0438457 - ÚH 2016 RIV DE eng J - Journal Article
Pivokonský, Radek - Filip, Petr - Zelenková, Jana
The role of the Gordon-Schowalter derivative term in the constitutive models - improved flexibility of the modified XPP model.
Colloid and Polymer Science. Roč. 4, č. 293 (2015), s. 1227-1236. ISSN 0303-402X. E-ISSN 1435-1536
Institutional support: RVO:67985874
Keywords : constitutive model * Gordon-Schowalter derivative * PTT model * PTT-XPP model * shear flow * elongational flow
Subject RIV: BK - Fluid Dynamics
Impact factor: 1.890, year: 2015 ; AIS: 0.37, rok: 2015
Result website:
https://link.springer.com/article/10.1007/s00396-015-3498-7DOI: https://doi.org/10.1007/s00396-015-3498-7

Constitutive models that complete the set of equations describing the flow of polymer melts should respect objective thermodynamics and stability conditions ensuring their validity in the whole range of possible deformation flow. However, in practice a very good description of flow situations can be achieved with the models not complying with the physical assumptions in all respects. Analogously to the term characterizing yield stress in empirical viscoplastic models, the term represented by the Gordon-Schowalter (GS) derivative in the differential constitutive models contributes to better fitting the experimental data, especially shear thinning. Efficiency of the recently presented modified XPP model (just one non-linear parameter per mode) implementing the GS derivative term (one additional non-affine motion parameter per mode) is improved (documented on LDPE, HDPE, and PVB materials), and a comparison with the exponential PTT and PTT-XPP models (a priori containing the GS derivative term) are presented.
Permanent Link: http://hdl.handle.net/11104/0245352