bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of Chemical Bonding in the Adhesion of Elastomers
Authors: Gent A. N. 
Published: February 2011

Abstract
A review is given of several studies of the effect of interfacial bonding upon the mechanical strength of an adhesive joint. In the first, polybutadiene layers were crosslinked by a free radical process while in contact with silane-treated glass. A direct proportionality was found between the minimum peel strength of the joint, at high temperatures and low rates of peeling, and the vinyl content of the silane treatment liquid. Covalent bonding between the diene polymer and vinyl groups on the treated glass was inferred. When radioactively tagged silanes were employed, extensive combination with the glass substrates was demonstrated. Again, the greater the amount of vinyl silane found on the treated glass surface, the greater the mechanical strength of adhesion between the treated glass and a polybutadiene overlayer. In another series of experiments, two partially crosslinked sheets of polybutadiene were pressed together before the crosslinking was taken to completion. The additional crosslinking was determined from measurements of the elastic properties and of the degree of equilibrium swelling by a compatible liquid. Again, the mechanical strength of adhesion between the two sheets under threshold conditions was found to be directly proportional to the inferred degree of interfacial interlinking. Thus, at least at high temperatures and low rates of peel, there is substantial evidence for a direct correlation between the mechanical strength of a joint and the degree of interfacial chemical bonding. Moreover, the relationships established in these studies allow other bonding systems to be diagnosed as chemical or physical in nature. For example, a dramatic increase in the strength of adhesion between two crosslinked polybutadiene layers was observed if they were exposed to air or oxygen for periods of an hour or two before being pressed into contact. It is inferred that interfacial chemical bonds are formed as a consequence of rapid surface oxidation reactions.
Characterization of the Structures of Diene Polymers by NMR
Authors: Harwood H. James 
Published: February 2011

Abstract
Nuclear magnetic resonance spectroscopy (NMR) has become a very powerful tool for characterizing the structures of elastomers, providing information about their compositions and the arrangements of their constituents along their chains. Elastomers derived from diene monomers by homopolymerization or copolymerization can be very difficult to characterize because of the large number of structural features that may be present. Dienes can be incorporated as 1,2, 3,4, cis-1,4, or trans-1,4 units, and also as cis-4,1 or trans-4,1 units in some cases, for example. This leads to the possibility of head-head and tail-tail linkages as well as head-tail linkages and to the possibility of several stereochemical arrangements existing between pairs of 1,2-units. In spite of this difficulty, quantitative information about the structural characteristics of polymers derived from dienes can be obtained from their NMR spectra, and this information has been very useful in studies on polymerization mechanisms and elastomer properties. In some cases, it is possible to study the structures of growing chain ends by NMR spectroscopy. This, of course, provides valuable information about the polymerization mechanism. Nuclear magnetic resonance can be used to monitor chemical changes occurring in elastomers, such as oxidation or vulcanization. It can also provide information about the dynamic characteristics of elastomeric chains. Reviews on the characterization of elastomer structure by nuclear magnetic resonance are available, but developments in the characterization of polymers derived from dienes have occurred so rapidly that it is appropriate to review this specific topic at this time.
Recent Advances in the Chemical Modification of Unsaturated Polymers
Authors: Schulz D. N. , Turner S. R. , Golub M. A. 
Published: February 2011

Abstract
This article surveys recent advances in the chemical modification of unsaturated polymers, with emphasis on the literature since 1974. Among the topics covered are hydrogenation, halogenation, cyclization, isomerization, epoxidation, cycloaddition, sulfonation, carbenation, and silylation. The olefin functionality is a useful target for modification because of its varied reactivity, and recent work in unsaturated polymer reaction chemistry has yielded significant discoveries and valuable new information. For example, modern synthetic reagents and catalysts (e.g., as phase-transfer catalysts) have been advantageously employed to improve process and/or product quality. Synthetic techniques have been refined to allow the selective modification of specific polymer microstructures or blocks. Moreover, new structural and mechanistic insights have been derived from the judicious use of model compounds and/or specialized characterization methods. The relationship between chemically modified polymer structure and properties is being more clearly defined, and sequence effects are beginning to be appreciated. Finally, important new applications (e.g., elastomers, plastics, motor oil additives) have been discovered for chemically modified diene polymers.
Applications of Computerized Nuclear Magnetic Resonance and Infrared Spectroscopic Techniques to Rubber Analyses
Authors: Hirst Robert C. 
Published: February 2011

