bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymorphism in a metallocenic isotactic polypropylene as revealed by means of FTIR spectroscopy: Influence of the processing conditions
Authors: Lorenzo V. , Polo‐Corpa M.J. , Pérez E. , Benavente R. , de la Orden M.U. , Martínez‐Urreaga J. 
Published: February 2011

AbstractThe polymorphic structure in specimens of a metallocenic isotactic polypropylene, processed under different conditions, has been studied by means of wide‐angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The proportions of the different polymorphs have been evaluated, and the influence of the processing parameters (nucleating agents, cooling rate, and nature of the surface of the molds) has been analyzed. The combination of WAXS, DSC, and FTIR results confirms the adequacy of this last technique to obtain quantitative information about the competition between the crystalline phases of polypropylene. It has also been proved that the nature of the mold can enhance considerably the activity of beta‐nucleating agents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Methyl silsesquioxane/cyanate ester resin organic–inorganic hybrids with low dielectric constant
Authors: Zhang Zengping , Pei Jianzhong , Liang Guozheng , Yuan Li 
Published: February 2011

AbstractA kind of nonfunctional oligomeric silsesquioxane (SSQ), methyl silsesquioxane (Me‐SSQ), was used to modify cyanate ester (CE) resin in this article. First, Me‐SSQ was synthesized by the hydrolysis and condensation of methyltriethoxysilane. Then, a series of Me‐SSQ/CE hybrids containing 0, 1, 5, 10, and 20 wt % of Me‐SSQ were prepared. The effect of Me‐SSQ content on the reactivity, mechanical, dielectric, thermal, and hot/wet properties of materials was investigated. Fourier transform infrared spectroscopy was used to study the reactivity of hybrid CE resin systems, indicating that the addition of Me‐SSQ does not show significant effect on the conversion of CE. Mechanical and dielectric properties of the Me‐SSQ/CE hybrid materials were also studied. Impact strength of the Me‐SSQ/CE hybrids reaches its maximum value when Me‐SSQ content is 5 wt %. However, the flexural strength reaches the maximum value when Me‐SSQ content is 1 wt %. The Me‐SSQ/CE hybrid containing 20 wt % of Me‐SSQ shows a dielectric constant of 2.78, that is, much lower than the pure CE resin. At the same time, the dielectric loss of the Me‐SSQ/CE hybrids was slightly increased (tan δ < 0.006). Therefore, Me‐SSQ/CE hybrid is a promising candidate for high‐performance printed circuit board matrix materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Comparison of rheological properties of carbon nanotube/polycarbonate and carbon black/polycarbonate composites
Authors: Via Michael D. , Morrison Faith A. , King Julia A. , Caspary Jeffrey A. , Mills Owen P. , Bogucki Gregg R. 
Published: February 2011

AbstractConductive fillers are often added to insulating polymers to increase the composite conductivity. Adding fillers often increases the viscosity, which can make the material more difficult to process. In this study, 2–8 wt % multiwalled carbon nanotubes or 2–8 wt % carbon black were added to polycarbonate. The effects on composites' viscosities were studied with small‐amplitude oscillatory shear and capillary rheometer testing. The addition of carbon nanotubes and carbon black created yield‐stress materials with the yield‐stresses increasing with increased filler loadings. The addition of carbon black increased the steady‐shear viscosity of the composite at all shear rates for all loadings. The addition of the carbon nanotubes reduced the steady‐shear viscosity of the composite at high shear rates for all loadings. This is thought to be due to an internal lubrication of the flow (enhanced disentanglement) due to the presence of the carbon nanotubes. The lubrication effect saturates once 3 wt % carbon nanotubes has been reached. The observed rheological behavior of the carbon nanotube composites is markedly different than usually seen in filled systems. A yield‐stress‐modified Carreau‐Yasuda model was used to interpret the effects of carbon nanotube and carbon black fillers on carbon nanotube/polycarbonate and carbon black/polycarbonate composite viscosity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Dimedone and phenylazo dimedone chelates of europium as emitters in polymers
Authors: Seth Susannah , Aravindakshan K. K. 
Published: February 2011

