Modeling flow-induced crystallization in isotactic polypropylene at high shear rates

Peter C. Roozemond, Martin van Drongelen, Zhe Ma, Martien A. Hulsen, Gerrit W.M. Peters

Research output: Contribution to journalArticleAcademicpeer-review

26 Citations (Scopus)

Abstract

A model is presented to describe flow-induced crystallization in isotactic polypropylene at high shear rates. This model incorporates nonlinear viscoelasticity, compressibility, and nonisothermal process conditions due to shear heating and heat release due to crystallization. Flow-induced nucleation occurs with a rate coupled to the chain backbone stretch associated with the longest mode relaxation time of the polymer melt, obtained from a viscoelastic constitutive model. Flow-induced nuclei propagate in flow direction with a speed related to shear rate, thus forming shish, which increase the viscosity of the material. The viscosity change with formation of oriented fibrillar crystals (known as “shish”) is implemented in a phenomenological manner; shish act as a suspension of fibers with radius equivalent to the radius of the shish plus the attached entangled molecules? The model is implemented in a 2D finite element code and validated with experimental data obtained in a channel flow geometry. Quantitative agreement is observed in terms of pressure drop, apparent crystallinity, parent/daughter ratio, Hermans' orientation, and shear layer thickness. Moreover, simulations for lower flow rates are performed and the results are compared, in a qualitative sense, to experiments from literature.
Original languageEnglish
Pages (from-to)613
JournalJournal of rheology
Volume59
Issue number3
DOIs
Publication statusPublished - 2015
Externally publishedYes

Keywords

  • IR-104133

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