Determination of Uniaxial and Planar Extensional Viscosity Using High-Pressure Capillary Rheometry

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F70883521%3A28110%2F24%3A63583258" target="_blank" >RIV/70883521:28110/24:63583258 - 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

Determination of Uniaxial and Planar Extensional Viscosity Using High-Pressure Capillary Rheometry

Original language description

Extensional viscosity (η_e) represents one of the key rheological properties that has a significant influence on processing polymer melts. η_e can easily be determined from entrance pressure drop (Pen) measurements using a high-pressure capillary rheometer, orifice die (zero-length die) and the Cogswell method. When measuring Pen, there is a possibility that material exiting the orifice die may stick to the underneath, leading to an overestimation of Pen and inaccurate η_e. Typically, uniaxial, and planar η_e plays a crucial role in material processing. The ratio between uniaxial and planar η_e determines the magnitude of neck-in phenomenon (unwanted film width shrinkage during the casting process). While the measurement of uniaxial η_e is relatively simple, the determination of planar η_e is challenging because the generation of pure planar flow is complicated, and its measurement is therefore considered unsuitable for routine use. Based on the pioneering work of Zatloukal et al., the current designs of the ROSAND dies have been optimized to create a new series of FreeFlow circular and rectangular orifice dies. These dies prevent the possibility of overestimating the entrance pressure drop, allowing precise determination of uniaxial and planar η_e. This means uniaxial and planar η_e can be estimated for different materials under controlled conditions with minimal effort. In addition, using these FreeFlow orifice dies enables a new way of evaluating extrudate swell (Barus effect), which is frequently dismissed or overestimated in conventional orifice dies because the extrudate can fill the underside of the die due to inherent swelling leading to unwanted sticking. In addition to standard shear flow curves, measurements using the ROSAND capillary rheometer can now provide in-depth studies of extrudate swell including uniaxial and planar η_e. This information can be used in various simulations to achieve ecological, energy and resource efficiency.

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

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Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2024

Confidentiality

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