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CPP: Chemische Physik und Polymerphysik

CPP 16: Poster: Dynamics of Molecular Systems, Polymer Dynamics, Glass Transition, Crystallization, Electronic Properties of Polymers

CPP 16.23: Poster

Montag, 2. April 2001, 12:30–15:00, AT1

DYNAMICS OF REVERSIBLE MELTING REVEALED FROM FREQUENCY DEPENDENT HEAT CAPACITY — •Alaa Mohammed, Andreas Wurm, and Christoph Schick — University of Rostock, Dept. of Physics, Universitaetsplatz 3, 18051 Rostock, Germany

Heat capacity of semicrystalline polymers shows frequency dependence not only in the glass transition range. Also above glass transition and below melting temperature a frequency dependent heat capacity can be observed. The asymptotic value of heat capacity at high frequencies equals base-line heat capacity while the asymptotic value at low frequencies yield information about reversing melting. For PC, PHB and sPP the asymptotic value at high frequencies can be measured by TMDSC. For PCL and sPP the frequency dependence of heat capacity can be studied in quasi-isothermal TMDSC experiments. Comparison of measured base-line heat capacity with expected values from mixing rules for semicrystalline polymers yield information about the formation (vitrification) and disappearance (devitrification) of the rigid amorphous fraction (RAF). For PC and PHB the RAF is established during isothermal crystallization while for sPP only a part of the RAF is vitrified during crystallization. Devitrification of the RAF seems to be related to the lowest endotherm.