bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multicomponent Polymerization. II. The Effect of Mixing on Copolymerization in Continuous Stirred Tank Reactors
Authors: O'Driscoll K. F. , Knorr R. 
Published: February 2011

Abstract
Calculations have been carried out to describe the course of three vinyl copolymerizations which typify free radical copolymerizations. Conversion of monomer to polymer and copolymer average composition, as well as copolymer composition distribution (CCD), have been calculated for these three systems in batch reactors (BR) and in continuous stirred tank reactors which have perfect, homogeneous micromixing (HCSTR) or imperfect mixing which leads to segregation on the microscopic scale (SCSTR). The results of the calculations indicate that conversion and average composition behavior are not necessarily strongly dependent on mixing in a CSTR, although they are in some systems. However, the CCD is strongly affected by mixing in all systems where the composition drifts with conversion. The magnitude of the effect of mixing on CCD increases with conversion. In the limit, a SCSTR gives at high conversion the same CCD as a BR. A HCSTR always gives a monodisperse CCD. Limitations and applications of the calculations are discussed.
Morphological Study on Carbon Black Loaded Rubber Vulcanizate under Stretching
Authors: Shinomura T. , Takahashi M. 
Published: February 2011

Abstract
The morphological change of pure and carbon black loaded butyl rubber vulcanizates with elongation was studied by an electron microscopical method. The main noticeable observations were as follows. The number of cavities increases with the increase of elongation. The shape of cavities grows into longer spindle one with the increase of elongation. Carbon black aggregates break down with the increase of elongation. It is concluded that there are two types of cavitations in carbon black loaded rubber vulcanizates.
EPDM Vulcanization and High Temperature Compression Set
Authors: Baldwin F. P. 
Published: February 2011

Abstract
The data presented are suggestive of the following conclusions regarding the vulcanization behavior and high temperature compression set properties of low unsaturation EPDM polymers: 1. The olefinic residue derived from ENB is more reactive in conventional sulfur vulcanization than is the residue from MNB. However, the ENB residue is more prone to reversion reactions. 2. The structure of the olefinic residue present can have important bearing on the exact nature at the crosslinks produced at a given crosslink density. 3. The conversion of high to lower sulfur rank crosslinks appears to occur partly by a thermally induced interconversion process and partly by concerted reactions in which crosslink bond scission does not occur as a discrete step. Both the nature and the concentration of accelerator present should have important bearing on the competitive balance between these two processes as should the presence of free sulfur. 4. Since the presence of free sulfur can procrastinate the sulfur crosslink rank reduction process, the observed low rate (relative to highly unsaturated elastomers) of conversion of polysulfidic to lower rank crosslinks must be associated with the absence of a large “sink” for sulfur. Thus with a given curing system, stable crosslinks should be generated faster the higher the level of unsaturation present and the lower the sulfur concentration. 5. High temperature compression set performance is influenced not only by the formation of new crosslinks during heating under compression but also by the interconversion of polysulfidic linkages present in the initial vulcanizates. Thus two polymers containing different olefin residues can exhibit identical set properties but for different reasons. 6. In practical terms both crosslink density and stability can be maximized by a combination of a short, high temperature forming cure followed by a long heat soak at a lower temperature. This observation should have important bearing on the economics of production of quality mechanical goods from low unsaturation elastomers via injection molding, the heat soaking step being paid for by the reduction in accelerator cost and molding cycle time.
Predicting Tire Tread Performance from Composition. I
Authors: Lane J. H. , McCall C. A. , Gunberg P. F. 
Published: February 2011

