Toughness Enhancement of Nanostructured Amorphous and Semicrystalline Polymers |
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Authors: | Goerg H Michler Rameshwar Adhikari Sven Henning |
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Institution: | Institute of Materials Science, Martin Luther University Halle-Wittenberg, D-06099 Halle/Saale, Germany |
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Abstract: | An overview is given of different micromechanical deformation processes leading to an enhancement of toughness in heterophase polymers. The well-known mechanism of rubber or particle toughening of semicrystalline polymers was studied in HDPE and PP blends. In particular, the micromechanical processes in the semicrystalline polymer strands between modifier particles were investigated in detail, revealing processes of separation, yielding, breaking and twisting of lamellae. These processes are compared with lamellae forming amorphous SBS block copolymers with alternating soft (polybutadiene) and hard (polystyrene) layers. Depending on the deformation direction, the mechanism of thin layer yielding or chevron formation appears. In both polymeric systems, the initial stage of deformation is characterized by a plastic yielding of the soft phase with a reorganization of the hard (glassy or crystalline) lamellae. The second stage is determined by the alignment of the hard phase towards the deformation direction and the plastic yielding. Detailed comparison of these similar mechanisms in very different polymers with similar nanostructured morphology should help to improve toughening of amorphous as well as semicrystalline polymers. |
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Keywords: | electron microscopy micromechanical mechanisms morphology polyolefins SBS block copolymers: thermoplastic polymers toughness enhancement |
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