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COBEM 2023
27th International Congress of Mechanical Engineering
Rheological Characterization of Non-colloidal Suspensions with Non-Newtonian Bulk: Investigating the Impact of Microparticles
Submission Author:
LUIS HUMBERTO QUITIAN ARDILA , PR , Brazil
Co-Authors:
LUIS HUMBERTO QUITIAN ARDILA, Emiliano Bocardo da Cruz, Yamid José García Blanco, Diogo Elias da Vinha Andrade, Admilson Franco
Presenter: Emiliano Bocardo da Cruz
doi://10.26678/ABCM.COBEM2023.COB2023-0220
Abstract
The rheological behavior of complex fluids such as non-colloidal suspensions is currently a required topic in the cosmetic, food, and petroleum industries. The behavior of non-colloidal suspensions is complex since these are soft materials made from the dispersion of particles with diameters greater than 10 μm in a liquid matrix. The study of the rheological behavior of the yield strength of non-colloidal suspensions and thixotropic, is underexplored. The present work aims to analyze the particle size and concentration dependence on static and dynamic yield strength in viscoelastic non-colloidal suspensions. Carbopol with a concentration of 0.2%wt was used for preparing the non-colloidal suspensions with Polyamide particles with 5, 20, and 50 µm of diameter. Rheological measurements were performed in a rotational rheometer – TA instrument with cross-hatched parallel plate geometry, with gap of 1 mm. Steady-state flow curves were carried out to understand liquid-like behavior and determine dynamic yield strength; on the other hand, creep tests were conducted to measure the static yield strength. Finally, shear stress amplitude sweeps oscillatory tests were carried out to comprehend the suspension structure in the solid-like behavior. The experimental results indicate that compared to the pure Carbopol solution, the suspension of 5 µm particles exhibit an increase in yield strength, whereas the suspensions of 20 µm and 50 µm particles exhibited a decreasing behavior for this parameter. The decreasing behavior for the yield stress is more noticeable for 20 µm particles suspension. This effect could be attributed to the increase in the spacing between the base fluid and the particles, since the yield strength of the fluid is caused by the intermolecular forces of the microstructure of the fluid. Creep test depicts that the static yield stress behavior during yielding process, follows the same trend of the dynamic yield strength. The stress amplitude sweeps oscillatory tests revealed that Storage modulus (G') in the Small Amplitude Oscillatory Shear (SAOS) region decreased with an increase in particle concentration, but there were no significant variations observed between the 20 µm and 50 µm particles in the pre-yielding stage. These results indicate the presence of flow heterogeneities in the 20 µm and 50 µm suspensions. The suspension of particles displays a microstructure that weakened the Carbopol polymeric chains as a result of hydrodynamic interactions between the particles spacing.
Keywords
non-colloidal suspensions, Yield Strength, Polyamid Seeding Particles, Carbopol solutions, static and dynamic yield strength, viscoelastic non-colloidal suspensions
