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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 3625-3638 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The supermolecular structure of melt-crystallized segmented copoly(ether ester)s based on poly(tetramethylene terephthalate) and poly(tetramethylene oxide) is investigated by polarizing microscopy and electron microscopic techniques. Spherulites are formed on isothermal crystallization at supercoolings ΔTu 〈 30°C. The spherulites recrystallize to form dendritic structures on further annealing at higher temperatures. The spherulites and dendrites are builtup from lamellae which exhibit little variation concerning the thickness of their crystalline core. The internal phase boundaries in these systems are made visible with a newly developed staining method. A network of interlocked individual lamellae is formed on rapid quenching of the melt films. Row crystallization (shish-kebabs) is observed, if the melt is sheared during the crystallization. It is concluded from these observations that the chemical structure of the segmented copolymers bears little relevance for the supermolecular structure of these materials except for the thickness of the crystalline core of the lamellae which seems to be related to the molecular length of the hard segment sequences occurring with the highest concentration in the sample.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 231-235 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 3639-3651 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The isothermal melt crystallization of three segmented copoly(ether ester)s based on PBT as the hard and PTMO as the soft segments differing in their hard segment content was investigated. The kinetics of crystallization was studied using polarizing microscopy and DSC. Two regimes of crystallization were observed. Spherulitic structures of low crystallinity are formed via predominantly athermal nucleation in regime I at supercoolings ΔTu 〈 30°C. Ill-defined aggregations of lamellae grow at ΔTu 〉 30°C. The crystallization follows an apparent Avrami-equation; the Avrami-constants cannot be explained in terms of a simple model. The structure of the samples was investigated by SAXS and compared to the structure of samples crystallized by rapid quenching and subsequent annealing. Much higher long spacings are obtained on isothermal crystallization. The long spacing increases with decreasing ΔTu. It increases at constant ΔTu with decreasing average hard segment length contrary to the samples crystallized by subsequent annealing of the quenched melt. In this case polymers differing in composition do not differ with regard to the long spacing obtained at constant ΔTu. The modulus in the Hookean-range as derived from stress-strain curves at T 〉 Tg does not reflect the details of the morphology or chain architecture but it is found to depend logarithmically on the volume fraction of crystallinity in the sample. Data of pure PBT are described by the same relationship.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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