Berlin 2005 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 9: SYMPOSIUM: Polymer networks and beyond: From molecular structure to materials and biological functions POSTER

CPP 9.20: Poster

Samstag, 5. März 2005, 16:45–18:45, Poster TU D

Model treatment of tensile deformation of semi-crystalline polymers: Evaluation of temperature and crystallinity effects for low crystallinity polyethylenes — •Ke Hong and Gert Strobl — Physikalisches Institut, Albert-Ludwigs-Universität, Hermann-Herder-Str.3, 79104 Freiburg, Germany

A model constructed to treat tensile deformation of semi-crystalline polymers introduced in previous work is again applied to measurements on low crystallinity polyethylenes and is now used for an evaluation of temperature and crystallinity effects. We measured true stress-true strain relationships at constant strain rates, determined the elastic and plastic part of imposed strain in cyclic unload-relaxation experiments, and followed the stress-relaxation at fixed strains. The model treats the stress as arising from three contributions, quasi-static stresses originating from the stretched network of entangled chains in the fluid regions and from the force-transmitting skeleton of crystallites, plus the viscous forces described by Eyring’s equation. Adjustment of the measured data to the model provides a decomposition of the stress in the three parts. The results show that a rising temperature or a lowering of the crystallinity leads the shear modulus of amorphous network essentially unchanged, whereas crystalline stress and the viscous stress decrease.