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  • Polymer and Materials Science  (34)
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  • 1
    ISSN: 1057-9257
    Keywords: gallium nitride ; nanocrystallites ; detonation ; gallium azide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: High quality nanoscale, phase-pure hexagonal gallium nitride (GaN) crystallites have been synthesized by the thermal induced detonation of molecular precursors of the type (R3N)Ga(N3)3 (R=CH3, C2H5, etc.). The method allows the control of the particle size regime from 2 to about 1000 nm. X-ray diffraction and Rietveld simulations revealed an anisotropic platelet-like shape of the particles. The obtained GaN material was as well characterized by transmission electron microscopy and electron diffraction, photoluminescence spectroscopy, SEM, IR, RAMAN, thermal gas effusion/mass spectrometry, thermal analysis, elemental analysis. Gas absorption measurements (BET method) showed a specific surface area of about 90 m2 · g-1. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 10 Ill.
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  • 2
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurden die Verschiebungen untersucht, die durch Tris-(dipivaloylmethano)-europium und Tris-(dipivaloylmethano)-praseodym im NMR- Spektrum versehiedener Derivate substituierter Phenole hervorgerufen werden. Der Zweck dieser Arbeiten war, die Möglichkeiten zu erfassen, die diese Verschiebereagenzien als Hilfsmittel in der NMR-Analyse von Phenolharzen bieten, und Information über Verschiebungen bei Molekülen zu gewinnen, die mehr als eine Koordinationsposition besitzen.
    Notes: An investigation into the shifts induced in the NMR spectra of some derivatives of substituted phenols by tris(dipivalomethanato)europium and tris(dipivalomethanato)praseodymium is reported. The phenol derivatives were studied to ascertain the possible utility of the shift reagents as an aid in the analysis of phenolformaldehyde resins by NMR spectroscopy, and to gain information on induced shifts with molecules having more than one possible co-ordination site.
    Additional Material: 1 Tab.
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  • 3
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde eine Voruntersuchung des Einflusses unternommen, den die Verschiebereagenzien Tris-(dipivaloylmethano)-europium uncl Tris-(dipivaloylmethano)-pra-seodym auf das NMR-Spektrum des Diglyzidyläthers des Bisphenol A ausüben. Es ergab sich, daß die Signale der am Epoxidring anliegenden Protonen durch den Zusatz dieser Chelate weit mehr als die Signale der exozyklischen -OCH2-Gruppen verschoben werden. Die Verschiebung kann man durch den Zusatz eines Alkohols rückgängig machen, der vorzugsweise mit dem Verschiebemittel reagiert.
    Notes: A preliminary study has been made of the effects of the shift reagents Eu (DPM)3 and Pr(DPM)3 on the NMR spectrum of Bisphenol A diglycidyl ether (I). Protons attached to the epoxy ring were observed to shift appreciably more than protons of the exocyclic —OCH2— group, on addition of these chelates. The shifts could be reversed by addition of an alcohol, which interacted preferentially with the shift reagent.
    Additional Material: 4 Ill.
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  • 4
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: 13C-und 1H-NMR-Untersuchungen haben überzeugend gezeigt, daß die Hauptkomponente des Epoxidharzes aus Phenolphthalein und Epichlorhydrin ein aromatischer Diglycidyläther mit einem Lactonring ist und nicht eine chinoide Verbindung mit Glycidylätherund Glycidylesterstruktur.
    Notes: 13C- and 1H-NMR studies have shown conclusively that the main component of the epoxy resin derived from phenolphthalein and epichlorohydrin is an aromatic diglycidyl ether containing a lactone ring, rather than a glycidyl ether-glycidyl ester compound containing a quinoid ring.
    Additional Material: 1 Tab.
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  • 5
    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: A method for assessing extent of swelling of the gel fraction of formaldehyde-modified cottons, employing cupriethylenediamine hydroxide as the swelling agent, is described. Substantial differences in apparent specific volumes of swollen gel fractions are observed for cottons crosslinked by different processes to the same level of agent. The apparent crosslink density measured by the swelling of gel fraction increases with formaldehyde content of the cotton; at 0.20% formaldehyde the order of increasing crosslink density in the various processes of reaction is as follows: nonaqueous system (forms D and D′) 〈 aqueous system (forms W and W′) 〈swelling system (form F) 〈 vapor system (form V) 〈 bake-cure system (form C).
