bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Nondiscoloring Stabilizer System for SBR and Stereospecific Diene Polymers
Authors: Oberster A. E. , Cook W. S. , Smith G. E. P. 
Published: February 2011

Abstract
This article discloses the discovery and use of a class of imidazolidine-4-thiones as new stabilizers for unsaturated rubbers. Also reported is the preparation of the acid salts of one of these, 7, 14-diazadispiro[5.1.5.2]pentadecane-15-thione (DDPT) and its 7- and 14-nitroso derivatives. Several alkylated derivatives of DDPT were found to be equivalent to DDPT in nondiscoloring stabilization activity. The 7-nitroso derivative was found to be an active stabilizer and was found to counteract some slight cure activation inherent in the imidazolidine-4-thione structure. DDPT was shown to be an efficient polymer stabilizer providing excellent nondiscoloring polymers for use in various tire compounds. This compound was fully equivalent or superior to similar polymers prepared from other commercially available nondiscoloring stabilizers and antioxidants.
Accelerated Oxidations of Polyisoprene. III. Photosensitized Oxidations in Solution
Authors: Mill Theodore , Irwin Katherine C. , Mayo Frank R. 
Published: February 2011

Abstract
Measurements of oxygen absorption at 50° C showed methylene blue to be the most effective of several sensitizers tested. At a concentration of 0.01 mM, it gave a rate of oxidation which was about 12 times that in a control run in the light. About 1600 moles of oxygen were absorbed per mole of methylene blue. To obtain the same rate in the dark, about 100 times as much 2,2′-azobis(2-methyl-propionitrile) (AZBN) would have been required. At least in the initial stages of oxidation, this catalysis by methylene blue was not affected by addition of an oxidation inhibitor. Thus, the photosensitized oxidation is mostly a nonradical reaction.
Influence of Sulfur on Stability and Physical Properties of Peroxide Vulcanized Ethylene Propylene Copolymers
Authors: Dunn J. R. 
Published: February 2011

Abstract
In cumyl peroxide sulfur vulcanizates of ethylene propylene copolymers crosslinked with 4 phr of peroxide, polysulfidic crosslinks are present only at sulfur levels in excess of 0.5 phr in gum vulcanizates and 0.3 phr in black filled vulcanizates. Modulus attains a peak in the presence of 0.5 phr of sulfur in gum vulcanizates and 0.3 phr of sulfur in black filled vulcanizates. Modulus decreases when polysulfides are present. Tensile strength in gum vulcanizates increases continually with increasing sulfur content up to 2.5 phr. The increase in tensile strength is related to a rapid increase in ultimate elongation, promoted by mechanically labile polysulfidic crosslinks. Tensile strength in black filled vulcanizates exhibits peaks at 0.3 and 0.75 phr of sulfur. The first peak represents the technological recipe for this type of vulcanizate and arises from a peak in modulus. The second peak arises from increased breaking elongation promoted by polysulfidic crosslinks. Sulfides present in the vulcanizate act as antioxidants at all sulfur levels. When the sulfides contain one or two sulfur atoms, the antioxidant effect is mild but long lived. The polysulfides yield potent long lived antioxidants. The rapid nonoxidative degradation of the polysulfidic crosslinks is not accelerated by dithiocarbamate and proceeds after the reaction products have been removed by extraction. Dithiocarbamates are potent antioxidants in peroxide vulcanized ethylene propylene rubber both in the presence and in the absence of sulfur.
Fundamentals of Electron Microscopy of Heterogeneous Elastomer Blends. II
Authors: Marsh Peter A. , Voet Andries , Price L. D. , Mullens T. J. 
Published: February 2011

