bluuebunny/crossref_metadata_2025 huggingface dataset:
Anisotropy in Molded Nitrile Rubber
Authors: Blow C. M. , Demirli H. B. , Southwart D. W.
Published: February 2011

Measurements of linear swelling in solvent of small test pieces provide a useful means of investigating anisotropy in vulcanized products and components whose small size precludes the use of conventional tests on dumbbells, etc. Anisotropy has been found to be present in molded components. The extent of this is related to the material flow in the mold before or during vulcanization. There also appears to be an effect of flow on crosslink density. In this preliminary investigation the contribution of each of the various factors, e.g., filler- filler structure, polymer gel, polymer-filler interaction, tendency to prevulcanize, has not been established.
Influence of Morphology and Particle Size of Powdered Rubber on Mill Processing
Authors: Bleyie P. L.
Published: February 2011

The powdered rubber method leads to a considerable shortening of mill mixing time and hence to a reduction of the specific energy required. While the transition from granular material to powder (from above 1 mm to below 1 mm particle size) has considerable effect both on mixing time and on specific energy, the effect of size reduction on specific energy for sizes below 1 mm is substantially smaller than expected from the surface area increase, probably, because a large part of the energy is used for carbon black dispersion. No effect of specific surface on specific energy and mixing time was found.
Recent Developments in the Use of Multi-Station Injection Molding Machines
Authors: Rienzner H. J.
Published: February 2011

The major marketing of injection molding machines for rubber started in the early 1960's when machine designs were developed that incorporated accurate control of stock feeding, injection pressure, and heat generation in the compound. The injection process is an excellent method for taking advantage of van't Hoff's rule, according to which the crosslinking reaction time is reduced approximately 50 per cent for each 10° C rise in stock temperature. Therefore, a high temperature as the stock comes into the mold cavity is desirable for rapid cures and increased productivity. Ideally there would be no heat transfer from the mold to the stock or from the stock to the mold.
Identification of Elastomers in Tire Sections by Total Thermal Analysis. I. Tread and Black Sidewall
Authors: Sircar A. K. , Lamond T. G.
Published: February 2011

Total thermal analysis provides a reasonably accurate method for the identification of the polymers in tire treads or black sidewalls. DSC curves in nitrogen distinguish SBR, BR, or blends from NR or IR. Tg then distinguishes between these polymers, although confusion may arise in the case of blends of SBR/BR with a high proportion of BR. DTG curves confirm the findings of DSC and Tg. Thus, by combining all the techniques mentioned, it should be possible to establish the nature of the polymers with reasonable accuracy. The method is rapid, requires no sample preparation or treatment of the sample, and operator attention is not necessary once the experiment is started. An estimate of the proportion of carbon black in the recipe may also be obtained from the TG curve or by weighing the sample after DSC experiment in nitrogen.
Preliminary Studies on New Anti-Reversion Agents for the Sulfur Vulcanization of Diene Rubbers
Authors: Blok E. J. , Kralevich M. L. , Varner J. E.
Published: February 2011

Recently, new materials have been introduced that minimize the loss of crosslink density and properties caused by over-cure and/or high temperature applications. One of these new anti-reversion agents, 1,3-bis(citraconimidomethyl)benzene, compensates for the loss in crosslink density through the formation of new crosslinks. This paper evaluates various multifunctional acrylates to determine if they will function like 1,3-bis(citraconimidomethyl)benzene and reduce reversion through the formation of new crosslinks. The experimental data suggests that some of these acrylates form new crosslinks during overcure conditions and therefore are very effective at maintaining the modulus and tan delta values upon overcure.
Strain Energy Function for Filled and Unfilled Rubberlike Material
Authors: Shariff M. H. B. M.
Published: February 2011

A general separable form of strain energy function with linear parameters is developed so that if a standard curve fitting method is used only a handful of linear equations need to be solved; the proposed function is formulated in such a way that only a few parameters are required to characterized the rubberlike materials. One of the parameters is the Young's modulus and this could facilitate a curve fitting algorithm if the value of the Young's modulus is known. A single constant, strain energy function is also proposed. The predicted curves agree well with numerous experimental data.
Some Aspects on the Crosslink Reaction of Natural Rubber with Dipentamethylene Thiuram Tetrasulfide
Authors: González L. , Rodríguez A. , del Campo A. , Marcos-Fernández A.
Published: February 2011

