bluuebunny/crossref_metadata_2025_split huggingface dataset:
COMPUTATIONAL SIMULATION OF ELASTOMER NANOCOMPOSITES: CURRENT PROGRESS AND FUTURE CHALLENGES
Authors: Liu Jun , Zhang Liqun , Cao Dapeng , Shen Jianxiang , Gao Yangyang 
Published: May 2013

ABSTRACTIn the field of elastomer nanocomposites (ENCs), computational simulation technique is becoming more and more essential, as a result of its ability to provide important and clear information at the molecular level, which is always difficult to obtain or not accessible through experimental investigations. We focus on summarizing the progress achieved in the simulation research of three critical topics of ENCs, namely, (i) the dispersion mechanism (particularly polymer-mediated interparticle interaction, the “many-body” effect at high filler loading), (ii) the characterization of the nanoscale/microscale structure and dynamics [the modified chain configuration in the presence of nanoparticles (NPs), the interfacial binding strength determining the efficiency of the stress transfer, the possibly altered interfacial chain structure, interfacial segmental dynamics leading to the shift of the glass transition temperature Tg, the formation of the filler network and its structure, the chemical cross-linking process], and (iii) the macroscopic viscoelasticity (the Payne effect), mechanical reinforcement, and physical property (thermal conductivity). Since recently only limited simulation work has been carried out pertaining to ENCs, we discuss these three topics in light of the simulation and theoretical achievements of polymer nanocomposites (mainly polymer melts filled with NPs). Meanwhile, some relevant experimental studies are also included for better illustration. Furthermore, for each topic, three typically different reinforcing fillers, such as three-dimensional spherical, two-dimensional sheet, and one-dimensional rod NPs, separately corresponding to carbon black or silica, clay sheets, and carbon nanotubes intensively used in the practical applications of ENCs, are illustrated in order. In order to realize a comprehensive understanding of the structure–property relation and in the meantime to provide more practical guidelines for the engineering applications of ENCs, we investigate future simulation opportunities and difficulties.
X-RAY COMPUTED MICROTOMOGRAPHY OF RUBBER
Authors: Jago Karine Le Gorju 
Published: May 2013

ABSTRACTIn rubber science, X-ray computed microtomography (micro CT) is becoming an increasingly used technique to characterize 3D microstructures. As a first step, experimental methods, limitations, and data analysis are described. A review of published micro CT studies for rubber is reported. Examples of our recent works are presented, including investigations on samples or complex structures, for compact or foam rubbers. Micro CT is used to describe the evolution of microstructures relative to different processing steps, to environmental interaction, and to adaptation to a mechanical deformation. New insights and better understanding of damage mechanisms due to quasistatic, creep, and fatigue solicitations are presented from in situ micro CT experiments. Perspective studies are outlined.
GLASS TRANSITION IN RUBBERY MATERIALS
Authors: Roland C. Michael 
Published: May 2013

ABSTRACT
When the perturbation frequency imposed on a rubber falls within the glass transition zone of its viscoelastic spectrum, energy absorption is maximized. This phenomenon is the operative mechanism for various applications of elastomers requiring large energy dissipation. Nevertheless, a fundamental understanding of the glass transition is lacking. The diversity of properties that depend both on chemical structure and thermodynamic conditions makes modeling difficult and a first principles theory perhaps unachievable; indeed, the number of models for the glass transition seems to be inversely proportional to their ability to accurately describe the myriad behaviors. The progress made at quantifying the role of the thermodynamic variables temperature, T, and density, ρ, on the dynamics is described. An important aspect of the work was the discovery that relaxation times and viscosities of molecular liquids and polymers superpose when plotted against the scaling variable T/ργ, with the scaling exponent γ a material constant sensibly related to the nature of the intermolecular repulsive potential; thus, dynamic spectroscopy measurements can be used to quantify the forces between molecules. Other properties derive from the scaling behavior, including the Boyer-Spencer rule and the correlation of fluctuations in the potential energy with fluctuations in the virial pressure.
MICROSTRUCTURE AND MOLECULAR DYNAMICS OF ELASTOMERS AS STUDIED BY ADVANCED LOW-RESOLUTION NUCLEAR MAGNETIC RESONANCE METHODS
Authors: Saalwächter Kay 
Published: May 2013

