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  • Polymer and Materials Science  (34)
  • MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT  (24)
  • 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
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 1535-1547 
    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 reaction of α,ω-bis(dimethylamino) polytetramethylene oxide with various dihalides provided a series of elastomeric ionenes. The influence of dihalide structure on the reaction was studied and a number of substituents were found which dramatically increased the rate of polymerization and ultimate molecular weights achieved. These ionene elastomers were thermoplastic and it was shown that in some cases this result was due at least in part to a depolymerization reaction via a dequaternization of the ammonium links. Again, structural features in the dihalide were important not only for the reverse reaction, but for the repolymerization to high molecular weight elastomer as well. An uncharged “analogue” was also prepared to address the feature of microphase separation and compared with the above ionene materials.
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 1549-1565 
    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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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 10 (1966), S. 1777-1786 
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 119-140 
    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 standardization of notched Izod impact test data to normalized values of foot pounds per inch of notch is based on the assumption of a 1:1 increase in breaking strength with increasing notch width. This assumed relation is not supported by experimental tests on commercial thermoplastics. As notch width was increased from 1/8 to 1/4 to 3/8 to 1/2 in., nine of ten thermoplastics tested showed a decrease in normalized impact strength. Each material appears to show a characteristic loss in breaking strengths as the notch width increases. A technique developed for calibration of pendulum impact testers has been used to examine the variation of impact breaking strength in relation to the total kinetic energy of the hammer. Experimental tests show practically no change in impact strengths up to values that take 2/3 of the available hammer energy. Experimental work on the comparison of the impulse transferred by the hammer during breaking with impulse curves photographed by the Autographic Impact test show very good agreement for catastrophic breaks and fair agreement for plastic type breaks. The reduction in recorded impulse is attributed to the degrading of the sample during the plastic portion of the breaking cycle. The peak force of thermoplastics as measured by the Autographic Impact test increases as the temperature decreases from 100°C. or above to 0°C. Over the same temperature range flexural tests on small cantilever samples of these thermoplastics show the same thermal dependence for the flexural yield or permanent distortion stress. Plots of the impact peak forces and flexural yield stress at corresponding temperatures give a linear correlation. Each thermoplastic material exhibits a unique relation for this correlation between impact yielding and flexural yielding. This correlation between the impact and flexural tests over the range of temperatures is the first known experimental indication of a direct relation between impact properties and standard physical tests.
    Additional Material: 11 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 619-626 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The mechanisms of wear in ultra-high-molecular-weight polyethylene (UHMWPE) acetabular cups were investigated on both laboratory simulator-tested cups and a clinically retrieved component. Two different levels of wear process were identified: one characterized by the formation and detachment of platelet-like flakes from initial machining marks, and the other by the formation of fine ripples and fibrils by repeated passes of microscopic asperities on the femoral head. Both wear processes could be described by a criterion of critical plastic strain. A theoretical model was developed to account for the generation of the microscopic wear particles based on such a critical strain criterion. Its predictions of the dependence of the UHMWPE wear rate on surface roughness and applied load were in excellent agreement with previously published experimental correlations. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 13 (1979), S. 339-342 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 3 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 56 (1976), S. 157-162 
    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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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 27 (1972), S. 159-164 
    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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