bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Carbon Black Type in Filled Rubber Vulcanizates
Authors: Nabors Lester G. , Studebaker Merton L.
Published: February 2011

A system of analysis has been described which permits determining the type of rubber grade carbon black in a vulcanizate. The carbon black is removed from the vulcanizate by vacuum pyrolysis at 850° C and its reflectance after acid washing and compression at 15,000 psi and apparent specific volume at 703 psi are determined. These measurements permit estimation of particle size and “structure.” Supplementary analyses are required for channel blacks. The procedure is most precise when the analytical values are compared with analogous data obtained from carbon blacks of known properties when removed by the same procedure from similar vulcanizates. As in all qualitative analyses, the more information which is available to the analyst, the more reliably he is able to interpret his results.
A Simple Theory of Filler Reinforcement in Elastomers Subjected to Shear
Authors: Zorll Ulrich
Published: February 2011

The effects of a filler in an elastomer can be described by means of a theory based on a simple model in which the filler particles are assumed to be of uniform size, of cubic shape, and dispersed in such a manner as to occupy the points of a cubic space lattice. For the case of shear deformation, simple relations can be derived for the increase in the storage modulus G′ and the loss modulus, G″ of the bulk material with an increase in filler content. Furthermore, the theory predicts the temperature shift of two points which can be easily determined experimentally: the inflection point of G′ and the maximum of G″.
Mild Stress Softening and Dynamic Properties of Rubber Vulcanizates
Authors: Voet Andries , Cook F. Russell
Published: February 2011

Mild, reversible stress softening of vulcanizates loaded with carbon blacks of widely different structures and reinforcing characteristics was investigated by means of a novel electronic variable shear amplitude dynamic tester. The instrument yields low frequency dynamic data for vulcanizates in the range of double strain amplitudes of 3×10−5 to 1.0, covering nearly five decades. Mild reversible stress softening (up to 100 per cent amplitude) in a variety of vulcanizates investigated is caused by a reversible thixotropic breakdown of transient carbon chains, which contribute to reinforcement by an energy dissipating mechanism. Persistent, “fused” carbon chains contribute to reinforcement by their beneficial influence on the crosslink density of the vulcanizate. Elastomer and carbon chains respond independently to stress.
Crystallization in Stretched Polymer Networks. II. trans-Polyisoprene
Authors: Gent A. N.
Published: February 2011

Measurements are described of the rates of crystallization and crystal melting temperatures in stretched test pieces of trans-polyisoprene, crosslinked to various degrees. The increases in rate with extension are attributed to the corresponding increases in melting temperature and hence degree of supercooling. The rise in the melting temperature of both the α and β crystal forms is found to be in satisfactory agreement with Flory's treatment of oriented crystallization. Changes in tensile stress are also generally in accord with the formation of oriented crystallites. For the more lightly crosslinked materials, a pronounced rise in tensile stress occurred during the later stages of crystallization, at extensions below about 100 per cent. Reasons are given for attributing this phenomenon primarily to the relatively large contraction in volume on crystallization, rather than to the formation of folded-chain crystallites.
Polypropylene Oxide. IV. Preparation and Properties of Polyether Networks
Authors: Allen G. , Crossley H. G.
Published: February 2011

Stable vulcanizates of copolymers of propylene oxide and butadiene monoxide have been prepared and some physical properties studied. The cohesive energy density of a copolymer containing 84 per cent propylene oxide is determined from swelling measurements to be 83 cal cm−. The dynamic properties of the copolymer are similar to those of natural rubber. From a thermodynamic point of view the copolymer is more ideal in its rubbery behavior than natural rubber.
Cold Flow in High Impact Polystyrene
Authors: Arends C. B.
Published: February 2011

Eyring's theory of viscous flow has been applied to some mechanical properties of rubber modified polystyrenes. Yield strengths as a function of orientation, temperature, and rate of strain have been shown to be consistent with the theory. The temperature of transition from ductile to brittle fracture as a function of orientation has also been measured and found to be consistent with theoretical predictions.
Extraction of Admixed Polymers from Natural Rubber Vulcanizates
Authors: Cooper W. , Smith R. K.
Published: February 2011

Extraction by solvent of admixed poly(methyl methacrylate) or polystyrene from natural rubber vulcanizates is dependent on the crosslink density, the solvent, the molecular weight of the polymer, and the size of sample extracted. High molecular weight polymer is extracted very slowly, and in some cases several weeks of continuous extraction have been found necessary. The rate of extraction is increased, as would be expected, by solvents which swell the rubber strongly, and by increase in temperature of extraction. In some cases the vulcanization procedure degrades the polymer, while in others there is a possibility of cocrosslinking the rubber and polymer. Graft copolymers from rubber and methyl methacrylate or styrene possess similar characteristics when vulcanized. In consequence, analysis of the content of free homopolymer is subject to considerable uncertainty. In the analysis of these rubber and polystyrene mixtures by ozonolysis, polystyrene was found to be very susceptible to attack by ozone.
Chain Density in Rubber Networks
Authors: Bobear W. J.
Published: February 2011

