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Elongational Flow and Crystallization Behavior in Supercooled Melt Polymer
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Ito, Hiroshi / Kawamura, Takashi / Takimoto, Jun-ichi / Koyama, Kiyohito
Transient elongational viscosity ƒÉ of supercooled isotactic polypropylene (iso-PP) was measured under constant strain rate ƒÁ. In addition to the rapid increase due to entanglement which is commonly observed in polymer melts, ƒÉ in the supercooled state showed another (much more rapid) increase due to crystallization. In the case of low strain rate, the time ƒÑ at which this increase of ƒÉ started was independent of ƒÁ. Under high strain rate, on the other hand, ƒÑ was inversely proportional to ƒÁ. This means that there is a critical strain (crystallization strain) ƒÁc at which crystallization starts. ƒÁc was about 3.7 in this study.
Key words: Elongational flow / Crystallization / Supercooled state / Molecular orientation / Crystallization-inducing strain