ABSTRACTNuclear magnetic resonance (NMR) certainly belongs to the most powerful spectroscopic tools in rubber science. Yet the often high level of experimental and in particular instrumental sophistication represents a barrier to its widespread use. Recent advances in low-resolution, often low-field, proton NMR characterization methods of elastomeric materials are reviewed. Chemical detail, as normally provided by chemical shifts in high-resolution NMR spectra, is often not needed when just the (average) molecular motions of the rubber components are of interest. Knowledge of the molecular-level dynamics enables the quantification and investigation of coexisting rigid and soft regions, as often found in filled elastomers, and is further the basis of a detailed analysis of the local density of cross-links and the content of nonelastic material, all of which sensitively affect the rheological behavior. In fact, specific static proton NMR spectroscopy techniques can be thought of as molecular rheology, and they open new avenues toward the investigation of inhomogeneities in elastomers, the knowledge of which is key to improving our theoretical understanding and creating new rational-design principles of novel elastomeric materials. The methodological advances related to the possibility of studying not only the cross-link density on a molecular scale but also its distribution and the option to quantitatively detect the fractions of polymer in different states of molecular mobility and estimate the size and arrangement of such regions are illustrated with different examples from the rubber field. This concerns, among others, the influence of the vulcanization system and the amount and type of filler particles on the spatial (in)homogeneity of the cross-link density, the amount of nonelastic network defects, and the relevance of glassy regions in filled elastomers.
ASSIGNMENT OF NMR SIGNALS FOR CHLOROPRENE RUBBER BY TWO-DIMENSIONAL NMR SPECTROSCOPY
Authors: Saito Takayuki , Kawahara Seiichi , Ohtake Yoshito 
Published: May 2013

ABSTRACT
Various pulse techniques of NMR spectroscopy were applied to CR to assign some small signals in 13C and 1H NMR spectra for the rubber. First, the rubber was subjected to distortionless enhancement by polarization transfer and attached proton test. The small signals in the 13C NMR spectrum were assigned to secondary, tertiary, and quaternary carbons. Second, correlations between 13C and 1H were investigated by heteronuclear multiple quantum correlation, heteronuclear two bond correlation, and heteronuclear multiple bond correlation measurements to assign the small signals in the 13C NMR spectrum in detail. By using the resulting correlations between 13C and 1H, the small unassigned signals in 1H NMR spectrum were assigned to methylene and methine protons of the rubber.
SOYBEAN OIL PLASTICIZERS AS REPLACEMENT OF PETROLEUM OIL IN RUBBER
Authors: Petrović Zoran S. , Ionescu Mihail , Milić Jelena , Halladay James R. 
Published: May 2013

ABSTRACT
Polymerized soybean oils of different molecular weights were used as plasticizers in NR/SBR compositions. The oils of different molecular weights and viscosities were synthesized by cationic polymerization using a proprietary technology. Because vegetable oils have double bonds, they are not only viscosity depressants but also active participants in cross-linking reactions. Properties of elastomers extended with different concentrations of mineral oil or pure soybean oil were compared with elastomers extended by polymerized oils of different molecular weights at the same concentrations. It was found that polymerized soybean oil could be substituted for naphthenic process oil with minimal differences in mechanical and dynamic properties.
EXPERIMENTAL CHARACTERIZATION AND MODELLING OF LARGE-STRAIN VISCOELASTIC BEHAVIOR OF A THERMOPLASTIC POLYURETHANE ELASTOMER
Authors: Bartolomé L. , Aginagalde A. , Martínez A. B. , Urchegui M. A. , Tato W. 
Published: May 2013

ABSTRACTThermoplastic polyurethane elastomers (TPUs) are a kind of elastomer that can be processed as thermoplastics. These elastomers exhibit a highly nonlinear behavior characterized by hyper-elastic deformability. Furthermore, the mechanical behavior of these elastomers is time-dependent, that is, they exhibit a viscoelastic behavior. We describe the material response of a TPU under moderate strains (ɛ &lt; 1) by using an overlay visco-hyperelastic model assuming separation of time dependence from nonlinear stress–strain behavior. To achieve this goal, cyclic loading–unloading experimental tests are carried out for two homogeneous deformation states, uniaxial tension and pure shear, and the strain–stress data are then analyzed to fit a hyperelastic model. Conversely, a viscoelastic model is obtained from relaxation tests. Finally, the visco-hyperelastic model is implemented in a finite element calculation tool (ABAQUS), and the numerical results show a reasonable correlation with experimental data. As a result, a overlay visco-hyperelastic model depending on maximum strain is proposed.
NBR-PANI.DBSA BLENDS: EFFECT OF ELECTRON BEAM IRRADIATION
Authors: Yong K. C. 
Published: May 2013

