bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectroscopic Characterization of the Molecular Structure of Elastomeric Networks
Authors: Koenig Jack L. 
Published: February 2011

Abstract
In vulcanization, chemical crosslinks are formed across elastomeric polymer chains improving both the strength and elastic properties of the rubber. An understanding of the formation, structure, and stability of vulcanizates is therefore very important. Solid-state NMR and NMR imaging have been effective methods to study many different aspects of vulcanization. In solid-state NMR, several peaks appear in the C-13 spectrum of vulcanized rubber. Through model studies, NMR analysis, and chemical shift additivity calculations, these peaks were assigned to their respective vulcanizate structures. Once this assignment was made, the concentration of each vulcanizate structure formed could be followed with time under a variety of different conditions. In unaccelerated sulfur vulcanization of natural rubber (NR) and polybutadiene rubber (BR), many inefficient (cyclic or intramolecular) structures were formed as compared to intermolecular crosslinks. In accelerated NR and BR sulfur vulcanization, NMR was used to study vulcanizate concentration dependence on (a) type of formulation (efficient, semi-efficient, or conventional), (b) type of accelerator, (c) extent of cure, and (d) different concentration of ingredients (sulfur, activator, etc.). Solid-state NMR was also used to study different parameters in butyl rubber and to identify elastomers in binary blends of chloroprene rubber (CR) and NR, CR and chlorosulfonated polyethylene (CSM), NR and CSM, and styrene—butadiene rubber (SBR) and acrylonitrile—butadiene rubber (NBR) as well as the tertiary blend of NR/SBR/BR. In several studies, the effect of filler (carbon black or silica) on vulcanization was studied. Additionally, the thermo-oxidative degradation of sulfur vulcanizates in NR with heating time and temperature was observed using NMR. NMR imaging has been useful in the determination of internal inhomogeneities arising from inadequate mixing, gradients in crosslinking chemistry, filler distribution, blends, and coagents.
Reinforcement of General-Purpose Grade Rubbers by Silica Generated In Situ
Authors: Kohjiya Shinzo , Ikeda Yuko 
Published: February 2011

Abstract
The use of the sol—gel process on general-purpose grade rubbers is reviewed in the absence or presence of silane coupling agents. The sol—gel reactions of tetraethoxysilane (TEOS) in epoxidized natural rubber (ENR), styrene—butadiene rubber (SBR) or butadiene rubber (BR) vulcanizates produced silica generated in situ. This silica was found to be a good reinforcing agent by investigating tensile and dynamic mechanical properties and morphology observation by transmission electron microscopy (TEM). The amount of silica formed was limited by the degree of swelling of the rubber vulcanizate by TEOS which was the precursor of the silica. However, the dispersion of silica generated in situ was better than conventionally added silica due to its formation in place. Also, it was noted that the diameter distribution of in situ silica was monodispersed. Silane coupling agents, such as mercaptosilane, aminosilane, and bis(3-triethoxysilylpropyl) tetrasulfide, were compounded in the vulcanizates and their effects on silica generated in situ were evaluated. Their effects were significant. The dispersion of the silica in the rubbery matrix became better and the particle size became smaller and monodispersed, as observed by TEM, which improved mechanical properties. The superior properties of silica generated in situ have been studied further to elucidate the mechanism of reinforcement.
Environmental Effects of Recycled Rubber in Light-Fill Applications
Authors: Liu H. S. , Mead J. L. , Stacer R. G. 
Published: February 2011

Abstract
Tire shred processors use various mechanical means to reduce the waste stream of tires to components including rubber and steel. There is a stockpile of shredded rubber material in many states that is currently marketed mainly for use as Tire Derived Fuel (TDF). Civil engineering applications such as light landfill cover, and potentially landfill drainage layers are also attractive applications for shredded rubber material. Local environmental protection agencies and state public health officials have been reluctant, however, in some regions to allow recycled rubber to be used in civil engineering applications. An absence of data concerning long-term effects is often cited as justification for these bans. We summarized recent laboratory investigations conducted to quantify possible leachates from various recycled tire compounds. Extension of these results to reported field tests detailing the impact of recycled rubber on air, soil and water quality is also considered, as well as biological and toxicity issues. Finally, we identify areas where additional research is required and suggest approaches supporting “Better Use Determinations” for use of recycled tire rubber in these applications.
Rate-Dependent Modeling of a Highly Filled Vulcanizate
Authors: Coveney V. A. , Johnson D. E. 
Published: February 2011