Abstract
Electron and phase microscopy results show that most elastomer blends are heterogeneous, even after extended mixing. Blends of SBR/BR and SBR/EBR, however, are homogeneous. DTA data support these conclusions. Carbon black distribution studies indicate that carbon black does not transfer between elastomers during mixing. Polychloroprene exhibited a strong affinity for carbon black in blends with natural rubber. In this system, with the black predispersed in the natural rubber, the carbon black particles were observed at the polychloroprene interface but had not entered that phase.
Microstructural Variations in Commercial Carbon Blacks
Authors: Hess W. M. , Ban L. L. , Eckert F. J. , Chirico V. 
Published: February 2011

Abstract
Conventional and diffracted beam electron microscopy can be used to resolve the ultimate crystallite units in standard and heat treated carbon blacks. They are very sensitive in the detection of small differences in crystallite size and orientation. Combined with x-ray diffraction methods and conventional vulcanizate testing, high resolution electron microscopy appears to be a useful and practical means to study carbon black surface activity. All commercial blacks appear to conform in part to the Heckman and Harling concentric crystallite model. Surface activity appears to be related to the extent of this alignment; the less the tangential orientation of the graphite layer planes to the surface, the greater the surface activity. Heating carbon blacks in an inert atmosphere for varying times and temperatures (850 to 1400° C) causes a gradual depression of surface activity with increasing treatment severity, defined by increases in the size and concentric orientation of surface crystallites. At no time was the effect of carbon black on vulcanizate properties changed significantly by heat treatment without disrupting the initial orientation of surface crystallites. Carbon blacks differ in the rate of change of crystallite orientation in response to heat treatment. The initial degree of crystallinity, porosity, and surface volatile content all appear to affect the rate of crystallite orientation and growth. Increases in average crystallite height, Lc, are a good measure of effects of heat treatment in excellent agreement with changes in surface crystallite size and orientation observed with the electron microscope. Commercial ISAF carbon blacks of varied structure have relatively minor differences in surface crystallite orientation, indicating small differences in surface activity. The higher modulus and treadwear associated with the use of high structure blacks appear to be predominantly a result of the chain structure itself. Further evidence was obtained showing that black structure and surface activity are independent properties each of which can have a significant influence on vulcanizate properties such as modulus, treadwear, and hysteresis.
Characterization of Ethylene Propylene Block Copolymers by Proton Magnetic Resonance
Authors: Porter Roger S. 
Published: February 2011

Abstract
A high-resolution proton magnetic resonance compositional analysis has been developed for propylene polymers containing 0–40 weight per cent ethylene as either homopolymer or copolymer blocks. The test is independent of tacticity and provides qualitative information on copolymer sequencing and propylene chain structure. The analysis was developed using a series of standard reference polymers synthesized to contain various ratios of C14-tagged ethylene and propylene. The compositional standards were established by radiotracer analysis for C14 and by preparing weighed physical mixtures of homopolymers. Spectra were obtained at 200 ± 10° C by placing externally heated polymer solutions into a conventional probe of a Varian A-60 proton spectrometer. All measurements were made on ≤10 per cent polymer solutions in diphenyl ether. Analyses are accurate to about ±10 per cent at higher ethylene concentrations. The method is sensitive, with less precision, to below 1 per cent for ethylene either as blocks or homopolymer.
Morphological Changes in Latex Films
Authors: Bradford E. B. , Vanderhoff J. W. 
Published: February 2011

Abstract
The mechanism of latex particle coalescence has been considered by a number of investigators. Dillon and coworkers and later Henson and coworkers discussed the role of surface tension forces and the applicability of Frenkel's model for coalescence of spheres by viscous flow. Later Brown postulated that capillary forces derived from the water and air interfacial tension, when the evaporation of the water forms small radii of curvature, provide the major driving force for film formation. Voyutskii stated that the surface tension and capillary forces alone cannot account for the ultimate physical properties observed in cast latex films. He postulated the contribution of autohesion, that is, mutual interdiffusion of the free polymer chain ends across the particle, particle interface in the dried film. According to his hypothesis, this diffusion knits the film into one coherent, continuous mass. It has often been observed that physical properties of latex films improve with aging at room conditions. This improvement occurs after practically all the water has evaporated and the films are transparent. Thus, the empirical observations of such properties as scrub resistance indicate that the dry latex films undergo some change upon aging. The autohesion hypothesis might explain these results. In this study the electron microscope was used to study morphological changes which occur as a latex film ages. The magnification of this instrument allows the observation of individual particles in the film surface and the changes with aging.
Glass Transition of Crosslinked Polyurethan Elastomers and Initial Components
Authors: Lipatov Yu S. , Kerchas Yu Yu , Sinyavskii V. G. , Lipatnikov N. A. 
Published: February 2011

