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Journal of thermal analysis

, Volume 49, Issue 1, pp 57–70 | Cite as

Modulated differential scanning calorimetry in the glass transition region

VI. Model calculations based on poly(ethylene terephthalate)
  • B. Wunderlich
  • I. Okazaki
Polymers

Abstract

Temperature-modulated calorimetry (TMC) allows the experimental evaluation of the kinetic parameters of the glass transition from quasi-isothermal experiments. In this paper, model calculations based on experimental data are presented for the total and reversing apparent heat capacities on heating and cooling through the glass transition region as a function of heating rate and modulation frequency for the modulated differential scanning calorimeter (MDSC). Amorphous poly(ethylene terephthalate) (PET) is used as the example polymer and a simple first-order kinetics is fitted to the data. The total heat flow carries the hysteresis information (enthalpy relaxation, thermal history) and indications of changes in modulation frequency due to the glass transition. The reversing heat flow permits the assessment of the first and higher harmonics of the apparent heat capacities. The computations are carried out by numerical integrations with up to 5000 steps. Comparisons of the calculations with experiments are possible. As one moves further from equilibrium, i.e. the liquid state, cooperative kinetics must be used to match model and experiment.

Keywords

enthalpy relaxation glass transition heat capacity heat flow calorimeter hysteresis poly(ethylene terephthalate) temperature-modulated calorimetry TMC 

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Copyright information

© Akadémiai Kiadó 1997

Authors and Affiliations

  • B. Wunderlich
    • 1
    • 2
  • I. Okazaki
    • 1
    • 2
  1. 1.Department of ChemistryThe University of TennesseeKnoxvilleUSA
  2. 2.Chemical and Analytical Sciences DivisionOak Ridge National LaboratoryOak RidgeUSA

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