Measurement and Modeling of Uniaxial and Planar Extensional Viscosities for Linear and Branched Polyolefin Melts in Very Fast Flows

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F70883521%3A28110%2F23%3A63568338" target="_blank" >RIV/70883521:28110/23:63568338 - isvavai.cz</a>

Result on the web

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DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Measurement and Modeling of Uniaxial and Planar Extensional Viscosities for Linear and Branched Polyolefin Melts in Very Fast Flows

Original language description

In this work, novel rectangular [1-2] and circular [3-6] orifice (zero-length) dies were used to measure planar and uniaxial extensional viscosities as a function of strain, strain rate and temperature for polypropylene and polyethylene melts using Cogswell [2, 6-7] and Gibson [8-9] methodologies. The obtained experimental data were combined with shear and uniaxial extensional viscosity data determined at very high strain rates. The ability of a molecularized Generalized Newtonian Fluid (mGNF) [M. Zatloukal and J. Drabek, “Generalized Newtonian fluid constitutive equation for polymer liquids considering chain stretch and monomeric friction reduction for very fast flows modeling,” Physics of Fluids 33(8), 083106 (2021)], Giesekus [10] and explicit Yao [11-12] constitutive equations to describe the measured data was tested. For the first time, the monomeric friction coefficient for fully aligned chains was determined for linear and branched polypropylenes using a high-strain-rate limiting value of uniaxial extensional viscosity. It has been shown that including the effect of the chemical environment (i.e., the role of the oligomeric solvent) using a simplified version of the mGNF constitutive equation (instead of the commonly used Newton’s law) can significantly improve the ability of the Giesekus and Yao viscoelastic constitutive equations to describe the measured experimental data, especially at very high strain rates using adjustable parameters with a clear physical meaning. Since the friction coefficient of polyolefin melts controls the flow-induced crystallization and extensional rheology at high extensional rates, the obtained results are considered valuable not only with respect to the fundamental understanding of polymer physics and the development/validation of advanced constitutive equations, but also with regard to understanding the stability of non-Newtonian flows in advanced polymer processing, such as optimized production of polymer membranes for energy storage membranes via cast film process or filtration membranes prepared by the meltblown process used for example in the production of face masks.

Czech name

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Czech description

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Type

O - Miscellaneous

CEP classification

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OECD FORD branch

10404 - Polymer science

Project

<a href="/en/project/GA21-09174S" target="_blank" >GA21-09174S: Viscoelastic non-isothermal modeling of film extrusion process for membranes production including flow induced crystallization</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2023

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů