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  • Polymer and Materials Science  (174)
  • Wiley-Blackwell  (174)
  • American Chemical Society
  • EDP Sciences
  • National Academy of Sciences
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 31 (1996), S. 409-419 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The plastic flow behavior of wrought Co-27Cr-5Mo-0.05C alloy was investigated at 298 K as a function of grain size using uniaxial tension testing. The microstructures produced by deformation were characterized using X-ray diffraction, reflected light, and scanning electron microscopy. This study revealed that material with initially coarse face-centered cubic (fcc) grains exhibits larger uniform ductility than material with fine grain size. Typically, increasing the grain size from 7 to 70 μm reduces the yield strength by about 50% and increases the elongation to fracture from 12 to 30% with a small effect on the tensile strength. The material is capable of deforming uniformly to large strains without developing plastic instabilities until the point of fracture. This effect was found to be associated with the occurrence of transformation-induced plasticity (TRIP) in the coarse-grained material. TRIP enhances the material's ability to deform uniformly by maintaining a high rate of strain hardening during deformation. Smaller fcc initial grain size inhibits the transformation kinetics of the fcc-hexagonal close-packed phase transition according to the Olson-Cohen model. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 29-39 
    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: In der vorliegenden Arbeit wird der Einfluß der Verformungsamplitude, der Temperatur und der Frequenz auf die dynamischen Eigenschaften von SBR-Faserverbundstoffen untersucht. Der Einbau von Kurzfasern erhöht den Speichermodul bei beliebiger Verformungsamplitude. Je nach Fasertyp verringert sich die lineare Reaktionszone des Moduls auf die Verformung oder verschwindet vollkommen. Der Verlustfaktor tan δ ist größer bei Faserverbundstoffen, obwol die Signale größenmäßig sich nicht verändern, lediglich die entsprechende Verformung.Bei Temperaturanstieg verringert sich der Modulwert, jedoch ist dieser Abfall weniger stark ausgeprägt im Faser-SBR-Verbund. Die Relaxationsspektren zeigen eine maximale Dämpfung, die der Hauptrelaxation in der Elastomermatrix entspricht. Die Temperatur,bei der dieses Maximum auftritt, verlagert sich zu höheren Werten mitsteigender Anregungsfrequenz. Dadurch wird die Ermittlung der scheinbaren Relaxationsaktivierungsenergie möglich, die im Verbund Faser-Haftmittel-SBR höher ist (225-275 kJ/mol) als in dem faserfreien Stoff (194.6 kJ/mol) als Folge einer stärkeren Faser-Matrix-Wechselwirkung.
    Notes: This paper examines the effects of deformation amplitude, temperature and frequency on the dynamic properties of SBR-short fiber composites. The presence of the fiber increases the storage modulus at any deformation amplitude. Depending on the nature of the fiber, the linear response zone of the modulus versus deformation either diminishes or disappears. The loss factor tan δ is higher in fiber composites. Although the peaks do not vary in magnitude, they occur at different deformation amplitudes.Temperature increase causes the moduli to decrease, the gradient, however, being less pronounced for fiber composites. The relaxation spectra show a damping peak which correlates to the principal relaxation process in the elastomeric matrix. The temperature at which this peak appears is displaced towards higher values with increasing excitation frequency. This allows the determination of the apparent relaxation activation energy, which is higher in fiber plus adhesive composites (225 - 275 kJ/mol), as compared to the fiber-free composite (194 kJ/mol), as a consequence of stronger fiber-matrix interaction.
    Additional Material: 7 Ill.
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  • 3
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the cationic polymerization of trioxane initiated by perchloric acid is analyzed as a simultaneous polymerization and crystallization process. The details of the crystal growth such as nucleation, distribution of crystal sizes, development of growth spirals etc. have been investigated by electron and light microscopic techniques. The mechanism of polymerization can be understood as a catalyzed crystal growth. A well defined population of crystals is formed during a nucleation event at the start of the polymerization. An adsorption equilibrium with regard to the catalyst is then established in the presence of the rather large surface area of the growing polymer crystals. Assuming a Langmuir-type adsorption behaviour, the observed growth features (growth spirals) can be quantitatively interpreted on the basis of the BCF-theory of crystal growth. The current concepts on the molecular mechanism of cationic polymerization of cyclic formals have been modified such as to take into account that each chemical step of the polymerization is a building step of the crystal too.