AbstractTransparent polymers when incorporated with strongly fluorescent europium chelates were found to be responding to excitation with UV radiation. In this work, two novel europium chelates have been synthesized using the β‐diketones dimedone and phenylazo dimedone along with 1,10‐phenanthroline. These chelates were characterized by elemental analyses, magnetic susceptibility measurements, UV, IR, and ESI mass spectral techniques. The chelates synthesized with metal : β‐diketone : 1,10‐phenanthroline ratio 1 : 3 : 1 were incorporated into polymer matrices. Four polymers, polyethylene vinyl acetate or acetate (EVA), polystyrene (PS), poly methyl methacryalate (PMMA), and polyethylene glycol (PEG) were used for the studies. All these, except the liquid oligomer PEG were cast into thin films. PEG was used as such for the studies. The photoluminescence spectra of the plain polymers were found to be having peaks very close to the absorption peaks of the polymers doped with europium chelate. This observation can be used in optical devices. Thermal analyses like TG/DTG/DTA of the polymer films were conducted to ascertain the thermal stability of the material. The SEM analyses of the films indicated a smooth surface with uniform distribution of the doped chelate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Mesua ferrea L. seed oil based highly branched polyester/epoxy blends and their nanocomposites
Authors: Konwar Uday , Das Gautam , Karak Niranjan 
Published: February 2011

AbstractMesua ferrea L. seed oil based highly branched polyester and epoxy resins blends were prepared by mechanical mixing at different weight ratios. The best performing blend was used as the matrix for the preparation of nanocomposites with different dose levels of organophilic montmorillonite (OMMT) nanoclay. The prepared nanocomposites were characterized by X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Data resulting from the mechanical and thermal studies of the blends and nanocomposites indicated improvements in the tensile strength and thermal stability to appreciable extents for the nanocomposites with OMMT loading. The nanocomposites were characterized as well‐dispersed, partially exfoliated structures with good interfacial interactions. From the X‐ray diffraction analysis, the absence of d001 reflections of the OMMT clay in the cured nanocomposites indicated the development of an exfoliated clay structure, which was confirmed by transmission electron microscopy. The homogeneous morphologies of the pure polyester/epoxy blend and clay hybrid systems were ascertained with scanning electron microscopy. The tensile strength of the 5 wt % clay‐filled blend nanocomposite system was increased by 2.4 times compared to that of the pure blend resin system. The results suggest that the prepared nanocomposites have the potential to be used as active thin films for different applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Influence of chain microstructure on ethylene–norbornene copolymer film properties
Authors: Liu Shaojie , Yao Zhen , Chen Lin , Dai Bin‐Bin , Cao Kun , Li Bo‐Geng , Zhu Shiping 
Published: February 2011

AbstractThe effects of copolymer composition, copolymer composition distribution, and polar α‐olefin incorporation on transparency, refractive index, and hydrophilicity of resultant ethylene–norbornene copolymer films were investigated. It has been found that the transparency is mainly determined by the copolymer composition distribution. The samples having uniform compositions gave better transparency. However, the copolymer composition distribution had little effect on refractive index. The refractive index increased linearly with increasing norbornene content. Furthermore, the incorporation of polar α‐olefin with long carbon chain improved refractive index and hydrophilicity of the films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Effect of high temperature and the role of sulfate on adsorption behavior and effectiveness of AMPS®‐based cement fluid loss polymers
Authors: Lummer Nils Recalde , Dugonjić‐Bilić Fatima , Plank Johann 
Published: February 2011

