Dresden 2014 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 23: Glasses and Glass Transition I (Joint Session with CPP and DY)
DF 23.2: Vortrag
Donnerstag, 3. April 2014, 12:15–12:30, ZEU 114
Excess heat capacity and fictive temperature of polystyrene in a wide range of cooling and heating rates — •Gunnar Schulz1, Timur Vasilievich Tropin2, Yeong Zen Chua1, Jürn W. P. Schmelzer1, and Christoph Schick1 — 1Institut für Physik , AG Polymerphysik, Universität Rostock, Rostock, Germany — 2Frank Laboratory of Neutron Physics, Joint Institut for Nuclear Research, Dubna, Moscow region, Russia
The physical characteristics of polystyrene allow straightforward and reproducible measurements of heat capacity, Cp, glass transition temperature, Tg, and other properties. The possibility to reuse one sample for numerous cooling and heating cycles permits the investigation of the influence of the cooling and heating rates on Cp and Tg.
In our research, we conduct the cooling phases with various (constant) cooling rates, but the respectively following heating phases with only one heating rate. The comparison of the heat capacities observed after different cooling rates results in an excess Cp, which we also calculate by means of a model.
Our measurements furthermore yield the fictive temperature in the cooling rate range from 10−4 K s−1 to 104 K s−1. We compare these results with the dynamic Tg observed by means of temperature-modulated differential scanning calorimetry (TMDSC). The dependence of the fictive Tg on the cooling rate and the dependence of Tg on the modulation frequency turn out to be closely related.