    Additional Material: 24 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 2935-2940 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Linear poly(iminoethylene) was synthetised by cationic polymerization of 2-methyl-2-oxazoline using BF3—O(C2H5)2, SnCl4, and CH3COBF4 as initiators and in the presence or absence of CH3CN. The resulting product, poly(N-acetyliminoethylene), was then hydrolysed in basic medium. The resulting poly(iminoethylene) was identified and characterized by 1H NMR, 13C NMR, X-ray diffraction, and differential scanning calorimetry (DSC). The synthetised polymer will be used as a polymeric support in ionic-exchange resins as well as in macromolecular pesticides.
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  • 5
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis and thermal properties of a new type of side-chain liquid-crystalline polymers, incorporating ionic groups, are described. The polymers are obtained upon spontaneous polymerization (simultaneous quaternization and polymerization) of 4-vinylpyridine in the presence of ω-(4′-methoxy-4-biphenylyloxy)alkyl or 2-{2-[2-(4′-methoxy-4-biphenylyloxy)ethoxy]ethoxy}-ethyl bromide. Fully quaternized polymers of high molecular weight are obtained. As the analogous low-molecular-weight molecules previously studied these polymers form smectic mesophases, although the mesogenic groups, which include the pyridinium rings, are directly connected to the polyvinylic backbone.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 2793-2796 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 7
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependence of the viscosity of dilute solutions of poly(N-vinylcarbazole) in 1,4-dioxane on the temperature is studied by Moore's treatment. The numerical values of the constants from this treatment Ke, Kβ, and β indicate that this polymer in 1,4-dioxane assumes the characteristic behaviour of flexible polymers. The numerical values of the parameters KΘ and B from the Stockmayer-Fixman plot and the Mark-Houwink constants K and a are determined and the temperature coefficient of the unperturbed dimensions is evaluated for this system.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1,3,5-Trioxane (1) and 1,3-dioxep-5-ene (2) were copolymerized with BF3OEt2 at 65°C. The products, after base hydrolysis, were characterized by 13C and 1H NMR and were found to assume the chemical structure 4 of a copolymer containing oxymethylene and oxy-2-butenylene units with 4-hydroxy-2-butenyl and methoxy end groups, with the ratio of hydroxy-2-butenylene to methoxy end groups varying with experimental conditions. The copolymer demonstrates crystallinity and thermal stability comparable to poly(trioxane-co-ethylene oxide)s. Copolymer melting point was observed to decrease with increasing comonomer incorporation. The upper limit for incorporation of the comonomer 2 was found to be ca. 4 mol per cent. Viscosity and end group analysis (by 1H NMR) indicate molecular weights in the range of 104 to 105. The comonomeric unit demonstrates the ability to act as both a stopper against unzipping and as a trap for certain degrading agents.
    Additional Material: 3 Ill.
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  • 9
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A trisubstituted ethylene, 1-propene-1-ylidene dicyanate has been prepared via Knoevenagel reaction of acetaldehyde and malonitrile with β-alanine as a catalyst. This product has been copolymerized in bulk  -  with 2,2′-azoisobutyronitrile as an initiator  -  with styrene and 1-vinyl-2-pyrrolidone. Preliminary 1H and 13C NMR studies of the copolymers are in good agreement with an alternating structure besides minor proportions of homopolymers of styrene or 1-vinyl-2-pyrrolidone. The propagation mechanism has also been studied with 1H-1H correlation spectroscopy.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 1353-1359 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The apparent Young's modulus shows a linear relationship with junction density of chitosan films. The linear relationship of apparent Young's modulus with chitosan concentration is also observed. The linear relationship depends of the acid used in the casting solution. Relaxation times were of the order of 104 seconds, indicating a slow physical process. Stress-relaxation behavior of swollen chitosan films, prepared by solvent casting from dilute acetic or propionic acid solutions, can be represented by a one-component Maxwell model.
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