bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model Elastomeric Networks
Authors: Mark J. E. 
Published: February 2011

Abstract
Tetrafunctional and trifunctional model polymer networks of known crosslink density were prepared by end-linking a variety of hydroxyl terminated chains both in the undiluted state and in solution. The polymers employed were poly(dimethylsiloxane), atactic poly(propylene oxide), poly(ethylene oxide), poly(tetramethylene oxide), and poly(e-caprolactone), and the end-linking agents were alkoxy silanes and an aromatic triisocyanate. The resulting networks were studied (i) in elongation at 25°C, both in the unswollen state and swollen with a nonvolatile diluent, and (ii) in equilibrium swelling in benzene. The values of the elongation modulus in the limits at large and small deformations were found to be in good agreement with recent theoretical predictions for nonaffine and affine deformations, respectively (the latter corresponding to the case in which the displacements of the network chain vectors are a simple linear function of the macroscopic strain). Comparisons between the tetrafunctional and trifunctional siloxane networks showed that both of these moduli have very nearly the expected dependence on network functionality. The swelling equilibrium results were found to be in very good agreement with a recent theory of network swelling in which the closeness of the approach to the affine limit depends on both the network structure and the degree of swelling. None of the results provided evidence for very significant contributions from interchain entanglements. Several of the polymers, however, have large values of the "plateau modulus" in the uncrosslinked state, and are therefore generally considered to have high densities of entanglements of this type. The present results thus contradict the widely held notion that interchain entanglements should contribute to equilibrium elastomeric properties to nearly the same extent as they do to the dynamic, visco-elastic properties.
Rubber-Thermoplastic Compositions. Part IV. Thermoplastic Vulcanizates from Various Rubber-Plastic Combinations
Authors: Coran A. Y. , Patel R. 
Published: February 2011

Abstract
The ultimate mechanical properties (σB and εB) and elastic recovery (inversely measured by tension set) of dynamically vulcanized melt mixed rubber-plastic blends increase with the similarity of the rubber and plastic in respect to the critical surface tension for melting γc. They also increase with the crystallinity Wc of the plastic (resin) phase. Stiffness, as measured by Young's modulus E, increases with the differences in surface energy between the two phases.
Microdomain Structure and Some Related Properties of Block Copolymers. II. Plastic Deformation Mechanisms of the Glassy Component in Rubber-Toughened Plastics
Authors: Kawai Hiromichi , Hashimoto Takeji , Miyoshi Katsunori , Uno Hiroyuki , Fujimura Mineo 
Published: February 2011

Abstract
The toughening mechanism was investigated by means of mechanical and optical techniques including electron microscopy and polarized light scattering for wide variety of domain morphologies of di- and triblock copolymers and their blends with corresponding homopolymers. Two types of plastic deformation mechanisms of the glassy component are emphasized as the toughening mechanism. One is large plastic deformation of the glassy component, as bulk, followed by its plastic flow or fragmentation, depending on the di- or triblock sequence arrangement. The other is the development of a microcraze at the boundary of the rubber particle, and its propagation through the glassy matrix. The origins of the two types of plastic deformation mechanisms are postulated as hydrostatic pressure effects upon the high plasticity of the glassy component due to differences of Poisson's ratios between the glassy and rubbery components and also as stress concentration effects of the rubber particle at the glassy phase opposite to the equatorial zone of the rubber particle with respect to the principal stress direction. The nearer the volume fraction of the two components to 50/50, the more efficient are the hydrostatic pressure effects upon inducing high plasticity in the glassy component. On the other hand, the smaller the radius of curvature at the equatorial zone of the rubber particle, the more concentrated the stress level becomes to generate the microcraze and further microcracks. Thus, there must be an optimum size of the rubber particle to generate the microcrazes in the most efficient rate. The system of alternating lamellar microdomains is sufficient for the generation of high plasticity, but insufficient for the craze development due to a too large radius of curvature to elevate the concentrated stress, if any. The toughening mechanism in rubber-toughened plastics can be explained generally in terms of these counter-balanced factors for the two types of plastic deformation mechanisms of the glassy component.
Interfacial Considerations in Polysulfide Sealant Bonding
Authors: Usmani A. M. , Chartoff R. P. , Warner W. M. , Butler J. M. , Salyer I. O. , Miller D. E. 
Published: February 2011

