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  • 1995-1999  (2)
  • 1980-1984  (7)
  • Polymer and Materials Science  (5)
  • Inorganic Chemistry  (3)
  • Life and Medical Sciences
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Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2141-2149 
    ISSN: 0887-624X
    Keywords: polyimides ; 4-phenylethynylphthalic anhydride ; thermooxidative stability ; high-temprature MAS NMR ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of high glass transition temperature (Tg 〉 300°C), amorphous, soluble, poly-imide oligomers of controlled molecular weight endcapped with 4-phenylethynylphthalic anhydride endcapping agent is described. The 4-phenylethynylphthalic anhydride was employed to afford a higher curing temperature (380-420°C) which widens the processing window compared to unsubstituted acetylene-endcapped polyimides. The polyimides were synthesized via solution imidization techniques, using the ester-acid of various dianhydrides and aromatic diamines. A “ one-pot” procedure utilizing NMP as the solvent and o-dichlo-robenzene as the azeotroping agent reproducibly produced fully imidized, but yet soluble wholly aromatic polyimides. Thermally cured samples were prepared with gel contents of up to 98% that displayed good solvent resistance. Glass transition temperatures comparable to high molecular weight linear analogs were produced. These polyimides also show excellent thermal stability as judged by thermogravimetric analysis (TGA). Model phenylethynyl imide compounds were synthesized and used to follow and elucidate the nature of the products formed from the phenylethynyl curing by using high temperature magic-angle 13C nuclear magnetic resonance (MAS NMR). Preliminary results indicate that the cure reaction can be followed by MAS NMR. However, the nature of the products being formed during the curing process is difficult to determine by the solid-state MAS NMR alone. Differential scanning calorimetry (DSC) data clearly show that the model system does indeed melt and displays a wide window before the strong cure exotherm is observed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 1429-1437 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: ABA poly(styrene-b-isoprene) block copolymers with various molecular weights and composition were used as heat activated films in simple overlap glass joints. The influence of bonding temperature on their shear strength at break was investigated. On increase of temperature, the joint resistance for most of the copolymers passed through a maximum, which temperature was dependent on the molecular characteristics of the copolymers. The decrease in melt viscosity or chemical degradation could not explain the data. A morphological interpretation which fits well the present and previous observations is proposed and verified for one copolymer used in this work.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The volumes of the major tissue compartments, vascular space, interstitial space, and luteal cells, in the corpus luteum (CL) of 16-day pregnant rats were determined morphometrically after different fixation procedures. Ovaries were fixed by perfusion at physiologic pressures (PF), by immersion directly in fixative (IF), by immersion after clamping blood vessels to prevent escape of blood (IFC), or by immersion after administration of heparin to prevent blood clotting (IFH). Three CL in each of eight ovaries were examined for each fixation method. Total volumes were significantly larger in CL fixed by PF and IFC, and approximated physiologic volumes as assessed from frozen ovaries. Perfusion-fixed CL had significantly larger vascular and interstitial spaces and smaller cell volumes than immersion-fixed CL. Capillary surface area varied significantly between the four groups in accordance with absolute volume of vascular space. Estimated numbers of endothelial cells and amounts of connective tissue differed significantly, presumably due to difficulties in identifying these components in immersion-fixed CL with collapsed vessels. The fixation methods used caused substantial fluid shifts between the three major compartments. A theoretical approach for considering these shifts and the likely physiologic situation was developed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0044-2313
    Keywords: Ammonium yttrium bromide ; thermal decomposition ; thermochemical data ; phase transition ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigation on the Thermal Decomposition of Ammonium Yttrium Halides. III. Ammonium Yttrium Bromide, (NH4)3YBr6The decomposition equilibria of NH4Br and (NH4)3YBr6 were determined by total pressure measurements. It was shown by high temperature X-ray patterns and DTA that (NH4)3YBr6 and YBr3 show phase transitions in the measured temperature region. An endothermic transition of YBr3 starts near 300°C and is very slow. By interpretation of the thermal decomposition of (NH4)3YBr6, the enthalpy of formation, and the standard entropy was derived. In the system NH4Br/YBr3 only the described phase (NH4)3YBr6 exists.