ABSTRACT
The electron beam irradiation technique was successfully used to cross-link poly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonate [NBR-PAni.DBSA] blends. Significant increase in cross-linking densities of all blends with doses of irradiation (up to 200 kGy) was observed, and a reasonably high cross-linking density level (in the order of 1030 m−3) also was achieved. All electron beam–irradiated NBR-PAni.DBSA blends exhibited good tensile properties (with tensile strength up to ∼20 MPa), with values that are comparable to those of similar blends cross-linked with either conventional sulfur or peroxide techniques. This kind of irradiation-induced cross-linking technique (at doses up to 200 kGy) also did not interrupt the blends' electrical properties after the blends were sufficiently stabilized for at least 24 h. The irradiated NBR-PAni.DBSA blends also possessed good electrical properties, that is, a single conductivity percolation threshold and high conductivities up to the order of 10−2 S.cm−1. All of these findings indicate a good potential for using the electron beam irradiation technique to prepare highly cross-linked, electrically conductive NBR-PAni.DBSA blends.
DRYING KINETICS AND CROSS-LINKING OF SULFUR PREVULCANIZED THICK NATURAL RUBBER LATEX FILM
Authors: Jing Chen , Lei Yang , Jieping Zhong , Sidong Li , Yongjun Chen , Kui Xu 
Published: May 2013

ABSTRACT
In order to investigate drying kinetics of thick natural latex (NR) samples after film formation and the effect on cross-linking of NR latex during the drying process, we employed drying experiment methods, swelling methods, and Fourier transform infrared spectroscopy (FTIR) methods to study the drying and vulcanizing characteristics of NR latex. The results show that the drying temperature and thickness of film have obviously affected drying characteristics. The drying kinetic equation is achieved by mathematic fitting, and the Henderson and Pabis model MR = a exp(−kt) was the best fitted model for the thick NR latex film. The effect of the drying temperature on the drying constant was assessed employing an Arrhenius type equation, which can be expressed as k = 6746 exp[−39.9 × 103/(RT)] (R = 8.314 J mol−1 K−1). The drying constant exponentially decreased with the increasing film thickness. At the beginning of drying, the cross-link density increases rapidly, and up to the maximum value, it would slightly decrease with the prolonged drying time, which the results of FTIR also agree with.
DURABILITY TESTING OF SILICONE MATERIALS FOR PROTON EXCHANGE MEMBRANE FUEL CELL USE
Authors: Bhargava S. , O'Leary K. A. , Jackson T. C. , Lakshmanan B. 
Published: May 2013

ABSTRACT
Silicone resins are ideal candidates for proton exchange membrane fuel cells (PEMFC) sealing and gasketing. They have many advantages for PEMFC application, such as superior stability and longevity under harsh environments, low water absorption, and broad temperature range. However, as this work shows, silicone-based materials have one big drawback: low molecular weight siloxanes, oligomers, and/or degradation byproducts may readily migrate from the base material into the fuel cell membrane, forming glassy structures, reducing the mechanical durability, and ultimately fracturing the proton exchange membrane (PEM). A novel, in situ testing method has been developed to test the effect of siloxanes on PEMFCs. The mechanism for migration of cyclic siloxanes to the PEM interface, causing it to fail in a brittle fashion, is presented. A commercially available silicone gasket material was used as a case study to validate the mechanism. Optical microscopy, scanning electron microscopy, and inductively coupled plasma were used to perform failure analysis of the tested samples. Thermogravimetric analysis was used to measure the removal rate of low molecular weight cyclic siloxanes. Gas chromatography–mass spectrometry was used to separate the organic molecules off-gassing from the material at temperature and provide a mass spectrum of each component.
CRACK GROWTH BEHAVIOR OF STYRENE-BUTADIENE RUBBER, NATURAL RUBBER, AND POLYBUTADIENE RUBBER COMPOUNDS: COMPARISON OF PURE-SHEAR VERSUS STRIP TENSILE TEST
Authors: Andreini G. , Straffi P. , Cotugno S. , Gallone G. , Polacco G. 
Published: May 2013

