Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 23: Poster: Semicrystalline Polymers, Polymer Crystallization and Self-Assembly

CPP 23.2: Poster

Dienstag, 15. März 2011, 18:00–20:00, P2

Interplay between semicrystalline microstructure and viscoelastic properties of elastomeric polypropylenes — •Martin Neumann and Robert Magerle — Chemische Physik, TU Chemnitz, D-09107 Chemnitz

We aim at understanding how mechanical stress relaxation is affected by the heterogeneous microstructure of semicrystalline polymers. As a model system we study elastomeric polypropylenes (ePP) with different degrees of crystallinity and different molecular weights. Further control about the microstructure and the entanglement density is provided by the annealing temperature and time. With a microtensile testing setup integrated in a scanning force microscope (SFM) we study the nanoscale deformation processes within the microstructure of ∼1 µm thin films of ePP. Series of SFM images taken during straining and relaxation show a large variety of deformation processes: elongation, bending, kink formation, and fragmentation of individual crystalline lamellae into 10 nm large blocks (M. Franke, R. Magerle, to be published). The setup allows for different mechanical testing schemes, such as step-wise straining with simultaneous measurement of the temporal evolution of stress overshoot and relaxation. The stress relaxation process ranges over several hundreds of seconds and it resembles the stress relaxation behavior observed in polymer melts. Other experiments are straining with a constant straining rate, creep experiments at constant stress, and shearing. From this data viscoelastic material parameters, such as the elastic modulus and the elongational viscosity can be determined.