Abstract
Fourier transform spectroscopy is without doubt one of the most important developments in spectroscopy in the last few years. Although the basic principle had been known for many years, its applications in spectroscopy became practical only because of advances in small computer technology. In the case of nuclear magnetic resonance and infrared spectroscopy, the digital computer has had a special effect, in that it has caused, or at least made possible, the total redesign of NMR and IR instrumentation based on the Fourier transform (FT) concept. Because of its advantages over conventional methods, the FT method has caused great changes in NMR and IR spectroscopy, and FT instruments have made possible the solutions to many problems which previously were technically too difficult. NMR spectroscopy was reviewed in this Journal in 1976 and infrared spectroscopy was reviewed in 1972. Developments since those reviews will be emphasized here. In a short, selective review of this type, it is necessary to omit references to many excellent contributions in the literature. For very comprehensive listings of literature references, the reader may wish to consult the biennial reviews in “Analytical Chemistry” on NMR spectroscopy, infrared spectroscopy, rubber, analysis of high polymers, and coatings.
Energy Measures of Efficient Mixing
Authors: Nakajima N. 
Published: February 2011

Abstract
Several significant developments have taken place recently in the understanding of elastomer behavior in the internal mixer. An elastomer must be treated as a viscoelastic solid rather than a viscous fluid. The material behavior is recognized as transient instead of steady state. Elongational deformation plays an important role and the rate of such deformation is fast. Relevant fundamental properties are the viscoelastic properties at large deformations and ultimate properties. Views on the mechanisms of mixing have also changed recently. Instead of the laminar flow model, which accepts steady state shear flow, a comminution and lamination model has been proposed to represent large deformation, rupture, and recovery of the elastomer during mixing. With the comminution model and the fundamental measurements of rupture energy, a theoretical minimum mixing energy was estimated. The difference between the actual energy spent for mixing and the theoretical energy required is substantial. This suggests that there is room for saving energy through process improvements. Two examples of energy saving have been reported recently; one is the use of warm water cooling with an efficient heat transfer and another is a new configuration for four-wing rotors. The optimum processing temperature can be estimated from fundamental measurement of the ultimate properties of the elastomer. This points towards the use of warm water cooling. The new rotor design avoids impinging streams, which result in wasting energy for mixing viscoelastic material, although it mixes low viscosity fluids efficiently.
Curing of Fluoroelastomers by Peroxides
Authors: Apotheker D. , Finlay J. B. , Krusic P. J. , Logothetis A. L. 
Published: February 2011

Abstract
Peroxide-curable fluoroelastomers offer advantages in acid and steam resistance over their conventional counterparts. The peroxide-curability is provided by incorporating a bromine-based cure site in the vinylidene fluoride copolymers or terpolymers. The peroxide cure system comprises an aliphatic peroxide, an appropriate coagent, and an acid acceptor. The preferred coagent is triallylisocyanurate but other compounds having two or three olefinic groups attached to hetero atoms such as N, Si, or O are also effective. The concentration of the curesite monomer affects the rate, state, and stability of the cure. A cure mechanism is proposed in which the initiation step involves radical formation from peroxide decomposition and addition of the radicals to the coagent. Propagation involves the abstraction of bromine atoms from polymer molecules by coagent radicals to give fluorocarbon polymer radicals, which, in turn, add to coagent molecules to generate new radicals. This type of mechanism is supported by the cure characteristics, by the nature of the coagents, by analysis of the volatile by-products emitted during the cure, and by ESR data on model compounds.
Rubber-Thermoplastic Compositions. Part VI. The Swelling of Vulcanized Rubber-Plastic Compositions in Fluids
Authors: Coran A. Y. , Patel R. , Williams D. 
Published: February 2011

