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Crystallization behavior of poly(N-methyldodecano-12-lactam). III. Kinetics of isothermal crystallization

Authors

  • J. Kratochvíl,

    Corresponding author
    1. Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
    • Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
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  • A. Sikora

    1. Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
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Abstract

Differential scanning calorimetry, combined with Avrami theory, was used to investigate the kinetics of three steps of the complex crystallization process of poly(N-methyldodecano-12-lactam) (MPA): (1) primary melt crystallization at respective crystallization temperature (Tc), (2) additional crystallization at 30°C, and (3) recrystallization at 54°C. Kinetics of the three steps was discussed with respect to Tc. The Avrami exponent n of primary melt crystallization decreased between 2.5 and 1.9 in the range of Tc values of −10 to 20°C, which suggests heterogeneous nucleation, followed by two-dimensional growth, with a larger involvement of homogeneous thermal nucleation at greater supercoolings. The crystallization rate constant k decreased with increasing Tc. The value of n = 1.5 for additional crystallization implies a two-dimensional diffusion-controlled crystal growth with a suppressed nucleation phase. For Tc values ranging from −10 to 0°C and 0 to 20°C, k showed weak and quite strong decreasing dependencies on Tc, respectively. The recrystallization mechanism involved partial melting of primary crystallites and two-dimensional rearrangement of chains into a more perfect structure. The rate of this process was almost independent of Tc. The values of activation energies were derived for the three steps of MPA crystallization using the Arrhenius equation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 279–293, 2004

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