Abstract
Wet skid resistance of tread compounds, as measured by the British Portable Tester, and heat buildup, as measured by the Goodrich Flexometer, can be predicted accurately from a knowledge of composition and modulus, while wear resistance, as measured by the Pico Abrader, can be predicted with only fair accuracy. The predicting relations were developed using multiple regression analysis from data obtained in a designed experimental program. Independent variables included four polymers (emulsion SBR's of 0, 23.5, and 40% bound styrene and cis-polybutadiene), extender level, carbon black N−285 loading, and modulus. Field test results are presented for compounds selected to show improved wet skid resistance while maintaining wear and groove cracking resistance at present-day levels. Test conditions influencing tire wet skid testing results, particularly the phenomenon of partial hydroplaning, are discussed.
Vulcanization of Rubber with Aminomercaptotriazines
Authors: Westlinning H. 
Published: February 2011

Abstract
Aminomercaptotriazines are a new class of accelerators for rubber vulcanization. The kinetics of the vulcanization reaction and the yield of crosslinks depend strongly on the molecular structure of the accelerators. The vulcanization is highly resistant to reversion which is demonstrated by a smaller increase in heat generation under dynamic deformation as well as by higher vulcanization temperatures and longer vulcanization times. In natural rubber and synthetic polyisoprenes aminomercaptodisulfides produce high yields of crosslinks combined with high processing safety. Fatigue strength of natural rubber vulcanizates is considerably enhanced by air aging. In blends of NR and SBR with BR, sulfenamides of dimercaptotriazines produce a very stable vulcanizate combined with good processing safety. Rate of cure can be increased by combination with a mercaptan. With polydisulfides SBR can be crosslinked without elemental sulfur at all. The vulcanizates have a high fatigue strength and a high hysteresis.
Occurrence and Prevention of Changes in the Chemical Structure of Natural Rubber Tire Tread Vulcanizates during Service
Authors: Cunneen J. I. , Russell R. M. 
Published: February 2011

Abstract
The chemical structure of the tread vulcanizate of heavy-duty tires has been investigated before and after service on the road, and after testing under conditions designed to induce tread-lift. Significant changes occurred. These included a marked reduction in the concentration of polysulfide crosslinks, and an increase in the amount of monosulfide crosslinks and main chain modification. Experiments with vulcanizates made in the laboratory indicated that the structural alterations in the tires were due to thermal anaerobic reactions caused by heat build-up, and that they resulted in a deterioration in some of the physical properties of the tread vulcanizate. The rate of desulfuration of ‘model’ polysulfides has been found to depend critically upon the nature of the vulcanization recipe. These novel findings point the way to improving the stability of vulcanizates used in the treads of tires and, consequently, tire performance.
Modification of CIS-1,4-Polybutadiene with β-Naphthylamine
Authors: Kirpichev V. P. , Yakubchik A. I. , Maglysh G. N. 
Published: February 2011

Abstract
Modification of epoxidized cis-1 ,4-polybutadiene (ESKD) with β-naphthylamine has been studied. Reaction is carried out in sealed ampules in toluene solution, argon atmosphere and in pressure of phenol as catalyst. Effects of temperature, time, phenol quantity, and ratio β-naphthylamine :ESKD on reaction extent have been examined. Preliminary test shows high efficiency of the reaction product as a high molecular antioxidant for stereoregular rubbers.
Porosity Studies on Some Oil Furnace Blacks
Authors: Smith W. R. , Kasten G. A. 
Published: February 2011

Abstract
It is generally accepted that the internal area arising from pores in an oxidized carbon black does not contribute to performance characteristics in rubber. While such pores are available to nitrogen, commonly used in evaluating surface area, they do not appear to be accessible to an elastomer molecule. Thus in predicting performance from area measurements one should consider the external area. Of course, for a non porous black the external and total (BET) area will be identical. In the past, the electron microscope provided the only independent means of evaluating external area. However, with the development of oil furnace blacks, particularly the more recent grades of high structure, identification and measurement of individual particles becomes more difficult and the electron microscope procedure less reliable. However, in recent years the so called “t curve” procedure has come into prominence and appears to provide a useful comparative method for detecting porosity and, to a degree, its extent. The method is quite empirical and requires the selection of a “non porous” adsorbent to serve as a standard with which other samples may be compared. A number of standards have been proposed but that of de Boer appears to be most widely used. The de Boer standard is based on a calcined alumina. In undertaking porosity studies on carbon blacks it appeared to us from earlier studies on silicas and titanias that a non polarizing carbon would be preferable to an oxide surface. Accordingly, we have selected a fine thermal black as a t curve standard. The present paper presents some of the results of this study. They differ to a degree from those of other investigations in which the de Boer standard was employed.
The Load Dependence of Side Force and Self-Aligning Torque of Pneumatic Tires
Authors: Schallamach A. 
Published: February 2011