Abstract
It is necessary to examine the sealant-coating interface and consider the polymer-primer interaction for a complete understanding of interfacial bonding. Why a polysulfide sealant sticks to a fresh or “imaged” polyurethane coating surface and not to an “aged” polyurethane surface has been determined. Also, we were able to artificially age polyurethane coated surfaces and correlate artificial aging with natural aging by surface tension and contact angle measurements. The polyurethane kinetic studies indicate that unreacted isocyanate (NCO) groups at the surface quickly deplete in a matter of few hours under 60°C/95 percent R.H. condition. Both heat and moisture reduce the NCO concentration in bulk but at a moderately slower rate. Room temperature cure of the polyurethane was found to be very slow. Disappearance of residual NCO groups during aging coupled with hardening of the polyurethane surface appears to be the primary reason for inadequate adhesion with a polysulfide sealant to an aged polyurethane coating. Titanate primer reacts with polysulfide resin to give chemically bonded product, whereas no reaction with “aged” and “unaged” polyurethane coated surfaces was detected. The strong solvency of the primer, however, softens and lowers the glass transition temperature (Tg) of the polyurethane coating. Insofar as the polysulfide adhesion improvement onto “aged” polyurethane surface is concerned, we found that an alkyl phosphatotitanate and mercaptofunctional silane are effective adhesion promoters, whereas oxirane-functional silane and a polymeric isocyanate are ineffective primers. The SEM study of sealant-coating interface revealed that water is one of the most potent desorbing agents. The SEM method is quite valuable and should therefore be further refined. The adhesion of polysulfide sealant to new polyurethane surface can be attributed to the reaction of residual NCO groups with the polysulfide to form polythiourethane that resist desorption by JRF and moisture. Since “aged” polyurethane surfaces contain too few residual NCO groups, the resultant adhesion of the polysulfide sealant is poor. The use of a titanate primer, however, produces adequate adhesion. The titanate interacts with the polysulfide but does not react with the polyurethane surface. The titanate and solvent combination, however, interfaces with the polyurethane surface by softening it and producing microroughness and thereby increasing mechanical interlocking. Another reason the primer functions is by removing or lifting a monomolecular (or thicker) water layer from the polyurethane surface and allowing the sealant to “wet” or get “closer” to polyurethane. Incorporation of epoxy modification in a polysulfide sealant improves adhesion to “aged” polyurethane surface because epoxy groups can react with urethane groups. Additionally, hydroxyl and nitrogen groups may produce increased attractive forces.
Rubber-Thermoplastic Compositions. Part V. Selecting Polymers for Thermoplastic Vulcanizates
Authors: Coran A. Y. , Patel R. P. , Williams D. 
Published: February 2011

Abstract
Based on a few characteristics of the pure rubber and plastic components, rubber-plastic combinations can be selected, with a high probability of success, to give thermoplastic vulcanizates (by dynamic vulcanization) of good mechanical integrity and elastic recovery. The characteristics used in the selection are estimated surface energies, crystallinity of the hard phase (plastic) material and the critical chain length, of the rubber molecules, for entanglement. The best compositions are prepared when the surface energies of the rubber and plastic material are matched, when the entanglement molecular length of the rubber is low (high entanglement density) and when the plastic material is crystalline. Of course, it is required that neither the plastic, nor the rubber decompose in the presence of the other at temperatures required for melt mixing. Also, a curing system is required, appropriate for the rubber under the conditions of melt-mixing.
Glass Transition Behavior of Polyisoprene: The Influence of Molecular Weight, Terminal Hydroxy Groups, Microstructure, and Chain Branching
Authors: Kow C. , Morton M. , Fetters L. J. , Hadjichristidis N. 
Published: February 2011