AbstractThe fluid loss control performance of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS®)‐based copolymers added to cement slurries was studied at 27 and 100°C, respectively. It was found that effectiveness of these fluid loss additives solely relies on achievement of a high adsorbed amount on the surface of cement. At elevated temperature (100°C), CaAMPS®‐N,N‐dimethyl acrylamide copolymer (CaAMPS®‐co‐NNDMA) exhibits reduced adsorption and hence decreased fluid loss control of the cement slurry. The reason behind this behavior is poor calcium binding capability of the sulfonate anchor groups, which coordinate with calcium atoms present on the mineral surface. Whereas, an increase in the sulfate concentration present in cement pore solution instigates partial coiling of CaAMPS®‐co‐NNDMA and causes only a slight influence on the performance of this copolymer. The elevated sulfate content results from thermal degradation of ettringite, a cement hydrate mineral produced during the early stages of cement hydration. Incorporation of minor amounts (∼ 1.3 mol %) of maleic anhydride into this copolymer produces a terpolymer, which exhibits higher and more stable adsorption, even at high temperature. This effect is owed to the presence of homopolymer blocks of polycarboxylates distributed along the polymer trunk. On mineral surfaces, they present much stronger anchor groups than sulfonate functionalities, as evidenced by their higher calcium binding capability. Consequently, fluid loss performance of CaAMPS®‐co‐NNDMA‐co‐MA is little affected by temperature. Understanding the influence of temperature on the physicochemical interactions occurring between additives and the mineral surface can help to design more effective admixtures suitable for high temperature applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Pervaporation separation of isopropanol–water mixtures using mixed matrix blend membranes of poly(vinyl alcohol)/poly(vinyl pyrrolidone) loaded with phosphomolybdic acid
Authors: Mali Mukund G. , Magalad Veeresh T. , Gokavi Gavisiddappa S. , Aminabhavi Tejraj M. , Raju K. V. S. N. 
Published: February 2011

AbstractMixed matrix membranes of poly(vinyl alcohol) and poly(vinyl pyrrilidone) blends were prepared by loading with phosphomolybdic acid (PMA) and their pervaporation (PV) properties were investigated for the PV separation of isopropanol. Membrane performance shown a dependence on the extent of PMA loading. The 4 wt % PMA‐loaded blend membrane had the highest separation factor of 29991, which declined considerably at higher loading. The flux of 4 wt % PMA‐loaded membrane was lower than that of nascent blend membrane. Feed water composition and temperature influenced the PV performance. Solubility selectivity was higher than diffusion selectivity. Degree of swelling was smaller after PMA loading exhibiting better separation ability. The PV results were analyzed using the Flory‐Huggins theory and sorption was dominated by Langmuir's mode. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Isothermal crystallization kinetics of poly(butylene terephthalate‐co‐sebacate) copolymer
Authors: Zeng Zuoxiang , Zhang Hailing , Xue Weilan , Zhu Wanyu , Xiao Xiaoling , Sun Yu , Li Zhelong 
Published: February 2011

AbstractPoly(butylene terephalate) (PBT) and poly(butylene terephthalate‐co‐ sebacate) (PBTS) copolymers containing 5 mol % and 10 mol % sebacate components (Mn = 12,700–14,600) were synthesized by polycondensation. The isothermal crystallization kinetics and melting behaviors after isothermal crystallization of the polymers were investigated by differential scanning calorimetry (DSC). The equilibrium melting temperatures of the polymers were determined by Hoffman‐Weeks equation. Analysis of the crystallization kinetic data using the Avrami equation showed that the introduction of sebacate enhanced the crystallization of PBT in PBTS. And the Avrami exponent n varies in the range of 2.16–3.68, indicating that the isothermal crystallization follows two‐ and three‐dimensional growth mechanism. The isothermal crystallization activation energies of the polymers were also calculated by the Arrhenius equation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Polymorphism of Amino Acid‐Based Dendrons: From Organogels to Microcrystals
Authors: Kuang Gui‐Chao , Teng Ming‐Jun , Jia Xin‐Ru , Chen Er‐Qiang , Wei Yen 
Published: February 2011

AbstractThere is a delicate balance for a low‐weight molecule to behave as a gelator or crystal. The synthesis of two novel amino acid‐based naphthalene‐dendrons, Nap‐G1 and Nap‐G2 is described. Both dendrons display polymorphic properties in organic solvents. Nap‐G1 developed a fibrous network with β‐sheet architecture in cyclohexane but exhibited a spherulitic network in mixed solvents (chloroform/petroleum ether 1:5, v/v). On the other hand, Nap‐G2 acted as an efficient organogelator in chloroform but formed crystalline fibers in relatively high polarity solvents (such as acetone and methanol). Combinations of characterizations have been employed to study the polymorphism.
Stability analysis for a class of switched linear systems
Authors: Guo Rongwei , Wang Yuzhen 
Published: February 2011