Abstract
A conclusion to be drawn from this analysis of the load dependence of side force and self-aligning torque of pneumatic tires is that agreement between experimental and theoretical side force curves does not necessarily prove the soundness of the theory. On the other hand, even an inadequate theory is successful in suggesting a predictable and useful interrelation between load and slip dependence of the side force. Figure 4 demonstrates that quite a primitive transform of experimental data can lead to a unified presentation of its load and slip dependence although the resulting curve deviates quantitatively from theory in this particular case. This work forms part of a program of research undertaken by the Natural Rubber Producers' Research Association.
Heats of Reaction of Natural Rubber with Sulfur
Authors: Bekkedahl N. , Weeks J. J. 
Published: February 2011

Abstract
An adiabatic copper calorimeter was used to determine the heats of vulcanization of pale crepe natural rubber with sulfur for mixtures varying in composition from 0 to 32 per cent added sulfur. The side reaction that produces hydrogen sulfide was avoided by using reaction temperatures near 155° C. Heats of reaction at 25° C and at 155° C are reported. The enthalpy change at 25° C for compounds containing up to about 18 per cent sulfur is given in joules per gram of vulcanizate by the equation, ΔH25=−21.1·S with a standard deviation of 11 J/g. Here S is the percentage of combined sulfur. Above 18 per cent sulfur the heat of reaction at 25° C remains approximately constant at 380 ± 8 J/g. A comparison is made between the heat of vulcanization and the volume change on vulcanization, both as functions of combined sulfur, by making use of data in the literature.
Measurement of Chain Structure in Carbon Blacks
Authors: Voet A. , Aboytes P. 
Published: February 2011

Abstract
The dual structure of dispersed carbon blacks consists of an irreversible structure of particles coalesced in their formative stage, known as persistent structure and a reversible, transient structure created by mutual attractive forces between particles or persistent structural units. The shear dependence of dielectric constant as well as of electrical conductivities of carbon black dispersions can be explained from the dual structure. Direct measurement of the elastic shear modulus and dynamic conductivity of black reinforced vulcanizates, at amplitudes varying over an extremely wide range, permits evaluation of the contributions of persistent and transient carbon structures separately. A new approach measures persistent structures of blacks dispersed in a mineral oil by means of the minimum value of the conductivity-shear curve, while the transient structure is evaluated in terms of the initial conductivity increment with the logarithm of time immediately after cessation of shear. Relative structural numbers have been introduced by comparing the data with those of very low structure blacks of comparable particle size, dry ball-milled to remove all structural remnants.
Creep of Pure-Gum Vulcanizates of Natural Rubber
Authors: Wood L. A. 
Published: February 2011

