New aspects of yielding in semicrystalline polymers related to microstructure: Branched polyethylene |
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Authors: | F J Baltá-Calleja H G Kilian |
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Institution: | (1) Institute for Structure of Matter, CSIC, Madrid, Spain;(2) Present address: Abteilung Experimentelle Physik der Universität Ulm, Germany |
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Abstract: | The application of thermodynamics of eutectoid copolymers and a generalized Tabor-relation to relationships between mechanical properties (microhardness, yield stress) and microstructure in semicrystalline polymers is considered. The approach is illustrated by results on melt-crystallized low density polyethylene, investigated near the yield point at different temperatures. The success of the approach emphasizes that semicrystalline polymers, despite being viscoelastic hetereogeneous systems, give rise to a yielding process entailing the irreversible deformation of a larger number of crystals within cooperative super-structure units. Microhardness provides, within this context, a unique measure of the crystal size average. Comparison of calculated and experimental data favors the view of deformed crystals containing basal defective surface boundaries ( meso-crystals ) which yield cooperatively.Dedicated to Professor Dr. Dr. h. c. Armin Weiss on the occasion of his 60th birthday. |
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Keywords: | Semicrystalline polymers hardness yielding micro-structure crystal size |
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