Classifying the combined influence of shear rate, temperature, and pressure on crystalline morphology and specific volume of isotactic (Poly)Propylene

M.H.E. van der Beek, G.W.M. Peters, H.E.H. Meijer

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Abstract

The use of the Deborah number in classifying the effect of shear flow on the evolution of the specific volumeand resulting crystalline morphology is investigated. We distinguish between flows applied at large undercoolings and flows applied at low undercoolings. In the first case, the Deborah number provides a good classification tool to determine the influence of flow on the evolution of orientation and structural properties of the crystalline morphology and specific volume. Both the Deborah number related to the process of chain retraction (De_s) or the Deborah number related to reptation of chains (De_rep) can equally well be used to classify the influence of flow on the evolution of specific volume, as characterized by the dimensionless transition temperature and dimensionless rate of transition. If, however, flow is applied at relatively low undercoolings, remelting of flow-induced crystalline structures and relaxation of molecular orientation play a significant role after cessation of flow. Therefore, in these cases the use of Deborah (or alternatively Weissenberg) numbers is found to be of little use in this classification. Note that the Deborah numbers are used as a classification parameter to distinguish between different crystallization regimes and not as the driving force for flow induced crystallization.
Original languageEnglish
Pages (from-to)9278-9284
JournalMacromolecules
Volume39
Issue number26
DOIs
Publication statusPublished - 2006

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