Abstract
The creep of vulcanizates of natural rubber cured with varying amounts of dicumyl peroxide was compared with that of vulcanizates cured by typical conventional surfur-accelerator systems. The measurements involved indentation of a flat rubber disk as a function of time t and temperature T. The product of shear compliance J and T as a function of log t was represented by a family of curves with T as the parameter. For the vulcanizates cured with the sulfur-accelerator system, previous work has shown that the individual curves could be shifted along the abscissa to yield a single continuous curve with a slope which increased from a negligible value to a maximum and then decreased, continuing through a region of minimum slope which extended over about 7 decades of time before ending in a region of increasing slope. The value of the creep was 1.5–2.0% per decade in the region of minimum slope. When the same procedures were applied to the vulcanizates cured with dicumyl peroxide, the individual curves of JT against log t at each temperature did not yield a single continuous curve when shifted. In a limited region just above the glass transition temperature, the creep was appreciable, but neither a constant-activation-energy shift nor a Williams-Landel-Ferry shift was satisfactory. Above this region it was clearly impossible to obtain a single curve since the compliance-temperature product at a given time increased with increasing temperature while the corresponding creep of the dicumyl peroxide vulcanizates was generally too small (&lt;0.5% per decade) to be measured between 5 and 600 seconds, except when the compound contained less than 2.5 parts of effective dicumyl peroxide. Outside of these regions the shear modulus was found to increase linearly with temperature. The investigation included temperatures as high as 100° C and effective dicumyl peroxide concentrations as high as 25 parts per hundred of rubber. The present results for the modulus and creep of dicumyl peroxide systems show good agreement with the published data of Chasset and Thirion (obtained by stress relaxation at 30° C) and of Plazek (obtained by a torsion pendulum) over the ranges they investigated.
Laboratory Measurement of Abrasion Resistance Using a Free Flowing Abrasive
Authors: Thelin Jack H. 
Published: February 2011

Abstract
A laboratory abrader utilizing a free-flowing abrasive was described and some operational variables discussed. Various techniques and conditions of abrading elastomers of both practical and research interest were considered. In certain cases significant variations of abrasion resistances with depth of wear were indicated and speculatively related to the non-homogeneity of the samples involved. In addition, the mechanico-oxidative nature of abrasion was clearly demonstrated.
Research for a Uniform Quality Grading System for Tires. IV. Tread Wear
Authors: Brenner F. C. , Kondo A. 
Published: February 2011

Abstract
This research had as its objective the development of a test procedure for rating tires for tread wear. The results of preliminary experiments on roads of different composition and severity are discussed. The authors conclude that the course on which tires are to be rated should include several different pavements and a variety of maneuvers of unequal severity. Two courses, one near Bryan, Texas, and the other near San Antonio, Texas were designed on this principle. Eighteen brands of tires including bias, radial, and G78 belted bias tires were run on each course. The tires ranked in order of decreasing projected mileage on each course were highly correlated, although the mileages were not equal.
High Temperature Relaxation Transitions in Elastomers
Authors: Sidorovich E. A. , Marei A. I. , Gashtol'd N. S. 
Published: February 2011

Abstract
1. For binary mixtures of polybutadienes with differing molecular weights, a high temperature (or low frequency) transition was discovered, with the temperature-frequency position of the transition showing up as a function of the molecular weight of the low molecular weight constituents, and yet the transition does not depend on the concentration of these constituents. The value of the maximum for the mechanical loss tangent is determined by the concentration of low molecular weight components. 2. With regard to the viscoelastic behavior of the mixes at reduced temperatures, the transition reflects mainly the presence of the low molecular weight components, but at high temperatures the transition is indicative of the presence of the high molecular weight constituents. 3. The observed transition is associated with the manifestation of mobility of the molecules of the low molecular weight components, as a whole.
Relaxation of Stress and Electrical Resistivity in Carbon-Filled Vulcanizates at Minute Shear Strains
Authors: Voet A. , Cook F. R. , Sircar A. K. 
Published: February 2011