AbstractThis paper investigates the stability of a class of switched linear systems, and proposes a number of new results on the stability analysis. A novel analysis method is developed by using the 2‐norm technique, and then several stability results are obtained based on the new analysis method. It is shown that the main results obtained in this paper not only guarantee the stability of the systems under arbitrary switching, but also provide an algorithm to find the minimum dwell time (MDT) with which switches make the switched systems stable. Finally, several illustrative examples with numerical simulations are studied by using the results obtained in this paper. The study of examples shows that our analysis method works very well in analyzing the stability of some classes of switched linear systems and, moreover, it has some advantages over the common quadratic Lyapunov function method in some cases.Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Progress in understanding of weather systems in West Africa
Authors: Lafore J.‐P. , Flamant C. , Guichard F. , Parker D. J. , Bouniol D. , Fink A. H. , Giraud V. , Gosset M. , Hall N. , Höller H. , Jones S. C. , Protat A. , Roca R. , Roux F. , Saïd F. , Thorncroft C. 
Published: February 2011

AbstractThe major advances achieved during African monsoon multidisciplinary analysis in our physical understanding of the West African monsoon (WAM) system are reviewed. Recent research provides an advanced understanding of key WAM features. The Saharan heat low, the interactions of the monsoon flow with the surface and the reversed flow on top of it, all play a more important role than previously assumed, and interact according to the phase of the diurnal cycle of convection. Recent studies also emphasise the significance of upstream conditions in Central and East Africa, as well as strong interactions between midlatitudes and the WAM. Copyright © 2011 Royal Meteorological Society
New perspectives on land–atmosphere feedbacks from the African Monsoon Multidisciplinary Analysis
Authors: Taylor Christopher M. , Parker Douglas J. , Kalthoff Norbert , Gaertner Miguel Angel , Philippon Nathalie , Bastin Sophie , Harris Phil P. , Boone Aaron , Guichard Françoise , Agusti‐Panareda Anna , Baldi Marina , Cerlini Paolina , Descroix Luc , Douville Hervé , Flamant Cyrille , Grandpeix Jean‐Yves , Polcher Jan 
Published: February 2011

AbstractResearch into land–atmosphere coupling within the African Monsoon Multidisciplinary Analysis has highlighted the atmospheric impact of soil moisture on space scales of 5 km upwards and time scales of several days. Observational and modelling studies have shown how antecedent rainfall patterns affect new storms in the Sahel. The land feedback operates through various mechanisms, including a direct link to afternoon storm initiation from surface‐induced mesoscale circulations, and indirectly via a large‐scale moisture transport in the nocturnal monsoon. The results suggest potential for significant improvements in weather forecasting through assimilation of satellite data. Intriguing questions remain about the importance of vegetation memory on seasonal–interannual scales. Copyright © 2011 Royal Meteorological Society
Zur Schadensverteilung des durch Spannungsriss korrosion geschädigten vergüteten Spannstahls bei Brückenbauwerken
Authors: Bauer Thomas , Müller Michael , Patz Rüdiger , Wilhelm Tobias , Schwarz Johannes , Tue Nguyen Viet 
Published: February 2011

AbstractDie Aussagekraft der rechnerischen Untersuchung zur Abschätzung des Gefährdungspotentials infolge Spannungsrisskorrosion hängt entscheidend von den Annahmen zu Schädigungsverlauf und —verteilung des Spannstahls ab. Mit systematischer Untersuchung des aus einem Bauwerk entnommenen Spannstahls konnte festgestellt werden, dass die bisher angenommene Schadenskonzentration an einer Stelle, welche zum Ausfall des gesamten Spannglieds führt, sehr wenig wahrscheinlich ist. Viel wahrscheinlicher ist die drahtweise Schädigung mit unbegrenzter Anzahl der Risse über die gesamte Drahtlänge. Weiterhin ist keine Korrelation zwischen chemischer Zusammensetzung des Spannstahls bzw. zwischen Zusammensetzung des Verpressmörtels und der Versprödung des Spannstahls feststellbar. Weitere Untersuchungen zur Bestätigung der gewonnenen Ergebnisse sind wünschenswert.Damage distribution of hardened and tempered prestressing steel dues to stress corrosion in prestressed concrete bridges. The accuracy of the analysis to estimate the hazard potential due to the stress corrosion depends strongly on the assumption of the damage distribution and the damage progress of the prestressing steel in the constructions. Through a systematic test of the prestressing steel, which is taken from an old bridge, it is shown that the traditional assumption of a damage concentration with the breakdown of the whole tendon is less probable. Instead, the damage of single wires over its total length with unlimited number of cracks is considerably more probable. Furthermore, no correlation between the chemical compositions or mixtures of the grout and the brittleness of the prestressing steel is found. More investigations to check these results obtained in this study are preferable.
Geklebte Verbundbauteile aus Holz und hoch‐ bzw. ultrahochfesten Betonen
Authors: Schäfers Martin , Seim Werner 
Published: February 2011