Though difficult to prove from experimental data, the concept that network chain density is reflected in the Mooney-Rivlin C1 parameter has received fairly wide acceptance. In the present work, experimental stress strain measurements on natural rubber are shown to be consistent with the idea that the network chain density is directly related to the sum of the Mooney-Rivlin constants, C1 and C2; rather than to the C1 parameter only. The determination of elastically effective chain densities in polydimethylsiloxane networks is also discussed. A relationship is obtained for concentration dependence of the polydimethylsiloxane-toluene interaction parameter. The results are used to study the cure of polydimethylmethylvinylsiloxanes with “vinyl specific” peroxides. Experimental data favor the proposal that a trimethylene crosslink is formed by the reaction of a methyl group with a vinyl group through a free radical mechanism.
Migration of Extender Oil in Natural and Synthetic Rubber
Authors: Lewis James E. , Deviney Marvin L.
Published: February 2011

The migration of oil, and in particular, the migration of extender oils in rubber is being studied through the use of radioactive isotopes. Techniques have been developed for uniform carbon-14 labelling of the aromatic-polar fractions of extender oils by Friedel-Crafts reaction and for the uniform labelling of the paraffinic fraction by methylene diradicals generated during photolysis of diazomethane-C14. These techniques formed the basis for a comparative study of the diffusion rates of aromatic and polar, and paraffinic, fractions of a highly aromatic and a paraffinic extender oil in several rubbers which represent a wide range in type of polymeric structure. Faster diffusion rates of both aromatic and polar, and paraffinic fractions, were observed in polybutadiene and natural rubber than in SBR, EPT, and polychloroprene. In most rubbers, paraffinic materials migrated appreciably faster than aromatic and polar fractions. Experiments using Firestone flex blocks indicated that oil migration rates are higher under simulated working conditions than when the sample is subjected to heat treatment alone. Diffusion coefficients for the migrating fractions were calculated from an appropriate solution of the basic differential equation of diffusion using modern computer techniques. The methods which have been developed are suitable for fundamental studies to gain more insight into the mechanisms of diffusion. These experimental methods are also suitable for use in practical studies of oil migration under actual or simulated working and environmental conditions. Ultimately sufficient information should be obtained to permit an accurate prediction of the performance of an extender oil in selected rubbers on the basis of the physical properties of the oil and a quantitative knowledge of the major molecular types present in the oil.
Linear Elastomeric Block Polymers
Authors: Zelinski Robert , Childers C. W.
Published: February 2011

Polymer molecules containing chemically dissimilar segments have been investigated for many years. Their synthesis and characterization are challenging, and it is evident that their properties are often unusual and useful as witnessed by several books and reviews published on block and graft polymers. In this article we intend to review parts of this rapidly expanding area of polymer research of particular interest in rubber chemistry and technology, namely linear elastomeric block polymers. Sometimes the literature specifies the elastomeric nature of the products, on other occasions it does not. We have arbitrarily included those monomer combinations in which at least one monomer is known to form rubbery homopolymer. Urethan elastomers have been excluded because they have been extensively described elsewhere. In the broadest sense, block polymers are molecules in which two or more chemically dissimilar segments are joined end to end, a feature which distinguishes them from graft polymers. Each segment or block is usually a long sequence of units of a single monomer (A or B or C, etc.), but it may also be a long sequence of randomly copolymerized units (A plus B or C, etc.). Both types are known.
Oxidative Aging of Natural Rubber
Authors: Cunneen J. I.
Published: February 2011

In the last few years several reviews and books have been published on the aging of elastomers, but the overall view which they present of the oxidation of natural rubber and its vulcanizates still contains many puzzling features. Two of these are the variation of antioxidant efficiency in different types of vulcanizate, and the extent of the involvement of crosslink scission in the overall degradation process in sulfurated vulcanizates. Sometimes apparent contradictions have arisen from a failure to appreciate that aging of natural rubber vulcanizates depends primarily on four factors; the purity and type of rubber, the presence of additives, the type and extent of vulcanization, and the purification (if any) after cure. In many cases direct comparisons have been attempted without due consideration being given to all these factors, leading inevitably to some confusion. Recent work on the structure of vulcanizates has enabled the NRPRA to embark on a program of aging studies with vulcanizates of carefully controlled structure and complexity, which has already led to a better understanding of the processes involved in vulcanizate degradation. This review will attempt to elucidate the present state of knowledge, and will therefore be largely concerned with recent work at NRPRA, and its relation to previous studies. The review is divided into two main parts, they are: the effect of vulcanizate structure on aging, and the chemistry of oxidative scission reactions. Before attempting to rationalize the effect of vulcanizate structure on aging, structural characteristics of the most important types of vulcanizate are briefly discussed.
Study of Polymer Blends. II. Blending SBR Varying in Styrene Content with Polybutadiene
Authors: Fujimoto K. , Yoshimura N.
Published: February 2011