Abstract
The swelling of thermoplastic vulcanizates in immersion fluids is constrained. The amount of swelling is less than the average swelling of the rubber and plastic. The constraint in swelling increases with the difference between the swelling of vulcanized rubber and that of the plastic, per se. However, the swelling constraint decreases with increases in the amount of fluid imbibed by the plastic or hard phase material. The thermoplastic vulcanizates prepared by dynamic vulcanization swell less than do the thermosetting (less thermoplastic) compositions prepared by static vulcanization. Swelling is anisotropic, especially for the compositions containing major proportions of rubber.
Interply Behavior Exhibited in Compliant Filamentary Composite Laminates
Authors: Turner J. L. , Ford J. L. 
Published: February 2011

Abstract
Cord-rubber composite systems allow a visualization of interply shear strain effects because of the compliant nature of the matrix material. A technique termed the pin test was developed to aid this visualization of interply shear strain. The pin test performed on both flat pads and radial tires shows that interlaminar shear strain behavior in both types of specimens is similar, most of the shear strain being confined to a region approximately 10 interly rubber thicknesses from the edge. The observed shear strain is approximately an order of magnitude greater than the applied extensional strain. A simplified mathematical model, called the Kelsey strip, for describing such behavior for a two-ply (±θ) cord-rubber strip has been formulated and demonstrated to be qualitatively correct. Furthermore, this model is capable of predicting trends in both compliant and rigid matrix composites and allows for simplified idealizations. A finite-element code for dealing with such interply effects in a simple but efficient manner predicts qualitatively correct results.
Rubber Elasticity
Authors: Mark J. E. 
Published: February 2011

Abstract
Rubber elasticity may be operationally defined as very large deformability with essentially complete recoverability. In order for a material to exhibit this type of elasticity, three molecular conditions must be met: (1) the material must consist of polymeric chains, (2) the chains must be joined into a network structure, and (3) the chains must have a high degree of flexibility. The first requirement arises from the fact that the molecules in a rubber or elastomeric material must be able to alter their arrangements and extensions in space dramatically in response to an imposed stress, and only a long-chain molecule has the required very large number of spatial arrangements of very different extensions. This versatility is illustrated in Figure 1, which depicts a random spatial arrangement of a relatively short polymer chain. In this random arrangement, the chain extension (as measured by the end-to-end separation) is quite small. For even such a short chain, the extension could be increased approximately fourfold by simple rotations about skeletal bonds, without any need for distortions of bond angles or bond lengths. The second characteristic cited is required in order to obtain the elastomeric recoverability. It is obtained by joining together or “crosslinking” pairs of segments, approximately one out of a hundred, thereby preventing the extended polymer chains from irreversibly sliding by one another. The resulting network structure is illustrated in Figure 2, in which the crosslinks are represented by dots. These crosslinks may be either chemical bonds [as would occur in sulfur-vulcanized natural rubber' or physical aggregates (for example the small crystallites in a partially crystalline polymer or the glassy domains in a multiphase block copolymer). The last characteristic specifies that the different spatial arrangements be accessible, i.e., changes in these arrangements should not be hindered by constraints as might result from inherent rigidity of the chains, extensive chain crystallization, or the very high viscosity characteristic of the glassy state.
Development of Synergistic Curing Systems for Polychloroprene
Authors: Kato H. , Fujita H. 
Published: February 2011

Abstract
Of the dihydric phenols, catechol exhibited a significant synergistic accelerating effect on joint use with TMTD. Aging characteristics of catechol/TMTD accelerated CR vulcanizates were improved when the aromatic nucleus of the catechol was bonded to sulfur. Dicatechol sulfides (XX-125) derived from catechol and S2Cl2 gave improved thermal stability of the vulcanizates. Curing properties of XX-125 seemed enhanced by use with TMTD. A variety of practical CR accelerators has been developed by blending XX-125 with TMTD at the weight ratio to obtain the desired cure rates and physical properties. The essential nature of synergism in these curing systems has yet to be resolved. On detailed practical evaluation of CR vulcanizates cured by these accelerators, XX-125S, -R, -T and -U are suitable substitutes for NA-22 in curing CR.
Rubber Recycling—Upgrading of Scrap Rubber Powder by Vulcanization. II
Authors: Accetta A. , Vergnaud J. M. 
Published: February 2011

