Fine material effect on kaolin suspensions rheology

Abstract

A good rheological characterization can be used as a control parameter within the industrial processing of kaolin. The kaolin used was characterized by SEM, XRD, XRF and particle size. Also it was classified and separated in three sizes of fine material, which was introduced in suspensions with three different size distributions. The analysis was based on a rheological study of the fine particles influence, on the suspension viscosity. The results show that it is possible to modify the viscosity by altering the fines content without changing the solid fraction of the suspension. Suspensions of kaolin with 40% content of fines tend to decrease its viscosity value. Suspensions with quantities of fine greater than 60 %, increase the value of its viscosity. In the research are also presented the proposed mechanisms by which the presence of fine increases or decreases the value of the viscosity of a suspension.

Viscosity Factor (VF) Complementary to the Statistical Indicators Associated with the Rheological Behavior of Aqueous Solutions of Polyvinyl Alcohol

“…These parameters are related to each other by the Deborah number mentioned above, the same one defined by: [ 40 ]. According to Bustamante and Aguilera [ 41 ], the Deborah number is the main dimensionless number in rheology. One can identify liquid-type or solid-type rheological behaviors for a given material from it.…”

“…When the is close to 1, the material will present an intermediate behavior, called viscoelastic. As there is no structural change, the material's response is independent of the applied stress, and therefore, it presents linear viscoelasticity [ 41 ].…”

“…Yield effort is an important rheological variable in the case of suspensions subjected to relatively low or near-zero shear rates [ 41 ]. Normally, the yield stress is considered to have an invariant value for each viscoelastic fluid [ 46 , 47 , 48 , 49 ].…”

“…He also points out that the most popular equations used to describe liquids with yield stress are those of Bingham, Casson, and Herschel-Bulkley since these equations explicitly show the yield stress calculation. While Bustamante and Aguilera [ 41 ] conclude that the yield stress is related both to the sensitivity and precision of the viscometer or rheometer used in the experiments carried out at very low shear rates, as well as to the dynamics of the deformation, so this parameter cannot be assigned a unique value.…”

“…On the other hand, when the flow curve is analyzed in detail as the shear rate tends to zero, there is a region in which the slope can be considered fixed, so the apparent viscosity in this region tends to a fixed value and which is called Newtonian viscosity for a very small shear rate. On the other hand, when the shear rate tends to zero, the apparent viscosity tends to infinity, consequently, the values of tend to be too large so that the slope can be confused with the shear stress axis at the beginning of the flow curve, which is often reported as yield stress , although it does not necessarily exist [ 41 ].…”