ABSTRACT
Fatigue crack growth experiments on different carbon black–filled rubber compounds have been carried out to evaluate the influence of pure-shear and strip tensile testing mode by using sine and pulse as waveforms. In a previous set of experimental investigations regarding the influence of both waveform and tested material, it was found that the mode I of crack opening sometimes propagates too quickly to be properly monitored in tests involving strip-tensile specimens. An alternative test methodology based on pure-shear test mode has been investigated, optimizing both the shape of the specimen and the test equipment. Data obtained from the different compound formulations were consistent with the theoretical background and resulted in similar ranking of compound crack growth resistance for the two testing modes; in addition, pure-shear mode showed a higher sensitivity to formula variations.
OVERCOMING INCOMPATIBILITY PROBLEMS IN ELASTOMER BLENDS BY TAILORED SURFACE PROPERTIES OF RUBBER ADDITIVES
Authors: Dierkes W. , Tiwari M. , Guo R. , Datta R. , Talma A. , Noordermeer J. , van Ooij W. 
Published: May 2013

ABSTRACT
Rubber is a challenging composite material, whose functionality strongly depends on the affinity of the different materials in the composite and its morphology. One way to tailor polarity and chemistry of the filler surface is plasma coating. When using acetylene, thiophene, or pyrrole as monomers, the coating results in a reduced polarity of the filler compared with untreated silica, and unsaturated C–C bonds are formed on the surface. This improves the compatibility of the filler–polymer blends. In a SBR/EPDM blend, the filler–polymer compatibility is improved for all plasma-coated fillers compared with untreated silica. The best dispersion is achieved by plasma–pyrrole coating, as measured by the Payne effect and reinforcement parameter. The rubber–filler interaction is also highest for this blend, as measured by the bound rubber content. As expected, this results in improved tensile properties. In NBR/EPDM, the filler–filler interaction is significantly reduced by the plasma–pyrrole coating, which indicates a balanced compatibility of the pyrrole-treated silica in both polymers. The properties of the vulcanizate show the combinatorial effect of dispersion, filler–polymer interaction, polymer entanglements, and cross-link density. All plasma-treated, silica-filled NBR/EPDM materials show a considerable increase in tensile strength compared with untreated silica, with polyacetylene-treated silica resulting in the best properties. When plasma-coated curatives are used in SBR/EPDM blends, the scorch safety of the compounds is increased and the rupture energy is enhanced. In NBR/EPDM blends, all packages of the modified curatives provide an increased maximum torque compared with the control. Mechanical properties of the NBR/EPDM blend are improved even more than they are with SBR/EPDM. This indicates a more-balanced distribution of cross-links, along with a more-homogeneous carbon black dispersion over the different rubber phases. A better polarity match between additives and polymers usually results in improved material properties. The wide variety of monomers for the plasma polymerization allows researchers to tailor the surface properties of the additives.
Carboxymethyl Starch/Montmorillonite Aqueous Dispersions: The Effect of Components and Mixing Method on Rheoviscometric Characteristics
Authors: Wilpiszewska Katarzyna , Zdanowicz Magdalena , Spychaj Tadeusz 
Published: May 2013

ABSTRACTThe rheoviscometric properties of low and high substituted carboxymethyl starch (CMS) 2 wt% aqueous solutions and their dispersions with sodium, calcium, and organomodified montmorillonite (MMT) have been investigated. The influence of MMT type and content on viscosity of CMS (degree of substitution, DS, 0.90)/sodium MMT aqueous dispersions, their stability, and transparency during storage up to 18 months has been investigated. Moreover, the methods of MMT dispergation in low substituted CMS solutions (DS 0.15), that is, mechanical stirring or mechanical and ultrasonication stirring on viscosity have been compared. It resulted in higher viscosity when using the latter mixing procedure (7000 and 9250 mPa·s, respectively, at 1 rpm for CMS (DS 0.15)/7 phr calcium MMT). In addition, thermal resistance of native starch and both CMS with different DS values has been investigated. The results are important as far as commercial applications of CMS solutions or dispersions with MMTs are concerned. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2013, 32, 21353; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21353
Differentially Expressed Epigenome Modifiers, Including Aurora Kinases A and B, in Immune Cells in Rheumatoid Arthritis in Humans and Mouse Models
Authors: Glant Tibor T. , Besenyei Timea , Kádár András , Kurkó Júlia , Tryniszewska Beata , Gál János , Soós Györgyi , Szekanecz Zoltán , Hoffmann Gyula , Block Joel A. , Katz Robert S. , Mikecz Katalin , Rauch Tibor A. 
Published: May 2013

