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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 25: Poster: Stress Relaxation in Polymers - From single molecules to biological cells (joint focus with BP)

CPP 25.1: Poster

Mittwoch, 28. März 2012, 11:00–13:00, Poster A

Influence of the microstructure on the viscoelastic behavior of thin films of polypropylenes — •Martin Neumann, Toni Hille, and Robert Magerle — Chemische Physik, TU Chemnitz, D-09107 Chemnitz

With a microtensile testing setup that allows for simultaneous imaging with atomic force microscopy (AFM) we correlate the changes of the microstructure occurring during aging and deformation processes with the viscoelastic behavior of thin films of semicrystalline polymers. We study elastomeric polypropylenes (ePP) with different degrees of crystallinity (12% to 40%) and different molecular weights polymerized with metallocene catalysis. The films were annealed for several hours at different temperatures, which results in different microstructures and in turn different types of stress strain behavior and stress relaxation phenomena. For ePP films the elastic moduli are in the range between 0.2 and 10 MPa and the relaxation times between 2 s and 100 s. Cyclic loading experiments show changes of viscoelastic properties that are attributed to aging and crystallization processes. Series of AFM images measured at increasing strain show the deformation of individual lamella in spherulites in thin films of polypropylene with ultra-high molecular weight and 99% tacticity. At large deformations fractures and crazing between spherulites are observed.