Abstract
Many filled elastomers exhibit characteristic types of non-linear and weakly rate-dependent behavior not well represented by viscoelasticity. Previous attempts to overcome these problems are discussed. Recently, there has been particular interest in rate-independent “frictional”, such as triboelastic, models. In the current paper rate-dependent variants of triboelastic models are described. Essential aspects of the behavior of these models are discussed. Predictions for the models are compared with experimental data for sinusoidal deformation histories and stress relaxation tests.
Reinforcement of Silicone Elastomers with Treated Silica Xerogels: Silica—Silicone IPNs
Authors: Deng Qin , Hahn James R. , Stasser Jennifer , Preston Jeremy D. , Burns Gary T. 
Published: February 2011

Abstract
The use of silylated xerogels as reinforcing fillers in silicone elastomers was investigated. The silylated xerogels used in this study were mesoporous solids with a high degree of surface treatment and an open, interconnected high porosity. Some macropores were also present in the original xerogel particle. During compounding the original size of the xerogel particles is reduced substantially by fracture through the macroporous regions. The mesoporous regions of the xerogel are retained and exist as a uniform dispersion of filler particles in the siloxane polymer phase. The absence of a bound rubber phase, and the presence of an open porosity in the xerogel suggests reinforcement occurs via a silica—silicone interpenetrating network. This creates additional chain restrictions which lead to increases in modulus and other mechanical properties.
Elastomeric Comb-Shaped High Molecular Mass Poly(Oxyethylene) for Polymer Electrolyte: Morphology and Ionic Conductivity
Authors: Ikeda Y. , Wada Y. , Matoba Y. , Murakami S. , Kohjiya S. 
Published: February 2011

Abstract
The morphology, dynamic mechanical properties and ionic conductivity of high molecular mass comb-shaped poly(oxyethylene)s with tri(oxyethylene) side chains (TECs) were investigated, when LiClO4 was doped at the concentration of [Li]/[ —O—] = 0.05 ∼ 0.15. The samples were TEC-11 and TEC-18, the contents of tri(oxyethylene) side chain of which were 11 and 18 mol%, respectively. With increasing salt concentration, the glass transition temperature increased and the melting temperature decreased followed by the disappearance of the melting point. By adding the salt at the concentration of [Li]/[—O—] = 0.10 or 0.15, an alternative structure was suggested to be formed although the poly(oxyethylene) matrix was completely amorphous. Due to the morphological characteristics of TECs and the concentration of the salt, both TEC-11 and TEC-18 exhibit the high ionic conductivities of 10−4 S/cm at 30°C, when the salt was doped at the concentration of [Li]/[—O—] = 0.10. The high molecular mass, over 106, of TECs gave rubbery electrolyte films without chemically crosslinked structure. The addition of the salt to TECs decreased the shear storage modulus at room temperature and expanded the temperature range of the rubbery plateau region within the range of salt concentrations studied here.
Inelastic Neutron Scattering from Filled Elastomers
Authors: Nakatani A. I. , Ivkov R. , Papanek P. , Yang H. , Gerspacher M. 
Published: February 2011

Abstract
Inelastic neutron scattering experiments are powerful techniques for evaluating local molecular dynamics. These methods are especially sensitive to hydrogen atoms containing motions. An overview of these experimental techniques is presented. Neutron filter analyzer and time-of-flight spectroscopy methods are used to characterize the local dynamics of polymers in the presence and absence of fillers. Of particular interest is the comparison between bound rubber attached to the filler surface and the pure, unbound rubber. A commercial synthetic polyisoprene containing approximately 100% cis-1,4 isomers was compounded with three different carbon blacks: N299, G299 (graphitized N299), and N762. Soxhlet extraction on each of the samples was performed so that corresponding samples containing purely bound rubber with filler were obtained. The filter analyzer and time-of flight spectra show distinct differences between the bound and pure rubber as well as differences based on carbon black type. Correlation of the spectral differences to the type of carbon black and initial concentration of carbon black are discussed.
Effect of Ionic Content on the Properties and Structure of Viologen Elastomers
Authors: Murakami T. , Kohjiya S. , Ikeda Y. , Urakawa H. , Kajiwara K. 
Published: February 2011

