Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 14: Poster: Glasses I (jointly with DY)
CPP 14.9: Poster
Dienstag, 27. März 2012, 18:15–20:15, Poster A
Excess heat capacity and fictive temperature of polystyrene in a wide range of cooling and heating rates — •Gunnar Schulz1, Timur V. Tropin2, Jürn W. Schmelzer1, and Christoph Schick1 — 1University of Rostock, Institut of Physics, 18055 Rostock, Germany — 2Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
The physical characteristics of polystyrene allow us 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 an appropriate model.
Our measurements furthermore yield the fictive temperature in the cooling rate range from 10−4 Ks−1 to 104 Ks−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.