For this study of effect of SBR styrene content on blends of SBR and BR, polymer solubility was investigated by phase contrast microscopy, dielectric loss, and dynamic characteristics. Physical properties of blended rubber were also measured.
Observations on Fracture of Viscoelastic Bodies
Authors: Halpin J. C. , Polley H. W.
Published: February 2011

The Bueche-Halpin theory for the fracture of viscoelastic bodies is extended to predict the statistical variability of rupture data for both uniform and non-uniform excitation histories. The concept of cumulative damage is examined in light of some critical experimentation. It is shown that the geometry of the distribution is a sensitive “functional” of the excitation history and that the solution of this problem is the key step in the development of a general theory for fatigue.
Elastic Behavior, Birefringence, and Swelling of Amorphous Polyethylene Networks
Authors: Gent A. N. , Vickroy V. V.
Published: February 2011

Polyethylene networks were prepared by γ-irradiation of linear polyethylene, both molten and crystalline. Elastic and. photoelastic properties of the networks were studied at high temperatures, i.e., in the molten state. Equilibrium swelling was also measured in several solvents. Values of the crosslinking efficiency G of γ-radiation, the molecular weight Me between entanglements, the optical anisotropy α of the equivalent random link, and the polymer-solvent interaction parameter μ are deduced. Samples prepared by irradiation in the amorphous state showed markedly nongaussian elastic behavior. The presence of a large nongaussian term in the optical anisotropy is also deduced. The value of α obtained for swollen samples, which showed substantially gaussian elastic behavior, was 3.9×10−24, about one half of that obtained for dry samples. It corresponds to an equivalent random link of only about 5 CH2 units, on the basis of Denbigh's values for bond polarizabilities. The samples prepared by irradiation in the crystalline state also showed lower values for α, depending on the degree of crosslinking. This is attributed to the nonrandom chain configurations prevailing at the time of crosslinking. The same samples were found to show more nearly gaussian elastic behavior, which is attributed to the same cause.
Radiofrequency Heating of Rubber and Carbon Black Mixes
Authors: Langton N. H.
Published: February 2011

In conclusion, the simple model of a uniform array of spherical conducting particles of negligible size, when modified for a random distribution, enables predictions as to the maximum permissible loading of carbon black in a rubber/black mix that can be heated by dielectric heating without breakdown. The theory agrees qualitatively with the results of Gehman's theory of random filler dispersions. It is not possible to compare values given by the theory with experimental results, because there is no reliable data giving breakdown voltage figures for rubber/black mixes of known dispersion. However predictions given by the theory agree qualitatively with experiments.
Molecular Weight Effects in Adsorption of Rubbers on Carbon Black
Authors: Kraus Gerard , Gruver J. T.
Published: February 2011

The molecular weight dependence of the adsorption of polybutadiene on carbon black from a poor solvent, n-heptane, and bulk, i.e., the phenomenon of “bound rubber”, was investigated. For narrow distribution polymers the adsorption is proportional to Mn, where n = 0.14 for adsorption from n-heptane solution; n = 0.5 for adsorption from bulk. Anomalously low solution adsorption was observed for polymers of very high molecular weight (> 500,000). This is ascribed to a sieve effect by aggregates of carbon black particles which cannot be penetrated by the large molecular coils. In high structure blacks, which pack more loosely, and in large particle blacks, which form larger interstices between particles, onset of anomalous adsorption is shifted toward higher molecular weights.
SBR and BR Tread Performance as a Function of Carbon Black Properties
Authors: Micek E. , Lyon F. , Hess W. M.
Published: February 2011

All commercial tread grade carbon blacks, may be classified on the basis of electron microscope surface area and oil absorption. Similar industry wide grade classification on the basis of iodine number, tinting strength and oil absorption is considerably less reliable. However, among the blacks of individual carbon black suppliers, reasonably good classification of the tread grades is possible on the basis of these latter three carbon properties.
Normal Freezing of Solutions of Isobutylene Polymers and Copolymers
Authors: Dole-Robbe Jeanpierre
Published: February 2011

Normal freezing of dilute solutions of polyisobutylene in cyclohexane was examined. Variation in distribution coefficient with freezing rate and molecular weight of the solute was observed, as well as establishment of a gradient for molecular weight in the frozen charge. Polyisobutylene-polystyrene or poly (methyl methacrylate) copolymers were likewise frozen, in benzene solution.
Curative Diffusion between Dissimilar Elastomers and its Influence on Adhesion
Authors: Gardiner J. Brooke
Published: February 2011

The diffusion of common curatives, such as sulfur, TMTD, MBTS, and DOTG, at vulcanizing temperatures between butyl, chlorobutyl, or EPDM and natural rubber, SBR, BR, or neoprene has been studied by light microscopy and attentuated total reflectance infrared. Diffusion occurs with all these curatives. Curative solubility in rubber, which affects diffusion, has been measured at various temperatures. Prom this, distribution coefficients have been calculated by considering the system as a liquid-liquid extraction. These coefficients range between 0.7 and 10. Diffusion coefficients have been obtained, and the energy of activation for diffusion has been calculated. The effect of diffusion upon adhesion between rubbers is also discussed.
The Chemistry of Sulfur Curing. III. Effects of Zinc Oxide on the Mechanism of the Reaction of Cyclohexene with Sulfur
Authors: Wolfe James R. , Pugh Thomas L. , Killian A. Stanley
Published: February 2011