Abstract
Three viologen-type poly(tetramethylene oxide) (PTMO) ionenes with chloride anions (PTVs) were synthesized by living cationic polymerization, whose molecular masses of PTMO segments between the viologen units were 6100, 9800 and 12000 g/mol. The PTV films were elastomers and possessed the microphase-separated structure consisting of three phases, i.e., PTMO amorphous phase, PTMO crystalline phase and ionic aggregated phase. The effect of ionic content, i.e., the effect of molecular mass between the ionic segments on the higher-order structure and properties of the PTV films were investigated by differential scanning calorimetry, dynamic mechanical analysis, wide-angle X-ray diffraction and small-angle X-ray scattering (SAXS) measurements. The lower the ionic content was, the smaller the amorphous PTMO phase became and the more the long range-ordered structure of PTMO crystals of lamellae was regularly formed. This crystalline part significantly influenced the dynamic mechanical properties. The distance between the ionic domains became larger with the increase of the PTMO segments. The scattering peaks attributed to the crystalline phases and ionic domains were detected by SAXS for the PTV films whose molecular masses of PTMO segments were 9800 and 12000 g/mol. The distance between the ionic domains was changed little before and after the melting of PTMO crystals of PTV films.
TEM Observation of Natural Rubber Thin Films Crystallized under Molecular Orientation
Authors: Shimizu Toshiki , Tosaka Masatoshi , Tsuji Masaki , Kohjiya Shinzo 
Published: February 2011

Abstract
Morphology of natural rubber (NR) thin films crystallized under molecular orientation was examined by transmission electron microscopy (TEM). A thin film of NR (RSS#1) was made by casting its n-hexane (or benzene) solution onto the water surface, and prestretched up to a desired amount of strain (%). Each of the specimens thus prepared was introduced into a TEM column and isothermally crystallized at −25 °C with a cryo-transfer specimen-holder. Morphological observations in bright- and dark-field imaging modes revealed directly that the length of the lamellae, which were oriented perpendicular to the stretching direction, decreased with increasing strain. The result seems to be related to the population density of “γ-filaments” (named by Andrews) generated only by prestretching. Time-resolved bright-field observations by in situ TEM of the thin film prestretched up to a strain of 200% revealed the following. Though the film gave crystalline reflections in its selected-area electron diffraction even before isothermal crystallization, no well-defined lamellae were recognized. Subsequent isothermal crystallization for 2 h, however, formed well-defined lamellae oriented perpendicular to the stretching direction. This observation, conceivably, suggests that “γ-filaments” were formed immediately by prestretching and then the lamellae were nucleated on the γ-filaments at −25 °C.
Phosphonitrilic Fluoroelastomers—A New Class of Solvent Resistant Polymers with Exceptional Flexibility at Low Temperature
Authors: Kyker G. S. , Antkowiak T. A. 
Published: February 2011

Abstract
Many commercial elastomers exhibit good solvent resistance and high temperature stability but have limited use at low temperature. Fluorosilicone, which exhibits good low temperature properties, is limited in many dynamic applications by its poor physical strength. Phosphonitrilic fluoroelastomers are being developed for applications which require solvent resistance, low temperature flexibility, and good physical strength over a broad range of service conditions. A brief description of the synthesis and characterization of these new polymers has been presented in the forms of chemical, chromatographical, spectroscopical, physical testing, and rheological studies. The main object of this paper has been to provide an introduction to the art of processing, vulcanization, and reinforcement of these elastomers to produce useful commercial items. These fluoroelastomers can be processed on conventional equipment for dry-mixing rubber. Vulcanization can be effected with either organic peroxides or sulfur-accelerator cure systems. These vulcanizates can be reinforced with silicas, carbon blacks, or silane-treated clays to give stocks with a wide range of modulus, strength, hardness, and service temperatures (−80 to 400° F) in many service fluids and atmospheres. The exceptional solvent resistance, low temperature flexibility, and wide temperature service range indicate that phosphonitrilic fluoroelastomers should find use in items such as O-rings, Arctic fuel hose, lip seals, gaskets, and vibration damping services.
The Reactions of Crosslink Precursors in Natural Rubber
Authors: Morrison N. J. 
Published: February 2011

