True sample temperatures in isothermal differential scanning calorimetry scans and their effect on the overall polymer crystallization kinetics

Authors

  • J. A. Martins,

    Corresponding author
    1. Instituto de Polímeros e Compósitos (IPC)/Departamento de Engenharia de Polímeros, Universidade do Minho 4800-058 Guimarães, Portugal
    • Instituto de Polímeros e Compósitos (IPC)/Departamento de Engenharia de Polímeros, Universidade do Minho 4800-058 Guimarães, Portugal
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  • J. J. C. Cruz Pinto

    1. Centro de Investigação de Materiais Cerâmicos e Compósitos (CICECO)/Departamento de Química, Universidade de Aveiro, 3810-193, Aveiro, Portugal
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Abstract

The true temperature of a sample during isothermal crystallization is higher than the recorded differential scanning calorimetry program temperature because of two combined effects: the thermal resistance of the sample, which is mainly dependent on the thickness of the sample, and the release of the heat of crystallization. This is especially true for a low crystallization temperature, at which the heat of crystallization is released within a relatively short time. Isothermal crystallization is treated here as a nonisothermal process, and the values of the parameters obtained with single-mechanism equations (Avrami and Nakamura's) used in their description are compared. The validity of the procedure used for evaluating the temperature increase of a sample is analyzed and discussed (i.e., the evaluation of the thermal resistance of a sample as a function of its thickness). Some isothermal crystallization data obtained at relatively high supercoolings may be affected by errors if temperature corrections are not carried out. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 125–131, 2004

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