysis. III. White Sidewall Compounds of Neoprene Rubber Blends
Authors: Sircar A. K. , Lamond T. G. 
Published: February 2011

Abstract
DSC curves of sulfur-cured CR differ from peroxide-cured vulcanizates in the shape of the exotherm and the peak temperatures. The exothermic reaction, attributed to dehydrochlorination and subsequent crosslinking, is accelerated by sulfur. TG and DTG curves support this contention. In blends with NR, BR, or SBR, the second polymer intervenes in the crosslinking reaction, resulting in a lower residual weight for the CR network. White sidewall compounds of NR/CR or NR/CR/CSM can be identified by their DSC peaks in nitrogen, glass transition temperature, and DTG peaks. DSC and thermogravimetric curves supplement each other in the identification of these elastomers.
Molecular Structure of Elastomers Determined with Carbon-13 NMR
Authors: Carman C. J. , Baranwal K. C. 
Published: February 2011

Abstract
Characterization and identification of elastomers are important analytical needs for those involved in rubber technology. High resolution pulsed Fourier transform 13C NMR has been shown to be a powerful tool which can supply much detail as to sequence distribution, chain configuration, steric purity, or identification of polymer mixtures. One can also use 13C to distinguish polymer blends from copolymers of similar composition. This information about elastomers commonly used in the rubber industry provides not only a new tool for analytical problem solving, but also provides analytical information to guide the chemist as he makes elastomeric materials with structural features which impart specific physical properties.