Reaction of cyclohexene and sulfur at 140° followed by lithium aluminum hydride reduction of the polysulfide products results in the formation of cyclohexanethiol, 2-cyclohexene-1-thiol, cis- and trans-1, 2-cyclohexanedithiol, and cyclohexyl sulfide. If zinc oxide is present during the reaction, trans-1, 2-cyclohexanedithiol is the major product. In the absence of zinc oxide, cis-1, 2-cyclohexanedithiol is the major product. It is postulated that in the absence of zinc oxide the reaction proceeds via a free radical chain involving polysulfenyl radicals accompanied by a secondary polar addition reaction of hydrosulfide products with cyclohexene. Zinc oxide when present is postulated to initiate an ionic chain reaction which, due to its greater velocity, dominates the radical chain reaction.
Elastomer Rheology and Processing
Authors: White James Lindsay
Published: February 2011

The handling of raw elastomers in processing and fabricating equipment has been an important industrial operation for 150 years. It was an integral part of a sizable industry several decades before the molecular structure of rubber itself was realized or complex deformation-induced phase transitions and mechanochemical degradation reactions were thought to occur in these materials during processing. The rubber industry was already established when the classical organic chemical industries came into being and predates its sister plastics and synthetic fiber industries by three quarters of a century or more. It is ironic and rather unfortunate that the scientific study of rubber processing operations has been generally neglected while the basic processes of newer and sometimes smaller industries have received considerable attention, and even found their way into university engineering curricula. This is undoubtedly due to pecularities of the industry. Considerable amounts of fillers, oils, and other ingredients are added to rubber, which allow the rubber technologist to resolve processing problems through changing the (secret) composition of compounds rather than by scientific analysis. Certainly another reason is the polymer synthesis orientation (to some extent justified) of rubber industry research. During the years of the Rubber Reserve Program, when research was government supported and widely and openly publicized, there were considerable advances in knowledge of free radical homo-and copolymerization in solution and emulsion, but relatively little progress was made in the understanding of rubber rheology and processing.
Elastomers and their Adhesion
Authors: Crocker Guy J.
Published: February 2011

The last general review of elastomeric adhesion and adhesives appeared in this journal eight years ago. At that time an attempt was made, at least in a limited way, to develop the subject from its scientific beginnings and to present a fairly broad and connected picture. The objective of the present review will be more modest, an up-dating only. Much of what was said in the earlier review remains pertinent and relevant today, and no attempt will be made to restate such material in detail, although summarization of current status will be attempted. On the theoretical side, emphasis will be on those studies which have modified earlier views, disproved some theories or strongly confirmed others, or unified previously disconnected observations. On the technological side, emphasis will be on new applications for adhesives, new adhesive raw materials and techniques and the increased scope they offer, and new materials to be bonded with the problems and challenges they engender. For some time, growth in adhesives has consistently outstripped the general economy, and elastomeric adhesives have more than held their own as compared with other types. Adhesive production in 1965 was estimated at 3.2 billion solid pounds. Probably at least 10% of this could be considered elastomeric, and, if expressed in dollar value, would be a much greater proportion. A recent estimate of growth rate for adhesives and sealants was 10% per year, approximately twice that of the dry rubber industry. There is every reason to believe that this trend will continue in the foreseeable future as the former psychological resistance to “gluing” as opposed to rivets, bolts, nails, and welds fast disappears. Accelerating economic growth has stimulated technical advances, and the reverse, and this is reflected in a burgeoning literature.
Softening of Rubber by Deformation
Authors: Mullins L.
Published: February 2011

It has been known for many years that deformation results in softening of rubber and that the initial stress-strain curve determined during the first deformation is unique and cannot be retraced. Further the effect of repeated deformation is to cause rubber asymptotically to approach a steady state with a constant or equilibrium stress-strain curve. Softening in this way occurs in vulcanizates either with or without fillers although the effect appears to be much more pronounced in vulcanizates containing high proportions of reinforcing fillers. After the hardness test the simple extension stress-strain test is the test most widely used by rubber technologists. The conventional stress-strain curve is obtained on samples which have not been previously deformed and for design purpose the unique value of stiffness given by this curve may be of little significance. Thus it appears that the values of stress—strain properties determined after “conditioning” cycles of deformation would be of more practical use than the unique value obtained in the conventional test. In recent years much interest has been shown in the factors responsible for this softening behavior particularly in regard to the implications of the loss of the stiffening action of reinforcing fillers on the mechanism of reinforcement.
Viscoelastic Behavior of High Polymers at Large Deformations
Authors: Becker G. W. , Rademacher H.-J.
Published: February 2011

