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CPP: Chemische Physik und Polymerphysik
CPP 4: Poster: Dynamik in polymeren Systemen
CPP 4.10: Poster
Monday, March 11, 2002, 13:30–15:00, B
APPLICATION OF AN EXTENDED TOOL-NARAYANASWAMY-MOYNIHAN MODEL TO DESCRIBE VITRIFICATION AND COMPLEX HEAT CAPACITY MEASURED BY TEMPERATURE-MODULATED DSC — •Stefan Weyer1, Mikhail Merzlyakov2, and Christoph Schick1 — 1Universität Rostock, Fachbereich Physik, Universitätsplatz 3, 18051 Rostock — 2Texas Tech University, Lubbock, TX 79409, U.S.A.
Complex heat capacity in equilibrium can be considered as a compliance in the scheme of linear response. Nevertheless, often the Tool-Narayanaswamy-Moynihan (TNM) model is used to describe complex as well as total heat capacity in the glass transition region. A TNM-model extended by a non-Arrhenius temperature dependence of the relaxation time is applied to describe results from temperature modulated DSC (TMDSC) measurements. The temperature dependence of the relaxation time is independently determined by a VFTH-fit to heat capacity data. Only the stretched exponential factor and the non-linearity parameter of the TNM-model must be adjusted to describe the measured curves.
The model is capable to describe all features of the heat capacities measured in TMDSC scan experiments in the glass transition region of polystyrene and polycarbonate. This includes the curve shape, the frequency dependence, the cooling rate dependence and possible interference between vitrification and dynamic glass transition.