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  • 1985-1989  (2)
  • 1989  (2)
Material
Years
  • 1985-1989  (2)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 153-162 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Thermotropic liquid crystal polymers have been modeled as an array of highly ordered polyhedric nematic domains immersed in a less-ordered, nearly isotropic matrix. A function has been defined that expresses the elastic moduli of drawn fibers as a function of orientation and geometry of the nematic domains. When such a material is hot drawn in extension, the domains orient and elongate to produce an orthotropic fibrous phase. Equations are proposed to relate the elastic moduli of the fibers to the draw ratio and the extrusion conditions. Upon annealing of the hot drawn fibers, shrinkage occurs. It is proposed that the shrinkage is the result of a physical transformation from the fibrous state back to the nematic domain structure present before extrusion and drawing. The Avrami equation is used to describe the nucleation and growth processes controlling the shrinkage at constant annealing temperature. The model is shown to correlate experimental data on the elastic properties and the shrinkage of hot drawn PET/PHB60 liquid crystal polymer with the processing conditions.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 244-257 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Blends of polycarbonate (PC) and poly(ethylene terephthalate-co-p-oxybenzoate) (PET/PHB60) were prepared by melt-blending. Physical and/or chemical interactions between the two phases of the system were studied by thermal analysis and infrared spectroscopy. Rheological measurements in shear flow were carried out both in the low and high shear rate regions in the temperature range of the existence of the mesophase. At low liquid crystalline polymer (LCP) content, the blends showed flow curves similar to those of the unfilled PC, while at higher LCP percentages the rheological behavior of the pure LCP was resembled. Moreover, in the whole shear range, the viscosity values of such blends were in between those of the pure polymers. The influence of the addition of 10% LCP on the mechanical properties of the PC was investigated. Fiber-spinning was performed under different experimental conditions, and it was found that opportune drawing conditions are necessary to improve the modulus of the matrix. Morphological analyses of the pure LCP and of the blends were related to the rheological and mechanical behavior of these systems. While the LCP exhibited an elevated dimensional stability, the inclusion of the LCP in PC matrix did not improve the dimensional stability of the blends.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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