The mechanism of vulcanization of natural rubber with the sulfurating agent dipentamethylene thiuram was studied. On the transformation from crosslink precursor to crosslink, the route via disproportionation is preferred. In the presence or absence of zinc oxide and stearic acid as activators, the formation of the crosslink precursor follows similar processes, while the main difference is in the reaction induction times. In addition, the desulfuration reaction was favored by the presence of zinc oxide.
The Rheology and Processability of Tire Compounds
Authors: Schaal Stéphane , Coran Aubert Y.
Published: February 2011

The purpose of the work reported here was to define the parameters, which affect the rheology of tire compounds as well as their processability. Rheology was characterized over a wide range of shear rates. Processability was defined inversely as the roughness of the extrudate from the Monsanto Processability Tester (MPT) capillary rheometer. The roughness was measured by using image analysis of the extrudate surface contour. A good correlation was found between the extrudate roughness and the size of the Mooney peak (peak in apparent stress plotted against time for very small shear rates in a start-up flow experiment). The Mooney peak can be represented as a yield stress. The effects of storage time and temperature on the size of the Mooney peak (i.e., its increase as a function of storage time) was studied. The kinetics of degradation of processability was not found to follow an Arrhenius type of behavior. Finally, a physical descriptive model was proposed to represent filler—rubber structures.
The Effects of Certain Recipe Ingredients and Mixing Sequence on the Rheology and Processability of Silica- and Carbon Black-Filled Tire Compounds
Authors: Schaal Stéphane , Coran Aubert Y. , Mowdood Syed K.
Published: February 2011

The purpose of the work reported here was to study the effects of curing ingredients, filler such as silica and its moisture content, mixing sequence, and mixing scheme on the rheology and the loss of processability of the tire compounds at different storage temperatures. Rheology was characterized over a wide range of shear rates. For the retardation of the development of poor processability during storage of the compound (assumed to be caused, at least in part, by filler particle reagglomeration and formation of bound rubber), the most effective ingredients are diphenylguanidine (DPG), polyethylene glycol (PEG) and cyclohexylbenzothiazolesulfenamide (CBS), the latter being even more effective if the storage temperature is not too high (e.g., lower than 70 °C). Two orders of mixing were considered: (i) Y-mixing (the mixing of a silica-filled masterbatch with a carbon black-filled masterbatch), and (ii) all-in-one mixing (the mixing of the rubbers and fillers all at the same time, in a single batch). We also observed that the Mooney peak (peak stress in low-strain-rate start-up flow) and extrudate roughness (indication of poor processability) increase much more slowly with storage time for the Y-mixed compound than it does for the all-in-one-mixed compounds. Also, a low moisture level in the silica leads to poor processability as does high-temperature heat treatment during the mixing stage.
Stiffness of Rubber Bush Mountings Subjected to Radial Loading
Authors: Horton J. M. , Gover M. J. C. , Tupholme G. E.
Published: February 2011

Based on the classical theory of elasticity, an exact expression is derived for the radial stiffness of a cylindrical rubber bush mounting of finite length, in terms of modified Bessel functions. From this a convenient approximate representation is deduced. Some exact and approximate numerical results are compared with the experimental data which are available.
Raman Study of Kinetics of Graphitization of Carbon Blacks
Authors: Zerda T. Waldek , Gruber Tyler
Published: February 2011

Raman spectra of laser heated carbon blacks provide information on the dynamics of the graphitization process. Continuous wave and pulsed-laser heating is used. It is shown that two ordering mechanisms of distinctly different reaction rates are present during the heat treatment. The dominating mechanism, during the initial stages of graphitization, is characterized by a very fast rate. The rate during the later stages of the process, after the initial first couple of seconds, is orders of magnitude slower.
The Effect of Compressive Strain and Stress on Electrical Conductivity of Conductive Rubber Composites
Authors: Sau K. P. , Chaki T. K. , Khastgir D.
Published: February 2011

