Modeling flow-induced crystallization in isotactic polypropylene at high shear rates
| Autor: | Gwm Gerrit Peters, PC Peter Roozemond, Zhe Ma, Martin van Drongelen, MA Martien Hulsen |
|---|---|
| Přispěvatelé: | Processing and Performance |
| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: |
Pressure drop
Materials science Mechanical Engineering Nucleation 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Viscoelasticity 0104 chemical sciences law.invention Open-channel flow Shear rate Physics::Fluid Dynamics Mechanics of Materials law Compressibility General Materials Science Crystallization Composite material 0210 nano-technology Shear flow |
| Zdroj: | Journal of Rheology, 59, 613-642. Society of Rheology |
| ISSN: | 0148-6055 |
| DOI: | 10.1122/1.4913696 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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