Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 15: POSTER: Polymers and Biomaterials

CPP 15.20: Poster

Tuesday, March 9, 2004, 17:00–19:00, B

Rigid amorphous fraction and reversing melting of semicrystalline polypropylene — •Heiko Huth, Dmitry Mordvintsev, and Christoph Schick — Universität Rostock, Fachbereich Physik, Universitätsplatz 3, 18051 Rostock

For semicrystalline polymers the observed relaxation strength at glass transition is often significantly smaller than expected assuming a two phase model with crystalline and non-crystalline fraction. This observation leads to the three phase model introducing the rigid amorphous fraction (RAF) as a third fraction beside crystalline and non-crystalline fraction. This RAF is non-crystalline and in a glassy state at temperatures above the common glass transition. The RAF does not contribute to the heat of fusion or X-ray crystallinity nor to the relaxation strength at glass transition. Determination of the three fractions using calorimetric measurements is possible, knowing crystallinity and baseline heat capacity. Unfortunately, often an excess heat capacity due to reversing melting is observed. It is frequency dependent and disappears at higher frequencies. Using different methods for measuring frequency dependent heat capacity it is possible to determine baseline heat capacity in the high frequency limit. This approach was applied to polypropylene.