Abstract
The glass transition temperatures for a series of high-1,4 linear and star-branched polyisoprenes have been measured by differential scanning calorimetry. The Fox-Flory relation for the linear polyisoprenes was found to be Tg=Tg∞−1.76×104Mn−1. The influence of hydroxyl groups on Tg was also examined for low molecular weight (&lt;2.2×104) polyisoprenes.
Chemical and Scanning Electron Microscopy Studies on Fatigue Failure of Natural Rubber Vulcanizates
Authors: Mathew N. M. , Bhowmick A. K. , De S. K. 
Published: February 2011

Abstract
Gum and filled vulcanizates with both conventional and EV systems were tested in a De Mattia flexing machine at two temperatures, and the fracture surfaces were subjected to chemical analyses and SEM studies. The study shows that flexing failure is not accompanied by any major change in network structure. SEM studies show ductile failure of gum mixes. HAF black filled mixes show brittle failure which changes to quasi-ductile with the addition of antioxidant. At 100°C, flow of the matrix is more predominant.
One-Component Heat Curable Urethane Liquid Elastomers
Authors: O'Connor J. M. , Sessions W. J. , Lickei D. L. 
Published: February 2011

Abstract
Quite clearly this study does not fully achieve the objectives stated earlier. The data show that fairly good quality storage stable one-component elastomers may be produced from acrylic modified urethane oligomers thermally cured with polyfunctional mercaptans and peroxide. Unfortunately, some of the advantages of a liquid system are lost because a reinforcing filler must be added in order to achieve acceptable physical properties. At the levels studied in this design, the filler and % hard segment play only a minor role in influencing the physical properties of the system. Those oligomers with low average functionality and low unsaturation appear to give the best physical properties, and further improvements may be achieved by looking at higher molecular weight polyols which, for a given functionality, will produce oligomers with lower unsaturation. Clearly, our screening study was not extensive enough to fully elucidate the utility of this concept. In order to determine what order of properties may be achievable by this approach, it will be necessary to design experiments that consider the effects of the other variables not evaluated in our initial study. For instance, we held the mercaptan constant throughout this work. It is trifunctional and was used at a 10% excess. Beneficial effects may be achieved with less than an excess or a greater excess or by evaluating mercaptans with reduced or elevated functionality. The cure conditions should be optimized and the effect of conventional rubber accelerators or additives screened. The oligomer for the most part consists of a polyol. We chose to evaluate only the 1500 equivalent weight polyether polyols for most of our preparations. We indicated earlier that it may be beneficial to look at higher equivalent weight polyols in order to minimize the unsaturation for a given functionality. Also, urethanes derived from polyester polyols generally possess superior physical properties compared to those based on polyethers, and it may be worthwhile to examine polyester polyol based oligomers. Carbon black, as well as fully adequate mixing, should be looked at to completely define the process.
Short Jute Fiber Reinforced Rubber Composites
Authors: Murty V. M. , De S. K. 
Published: February 2011

Abstract
The following conclusions can be drawn from the above results and discussion: (1) The bonding between jute fiber and rubber matrix is poor without any bonding agent. (2) Addition of 5 phr silica is essential and sufficient for promoting adhesion between fiber and matrix of a mix containing 5 phr resorcinol and 3.2 phr (3) The jute fiber will act as a reinforcing filler only when added above a volume loading of 10 percent. (4) The aging resistance of jute fiber reinforced natural rubber composites is excellent beyond a fiber loading of 10 volume percent.
Mastication of Rubber
Authors: Fries H. , Pandit R. R. 
Published: February 2011

Abstract
As has been shown, peptizing agents act in the mechanochemical and thermooxidative breakdown of elastomers as radical acceptors at low temperatures and as oxidation catalysts at high temperatures. Modern peptizing agents usually consist of thiophenols or aromatic disulfides combined with metal complexes (chelates) of Fe, Cu, and Co, as catalysts for the oxidative breakdown. The composition must be such as not to affect the mechanical properties, stability, and aging of compounds and vulcanizates. Peptizing agents have practically no influence on the vulcanizate properties. Mastication can be carried out as a separate step or as an integrated part of the mixing process. When mastication is integrated with the mixing process, vulcanizate properties like flex fatigue resistance are improved. The principles discussed enable the compounder to select the most favorable mastication and mixing procedure for any given situation.
The Relationship between Heat Buildup and the Chemistry of Crosslinking Systems
Authors: Kempermann Theo 
Published: February 2011