Abstract
Vulcanizates from scrap tires have interesting mechanical properties that widen the range of their uses. These properties and dynamic characteristics (compression modulus, damping coefficient) undergo great changes as sulfur percentage is varied. This fact is particularly important in regard to the design of damping devices for the vibration absorption of industrial machines. The size of the machine as well as the vibration frequency must be taken into account to optimize the transmissibility factor of the damped system. The favorable results obtained for our materials in the damping of impact noises and their small compressibility foreshadow an efficient application in resilient coverings in buildings. Rubber slabs when stuck directly on the floor can be covered with a thin coating consisting, for instance, of thin tiles. The resilient covering can also be stuck on the floor and covered with lean mortar, a traditional way of laying tile.
Silica- and Clay-Reinforced Carboxylated Nitrile Rubber Vulcanized by a Mixed Crosslinking System
Authors: Chakraborty S. K. , De S. K. 
Published: February 2011

Abstract
The polymer-filler interaction of silica- and clay-filled XNBR vulcanizates has been analyzed. The presence of carboxyl groups in the polymer chain gives better polymer-filler interaction, and no coupling agent is essential. Properties of silica-filled XNBR vulcanizates containing different carboxyl contents in the polymer chain have also been studied. SEM studies of fracture surfaces have been made to understand the failure behavior of gum and filled vulcanizates.
Dispersive Mixing in Internal Mixers—A Theoretical Model Based on Agglomerate Rupture
Authors: Manas-Zloczower I. , Nir A. , Tadmor Z. 
Published: February 2011

Abstract
The mixing of solid additives into a matrix of rubber or plastics is an energy intensive process. Such a mixing operation generally involves rupture of agglomerates formed by the solid phase, separation of closely packed particles after rupture, and distribution of the separated particles throughout the polymeric matrix. Dispersive or intensive mixing refers primarily to the first two steps, whereas, the third step is by and large an extensive mixing process. Depending upon the polymer-additive system and mixer machine design, each of these steps may be rate determining. The most important and most investigated system is the carbon black-elastomer system. Mixing of such a system is generally carried out in batch Banbury type internal mixers (Figure 1). The dispersive mixing process in internal mixers is quite complex with many subtle features. A detailed review of the subject is outside the scope of this paper. However, careful reading of reviews and publications in the field, indicate that a great deal is known about the mixing process in internal mixers, the scale-up procedures using various criteria, the effect of the mixing process and mixer geometry on processability and ultimate properties, and the flow patterns and fluid dynamics in the various regions of mixers. However, there seems to be no published attempt to a priori predict the mixing process from fundamental considerations.
The Rheology and Processing of Olefin-Based Thermoplastic Vulcanizates
Authors: Goettlier L. A. , Richwine J. R. , Wille F. J. 
Published: February 2011

