Extensional viscosity measurements using new FreeFlow dies to understand polyolefin melt processing instabilities (Invited Lecture)

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F70883521%3A28110%2F24%3A63580499" target="_blank" >RIV/70883521:28110/24:63580499 - 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

Extensional viscosity measurements using new FreeFlow dies to understand polyolefin melt processing instabilities (Invited Lecture)

Original language description

Extensional viscosity (ηe) represents one of the key rheological property that has a strong influence on the processability of polymer melts. The ηe can be easily determined from entrance pressure drop (Pen) measurements using a high-pressure capillary rheometer, an orifice die (zero-length die) and the Cogswell method [1]. When measuring Pen, it can happen that the material leaving the orifice die sticks to the bottom side of the die [2-4], leading to an overestimation of Pen, and ηe cannot be determined accurately. Typically uniaxial and planar ηe plays a crucial role in material processing. For example, their ratio determines the level of neck-in phenomenon (undesired shrinkage of the film in the width direction during the film casting process) [5]. While the measurement of uniaxial ηe is a relatively simple experimental task, the determination of planar ηe is challenging because the generation of pure planar flow is complicated and its measurement is therefore considered inappropriate for routine use [6]. Based on our previous work [4,7-10], a new series of multi-piece inert circular and rectangular orifice dies have been developed and successfully tested, which prevent the possibility of overestimating the entrance pressure drop and enable the accurate determination of uniaxial and planar ηe. In addition, the use of these inert orifice dies allows a new way to evaluate the extrudate swell and die lip build-up phenomena, which are often hidden in conventional orifice dies, as the flowing material tends to fill the underside of the die due to its stickiness.AcknowledgementsThe author wish to acknowledge the Grant Agency of the Czech Republic (Grant No. 24‐11442S) for the financial support. The author also wishes to thank NETZSCH Gerätebau GmbH for providing the Rosand RH10-2 capillary rheometer.References[1] Cogswell F. N.: Converging flow of polymer melts in extrusion dies. Polymer Engineering &amp; Science, 12(1), 64-73 (1972).[2] Kim, S., Dealy, J.M.: Design of an orifice die to measure entrance pressure drop. Journal of Rheology, 45(6), 1413-1419 (2001).[3] Aho J., Syrjälä S.: Determination of the entrance pressure drop in capillary rheometry using Bagley correction and zero-length capillary. Annual Transactions of the Nordic Rheology Society, vol. 14 (2006).[4] Zatloukal M., Musil J.: Analysis of entrance pressure drop techniques for extensional viscosity determination. Polymer Testing 28(8), 843-853 (2009).[5] Barborik, T., Zatloukal, M.: Steady-state modeling of extrusion cast film process, neck-in phenomenon, and related experimental research: A review. Physics of Fluids, 32(6), art. no. 061302 (2020).[6] Dealy J. M., Read D. J., Larson R. G., Structure and Rheology of Molten Polymers, 2nd Edition, Hanser Publisher Munich (2018).[7] Zatloukal M.: Measurements and modeling of temperature-strain rate dependent uniaxial and planar extensional viscosities for branched LDPE polymer melt. Polymer, 104 (2016) 258-267.[8] Zatloukal, M., Musil, J., Extrusion Head with Inert Capillary of Zero Length, Patent CZ 304382 B6 (2014). [9] Zatloukal, M., Extrusion Head with Inert Flat Slit of Zero Length, Patent CZ 305409 B6 (2015).[10] Zatloukal, M., Extrusion head with inert outlet slit, especially for high outlet velocities of polymer melts, Patent CZ 309071 B6 (2021).

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/GA24-11442S" target="_blank" >GA24-11442S: Rheology and modeling of polymer melt flows at very high strain rates with respect to the production of meltblown nanofibers</a><br>

Continuities

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

Publication year

2024

Confidentiality

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