Stress relaxation at different strains, and retarded deformation at different stresses were measured for rod-shaped test specimens of plasticized PVC in tension. Temperature was varied in such a way that changes in properties of the material, within the entire range from the glassy-amorphous to the quasi rubber-elastic states, could be comprehended. From results of the two types of experiment it was concluded that outside of the linear stress region, and at all temperatures, the time and deformation dependence of stress could be separated, but this was not possible for the time and stress dependence of strain.
EV Systems for NR. I. The Purpose of Efficient Vulcanization and Development of Curing System
Authors: Skinner T. D. , Watson A. A.
Published: February 2011

By means of a simple relaxed modulus test, a comparison has been made of the efficiency of sulfur utilization of various vulcanizing systems based on commercially available accelerators, or accelerator combinations, plus elemental sulfur or a sulfur donor. These initial experiments indicate three ways of increasing efficient use of sulfur for crosslinking: (1) the employment of synergistic combinations of accelerators; (2) the use of a high accelerator/sulfur ratio; (3) the substitution of elemental sulfur by a sulfur donor. Characterization of the networks formed using the EV systems developed shows that it is possible to obtain systems which are as efficient as the “sulfurless” TMTD-zinc oxide system in terms of the number of sulfur atoms combined in the network per chemical crosslink present. Independent evidence, gained by the use of chemical probes, has established that the network formed by an EV system contained only monosulfidic crosslinks and that little modification of the main chains by sulfur had occurred.
An Internally-Consistent Thermodynamics for Elastomers
Authors: Livingston H. K. , Reghi G. P.
Published: February 2011

Thermodynamic relations for solids in the rubbery state can be obtained from the Jacobian table, Table I. Numerical data that have been obtained under conditions of optimum reversibility have the same significance as has been assigned by Krigbaum and Roe and previous authors. However, with a thermodynamics specifically designed for rubbery solids, it is possible to apply directly the equations of heat and work to obtain the specific heat at constant length. This quantity should be related to molecular vibrations and molecular structure. If so, rubber thermodynamics may help increase our understanding of polymers in the rubbery state.
Tracer Diffusion in Rubber and Benzene Mixtures and its Relation to Mutual Diffusion
Authors: Pattle R. E. , Smith P. J. A. , Hill R. W.
Published: February 2011

The tracer diffusion coefficient of radioactive benzene in mixtures of benzene and rubber at 25° C has been measured over the whole range of composition. Variation of diffusion coefficient with composition can be described by a formula of the Fujita type. Results have been combined with published values of the mutual diffusion coefficient and the thermodynamic properties. They are interpreted in terms of a “one-process” theory and show that mobility of benzene molecules in mutual diffusion at low concentrations of rubber is greater than that in tracer diffusion by a factor which rises to 4.2 when the concentration of rubber is 5%. Results are incompatible with the “two-process” theory of diffusion, unless this theory is modified by inclusion of an adjustable parameter.
Diffusion of Liquids in Crosslinked Rubbers
Authors: Southern E. , Thomas A. G.
Published: February 2011

Diffusion of various liquids in natural rubber vulcanizates has been studied by following the kinetics of the mass uptake of a rubber sheet immersed in the liquid. An anomaly in the mass uptake-time relation is due to stresses set up in the sheet during swelling and to their variation as swelling proceeds. This anomaly has been eliminated by using specimens constrained laterally, by bonding to metal backing plates, which maintains boundary conditions constant during swelling. At the liquid concentrations used, the diffusion coefficient depends mainly on the liquid viscosity rather than compatibility of the rubber and liquid. Neither amount of carbon black filler nor of crosslinking of the rubber has a significant effect on the diffusion coefficient measured at relatively high liquid concentrations.
Effect of Network Breakdown and Re-Formation on the Swelling of Rubbers in Compression
Authors: Treloar L. R. G.
Published: February 2011

Effect of changes in network structure on equilibrium swelling of a crosslinked rubber subjected to uniaxial compressive stress is calculated on the basis of the ‘two-network’ hypothesis. Equations are also derived for compressive force and amount of elastic recovery after removal of the stress. Numerical examples are given to illustrate effects predicted by the theory for a rubber in a good swelling agent.
Problems Concerning Adhesion of Steel Wire and Steel Cord in Rubber
Authors: Maeseele A. , Debruyne E.
Published: February 2011

