Regensburg 2002 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

CPP: Chemische Physik und Polymerphysik

CPP 4: Poster: Dynamik in polymeren Systemen

CPP 4.10: Poster

Montag, 11. März 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.