On the elusive nature of Carbopol gels: “model”, weakly thixotropic, or time-dependent viscoplastic materials?

0524753 - ÚMCH 2021 RIV NL eng J - Journal Article
Younes, E. - Himl, M. - Starý, Zdeněk - Bertola, V. - Burghelea, T.
On the elusive nature of Carbopol gels: “model”, weakly thixotropic, or time-dependent viscoplastic materials?
Journal of Non-Newtonian Fluid Mechanics. Roč. 281, July (2020), č. článku 104315. ISSN 0377-0257. E-ISSN 1873-2631
Institutional support: RVO:61389013
Keywords : carbopol * rheology * yield stress
OECD category: Polymer science
Impact factor: 2.670, year: 2020
Method of publishing: Open access
https://www.sciencedirect.com/science/article/pii/S0377025720300835?via%3Dihub

The question of whether Carbopol gels always behave as “model” yield stress material is addressed experimentally. Prompted by several simple hydrodynamic experiments performed with Carbopol gels that can not be fully understood within the commonly accepted “model” picture, we revisit the yielding behaviour of a Carbopol gel. When subjected to a loading/unloading process, the yielding of the Carbopol is gradual and exhibits a rheological hysteresis. By in-situ visualisation of the microstructure it is demonstrated that these features do not originate from a micro-structural damage of the micro-gel. A systematic description of the role of the rate at which the material is forced (loaded or unloaded) on the yielding scenario is given. In closing, the question of how simple a scalar model can be and yet accurately describe the experimentally observed yielding scenario of a Carbopol gel in a rheometric flow is addressed. It is concluded that simple scalar models may do such job as long as they are not too simple and include a minimal amount of physical ingredients.
Permanent Link: http://hdl.handle.net/11104/0309066