A research program, employing specially adapted techniques, was conducted on the bonding phenomena of steel reinforcements in rubber. Most of this work has a bearing on the problem of steel wire and cord in varying compounds. In most cases the metal-to-rubber bonding agent used was a copper alloy, especially brass. Some experiments were also made with nonmetallic adhesives. The influence of numerous possible variables of steel wire and cord on the adhesion in several well-defined rubber compounds was examined thoroughly. It was found that the compound itself played an important part in the process of metal-to-rubber bonding. Hence the research program was extended to the influence of rubber compounding on wire adhesion. The research on adhesion phenomena is far from finished. The reaction mechanism of bonding metals to rubber looks very complex. Both metal and rubber are responsible for the actual measured bond strength. Research on adhesion therefore appears to belong to the field of the metallurgist as well as to the field of the rubber chemist and the tire maker. A close cooperation on this problem might prove as fruitful to the wire as to the tire manufacturer. We should appreciate any information or suggestion that might be offered.
Identification of Organic Compounding Ingredients in Vulcanized Rubbers by Thin Layer Chromatography
Authors: Nagasawa K. , Ohta K.
Published: February 2011

As a result of a search for a method for the simultaneous analysis of organic compounding ingredients in vulcanized rubber by one dimensional and two dimensional thin layer chromatography, a method was discovered by which it was possible to identify directly 24 accelerators and 19 antioxidants. The sample was developed on a Wakogel B-5 (silica gel) plate with chloroform/benzene (10/9) in one direction and then with ethanol in the other direction. The plate was sprayed with formalin/sulfuric acid (1/4) and then heated for one hour at 120° C. It was found that the 43 compounding ingredients could all be identified from their Rƒ values and the colors of the spots. Good results were also obtained in the actual analysis of the organic compounding ingredients in vulcanized rubbers. Investigation of interference by the base rubbers showed that the organic compounding ingredients could be identified. Translator's note: According to the English summary, the silica gel contains 5% of calcined gypsum. This is not mentioned in the Japanese text.
Basic Principles of Hose Design
Authors: Harkleroad W. I.
Published: February 2011

Fundamentals of hose design have not changed with the introduction of new and improved component materials. Hose consists of three basic elements which are tube, reinforcement, and outer cover—with each serving a primary function. The tube or inner liner contains and resists the fluid conveyed and transmits forces created by the internal pressures to the strength member. The reinforcement or strength member contains the forces created by the fluid pressure. The outer cover protects hose reinforcement and resists external environment and damage. This paper is primarily concerned with the design concepts of the strength member or reinforcement as a functional component to resist and control forces created in service. Design principles relating to reinforcement angle, burst strength, and length change under pressure are presented for various hose styles. Braided, spiral, wrapped, loomed, wrapped ply and knitted hose styles are reviewed and compared. Reinforcement materials, their types, relative strengths and advantages are summarized. Examples of specific applications of hose are presented to illustrate hose design principles in action in industry.
Extrusion of Polymer Melts and Melt Flow Instabilities. I. Experimental Study of Capillary Flow and Extrudate Distortion
Authors: Bialas Gene A. , White James L.
Published: February 2011

The extrusion of molten plastics, elastomers and fibers represent an important industrial operation. The rate of extrusion of melts through dies is limited by the onset of a flow instability. This phenomenon consists of a change in flow from uniform to irregular that results in the production of rough and distorted extradates drastically different from the smooth cylinders obtained at lower rates. Extrusion melt flow instability is observed in the entire spectrum of polymer melts ranging from silicone gums through nylon and polyolefin plastics to raw elastomers. Since the first descriptions of this phenomena in the 1940's considerable research effort has been expended in this area with limited agreement. It is the purpose of part I to: (1) present new experimental data on capillary flow of polymer melts and extrudate distortion, and (2) to review critically the literature on extrudate distortion.
Extrusion of Polymer Melts and Melt Flow Instabilities. III. Theoretical Analysis of Extrusion through a Slit Die
Authors: White James L.
Published: February 2011

In the previous sections of this paper we have discussed our own and other experimental studies of flow instabilities in the extrusion of polymer melts as well as various theories of the mechanism of initiation of the instability. It is our belief that one of the keys to a deeper understanding of this phenomenon is a fuller analytical understanding of the stress and velocity fields in the composite reservoir, capillary, and extrudate system. It is to this problem that we turn our attention here. The velocity, stress-field problem in the entrance region of a conduit being fed from a reservoir has received considerable attention for Newtonian fluids. Most authors have followed Schlichting and Goldstein in using boundary-layer theory to analyze this problem. While there are a number of such solutions for viscous non-Newtonian and viscoelastic fluids, they are of little interest for polymer melts. This is not only because they represent a high Reynolds number, inertia-dominated asymptote but because they neglect all phenomena occurring in the reservoir feeding the conduit. Of more interest are the low Reynolds number creeping flow solutions for Newtonian fluids which are based upon the work of Sampson (see also Roscoe and Weissberg). A decade ago Tomita published a pioneering analysis of the creeping flow of a viscous non-Newtonian (power-law) fluid into a sharp edge entrance of a capillary. More recently LaNieve and Bogue have analyzed the creeping flow of a Coleman-Noll second order into the capillary entrance. A recent study of the entry problem has been made by Metzner, Uebler, and Chan Man Fong. The related problem of creeping flow of a viscoelastic fluid in a converging channel or cone has been analyzed by Adams, Whitehead, and Bogue and Kaloni. While the former authors computed the stress field for a second-order fluid and an integral constitutive equation in a presumed velocity field, Kaloni actually evaluated velocity profiles and predicted the formation of secondary flows. A more intuitive, but far less rigorous approach to extrusion of a viscoelastic fluid has been taken by Dexter and Dienes and Smith. These authors presume a virgin material to enter a capillary die in fully developed flow and utilize the theory of linear viscoelasticity to evaluate the stress field.
Processibility of Rubbers and Usefulness of the Mooney Viscometer
Authors: Ninomiya Kazuhiko , Yasuda Genichi
Published: February 2011