The electrical conductivity changes significantly when compressive strain and stress are applied on the conductive rubber composites derived from acrylonitrile—butadine rubber (NBR), ethylene—propylene—diene rubber (EPDM) and their 50:50 blend. The resistivity increases during application of compressive strain. However, the change of electrical resistivity depends on strain amplitude, amount of filler loading and type of polymer matrix. The change of resistivity with time for compressed samples has also been registered. But, during application of compressive stress (pressure), the resistivity is found to decrease for NBR and increase for EPDM and dual behavior is observed in blend. All the increase and decrease of resistivity with the application of stress and strain is explained on the basis of formation and destruction of a conductive network, which further depends on viscosity (stiffness) of the matrices. The observations are supported by the similar experiments with conductive silicone rubber composites.
A Model for Rubber Degradation under Ultrasonic Treatment: Part II. Rupture of Rubber Network and Comparison with Experiments
Authors: Yashin V. V. , Isayev A. I.
Published: February 2011

A simple theoretical model of network degradation around ultrasonically pulsating cavities is considered. The model is based on the concept of overstressed chains and provides a simple tool to estimate a number of chains which should be involved in mechanochemical degradation at a given amplitude of ultrasonic pulsation. High amplitude cavitation with no collapse-like effects is demonstrated to result in significant reduction of the rubber crosslink density. This model also predicts considerable effects of rubber degradation on elastic properties of rubber around a pulsating cavity including certain irreversible effects and residual deformations. The Dobson—Gordon theory of rubber network statistics is employed in order to interpret the experimental data on the dependence of gel fraction in devulcanized rubbers on crosslink density in the gel. Application of the approach to devulcanized styrene—butadiene rubber (SBR) and silicone rubber demonstrates that the assumption on spatial—temporal randomness of rubber degradation allows us to achieve a fairly good agreement between experimental and theoretical data.
Analysis of Rubber Particles Produced by the Solid State Shear Extrusion Pulverization Process
Authors: Bilgili E. , Arastoopour H. , Bernstein B.
Published: February 2011

Vulcanized natural rubber was pulverized using a single screw extruder in a non-cryogenic Solid State Shear Extrusion (SSSE) process where rubber granulates were subjected to high compressive and shear stresses. The produced particles had diameters ranging from 40 to 1700 µm. Reprocessing of the produced powder resulted in a narrower particle size distribution. Considerable heat generated in the extruder due to friction caused surface oxidation of the fine rubber particles and, in turn, initiation of agglomeration of a portion of the produced particles. Physical, chemical, and thermal analyses were performed on the produced rubber particles and the rubber granulates to determine the effects of the pulverization process. The produced particles had irregular shapes with rough surfaces. The external surfaces of the particles were porous, but no microporosity was detected by nitrogen BET analysis. Swelling and extraction experiments showed that both the crosslink density and gel fraction of the particles were lower than those of the rubber granulates. The reprocessing of the produced particles caused further reduction in the crosslink density and the gel fraction. A correlation was established between the crosslink density and the gel fraction. Thermal analysis revealed similar behavior of all particles and the granulates in a nitrogen environment, but there was considerable thermo-oxidative degradation of the fine particles in air. The chemical analysis indicated that some of the bonds were broken during the pulverization process, and partial devulcanization had taken place.
Bromination of Butyl Rubber in the Presence of Electrophilic Solvents and Oxidizing Agents
Authors: Kaszas Gabor
Published: February 2011

Bromination of 1,4-isoprene units in butyl rubber proceeds by substitution leading to the formation of hydrogen bromide as byproduct. In-situ conversion of HBr back to bromine is possible by the use of oxidizing agents but the reaction is very slow and oxidation of the polymer may occur. The reaction is complex and is typically conducted in a two-phase system. It has been found that the rate-controlling step is the bromination of the 1,4-isoprene unit in the organic phase, and not the oxidation of HBr to Br2 in the water phase or the mass transfer of HBr or Br2 between phases. Increasing the electrophilicity of the organic phase dramatically increased the overall rate. A 90–95 wt % conversion of bromine was achieved in one minute. Side or consecutive reactions (oxidation of the polymer, hydrobromination of the unsaturation, rearrangement or dehydrohalogenation of the main product) could be avoided, allowing the synthesis of a highly uniform material.
Spectroscopic Characterization of the Molecular Structure of Elastomeric Networks
Authors: Koenig Jack L.
Published: February 2011