ObjectiveTo identify epigenetic factors that are implicated in the pathogenesis of rheumatoid arthritis (RA), and to explore the therapeutic potential of the targeted inhibition of these factors.MethodsPolymerase chain reaction (PCR) arrays were used to investigate the expression profile of genes that encode key epigenetic regulator enzymes. Mononuclear cells from RA patients and mice were monitored for gene expression changes, in association with arthritis development in murine models of RA. Selected genes were further characterized by quantitative reverse transcription–PCR, Western blot, and flow cytometry methods. The targeted inhibition of the up‐regulated enzymes was studied in arthritic mice.ResultsA set of genes with arthritis‐specific expression was identified by the PCR arrays. Aurora kinases A and B, both of which were highly expressed in arthritic mice and treatment‐naive RA patients, were selected for detailed analysis. Elevated aurora kinase expression was accompanied by increased phosphorylation of histone H3, which promotes proliferation of T lymphocytes. Treatment with VX‐680, a pan–aurora kinase inhibitor, promoted B cell apoptosis, provided significant protection against disease onset, and attenuated inflammatory reactions in arthritic mice.ConclusionArthritis development is accompanied by changes in expression of a number of epigenome‐modifying enzymes. Drug‐induced down‐regulation of the aurora kinases, among other targets, seems to be sufficient to treat experimental arthritis. Development of new therapeutics that target aurora kinases can potentially improve RA management.
Optimization of neutral protease production from Bacillus subtilis: Using agroindustrial residues as substrates and response surface methodology
Authors: Zhu Ming‐Jun , Cheng Jing‐Rong , Chen Hong‐Tu , Deng Mao‐Cheng , Xie Wen‐Hua 
Published: May 2013

AbstractStatistically based experimental designs were applied to optimize the fermentation medium and cultural conditions for the maximization of neutral protease using three agroindustrial residues (cassava pulp, soybean meal, and wheat bran) and Bacillus subtilis DES‐59. The Plackett–Burman design was used to evaluate the effects of variables such as the concentration of substrates, initial pH, shaker's rotating speed, temperature, inoculum size, and incubation time. Among the eight parameters, three significant variables (cassava pulp, soybean meal, and inoculum size) were selected for the optimization study, in which a central composite design was used to optimize the concentrations of cassava pulp and soybean meal and inoculum size and investigate the interactive effects of the three variables. The optimal parameters obtained from response surface methodology are 37.78 g/L of cassava pulp, 15 g/L of soybean meal, and 6.5% (v/v) of inoculum size, respectively, resulting in a maximum neutral protease activity of 4107 ± 122 U/mL.
Cancer survival disparities by health insurance status
Authors: Niu Xiaoling , Roche Lisa M. , Pawlish Karen S. , Henry Kevin A. 
Published: May 2013

AbstractPrevious studies found that uninsured and Medicaid insured cancer patients have poorer outcomes than cancer patients with private insurance. We examined the association between health insurance status and survival of New Jersey patients 18–64 diagnosed with seven common cancers during 1999–2004. Hazard ratios (HRs) with 95% confidence intervals for 5‐year cause‐specific survival were calculated from Cox proportional hazards regression models; health insurance status was the primary predictor with adjustment for other significant factors in univariate chi‐square or Kaplan–Meier survival log‐rank tests. Two diagnosis periods by health insurance status were compared using Kaplan–Meier survival log‐rank tests. For breast, colorectal, lung, non‐Hodgkin lymphoma (NHL), and prostate cancer, uninsured and Medicaid insured patients had significantly higher risks of death than privately insured patients. For bladder cancer, uninsured patients had a significantly higher risk of death than privately insured patients. Survival improved between the two diagnosis periods for privately insured patients with breast, colorectal, or lung cancer and NHL, for Medicaid insured patients with NHL, and not at all for uninsured patients. Survival from cancer appears to be related to a complex set of demographic and clinical factors of which insurance status is a part. While ensuring that everyone has adequate health insurance is an important step, additional measures must be taken to address cancer survival disparities.