Abstract
Measurements have been made of the relaxation of stress and electrical resistivity of carbon black-loaded vulcanizates subjected to shear deformation varying between 0.5 and 20%. Samples were initially brought into an equilibrium state by the application of a sinusoidal shear strain for a period of time long enough to ensure equilibrium condition, established by constancy in the dynamic stress- and resistivity-time cycles at each selected strain amplitude. It could be shown that at the small strains employed all phenomena were completely reversible, indicating the absence of rupture of elastomer chains or crosslinks and of strong bonds between carbon and elastomer, as well as of chemical aging. The shear stress relaxation rates show a small initial decrease with deformation and are fairly constant over the rest of the deformation range. Carbon black loading increases the rate—the more, the smaller the particles and the higher, the higher the loading—but the rate is independent of the carbon structure. Actual initial stress values follow the expected stress-strain relations. Resistivity relaxation rates, on the other hand, show a very rapid increase with shear deformation, more pronounced at higher structures and for smaller particles. Initial resistivity values are in complete accord with the dynamic behavior of vulcanizates. An explanation of the shear stress relaxation rates of the loaded vulcanizates has been made on the basis of reestablishment of previously disrupted weak bonds between particles and elastomer chains. Resistivity relaxation rates could be explained by assuming rebuilding of disrupted transient structures, while the unusual behavior of Graphon, with a zero relaxation rate, appears to be caused by its lack of bonding to elastomer chains. Finally, there are indications that the equilibrium resistivity behavior of a carbon-loaded vulcanizate subjected to shear strain at increasing amplitudes under reversible conditions is closely parallel to the reinforcement characteristics of the carbon black filler. Measurement at higher temperature permits calculation of an activation energy which appears to correspond to physical interaction.
Relaxation of Stress and Electrical Resistivity in Carbon-Filled Vulcanizates at Moderate and High Extensions
Authors: Sircar A. K. , Voet A. , Cook F. R. 
Published: February 2011

Abstract
Measurements have been made of the relaxation of stress and electrical resistivity of stretched carbon black-loaded vulcanizates throughout the elongation range up to break. Data were obtained for vulcanizates with a number of carbon blacks, varying in particle size and in structure. The influence of the degree of loading as well as of the type of elastomer was investigated. In a gum vulcanizate there is initially a decline in rate of stress relaxation at increasing elongation as a result of the limited extensibility of the elastomer chains, followed by a constant rate at higher extensions. The level for a carbon-loaded vulcanizate is always higher than for the gum. At lower elongations this is due to an additional relaxation mechanism, the reformation of broken weak bonds between elastomer and filler particles upon standing. At medium and higher elongations, the stress relaxation rate for the carbon-filled vuleanizates increases sharply with increasing extension, due to persistent carbon chain alignment and, at still higher elongation, to rupture of carbon-elastomer bonds, both phenomena leading to additional modes of stress relaxation. Resistivity relaxation rates reflect changes in carbon black distribution. An initial increase at small extensions is due to rebuilding of destroyed transient structures. A decrease in relaxation rates for medium extension ranges is caused by persistent carbon chain alignment, less pronounced at increasing elongation. At the higher elongations carbon-elastomer bonds arc broken, leading to randomization of chains, resulting in negative relaxation rates with higher structure blacks at the highest elongations. All such effects depend to a large extent on the carbon structures. The influence of loading level, of particle size and of elastomer type is discussed.
Formulation for Continuous Vulcanization in Microwave Heating Systems
Authors: Ippen J. 
Published: February 2011

Abstract
For a number of years the rubber industry has been trying to make its processes as continuous as possible. Techniques which dispense with interruptions are particularly desirable in the production of strip and hose, for extrusion is a continuous process whose interruption for the purpose of enabling the goods to be cured is both illogical and unsatisfactory. Several continuous vulcanization methods, such as the use of hot air and the liquid curing method, are receiving attention. A new development in this field is the use of microwave for vulcanization. Microwave curing is a valuable supplement to other continuous vulcanization methods, in comparison with which it offers advantages in some respects.
Hydrolytic Stability of a New Urethane Elastomer
Authors: O'Shaughnessy F. , Hoeschele G. K. 
Published: February 2011

Abstract
A new polyether based liquid casting urethane elastomer having excellent abrasion resistance, improved electrical properties, and superior hydrolytic stability has been described. A good balance of working life, physical properties, and overall handling ease are provided when MDA is used as the curing agent. These elastomers may be safely used as the contact surface of articles intended for use in handling bulk quantities of dry food. This unique combination of properties indicates many practicable applications.