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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 1161-1167 
    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: In the biphenol-type epoxy resin cured with catechol novolac (CN), a very weak glass transition and, thus, a very high rubbery modulus were observed. On the other hand, the glass transition was clearly observed in the system cured with phenol novolac (PN). This means that the micro-Brownian motion of network chains is highly suppressed in the system cured with CN. The reason for this suppression of the chain motion in the CN-cured system has been pursued from the viewpoint of the conformation of network chains. The disappearance of the glass transition in the biphenol-type resin depends on the formation of the active hydrogens in the curing agents. Thus, it was suggested that the suppression of the micro-Brownian motion is due to the orientation of the biphenyl groups in the network. Moreover, it has been shown that the mechanical and bonding strength at high temperature is considerably improved by the suppression of the network chain motion in the CN-cured biphenol resin system. © 1995 John wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 397-405 
    ISSN: 0887-6266
    Keywords: mesogenic epoxy resin ; liquid crystalline thermosets ; anisotropy ; network chain orientation ; heat resistance ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The epoxy resin containing a typical mesogenic group such as biphenol was cured with catechol novolak and aromatic diamines which have neighboring active hydrogens. In the biphenol-type epoxy resin cured with catechol novolak, 4,4′ diaminodiphenylmethane, and p-phenylenediamine (PPD), the glass-rubber transition almost disappeared, and thus a very high elastic modulus was obtained in the high temperature region. It is clear that the thermal motion of the network chains is significantly suppressed in these cured systems. In addition, in the PPD-cured system, a characteristic pattern like a schlieren texture was clearly observed under the crossed polarized optical microscope. Thus we conclude that the mesogenic group contained in the epoxy molecule is oriented in the networks when the mesogenic epoxy resin is cured with phenols and diamines which have neighboring active hydrogens. On the other hand, the biphenol-type resin cured with 3,3′,5,5′-tetraethyl-4,4′-diamino diphenylmethane (TEDDM) showed a well-defined glass-rubber transition and, thus, a low rubbery modulus. In this cured system, no characteristic pattern was observed under the crossed polarized light. These results show that the large branches, such as ethyl groups on the network chains, prevent the orientation of network chains which contain the mesogenic group. © 1997 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 2217-2222 
    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: Composite films composed of poly(diisopropyl fumarate-co-styrene) (PFS) and nematictype liquid crystal (E8) (40/60 by weight) were prepared by solvent casting in chloroform at room temperature. Scanning electron microscopy measurement showed that a liquid crystal phase is continuously embedded in a spongy-like PFS martrix. Optical responses of the composite films under the conditions of an externally imposed ac electric field (60-240 Vp-p, 10-1000 Hz), temperature (290-355 K), and a film thickness (8-16 μm), were determined using an He-Ne laser (wavelength 632.8 nm). The results obtained indicated that, under the conditions imposed, the output can be continuously controlled, and the response time is only of several milliseconds or less. In addition, the response to temperature sweep, heating and cooling, was reversible with only a delay, and it was interpreted in terms of the rigidity and thermal stability of the matrix polymer. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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