    Notes: Durch Gesamtdruckmessungen wurden die Zersetzungsgleichgewichte von NH4Br und (NH4)3YBr6 ermittelt. Hochtemperatur-Röntgenaufnahmen und DTA zeigten, daß bei (NH4)3YBr6 und YBr3 im untersuchten Temperaturbereich Phasenumwandlungen erfolgen. Eine endotherme Umwandlung von YBr3 erfolgt oberhalb von 300°C und verläuft sehr langsam. Die Auswertung der thermischen Zersetzung von (NH4)3YBr6 liefert die Bildungsenthalpie ΔHBo((NH4)3YBr6,f,298) = -402 ± 7 kcal/mol und die Standardentropie So((NH4)3YBr6,f,298) = 134 ± 9 cal/Kmol. Eine weitere komplexe Phase existiert im System NH4Br/YBr3 nicht.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2217-2225 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structural evolution with temperature of an anionically synthesized ABA poly(styrene-b-isoprene) (SIS) lamellar block copolymer (total molecular weight 45,000; isoprene content 38% by weight) was studied by melt-rheological measurements, electron microscopy, and x-ray and light diffraction. Above 225°C, the dynamic viscosity was found to be independent of frequency up to a critical frequency. The variation of the elastic modulus confirmed the occurence of a transition between 215 and 225°C. For the temperature range considered, all results superimposed well on a two-branch master curve. It was concluded that above 225°C, our SIS behaves like a Newtonian material, whereas for lower temperatures and/or higher frequencies classical non-Newtonian behavior is found. The melt-rheological properties were explained by microscopy and diffraction investigations, which allowed us to follow morphological changes as the temperature was raised. It was found that the two-phase lamellar structure is progressively destroyed, and the transition temperature of 225°C corresponds to the temperature above which complete mixing occurs.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 389-398 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The glass transition behavior of two sets of ABA poly(styrene-b-isoprene) block copolymers was examined by differential scanning calorimetry. In one series, the triblock copolymers had different total molecular weights and the same (30 wt %) polyisoprene content, in the other, the molecular weight was constant (30,000 g/mol) and the elastomer content was the variable. For all triblock copolymers studied, the data show an inward shift for the glass transition temperatures Tg of the corresponding homopolymers. This shift increases for the rigid-phase Tg as the polystyrene block length decreases. Depending on their molecular characteristics, two, three, or only one Tg were found. The third Tg was interpreted in terms of the existence of an interphase. Some of these conclusions could be confirmed by transmission electron microscopy.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 497 (1983), S. 199-205 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 493 (1982), S. 65-76 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Hexachloroniobates(V), -tantalates(V), and -antimonates(V): AIMVCl6 (AI = Na, K, Tl, NH4, Rb, Cs; MV = Nb, Ta, Sb)Hexachlorometallates(V) AINbCl6, AITaCl6, and AISbCl6 (AI = Na, K, Tl, NH4, Rb, Cs) have been prepared by reaction of the binary components at 280°C (niobates), 300°C (tantalates), and in POCl3 solution (antimonates), respectively, and were investigated by Raman spectroscopy and X-rays with the Guinier-Simon technique. The low-temperature modifications of AIMCl6 (AI = K, Tl, NH4, Rb, Cs with the exception of KNbCl6) are isotypic to CsWCl6 with isolated octahedra ∞0[MCl6]. The high-temperature modifications crystallize cubic face-centered. Raman spectra of KNbCl6, NaNbCl6 and NaTaCl6 support a formulation like e. g. K2[Nb2Cl10]Cl2 with isolated edgesharing bioctahedra ∞0[(NbCl4/1tCl2/2e)2].
    Notes: Die Chloride AINbCl6, AITaCl6 und AISbCl6 (AI = Na, K, Tl, NH4, Rb, Cs) werden aus den binären Komponenten bei 280°C (Niobate), 300°C (Tantalate) bzw. aus POCl3-Lösung (Antimonate) dargestellt und ramanspektroskopisch bzw. röntgenographisch (Guinier-Simon-Technik)untersucht. Die Tieftemperaturformen von AIMCl6 (AI = K, Tl, NH4, Rb, Cs, außer KNbCl6) sind mit CsWCl6 isotyp (isolierte Oktaeder ∞0[MCl6]). Die Hochtemperaturformen kristallisieren kubisch-flächenzentriert. Ramanspektren von KNbCl6, NaNbCl6 und NaTaCl6 sprechen für eine Formulierung gemäß z. B. K2[Nb2Cl10]Cl2 mit „isolierten“, kantenverknüpften Doppeloktaedern ∞0[(NbCl4/1tCl2/2k)2].
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 19 (1981), S. 463-467 
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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