Abstract
An attempt has been made to describe the mutual correlation of different heat buildup test methods. The results are, for example in the case of the Goodrich flexometer, affected by no fewer than four relevant parameters (E′, tan δ, Δh and h), with their initial values and with their changes in time; so we are concerned with a complex and not easily analyzed system. However the following conclusions can be made: Heat buildup must be regarded as a dynamic cyclic process entailing mechanical work and aging. Much more importance should be attached to the results of long-time tests than to the results of short-time tests. Depending on the duration of the test, completely different results may be obtained. Tests that do not result in permanent deformation of the test specimen are preferable. A method of test in which the specimen of constant dimensions is subjected to a constant and alternating deformation has yet to be developed. Assumptions drawn from the results of laboratory tests may prove completely untrue for tires owing to the phenomenon of sulfur migration from the belt zone into the tread. Laboratory tests clearly favor systems containing little sulfur; tire tests confirm only to a limited extent the desirability of using low-sulfur systems. For laboratory tests, it is therefore preferable to use a constant amount of sulfur, which should not be too small. The results obtained by varying the chemistry of the crosslinking system may be summarized as follows: The heat buildup falls as the amount of sulfur is reduced. Thiazole accelerators give better results than sulfenamides. Sulfenamides give better results than basic accelerators. Some retarders have unfavorable effects. Dithiophosphates have favorable effects in the low-sulfur system.
Some Rheological Aspects of the Peel Strength of Rubbery Adhesives
Authors: Gent A. N. , Hamed G. R. 
Published: February 2011

Abstract
The strength of adhesion between two types of SBS triblock elastomer and polyethylene terephthalate (Mylar) has been measured using a peeling geometry. Three aspects of the measured strength have been studied: its dependence upon thickness of the elastomeric adhesive layer, its dependence upon the speed of peeling, and the occurrence in some circumstances of tearing failure of the elastomer, rather than interfacial separation. The bond with the stiffer SBS elastomer (Kraton 1101) had a peel strength that was independent of thickness over the range studied: 0.1–6 mm. However, the peel strength with the softer SBS material (Kraton 3202) increased linearly with thickness before reaching a constant value at thicknesses greater than about 2 mm. This difference in the dependence of the peel strength upon thickness of the adhesive layer for the two elastomers is attributed to the formation of a relatively thin plastically-yielded layer at the peel front in the former case but not in the latter. The dependence of the peel strength of the Kraton 1101-Mylar bond upon the rate of peeling was strongly influenced by the degree to which equilibrium wetting had been achieved before testing. At low levels of interfacial interaction, the peel strength increased markedly with peeling rate, whereas, when the interaction was relatively strong, the strength did not vary much with changes in the rate of peeling. These features are again attributed to the tensile stress-strain behavior of this elastomeric adhesive, and the occurrence of plastic yielding under high local stresses. The adhesion between Kraton 3202 and Mylar underwent a transition in failure mode from rubber failure to interfacial detachment as the peeling rate was increased. The peeling rate at which the transition occurred was found to be proportional to the thickness of the adhesive layer, in accordance with a characteristic rate of straining. This transition is also attributed to ductile processes within the adhesive.
Filler Choices in the Rubber Industry
Authors: Dannenberg E. M. 
Published: February 2011