Abstract
Differential thermal and thermomechanical methods were used to investigate glass transitions in many polyurethan elastomers and their initial components—oligoesters and linear prepolymers. Glass transition temperature of oligoesters increases with higher molecular weight to a certain limit, corresponding to a molecular weight of 4000, after which it remains unchanged with increase in molecular weight. This value corresponds to the mechanical segment of the oligomer. Unlike oligoesters, for prepolymers with the same length of oligoester unit, glass transition temperature increases with higher urethan group concentration in unit volume and not with increase of molecular weight. Presence of polar urethan groups and not the three dimensional structure of elastomers has the main effect on increase of glass transition temperature of polyurethan elastomers, as compared with initial oligoesters. Elasticity of polyurethan depends on length of the polyester unit and the chain segment between the units of the network mainly formed by physical bonds.
Reinforcement of Polymers. I. Tear Resistance of Filled Mixes and Adhesion of Elastomer to Filler as a Function of Duration and Temperature of Elastomer and Filler Contact
Authors: Raevskii V. G. , Yagnyatinskaya S. M. , Episeeva S. N. , Voyutskii S. S. 
Published: February 2011

Abstract
In accordance with the concepts being developed by the authors of the present paper, the influence of fillers on the properties of filled systems is determined by adhesion of the polymer to the filler. There are indications of the significance of this factor in many papers dealing with the study of reinforcement. However, they do not advance adhesion as a basic factor which determines reinforcement. This has become possible after the development of a procedure for the evaluation of adhesion of polymers to powdered fillers. This paper lists experimental data on the correlation between the duration and temperature of contact of the elastomer with filler particles on the tear resistance of filled mixes, on one hand, and the time and temperature dependence of the adhesion of the system components to one another, on the other. The selection of tear resistance as a characteristic of the physicomechanical properties of the system is governed by the fact that failure starts, as a rule, from a random local defect. Most frequently this is a small cut or surface crack. For this reason, the assertion of a number of researchers that the operating properties of products are more fully characterized by tear resistance rather than by tensile strength is fully acceptable. Besides, tearing is the most general type of destruction of materials, inasmuch as it takes place during rupture as well as during wear.
Separation of Molecules with Linear and Branched Structures in Natural and Styrene-Butadiene Rubbers
Authors: Dogadkin B. A. , Igumnoya A. V. , Kuleznev V. N. 
Published: February 2011

Abstract
The possibility of separating linear and branched polymer molecules by chromatography on silica gel is demonstrated. Removal of microgel from styrene-butadiene rubber, SKMS-30 increases the mechanical strength of its vulcanizates; removal of microgel from natural rubber, conversely, reduces the strength. The existence of an optimum branched-structure concentration which insures a gain in various mechanical properties is postulated.
Correlations between Structure of Elastomers and the Mechanism of their Degradation by Ozone
Authors: Salomon G. , van Bloois F. 
Published: February 2011