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 1717-1731 
    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: The effects of absorbed moisture on the cure reactions and subsequent solid-state properties of a high-performance epoxy system were investigated in this study. The resin systems investigated were a model system, TGDDM-Novalac-DDS-BF3:MEA (TNDB), and its commercial analog, Hercules 3501-6. The samples were exposed to three environments: a liquid water environment at 50°C; an 85% relative humidity vapor environment at 50°C; and an evacuated, desiccated atmosphere at 22°C. Differential scanning calorimetry (DSC) thermograms were obtained for the Hercules 3501-6 formulation as well as various compositions of the TNDB system for samples exposed to each of the three environments. Moisture was found to accelerate the cure especially for formulations exposed to the vapor environment. Dynamic mechanical experiments were also performed on cured, thin film samples. The “wet” samples were produced by adding water to the resin mixture prior to B-staging. The moisture was shown to increase the extent of reaction, but produce a slightly lower degree of crosslinking as related to the sample's glass transition. This has been attributed to chain-extension reactions, such as the hydroxyl-epoxide etherification reaction, which are favored in the presence of hydroxyl groups from water.
    Additional Material: 12 Ill.
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  • 7
    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: A series of segmented ionene polymers based on the reaction of α,ω-bis(dimethyl amino)polytetramethylene oxide with various dihalide compounds were investigated with respect to their structure-property behavior. The placement of quaternary ammonium ions and halide counterions along the polymer chains was varied by changing the molecular weight of the PTMO soft segment and the structure of the dihalide linking agent. The techniques of dynamic mechanical spectroscopy, thermal analysis, small angle X-ray scattering, and stress-strain behavior analysis were applied. For the case when the PTMO soft segment was amorphous, the ambient temperature properties of these materials displayed low modulus, high strength, and high elongation elastomeric behavior with tensile strength enhanced by the strain-induced crystallization of the PTMO. A high level of phase separation existed between the dihalide component relative to the PTMO soft segment. Due to the Coulombic association of the ionene species, these materials displayed many similarities to the segmented urethane ionomers. In particular, distinct domain structure was noted by SAXS, whose dimensional scale was similar to the segmented urethanes. It was also shown, however, that the driving forces for the microphase separation was caused by favorable electrostatic or Coulombic interactions in contrast to segment-segment incompatibility features as in the segmented urethanes.
    Additional Material: 9 Ill.
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  • 8
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Verbindungen der Strukturformeln [π-C5H5M(CO)nX] (M = Fe, n = 2; M = Mo, n = 3; X = CH3, CH2C6H5, CH2Si(CH3)3, CH2OCH3, Sn(C6H5)3, SnCl3, HgCl, I), [Mn(CO)5CH3], und [(π-CH3C5H4)Mn(CO)3] wurden als Katalysatoren für die Härtung von Epoxidharzen unter verschiedenen Bedingungen geprüft. Es wurde gefunden, daß die Verbindungen [π-C5H5Fe(CO)2R] (R = CH3, CH2C6H5) und [π-C5H5Mo(CO)3CH3] wirksame lichtempfindliche Beschleuniger für die Anhydridhärtung von Expoxidharzen sind. Der Aktivierungsmechanismus wird diskutiert.
    Notes: Compounds of the types [π-C5H5M(CO)nX] (M = Fe, n = 2; M = Mo, n = 3; X = CH3, CH2C6H5, CH2Si(CH3)3, CH2OCH3, Sn(C6H5)3, SnCl3, HgCl, I), [Mn(CO)5CH3], and [(π-CH3C5H4)Mn(CO)3] have been examined as catalysts for the cure of epoxy resins under various conditions. It was found that the compounds [π-C5H5Fe(CO)2R] (R = CH3, CH2C6H5) and [π-C5H5Mo(CO)3CH3] are active photosensitizing agents for the anhydride cure of certain epoxy resins. The mechanism of the process is discussed.
    Additional Material: 1 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 33 (1982), S. 9-13 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The influence of surface contaminations on isothermal charge decay of electrets of (tetrafluoroethylene-hexafluoropropylene) copolymer was investigated. Carefully rinsed samples showed increased charge stability in comparison with not treated or open stored samples. The results are explained by the partial destruction of the isolating properties of FEP by dust particles.
    Notes: Der Einfluß von Oberflächenverunreinigungen auf den isothermen Ladungsabbau bei Elektreten aus Tetrafluorethylen-Hexafluorpropylen-Copolymer (FEP) wird untersucht. An sorgfältig gespülten Proben ist eine deutliche Erhöhung der Ladungsstabilität im Vergleich zu unbehandelten bzw. offen gelagerten Proben zu beobachten. Die Ergebnisse werden mit der teilweisen Zerstörung der Isolationseigenschaften des FEP durch eindringende Staubpartikel in Verbindung gebracht.
    Additional Material: 7 Ill.
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  • 10
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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