Abstract
A wide variety of inorganic fillers are produced for the rubber industry. The most important are the clays, precipitated silicas and silicates, and the ground and precipitated calcium carbonates. The silicas and silicates provide the broadest particle size range falling into the carbon black range from FEF (N550) to finer than SAF (N110). The clays and calcium carbonates are in the larger carbon black particle size range from coarser than thermal black (N990) to FEF (N550). if particle size were the only important parameter determining the usefulness of rubber fillers, these products would meet the requirements presently served by carbon black. Their failure to be interchangeable with the carbon blacks is due to their lower modulus and reinforcement performance. These deficiencies are caused by the nature of their surfaces, which are generally more polar and hydrated than carbon black. This makes them more difficult to adhere to and interact with the rubber phase. In order to improve the surface interaction of inorganic fillers with hydrocarbon rubbers, a number of new polymer-reactive, surface-treated products have been introduced. The addition of silane coupling agents during mixing has also been recommended. Silane treated clays and talc, and polymer-grafted clay and calcium carbonate are commercially available. These products are better than their base materials. For some applications, they have been suggested as alternatives to the lower reinforcing grades of carbon black. For the higher reinforcing carbon blacks, only the precipitated silicas with silane additives can be considered as alternatives. However, in tire tread applications, the performance of these combinations has not been clearly defined, and the high cost of the silanes makes their use with silica prohibitive. A more economic method for coupling may result from recent research on functionalized polymers capable of reacting with the surface silanol groups of silica. This survey also includes two finely divided carbonaceous fillers made from coal and petroleum coke. Blends of these materials with more reinforcing carbon blacks and other fillers have been recommended as alternatives to the carbon blacks in the thermal to SRF range. A number of commercial fillers have been suggested as alternatives to the lower reinforcing grades of carbon black for some applications. There are no satisfactory substitute products for the medium to high reinforcing grades of carbon black.
Current Trends in Fluoroelastomer Development
Authors: Albin L. D. 
Published: February 2011

Abstract
Recent advances in the automotive, petroleum, and energy-related industries have created applications for high-performance elastomers, which often require chemically resistant elastomers with improved high-temperature operating capability. Fluoroelastomers are uniquely capable of withstanding high temperatures in conjunction with aggressive chemicals, fuels, and lubricants. While a number of reviews concerning fluoroelastomers have been published in the last three years, this paper will concentrate on recent developments that have improved fluoroelastomers to meet the requirements of new high-performance applications. Three types of fluorine-containing elastomers—fluorocarbon, fluorosilicone, and fluoroalkoxyphosphazene (phosphonitrilic)—are commercially available. The fluorocarbon elastomers have the highest fluorine content, with general grades having between 53 and 70% fluorine. The high fluorine content of these specialty elastomers imparts exceptional resistance to attack by fuels, oils, and corrosive chemicals. The excellent resistance to high-temperature aging for extended periods of time results in a temperature use range of −46 to 320°C. Fluoro-carbon elastomers are produced in the United States by 3M (“Fluorel” Brand fluoroelastomer) and Du Pont (“Viton” Brand fluoroelastomer) and outside the United States by Montedison (Italy, “Technoflon” Brand fluoroelastomer), Daikin (Japan, “Daiel” Brand fluoroelastomer), and Asahi Glass (Japan, “Aflas” Brand elastomer, a copolymer of tetrafluoroethylene and propylene). Fluorosilicone and fluoroalkoxyphosphazene elastomers contain 30–40% fluorine. Although the fluorine content of these elastomers is less than that of fluorocarbon elastomers, it is high enough to provide moderate chemical resistance to many fluids. The flexible nature of the heteroatoms of the polymer chain backbone in fluorosilicone and fluoroalkoxyphosphazene elastomers results in excellent low-temperature flexibility, giving them a temperature use range of −54 to 230°C. Fluorosilicone elastomers are produced by Dow Corning (“Silastic”) and General Electric (“FSE”), while fluoroalkoxyphosphazene elastomers are produced by Firestone (“PNF”). This paper is a discussion of developments in fluorocarbon elastomer technology that have led to successful use in demanding applications which require high-performance elastomeric parts. Typical properties of fluorocarbon elastomers and improved properties resulting from cure system development and variations in the fluorine content of this type of elastomer will be presented. Applications for fluorocarbon elastomers in the automotive, petroleum, and energy-related industries will be illustrated.