Abstract
Ozone cracking is treated as a special case of stress corrosion. The correlation between delayed fracturing, stress and strain is explained in terms of changing crack geometry. Structural relationships have been studied in the region of minimum, critical stress. Two groups of ozone sensitive polymers can be distinguished: in highly ozone sensitive materials cracks are initiated at very low values of stored elastic energy, while initiation in the more resistant butyl rubbers and EPT rubbers occurs only at much higher values of stored elastic energy. The rate of cracking in neoprene is shown to be much less stress sensitive than the corresponding rate in other polydiene rubbers. It is conjectured that this favorable property of neoprene depends on the rheological behaviour of the ozonized surface layer.
Blends of cis-1,4-Polybutadiene with Natural or Styrene Butadiene Rubber
Authors: Fujimoto K. , Yoshimiya N. 
Published: February 2011

Abstract
Temperature dependence of dielectric loss, mechancial loss, and dynamic modulus were measured to study polymer blending. Results were as follows: Dielectric loss and dynamic modulus of NR—BR blends showed two peaks corresponding to NR and BR, indicating that the blends were microheterogeneous. A single, broad maximum absorption band observed for SBR—BR blends indicated that the blends were microhomogeneous. Mill mixing and solution mixing of NR and BR made very little difference in blended state and physical properties. Nearly homogeneous SBR—BR blends can be obtained with a few minutes mill mixing. In vulcanization of NR—BR blends, BR was overcured rapidly due to migration of sulfur and accelerators from NR.
Chemical Stress Relaxation of Polyacrylate Elastomers
Authors: Singh Ajaib , Weissbein L. 
Published: February 2011

Abstract
The continually widening range of thermal stresses imposed on elastomeric parts used in the automotive and aeronautical fields intensifies both the need for more thermally versatile elastomers and the need for effective laboratory methods for evaluating elastomer performance. Because stress relaxation provides a means of gauging product performance under both high temperature and external stress that approximate conditions of use, this technique gives a good estimation of an elastomer's commercial potential and its adaptability to a particular application. To demonstrate the value of stress relaxation, the thermal stability of a polyacrylate elastomer crosslinked with various curatives and the effect of certain additives on thermal stability were studied. Polyacrylates are of major interest for applications that require a high degree of thermal stability because of their ability to perform well over wide temperature ranges (−25° to 400° F). These elastomers are mainly copolymers of ethyl acrylate and a chlorine containing monomer such as vinyl chloroethyl ether. Some newer types are based on ethyl and butyl acrylates and chlorine free monomers such as epoxides and substituted amines. Generally, polyacrylates are compounded and prepared for curing according to standard techniques and they can be crosslinked with a variety of curative systems. Curing is accomplished at between 300° and 400° F in times ranging from 45 seconds to 45 minutes, depending on the elastomer and curing recipe used. The thermal stability of these elastomers is frequently determined by measuring the percentage changes in physical properties, e.g., tensile strength, elongation, modulus, after oven or oil aging or both at elevated temperatures. However, heat aging is carried out with no external stresses applied to the test specimens and the physical measurements before or after aging are made at room temperature. Although this type of test has some value, the results do not necessarily reflect the behavior of the elastomers in practice, as is the case with stress relaxation.
Tire Durability with Nitrogen Inflation
Authors: Sperberg L. R. 
Published: February 2011

Abstract
All tires fail due to interior oxidative deterioration, structural defects from manufacturing errors, improper tire design, road hazards, and exterior cracking caused by ozone and ordinary oxidation, most important being interior oxidative deterioration. This failure cause, while being most important, is least understood and appreciated. Oxidative deterioration of tires starts within the interior gas chamber, which acts triply for ride cushioning, as the reservoir of heat generated by the running tire, and as the vessel which contains oxygen to effect the tire's destruction. Arrhenius' law and the mass action law of chemical reactions are followed in that oxidative deterioration is governed by heat (temperature) and oxygen concentration. Since hysteresis (running temperature) can only be controlled within limits, lowering the oxygen concentration of the inflating gas is the only remaining way of inhibiting oxidative deterioration of tires, which is a cumulative effect of time, temperature and interior oxygen concentration. Five carefully controlled passenger and truck tire tests were run during the past eighteen months to investigate oxidation phenomena. In each test, one half the test sample was inflated with ordinary air, the other half with an inert gas to reduce the oxygen concentration. Over 2.5 million tire miles were run in these five tests. A sixth test involving over eighty truck tires was run more than 6.5 million tire miles during the past 36 months to observe the oxidative effect of air inflation upon inner tubes and tire body deterioration. All six tests show strikingly that oxygen-free inflation gas has a profound and major beneficial effect upon overall tire endurance and upon tire wear. Actual performance data show tire endurance of passenger tires to be improved an average of 22 per cent when oxygen concentration is reduced to 0.6 per cent and wear improvement of 15 per cent at a point where tires were only 64 per cent worn.
Laboratory Tire Groove Cracking Test
Authors: Vance Roy M. , Burgess Kenneth A. 
Published: February 2011

