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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 42 (1991), S. 319-322 
    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: In Poly(vinylidenfluorid) (PVDF) kann die Dipoldrehung im elektrischen Feld anhand der Absorptionsänderung der Infrarotbanden bei 445 cm-1 und 510 cm-1 verfolgt werden. Anknüpfend an vorhergehende Untersuchungen wurde an PVDF-Folien mit aufgedampften infrarotdurchlässigen Elektroden ein stufenweise erhöhtes Feld angelegt und das Infrarotspektrum aufgenommen. In Anlehnung an das früher entwickelte Modell wurden die normierten Absorptionen der beiden Banden gegeneinander aufgetragen, wobei sich eine Abweichung vom erwarteten linearen Zusammenhang in der Feldabhängigkeit der Absorption beider Banden zeigte. Interpretiert wird diese Abweichung mit der feldinduzierten Zunahme des Anteils langer Trans-Sequenzen.
    Notes: In poly(vinylidene fluoride) (PVDF) the rotation of the dipoles in an electric field can be followed by the change of the infrared absorption bands at 445 cm-1 and 510 cm-1. Referring to preceding measurements on PVDF foils with evaporated infrared transparent electrodes a stepwise increased field was applied. Following the formerly developed model, the normalized absorptions of both bands were plotted one against the other. A deviation from the expected linear relation in the field dependence of both absorption bands was found. This behaviour is interpreted by an increase of the amount of long trans sequences.
    Additional Material: 4 Ill.
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  • 12
    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 aromatic heterocyclic polymer polyoxadiazole is of interest for special applications because of its high thermal stability. Using a laboratory equipment the spinning parameters jet draw rate and plastic drawing have been varied. The effect of spinning conditions on the material parameters elongation at break, tenacity and modulus was investigated. To achieve higher values of tenacity and modulus, a jet draw rate of 2 and plastic drawing ratio of 1.5 to 2.0 were found to be optimal. Also the increase of fibre length at stress-free heating has been studied. With varying jet draw rate and plastic drawing ratio both positive and negative changes of fibre length have been observed. The results are explained by superposition of spontaneous extension and shrinkage.
    Notes: Polyoxadiazol, ein aromatisches heterocyclisches Polymer, ist aufgrund seiner hohen thermischen Stabilität für eine Reihe von Einsatzzwecken interessant. Mit einer Laborspinnanlage wurden die Spinnbedingungen Düsenverzug und Grad der plastischen Reckung variiert und deren Einfluß auf die Materialparameter wie Bruchdehnung, Festigkeit und Modul untersucht. Zur Erreichung höherer Festigkeiten und Moduli erwiesen sich ein mittlerer Düsenverzug von 2 und ein eher niedriger plastischer Reckgrad von 1,5 bis 2 als günstig. Ebenfalls untersucht wurde die Längenzunahme der Fäden bei lastfreier Temperung. Je nach Düsenverzug und plastischem Reckgrad wurden sowohl positive als auch negative Längenänderungen gefunden, die mit der überlagerung von spontaner Dehnung und Schrumpf erklärt werden.
    Additional Material: 7 Ill.
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  • 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 current understanding of the electrical properties of polyethylene and poly(viny1idenc fluoride) scrviug as model substances or nonpolar and polar polymers is rcviewed. Experimental results on the chargc transport process in PE and field induced structure transitions as well as pyroclectric and piezoelectric properties of poly(viny1idenc fluoride) are presented.
    Notes: Nach einem Überblick über das gegenwärtige Verständnis elektrischer Eigenschaften zweier als Modell substanzen für nichtpolare bzw. polare Strukturen dienender Polymere werden experimentelle Resultate zum Ladungstransportprozeß in Polyethylen und zu feldinduzierten Strukturübergängen in Poly(vinylidenfluorid) sowie dessen pyro- und piezoelektrischen Eigenschaften vorgestellt.
    Additional Material: 5 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 46 (1995), S. 64-67 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Permittivity ∊′ and dielectric loss ∊″ of novolac have been determined in the temperature interval from  - 150 to 150°C and in the frequency interval from 102.5 to 106 Hz. Novolac exhibits a main and a secondary relaxation process. For the main relaxation a master curve of ∊″ was calculated, the shape of which was described by the Havriliak - Negami function (HN). The parameters of the HN fit were interpreted by a model that relates the values to the polymer structure. Furthermore, the temperature dependence of the dielectric relaxation times was analyzed by a WLF approach for the main relaxation and an Arrhenius approach for the secondary relaxation. The dielectric relaxation times of the main relaxation were correlated with the electrical conductivity and the melt viscosity.
    Additional Material: 4 Ill.
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  • 15
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 16
    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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  • 17
    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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  • 18
    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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  • 19
    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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  • 20
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The modification of epoxy resins by reactions involving their hydroxyl groups is described. For example, reactions with enol ethers, acrylonitrile, ethyl acetoacetate and certain other carboxylic esters, or triethyl orthoformate, gave products which had reduced reactivities towards various hardeners, and which therefore gave lower peak temperatures on cure and/or longer usable lives. Suitable modification of epoxy resins with various other reagents(certain acid anhydrides, epichlorohydrin, or N-hydroxymethylacrylamide) introduces additional useful functional groups. The uses of a diisocyanate and of α-naphthyl isocyanate to modify epoxy resins or their mixtures prior to GPC analysis are also mentioned.
    Additional Material: 5 Ill.
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