Abstract
The HPLC technique has been applied to the identification and estimation of individual isomers of model mono- and di-sulfidic pendent groups. Extensive analysis of the products of the reactions of model crosslinks was achieved by a combination of HPLC and GLC, and many of the results are summarized in Figure 2. The products comprised model crosslinks, model monosulfidic pendent groups, and olefins. The effects of temperature, solvent, and vulcanization residues upon the yields of these products were determined for models for crosslink precursors at the methyl and both methylene sites in the polyisoprene chains of natural rubber.
Silica Properties/Rubber Performance Correlation. Carbon Black-Filled Rubber Compounds
Authors: Okel Timothy A. , Waddell Walter H. 
Published: February 2011

Abstract
The effectiveness of predicting rubber performance based on measured silica physical properties in silica- and carbon black-filled compounds is presented for three rubber formulations: an off-the-road tire tread, a wire coat stock and a V-belt. Correlation and regression analyses were performed using SAS software for sixteen physical properties of thirteen precipitated silicas, and sixteen rubber compound performance characteristics of the three compounds. Silica physical properties studied include various measurements of surface area and structure, particle size, pH and impurities. Rubber performance characteristics studied include cure properties and physical properties such as stress/strain, tear strength, cut growth resistance, abrasion resistance and heat build-up. The present study confirms that silica surface area is the single best predictor of the effect that varying silica physical properties have on the physical performance of cured, carbon black-filled rubber compounds containing precipitated silica. Silica structure, as measured by DBP absorption and nitrogen or mercury pore volume, is a secondary predictor of certain rubber physical properties. The confidence limits of the predictions is dependent upon the concentration of precipitated silica used in the carbon black-filled rubber compound.
Disease and Phenotype Data at Ensembl
Authors: Spudich Giulietta M. , Fernández‐Suárez Xosé M. 
Published: February 2011

AbstractBiological databases are an important resource for the life sciences community. Accessing the hundreds of databases supporting molecular biology and related fields is a daunting and time‐consuming task. Integrating this information into one access point is a necessity for the life sciences community, which includes researchers focusing on human disease. Here we discuss the Ensembl genome browser, which acts as a single entry point with Graphical User Interface to data from multiple projects, including OMIM, dbSNP, and the NHGRI GWAS catalog. Ensembl provides a comprehensive source of annotation for the human genome, along with other species of biomedical interest. In this unit, we explore how to use the Ensembl genome browser in example queries related to human genetic diseases. Support protocols demonstrate quick sequence export using the BioMart tool. Curr. Protoc. Hum. Genet. 69:6.11.1‐6.11.34 © 2011 by John Wiley & Sons, Inc.
Alkylation – Heterogeneous
Authors: Corma Avelino , Martínez Agustín 
Published: February 2011

AbstractAlkylate gasoline produced by the reaction of isobutane with light olefins is a high value blending component of the gasoline pool owing to its high octane (both RON and MON) and its clean burning properties. In the first part of this article, the main aspects of the actual alkylation technology based on H2SO4or HF liquid‐acid catalysts are described, including the proposed reaction mechanisms, the influence of operating variables on product quality, and a brief description of the commercial sulfuric and hydrofluoric alkylation processes. Special emphasis is given in this part to the recent developments directed to improve the efficiency of the actual liquid‐acid alkylation processes, as well as to reduce the potential dangers associated with the use of H2SO4and HF catalysts. In the second part of the article, the latest achievements in the use of environmental friendly solid acids as a desirable alternative to the liquid‐acid alkylation technology are reviewed. The different solid acids studied as potential alkylation catalysts include supported Brönsted and Lewis acids, exchange resins and composites, zeolites, sulfated metal oxides, and heteropolyacids and their salts. Their catalytic activity, selectivity, and stability in relation to the isobutane alkylation reaction are discussed. Finally, different reactor configurations and processes proposed for solid acid alkylation are also addressed.
Alkylation—Heterogeneous
Authors: Martínez Agustín , Corma Avelino , Prieto Gonzalo , Arribas María A. 
Published: February 2011