Processibility is best for any kind of rubber when it exhibits the same rheological behavior as a properly masticated natural rubber. The relaxation spectrum was proposed as a most influential material factor in describing the rheological material characteristics in the processibility of rubbers. A standard shape of relaxation spectrum of the raw rubber which would give the processibility close to the best was suggested, and the effects of molecular weight distribution on the processibility was discussed in terms of the relaxation spectrum. A semi-quantitative interrelation was given between the Mooney viscosity and the relaxation spectrum and the validity of this relation illustrated with experimental data. It was shown that the Mooney viscometer can be used not only for the fundamental test but also for the performance test for processibility of raw rubbers. The time-dependent shear stress at constant shear rate and the subsequent stress relaxation were analyzed in terms of the relaxation spectrum, the strain-at-break, and the elastic strain at steady flow using the concepts of the critical relaxation time, the rupture process in the physically crosslinked molecular network, and the existence of the Mooney's rheological unit. It was then shown that six time-independent material parameters are necessary to describe the mechanical behavior of raw rubbers as measured with a Mooney viscometer. Interrelations between those six parameters and the relaxation spectrum and two other material factors were given and verified. It was shown that three of the six parameters are related only to the relaxation spectrum and the remaining ones also depends at least partly on the relaxation spectrum. This indicates that the relaxation spectrum is the most influential material factor in determining processibility. In the appendix, the shearing period dependence of viscous and elastic components of the shear stress, the delta Mooney and the qualitative similarity between the dynamic and the stead-fiow non-Newtonian viscosities were briefly discussed.
Polymer Crystallization History and Resultant Properties
Authors: Collier John R.
Published: February 2011

Mechanical properties of semicrystalline polymeric materials are strongly influenced by the morphology into which these materials crystallize. In addition the morphology can be altered by changes in crystallization temperature and regime, crystallization pressure, melt treatment conditions, shear history, and probably other processing conditions. The mechanical properties reflect the changes in morphology not only in the initial moduli values but also the overall stress-strain relationships, including the fracture mechanism. A strong influence is noted, at least in the polymers cited, even when slight changes occur in average spherulite size, spherulitic fine structure, and in the nature of interlamellar ties. Smaller, finer textured spherulites with higher interconnections arc apparently more susceptible to yielding by neck formation and elongation to high values than are the larger, coarser textured spherulites than tend to fail by random brittle failure mechanisms at low elongations. In addition, if the chlorinated polyether (Penton) is typical of slowly crystallizing polymers, the change from spherulitic morphology obtained during crystallization from the melt to the small platelet morphology obtained during slow crystallization from quenched glassy state has a complex effect on mechanical properties. The specimens slowly crystallized from the glass exhibit initial shear and tensile moduli values higher than those exhibited for rapid crystallization from the melt and rapid crystallization from the glass, but lower than the corresponding values for slow crystallization from the melt. In addition, the only specimens of this chlorinated polyether that exhibited the ability to draw to high degrees of elongation (as a result of yielding by a necking phenomenon) were those crystallized slowly from the quenched glassy state.
The Formulation of a Mathematical Model for Plasticating Screw Extrusion
Authors: Tadmor Zehev , Klein Imrich
Published: February 2011

The theory of plasticating extrusion has reached the stage where scientific design methods can replace the empirical ones. It is possible today to build a mathematical model comprising the whole plasticating extruder. This model predicts the temperature and pressure profiles along the extruder, the solids content everywhere in the extruder, the total power requirements and even the temperature fluctuations of the extruder. These developments were made possible by the recent mathematical formulation of the melting mechanism in the extruders, by a more accurate formulation of the melt conveying theories and by the availability of high speed digital computers. The development of such a mathematical model is discussed in this paper. The model has been built by a stepwise process of improving existing theories and eliminating critical simplifying assumptions and undue complexities. This has been accomplished by comparing the computer simulated results with their experimental counterparts. The application of the mathematical model to screw design, and to critical analysis of working extruders is also discussed.
Oxidative Aging of Natural Rubber Vulcanizates. Part III. Crosslink Scission in Monosulfidic Networks
Authors: Colclough T. , Cunneen J. I. , Hrggins G. M. C.
Published: February 2011

