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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3479-3491 
    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: Preoriented isotactic polypropylene was uniaxially drawn at various testing directions and testing temperatures. Change of the molecular aggregation state in amorphous region with extension was elucidated by measurements of melting temperature, enthalpy of fusion, and birefringence at each stage of extension. Melting temperature depends on both crystallite thickness and orientation function of amorphous chains. It is assumed that the enthalpy change of amorphous region takes place when oriented amorphous chains are transformed into random state by heating. The ratio of the enthalpy change of amorphous region in the sample after extension to that in the sample before extension monotonously increased with increasing orientation function of amorphous chains, fa, independent of testing direction and testing temperature. Increase of true stress with drawing led to increase of fa. Increase of fa with extension depended on the testing angle θ between the testing direction and the direction of the crystal c-axis of the preoriented sample, and fa most remarkably increased in extension at θ = 45°.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 2091-2103 
    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: Preoriented isotactic polypropylene was used to clarify the molecular process in zone-drawing with which the necking part is confined in a thin heating zone during uniaxial drawing. The process was analyzed on the basis of rate process, the mechanical properties of zone-drawn samples, and the superstructural change during zone-drawing. The values of activation energy for deformation, ΔH*, and the activation volume, ΔV*, were affected by the deformation mechanisms preferentially taking place during the zone-drawing. The attainable maximum modulus of zone-drawn sample at θ = 45° was larger than those at θ = 0° and 90°. The highest strength was also obtained at θ = 45°. The values of modulus and strength strongly depended on both the orientation function of the crystal c-axis and the orientation function of amorphous chains. In the region of a very high zone-drawing rate, in which microcracks are preferentially formed, both modulus and strength decreased, whereas they increased with increasing the zone-drawing rate below this region, giving the optimum condition for achieving the maxima in the modulus and strength.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 1063-1077 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The oriented superstructure of poly(vinylidene fluoride) is controlled by using a forced-quenching type of zone drawing apparatus. Systematic variation of the weight fraction χ(I) of form-I crystals and the orientation function fa of amorphous chains shows that the piezoelectricity increases with increasing χ(I) and fa. A change in the state of molecular aggregation during poling is also effective in increasing the piezoelectricity and the orientation of the crystal b axis along the poling direction. Equations relating piezoelectricity to the form-I crystallinity, the orientation of amorphous chains, and the orientation of the crystal b axis along the poling direction are derived. These are based on a mechanical model having regions of taut tie molecules in parallel with composite regions consisting of crystalline and amorphous blocks in series.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 22 (1984), S. 245-254 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of poling temperature on piezoelectricity and its thermal stability were investigated on the basis of the thermal molecular motion associated with the crystalline region. This was done by using a film of highly oriented poly(vinylidene fluoride) containing form-I crystals. The film was prepared by a zone-drawing apparatus of the forced-quenching type. The piezoelectric stress constant e31 is a monotonically increasing function of the poling temperature which becomes steeper above ca. 320 K and again at ca. 400 K. The degree of orientation of the crystal b axis generated by poling also increases more steeply with poling temperature above ca. 320 K and again at 400 K. These temperatures correspond, respectively, to the crystalline dispersion temperature at 11 Hz, designated as αc, and the initiation temperature Tpm of large-scale molecular motion corresponding to premelting of form-I crystals. Thus the effect of poling temperature on piezoelectricity closely reflects the moleculer motion in form-I crystals. The annealing temperature T'a at which e31 decreases to 70% of that of unannealed sample by annealing a poled sample increases with the poling temperature and again this increase is steeper above poling temperatures of ca. 320 K and ca. 400 K. Thus the decay of piezoelectricity depends on both the αc temperature and Tpm.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 12 (1974), S. 623-628 
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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