Abstract
A new laboratory test for evaluating groove cracking of tire treads was developed. The tread section, including the carcass of a tire, is flexed under similar stress and temperature conditions as in actual tire service. Whole or multiple tread sections may be tested. The test is much less expensive than either road or indoor wheel tests. The test gives results that are reproducible and which are in accord with actual tire performance. In SBR/BR passenger tire tread formulations, finer carbon blacks or lower structure carbon blacks produce more groove cracking in this laboratory test; trends also observed in actual service. The inhibiting effect of antioxidants on groove cracking was demonstrated. In NR/BR treads, inversion of the structure effect was observed. Evidence has also been obtained that the test is capable of correctly predicting the effect of a tread design change upon groove cracking.
Discussion
Authors: Horne W. B. 
Published: February 2011

Abstract
Mr. W. B. Horne (NASA, Hampton, Virginia)—Results in the two papers are in agreement with NASA research results. The papers treated the subjects of tread material, tire construction, road surface texture, and tread design very thoroughly. But one essential ingredient to the problem has been left out of the paper discussions, and that is, the effect of water depth. The importance of the water depth effect, and the need to inform both public and government authorities about the importance of removing worn tires from automobiles for the safety of all, is discussed and illustrated very fully by Leland. An example of what happens when the water depth is 0.4 in. is shown in Figure 1. It can be seen that the water penetrates the tire imprint much more rapidly than in shallow water. The effect of road surface texture on braking friction coefficient is illustrated by the data shown in Figure 2. A smooth tread aircraft tire was successfully braked on five different road surfaces ranging in texture from a large aggregate asphalt surface to wet ice. These surfaces are classified as damp in wetness. The surfaces at the time of testing were wet to the touch but did not have any puddles or standing water. Under this condition, damp smooth concrete (smooth as a table top) gave friction values as low as wet ice. This drastic friction loss decreased as the road surface texture increased. It will be noted that the smooth aggregate asphalt data did not fall off in speed as was shown by Maycock in his paper in Figure 15. In Figure 3 the water depth on the smooth concrete and large aggregate asphalt surface was increased from a damp condition to a flooded condition (0.1–0.2 in.). The character of the friction changes of these surfaces due to change in water depth is remarkable. For example, the smooth concrete increased slightly in value. This is an apparent increase, however, because the deeper water produces a fluid drag term which adds to the tire-surface braking force and gives a higher friction coefficient. This is an academic point, however, since the smooth concrete surface is producing viscous hydroplaning even at low speeds. On the other hand, the asphalt surface which alleviated the viscous hydroplaning effect under damp conditions does not prevent dynamic hydroplaning from occurring to the tire when this surface is flooded to a depth of 0.1 to 0.2 in. To summarize, any surface must be evaluated under a range of water depths before its wet friction qualities can be properly evaluated. Smooth tread tires or badly worn patterned tires have demonstrated poor friction capabilities on most wet or flooded surfaces. For this reason, both aircraft and automobile tires should be removed and replaced before wear produces a smooth tread condition.