A natural rubber vulcanizate containing almost entirely monosulfidic crosslinks was oxidized in oxygen and with tert-butyl hydroperoxide. The changes in physical properties due to oxidation were followed by stress—strain measurements, and the changes in chemical structure were investigated with chemical probes, and by spectroscopic methods. The results show that when the oxidized vulcanizates are heated at 75° C, the monosulfidic crosslinks are broken, that crosslinks containing two sulfur atoms are formed, and that conjugated diene and triene structures are introduced into the main polyisoprene chains.
Volume Change Measurements in the Study of Rubber-Filler Interactions
Authors: Shuttleworth R.
Published: February 2011

A new type of measurement using an extension-dilatometer is described and used in an attempt to provide a more adequate understanding of the mechanism of reinforcement. A description of the dilatometer is given together with some of the results obtained. These results are discussed in the light of a recently proposed mechanism of reinforcement.
Structure of Vulcanized and Unvulcanized SBR/BR Blends
Authors: Yoshimura N. , Fujimoto K.
Published: February 2011

Mainly from the temperature dependence of transitions in dynamic modulus, loss tangent, and dielectric loss, associated with microbrownian motions of main chains, it was concluded that blends of NR and BR are microheterogeneous and those of SBR and BR are almost microhomogeneous. Furthermore, even SBR/BR blends tended to be heterogeneous if the styrene content in SBR was increased. On the other hand, unvulcanized SBR/BR blends have been reported to be heterogeneous from observation of phase contrast micrographs. To investigate this vulcanization effect further, measurements of temperature dependence of dynamic modulus and tan δ of unvulcanized blends were compared with those of vulcanized blends.
Physics of the Slipping Wheel. I. Force and Torque Calculations for Various Pressure Distributions
Authors: Livingston D. I. , Brown J. E.
Published: February 2011

Slipping wheel theory has been extended to predict the dependence of the lateral force and of the aligning torque on the nature of the pressure distribution over the contact patch between the wheel and the ground. Expressions have been derived for both side force and aligning torque as functions of the slip angle under: uniform pressure distribution, which applies to the behavior of an inflated membrane wheel; elliptical distribution, which describes the behavior of a solid wheel; and parabolic distribution. All appear appropriate in some respect to the actual tire.
Preparation of Epoxide Rubber Containing Allylic Chloride
Authors: Gurgiolo A. E.
Published: February 2011

New epoxide monomers have been prepared that contain allylic chlorine. These have been copolymerized with propylene oxide to give polymers that also contain allylic chlorine. This type of propylene oxide rubber can be vulcanized with a mixture of magnesium oxide and zinc oxide eliminating the need for sulfur in the vulcanization recipe. This work presents an indirect proof of the allylic structure of neoprene and substantiates the theory of vulcanization of neoprene by magnesium and zinc oxides.
General Method for Approximating the Tire Contour Integral for Arbitrary Cord Path
Authors: Mavrigian G. , Gehman S. D.
Published: February 2011

It has been shown that the tire contour integral can only be evaluated exactly in terms of elementary functions and elliptic integrals in special cases. Approximate numerical methods, with computer programming, have been used heretofore to calculate contours which result from conventional, bias-angle tire construction, by assuming the cord path: ρ/cos α=ρ0/cos α0. In calculating the contours, for deflected tires having such a cord path, a new approximate method of evaluating the contour integral was described which expressed the contours in terms of elliptic integrals.
Measurement of Curative Diffusion Between Rubbers by Microinterferometry
Authors: Gardiner J. Brooke
Published: February 2011

Diffusion of sulfur and MBTS across interfaces between dissimilar rubbers has been measured by microinterferometry. This technique involves the comparison of optical path length through refractive index gradients, due to diffusion, against that of a reference area. Differential diffusion coefficients are obtained showing considerable change in coefficient with curative concentration. Diffusion of sulfur between NR, SBR, and BR is quite similar to diffusion in the homo-polymer. Butyl rubber has a much lower diffusivity and limits diffusion of a curative from another rubber. The method also can be used for dissolution measurements on curatives. Microinterferometry is particularly useful in obtaining concentration and diffusion data at short distances from an interface.
A New Tire Expansion Rule and Its Use in Tire Design Computations
Authors: Leibee J. B. , Schaffers W. J.
Published: February 2011

The carcasses of most early automobile tires were built by stretching bias cut, rubberized, square woven fabric more than once around the major circumference of a toroidal core. By 1914, two crossed rubber coated cord warps had been substituted for each layer of fabric. In the twenties, the core was replaced by a cylindrical building drum and the tires were subsequently expanded by air pressure to the toroidal shape. In all of these cases an initially flat fabric or crossed warps were made to conform to the surface of a toroid without folding or appreciable cord length change. Close examination showed that the tiny rhombuses between adjacent cords were stretched more in the circumferential direction in the crown than in the sidewall. The obvious analogy to a pantograph with hinged members of constant length provided the key to cord angle and drum set calculations needed for carcass design. The geometrical consequence of the assumption of constant rhombus side length is the well known cosine rule
The Effect of Temperature of Test on Abrasion Resistance by the Pico Method
Authors: Ozer Ali , Partridge E. G.
Published: February 2011

The following conclusions may be reached from the results: