Physical and mechanical properties of polyethylene for pipes in relation to molecular architecture. 1. Microstructure and crystallisation kinetics

Ethylene/alpha-olefin copolymers having bimodal molar weight distribution are investigated in comparison with unimodal copolymers in order to understand the incidence of the molecular architecture on the stress cracking resistance. The preferred introduction of the co-units in the longest chains of...

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Bibliographic Details
Published in:Polymer (Guilford) 2001-09, Vol.42 (20), p.8425-8434
Main Authors: Hubert, L, Seguela |h D. R., Vigier |h G., Degoulet |h C., Germain |h Y.
Format: Article
Language:English
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Summary:Ethylene/alpha-olefin copolymers having bimodal molar weight distribution are investigated in comparison with unimodal copolymers in order to understand the incidence of the molecular architecture on the stress cracking resistance. The preferred introduction of the co-units in the longest chains of bimodal copolymers is suggested to favour the occurrence of intercrystalline tie molecules during crystallization. The more complex is the molecular architecture, the greater is the difficulty for crystallization by regular chain folding. Correlations between kinetics, molecular architecture and molecular topology of unimodal copolymers no longer hold when considering bimodal copolymers. In contrast, the crystal surface free energy proved to be sensitive to topological changes resulting from molecular architecture modifications. (Original abstract - amended)
ISSN:0032-3861