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  • 1
    Electronic Resource
    Electronic Resource
    Structural Development During Thermal Fractionation of Polyethylenes (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 245-255 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; metallocene ; polyethylenes ; SAXS ; synchrotron radiation ; thermal fractionation ; WAXD ; Ziegler-Natta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study, the stepwise isothermal crystallization or thermal fractionation of Ziegler—Natta and metallocene based polyethylenes (ZN-PE and m-PE) with two kinds of branch lengths (ethyl and hexyl) and branch compositions were studied using simultaneous synchrotron small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The crystal long period and the invariant were determined by SAXS, and the variations of crystal unit cell parameters and the degree of crystallinity were determined by WAXD. The arithmetic mean length (Ln), the weightedmean length (Lw) and the broadness index (Lw/Ln) of the studied polyethylenes were previously determined by DSC. Results from these studies were interpreted using the model of branch exclusion, which affects the ability of the chain-reentry into the crystal phase. Multiple SAXS peaks and step-change in crystallinity change (WAXD) were seen during heating, which corresponded well with the crystal thickness distribution induced by stepwise crystallization. The effects of the heterogeneity of the 1-olefin branch length and the distribution on the crystal long period and the invariant as well as the degree of crystallinity were discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010100432613
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal Properties of the Polyamide from 2-Methylpentamethylenediamine and Dodecanedioic Acid (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 519-530 
    Details
    ISSN: 1572-8943
    Keywords: branched diamine ; crystal structures ; dielectric properties ; dodecanedioic acid ; mechanic properties ; 2-methylpentamethylenediamine ; modulated DSC ; polyamides ; polymorphism ; SAXS ; Synchrotron X-ray ; WAXD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The polyamide from 2-methylpentamethylenediamine and dodecanedioic acid (MPMD-12) has been studied by differential scanning calorimetry, dynamic mechanical analysis, dielectric analysis, X-ray crystallography, and simultaneous small and wide-angle X-ray scattering using synchrotron radiation. The polymer exhibits polymorphism which is shown to be associated with the incorporation of the branched diamine. At relatively low temperatures, the crystal structure is similar to the gamma form which has been found in many other polyamides. At higher temperatures, a new delta form appears in which the diamine moiety adopts a bent conformation. In this form, the chains follow a zig-zag pattern with two chemical repeats units per crystallographic repeat with a shortening of about 10% along the c-axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010101927587
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