Regensburg 2002 – wissenschaftliches Programm
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SYPF: Struktur und Dynamik in dünnen Polymerfilmen
SYPF 1: Structure and Dynamics in Thin Polymer Films
SYPF 1.8: Vortrag
Donnerstag, 14. März 2002, 12:00–12:20, H37
Morphology and crystallization behavior of elastic polypropylene — •Sabine Hild1, Andreas Boger1, Bernd Heise1, Carsten Troll2, and Bernhard Rieger2 — 1Experimental Physics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm — 2Inorganic Chemistry II, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm
The physical properties of polypropylene are determined by their chain microstructure. The application of new metallocene catalysts enables to synthesize homogeneous polypropylenes (PP) with variable amount of single stereo-errors and short syndiotactic sequences. When the amount of isotactic pentads is below 40% such PP exhibit intrinsic elastic behavior. The origin of the elasticity is still not definitely enlightened. A two-phase morphology is proposed where the non-crystallizable amorphous part of the chain forms the matrix and the regular mainly isotactic part the cross-links.
Scanning Force Microscopy (SFM) investigations of an elastic PP with 36% isotactic pentads confirm this model: Needle-like aggregates in a soft matrix have been visualized. To learn more about the composition and formation of these aggregates time-depended X-ray spectroscopy and DSC measurements have been performed. These experiments indicate that the formation of ordered regions takes places in a two-step process. SFM experiments approve the proposed two-step mechanism: In the first step lamellar crystals are formed which act as nucleus for further crystallization of string-like aggregates.