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

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

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

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

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

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

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

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

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

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

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

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.
Object Modelling and Tracking in Videos via Multidimensional Features
Authors: Jiang Zhuhan
Published: February 2011

We propose to model a tracked object in a video sequence by locating a list of object features that are ranked according to their ability to differentiate against the image background. The Bayesian inference is utilised to derive the probabilistic location of the object in the current frame, with the prior being approximated from the previous frame and the posterior achieved via the current pixel distribution of the object. Consideration has also been made to a number of relevant aspects of object tracking including multidimensional features and the mixture of colours, textures, and object motion. The experiment of the proposed method on the video sequences has been conducted and has shown its effectiveness in capturing the target in a moving background and with nonrigid object motion.
Energy-Efficient Relaying Strategy with Network Coding in Two-Way Parallel Channels
Authors: Hu Ning , Chen Xiang , Zhong Xiaofeng , Slimane Ben , Li Yunzhou , Wang Jing
Published: February 2011

We consider a two-way communication assisted by parallel regenerative decode-and-forward relays operating in orthogonal channels. In a system with limited channel state information at each source and relay node, an optimum distributed power allocation strategy is proposed to minimize the total transmit power, providing a target signal-to-noise ratio at each destination with a target outage probability. Moreover, combined with opportunistic relaying and network coding, a distributed decision mechanism is proposed for the relay node to decide whether to help the transmission or not. In this proposal, each source works out the transmit power and the decision threshold then broadcasts them. The selected relay compares the decision threshold with the channel gain of its weaker relay-to-destination link, then determines whether to forward the networkcoded data or not. Simulation results show the advantage of this strategy in terms of energy efficiency for a two-hop two-way communication scenario. The proposed strategy is very flexible as it can trade outage to power consumption and vice versa.
Intrasellar Chondroid Chordoma: A Case Report
Authors: Hirosawa Renata M. , Santos Antonio B. A. , França Mariana M. , Fabris Viciany Erique , Castro Ana Valéria B. , Zanini Marco A. , Nunes Vania S.
Published: February 2011

Chordomas are tumors derived from cells that are remnants of the notochord, particularly from its proximal and distal extremes, they are mainly midline and represent approximately 1% of all malignant bone tumors and 0.1 to 0.2% of intracranial neoplasms. Chordomas involving the sellar region are rare. Herein, we describe a 57-year-old male patient presenting with a history of retro-orbital headache, progressive loss of vision, and clinical features of hypopituitarism, for over 2 months. During evaluation, the CT scan revealed a large contrast-enhancing intrasellar tumor with a 3.6-cm largest diameter. The patient underwent transsphenoidal partial resection of the tumor, and histological examination was consistent with the diagnosis of chondroid chordoma. Although chordomas are rare, they may be considered to constitute a differential diagnostic of pituitary adenomas, especially if a calcified intrasellar tumor with bone erosion is diagnosed.
Dynamics of a Compact Operator
Authors: Lim Teck-Cheong
Published: February 2011

Let be a compact linear (or more generally affine) operator
from a Banach space into itself. For each , the sequence of iterates , , 1, and its averages , 1, are either
bounded or approach infinity.
Low-Complexity Inverse Square Root
Approximation for Baseband Matrix Operations
Authors: Salmela Perttu , Burian Adrian , Järvinen Tuomas , Happonen Aki , Takala Jarmo Henrik
Published: February 2011

Baseband functions like channel estimation and symbol detection of sophisticated telecommunications systems require matrix operations, which apply highly nonlinear operations like division or square root. In this
paper, a scalable low-complexity approximation method of the inverse square root is developed and applied in
Cholesky and QR decompositions. Computation is derived by exploiting the binary representation of the fixedpoint
numbers and by substituting the highly nonlinear inverse square root operation with a more implementation
appropriate function. Low complexity is obtained since the proposed method does not use large multipliers or
look-up tables (LUT). Due to the scalability, the approximation accuracy can be adjusted according to the targeted
application. The method is applied also as an accelerating unit of an application-specific instruction-set processor
(ASIP) and as a software routine of a conventional DSP. As a result, the method can accelerate any fixed-point
system where cost-efficiency and low power consumption are of high importance, and coarse approximation of
inverse square root operation is required.
Disease and Phenotype Data at Ensembl
Authors: Spudich Giulietta M. , Fernández‐Suárez Xosé M.
Published: February 2011

