0454842 - ÚH 2016 FR eng C - Conference Paper (international conference)
Pivokonský, Radek - Filip, Petr - Zelenková, Jana
Modified XPP model with a reduced number of parameters.
10th Annual European Rheology Conference, Book of Abstracts. Nantes: GFR, 2015.
[10th Annual European Rheology Conference. Nantes (FR), 14.04.2015-17.04.2015]
Institutional support: RVO:67985874
Keywords : XPP model * polymer * PTT-XPP models * PTT models
Subject RIV: BK - Fluid Dynamics

For a simplification of fitting procedure of the eXtended Pom-Pom (XPP) model, its modification (a reduction of the non-linear parameters) has been recently proposed [R.Pivokonsky, P.Filip - Coll. Polym. Sci. 292 (2014), 2753-2763]. It has been shown a good agreement between the modified XPP model predictions and the steady and transient shear and elongational characteristics for various commercial polymers. However, in some cases both models comply with the elongational data but overpredict shear viscosity. A comparable behaviour is also exhibited by the PTT and PTT-XPP models, if the upper-convected derivative is assumed. The aim of this contribution is to adapt the modified XPP model in such a way that a prediction of both elongational and shear viscosity is qualitatively balanced with a good accuracy of both experimental data. This can be achieved by an introduction of the Gordon-Schowalter derivative term instead of the upper-convected term in the governing equations. It makes possible to fit shear thinning with almost no impact on elongation characteristics. However, the usage of this term is accompanied by spurious oscillations in transient shear characteristics. The predictive/fitting capabilities of the modified XPP model with and without the Gordon-Schowalter derivative term has been tested using linear and branched polymer melts. Efficiency of the proposed model in comparison with the exponential PTT and PTT-XPP models (a priori containing the Gordon-Schowalter derivative term) is also presented.



Permanent Link: http://hdl.handle.net/11104/0255473