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

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. (C) 2003 Wiley Periodicals, Inc.

keywords

INSTANTANEOUS NUCLEATION; DENSITY

subject category

Polymer Science

authors

Martins, JA; Pinto, JJCC

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