Abstract
Olefinic thermoplastic vulcanizates (OTV's) comprise rubber in the form of discrete, completely crosslinked particles uniformly dispersed in an olefinic thermoplastic matrix. By their nature, they flow like filled polymer melts: die swell is low, and shows evidence of a particle association at low shear rate and high temperature; viscosity obeys a power law relationship with shear rate over a wide range. In place of a Newtonian plateau at low shear rate, the viscosity of OTV's begins to rise precipitiously in building toward a yield stress. As with other olefinic thermoplastic elastomers, their viscosity is more highly sensitive to shear rate than to temperature. Both shear viscosity and die swell were measured for evidence of morphological character and definition of fabricability. Due to their high shear sensitivity, these OTV's can be easily processed by injection molding and extrusion. Processing temperatures are not critical, but lower ranges are preferred to optimize appearance and promote melt stability. The thixotropic nature of the melt minimizes drooling and allows easy cooldown without distortion of the formed part. Melt viscosity is little affected by moisture or repeated processing. Although melt extensibility is only moderate, it is sufficient to qualify these materials for most extrusion and blow molding applications. Low shear processing, such as the compression molding of prototype parts or calendering, is equally feasible. Thus, olefinic thermoplastic vulcanizates can be fabricated under a wide range of conditions by using conventional plastics processing tooling and methodology. They represent a versatile class of new elastomers that can be economically processed for across-the-board applications in industrial rubber products.
Chain Extension Studies Relevant to the Completeness of End-Linking in Elastomeric Polyurethane Networks
Authors: Mark J. E. , Sung P. H. 
Published: February 2011

Abstract
Polyurethane elastomers may be prepared by end-linking hydroxyl-terminated (atactic) poly(propylene oxide) chains with an aromatic triisocyanate. As is invariably the case, networks thus formed are insoluble and very difficult to analyze with regard to the completeness of the end-linking reaction. Relevant information can, however, be obtained by studying the products of the analogous reaction, between a structurally similar diisocyanate and the same polymer chains, under identical conditions. Since both reactants now have functionalities less than three, the reaction gives chain extension rather than crosslinking (gelation), and it is now possible to measure molecular weights before and after the reaction. Such experiments were carried out using diphenylmethane-4,4′-diisocyanate with poly(propylene oxide) chains which had viscosity-average molecular weights ranging from 10−3Mv=1.15−4.50 g mol−1. Values of Mv were found to increase by factors of 20–30, which indicates high extents of reaction. These results are relevant with regard to the probable efficiency of polyurethane curing techniques, and also for the characterization of “model” networks used in the quantitative evaluation of the molecular theories of rubberlike elasticity.
Improved Adhesion of EPDM Sulfur Vulcanizates to RFL-Treated Fabrics
Authors: Tomlinson Richard W. 
Published: February 2011

Abstract
EPDM stocks containing 5-norbornene-2,3-dicarboxylic anhydride and cobalt naphthenate, when sulfur vulcanized onto RFL-treated fabrics, show a significant increase in peel adhesion properties. EPDM's containing ENB, as the termonomer, have been found to give the best results. The accelerator is an important part of the total adhesion system. Only the slower curing types are applicable, such as sulfenamides and thiazoles. Both soluble and insoluble sulfur yield equivalent adhesion properties, but the insoluble form has the advantage of producing a higher modulus stock. This adhesion system is applicable to only RFL-treated fabrics in which the latex is a styrene-butadiene-vinyl pyridine type. Reduction of compounded stock cost is possible by increased filler loadings or by the use of a skim coat technique, while still providing improved adhesion properties. Variations in both carbon black and oil levels produce corresponding changes in modulus development and curing time. These properties can be used to predict adhesion results.
Factors Influencing the Mechanical Behavior of Raw Unfilled Natural Rubber
Authors: Campbell D. S. , Fuller K. N. G. 
Published: February 2011

Abstract
The influence of gel and soluble nonrubbers on the relaxation behavior of raw, bale NR has been studied by testing fractionated and solvent-extracted rubber. The fractionation was carried out by progressive dissolution, each fraction being recovered by evaporation of the solvent. The tests were performed in tension for extensions up to 70%. Removal of the soluble nonrubbers from the bale was found to decrease the rate of stress relaxation quite markedly, especially at longer times. The fractions fell broadly into three categories: sol rubber, “sol + microgel”, and undissolved macrogel. The last, in the case of the more complete dissolution, was an extremely stiff, almost nonrelaxing material. Despite this, the relaxation behavior of the whole bale rubber was closely reproduced by the “sol / microgel” fraction. Comparison of this fraction with the sol rubber showed that the microgel had predominantly a stiffening effect, though it did also significantly reduce the rate of relaxation.