AbstractDas primäre Ziel der vorliegenden Untersuchungen besteht darin, wesentliche Grundlagen für die Bemessung biegebeanspruchter Verbundbauteile aus Holz und hochfesten bzw. ultrahochfesten Betonen (UHPC) mit geklebtem Verbund zu ermitteln. Weiterhin wird ein Testverfahren für die experimentelle Untersuchung der Verbundfestigkeit geklebter Holz‐Beton‐Verbunde vorgeschlagen. Es werden zwei mechanische Modelle zur Beschreibung des Verbundverhaltens vorgestellt. Neben der Theorie des Verschieblichen Verbunds, die bereits 1953 von Volkersen hergeleitet wurde, wird in diesem Zusammenhang die linear elastische Bruchmechanik (LEBM) herangezogen. Der Versuchsaufbau und die wesentlichen Ergebnisse der experimentellen Untersuchungen werden vorgestellt. Die Verbundversuche belegen, dass das Verbundversagen in den meisten Fällen im Holz, nahe der Klebfuge auftritt. Auf der Grundlage der Verbundversuche wird ein Vorschlag für die Bemessung biegebeanspruchter Bauteile angegeben. Dieser wird mit Hilfe zweier Vierpunkt‐Biegeversuche im Bauteilformat validiert.Bonded Timber‐Concrete‐Composite Structures with high‐ resp. ultrahigh performance Concretes. The main ambition of the present investigations is to develop the basic information for the design of adhesive bonded composite members from timber and UHPC. Furthermore, a standard test setup for the experimental determination of the bond strength of timber‐concrete composites will be derived. Two mechanical models for the description of the bond behaviour will be documented. The theory of the compliant bond, which was already introduced by Volkersen in 1953 and the linear elastic fracture mechanics (LEFM) are possible approaches for this purpose. The setup and the main results from experimental investigations on the bond behavior will be presented. It is found that the bonding failure occurs in timber close to the bond‐line in most cases. In general, the ultimate loads can be estimated by Volkersen’s theory. On the basis of the bond investigations, recommendations for the design of bending members are given. These recommendations are validated by two full‐scale bending tests. Additional strain‐ and deformation‐measurements proved, that the assumptions which were taken for the design of bending members are sound.
Untersuchungen zur Festigkeit und Tragfähigkeit von Holz unter dem Einfluss chemisch‐aggressiver Medien
Authors: Rug Wolfgang , Lißner Angelika 
Published: February 2011

AbstractHolz zeigt eine hohe Beständigkeit gegenüber den meisten Chemikalien in allen drei Aggregatzuständen. Aus diesem Grund wird es häufig für Baukonstruktionen von chemischen Fabriken oder Lagerhallen für chemische Stoffe eingesetzt. Der Beitrag befasst sich mit dem aktuellen Stand der Erfassung der Korrosion und ihres Einflusses auf die Festigkeit von Holz und Brettschichtholz. Es wird die Berücksichtigung derartiger Einflüsse durch einen Modifikationsbeiwert” “Aggressive Medien” bei der Bemessung von Holzbauteilen erläutert.Studies on the strength and ultimate limit design of timber under the influence of chemically aggressive media. Timber has a high resistivity to chemically aggressive agents. This is one of the reasons why timber structures are frequently being used in the construction of storage halls for chemical materials or of industrial buildings with aggressive environment. In this paper the state of the art of corrosion in timber and the consideration the chemical action by using a modification factor in the limit state design is presented.