Biological 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

Alkylate 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

Alkylate 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

Catalyzed 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

This 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

The 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.
Oxygenates Synthesis – Homogeneous
Authors: Whyman Robin
Published: February 2011

The current status of direct (from CO/H2) and indirect (via methanol, formaldehyde, or methyl acetate) homogeneously catalyzed C1chemistry based routes for the selective production of the oxygenates methanol, ethanol, and ethylene glycol (including higher alcohols, diols, and acetate esters); acetic and propionic acid; ethyl and vinyl acetate; acetic anhydride; and methyl formate is described. While none of the direct synthesis gas based routes have been commercialized, largely because of low catalytic activities and extreme operating pressure requirements, indirect routes including the Co‐, Rh‐, and Ir‐catalyzed carbonylation of methanol to acetic acid and the Rh‐catalyzed carbonylation of methyl acetate to acetic anhydride, together with the coproduction of both, are well‐established commercial processes. The majority of these transformations are uniquely homogeneously catalyzed. Although mechanistic pathways associated with the carbonylation of methanol to acetic acid are well‐established, uncertainty surrounds the mechanism of the initial step in the reduction of CO, to a purported formyl intermediate, during its direct conversion to oxygenates. A characteristic mechanistic feature of the latter chemistry is the operation of kinetic reaction control that is manifest in the absence of the thermodynamically favored products, hydrocarbons (particularly methane); with the exception of catalysts for methanol manufacture, this behavior is in sharp contrast to that of typical heterogeneous catalysts for synthesis gas reactions.
Oxygenates Synthesis—Homogeneous
Authors: Whyman Robin
Published: February 2011

The current status of direct (from CO/H2) and indirect (via methanol, formaldehyde, dimethyl ether, or methyl acetate) homogeneously catalyzed C1chemistry based routes for the selective production of methanol, ethanol, and ethylene glycol (including higher alcohols, diols, and acetate esters), acetic acid, propionic acid and methyl propionate, ethyl and vinyl acetate, acetic anhydride, and methyl formate is described. Whereas none of the direct routes have been commercialized, largely because of low catalytic activities and extreme operating pressure requirements, indirect routes including the Co‐, Rh‐, and Ir‐catalyzed carbonylation of methanol to acetic acid, Rh‐catalyzed carbonylation of methyl acetate to acetic anhydride (and coproduction of both), and Pd‐catalyzed methoxycarbonylation of ethylene to methyl propionate comprise established commercial processes. The majority of these transformations are uniquely homogeneously catalyzed.

Although mechanistic pathways associated with the carbonylation of methanol to acetic acid are well established, uncertainty still surrounds the mechanism of the initial step in the reduction of CO, to a putative formyl intermediate, during its direct conversion to oxygenates. A characteristic mechanistic feature of the latter chemistry is the operation of kinetic reaction control that is manifest in the absence of the thermodynamically favored products, hydrocarbons (particularly methane); with the exception of catalysts for methanol manufacture, this behavior is in sharp contrast to that of typical heterogeneous catalysts for synthesis gas reactions.
Aldol Reaction—Homogeneous
Authors: Xu Li‐Wen , Li Li , Cai Yong‐Feng
Published: February 2011

The aldol reaction is one of the oldest and important methods for the construction of carbon–carbon bonds in organic chemistry. Over the last 30 years, tremendous efforts have resulted in the development of many highly sophisticated and efficient catalytic methods of modern aldol reactions in catalytic chemo‐, regio‐, enantio‐, and diastereoselective manners. This review outlined those efforts in homogeneous catalysis and discussed with selected examples (331 publications) according to the different elemental types of catalysts, for example, transition metals and rare earth metals based Lewis acids, main group metals based catalysts, multifunctional catalysts, and metal‐free catalysts.