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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 2455-2465 
    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 this article we present overall crystallization characteristics of five polycaprolactone samples with mean molecular weights ranging from 50,000 to 400,000. The crystallization temperatures and heats of crystallization are determined as a function of mean molecular weight as well as for cooling rates in the range 0.31 to 40 K/min. Our results show a decrease in crystallization temperature from 320 to 300 K at increasing molecular weight and cooling rate. The heat of crystallization shows a slight decrease within the cooling rate interval and a decrease from about 68 to 48 J/g with increasing molecular weight. We analyze the continuous cooling data according to the Ozawa model for nonisothermal crystallization and compare them with our isothermal data analyzed with the Avrami model. Both the Ozawa and Avrami models give exponent parameters in the range 2.9 to 3.6. In the investigated temperature range and for all samples, we find a nucleation controlled crystallization. At the lowest temperatures, the Ozawa analysis indicates an increasing dependency on limitations in chain mobility. The higher molecular species have in general a slower crystallization rate, with half crystallization times increasing with a factor of about five within the molecular weight range at 320 K. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 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 32 (1994), S. 1999-2003 
    ISSN: 0887-6266
    Keywords: polytridecanolactone ; specific heat capacity ; melting ; crystallization ; transition enthalpy ; differential scanning calorimetry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An investigation of the thermodynamical properties of polytridecanolactone (PTDL) was made with the aid of a differential scanning calorimeter (DSC). PTDL is a linear polyester and belongs to the polylactones, which have been poorly investigated. In this paper we contribute with specific heat capacity in the range 180-400 K, and melting and glass transition characteristics. Further, we present unique results corresponding to the effect of different cooling rates on crystallization temperatures and crystallization energies. PTDL has a melting temperature of 350 K, and a glass transition at about 237 K. The crystallization results show that PTDL crystallizes easily, with a crystallization degree of about 80%. In addition, the crystallization energy decreases with increasing cooling rate, and levels out at a constant value at higher cooling rates. The crystallization temperature, on the other hand, shows an increasing sensitivity of cooling rate, where the supercooling is increasing more rapidly at higher cooling rates. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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