AbstractAlkylate or alkylation gasoline is produced by reacting isobutane with light olefins, generally the C3–C4cut from catalytic cracking (FCC) units, in the presence of a strong acid catalyst. The alkylate product is mostly composed of a mixture of high octane isoparaffins being almost free of sulfur, olefins, and aromatics, thus making it a valuable component ofreformulatedgasoline. Unfortunately, today's commercial alkylation processes rely on the use of noxious HF and H2SO4liquid acids as catalysts and this imposes serious limitations, especially in the case of HF‐catalyzed processes, to expanding the worldwide alkylation capacity to the levels one might ideally envisage. This prompted to an intensive research work in the past 30 years in both academy and industry looking for alternative environment friendly solid acid catalysts that overcome the limitations of the current alkylation technologies. Since then, different types of solid acids, among which zeolites have deserved particular attention, have been investigated leading to outstanding advances in both catalyst and process design as well as in fundamental knowledge (nature of active sites, mechanism, etc.) that allowed several solid acid alkylation technologies being, at present, offered for commercialization. Unfortunately, refiners are still reluctant to assume the economic risks associated with the installation of a new alkylation technology, even if competitive, unless tighter environmental regulations become operational.In this article, the latest achievements in the use ofgreensolid acid catalysts as potential alkylation catalysts are reviewed. After a short introduction, the main features of the different solid acids so far studied, including supported Brønsted and Lewis acids, acid resins both supported and unsupported, zeolites, sulfated and tungstated transition metal oxides, and heteropolyacids and related materials, in the alkylation reaction are addressed. Although they cannot be considered as true solid acids, the potential of ionic liquids as alkylation catalysts is also discussed. Finally, a brief description of the different solid acid alkylation processes so far developed is included, with special emphasis on the catalyst and reactor designs.
Cyclopropanation
Authors: Noels Alfred F. 
Published: February 2011

AbstractCatalyzed reactions are quite usually the most versatile and direct way to cyclopropanes. Central to all synthetic efforts is the ability to control the relative and absolute stereochemistry around the cyclopropane ring. Recent developments in olefin cyclopropanation with transition metal complexes based mostly on palladium, copper, and rhodium are summarized where the carbene precursor is a diazocompound. Related metal‐mediated cyclopropanation reactions such as the Kulinkovich hydroxycyclopropanation, the Simmons–Smith reaction, and assymetric variations thereof are also considered, as well as less studied synthetic methods that involve cyclopropanation with electron holes, selenium‐assisted cyclopropanation, and cyclopropanation with lithiated sulfones. Recent breaktroughs in enantioselective cyclopropanation of double bonds with chiral copper and rhodium catalysts are compared and illustrated with different examples, inter alia for the synthesis of natural products.Related reactions such as the cyclopropenation of carbon–carbon triple bonds and the aziridination of double bonds can be promoted with the same families of catalysts. These methodologies offer ready synthetic entries into many new molecules, including natural compounds.
Cyclopropanation
Authors: Yeung Chi‐Tung , Kwong Hoi‐Lun 
Published: February 2011

AbstractThis review provides an overview of cyclopropanation that utilizes different methods. To have a more focused discussion, we concentrate on catalytic reactions that combine two fragments of two‐ and one‐carbon units to give a final three‐membered carbocycle. However, other important syntheses are also discussed to provide a more comprehensive overview.
Hydroformylation—Homogeneous
Authors: Mika László T. , Ungváry Ferenc 
Published: February 2011

AbstractThe hydroformylation or oxo‐synthesis is one of the most important transition metal assisted homogeneous catalytic transformation, providing industrial‐scale production of aldehydes and alcohols. The hydroformylation—homogeneous article presents the basic chemistry and kinetics of hydroformylation, solvents of hydroformlylation, and side reactions accompanying hydroformylation. The detailed reaction mechanisms related to the cobalt‐ and rhodium‐modified and unmodified catalysts are presented as well. The chemistry of the individual steps of the classic catalytic cycle based on results of model reactions and spectroscopic investigations is discussed and is followed by an overview of different catalyst modifiers such as phosphine and phosphite ligands.