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A rheological study was carried out on suspensions based on oil and filler agents of two types, one of which was ultradispersed (nanoscale). The influences of the dispersive phase and the polarities of main and dispersed fillers were determined. Experiments were carried out using a rotational viscosimeter operating in two regimes: with a constant rate of shear and under a combination of shear deformation and orthogonal vibration.

In this paper, concepts of the anisotropic nature of the flow of structured dispersions accompanied by disruption of a structure under continuous shear in layers oriented in the direction of shear flow are developed. The mechanism for the appearance and evolution of alternating solid and liquid fluid layers, together with disruption of the structure for cluster aggregates of particles of the dispersed phase, is shown experimentally, theoretically, and by computer simulation. The observed phenomena and those described in this paper significantly affect both the conditions for determination and description of rheological properties of structured dispersions and the technology of their production, processing, and formation of dispersed composite materials on their basis.

Ever since P. A. Rebinder and his collaborators [1, 2, 4] published their article, it has been commonly accepted that in the range of minute deformation rates, the Newton character of a flow of structured disperse systems (pastes and suspensions) prevails. According to [1, 2], this region of viscosity is called the highest Newton viscosity of almost undisturbed structure, η0. In the present study, it was revealed that for, systems with lyophobic interactions between particles, in the region previously considered to be a region of Newton viscosity η0, a nonlinear dependence of the viscosity on shear stress is observed as the shear rate increases in the range \( 0 \leqslant \dot \varepsilon \leqslant 10^{ - 3} s^{ - 1} \). Thus, the viscosity increases up to the yield point Pk, at which point the avalanche decomposition of the structure begins, first into coarse aggregates and, subsequently, as their decomposition develops, into the smaller aggregates.

Regularities of the adsorption of ethylhydroxyethylcellulose (EHEC) hydrophilic polymer on a surface of inorganic pigments of TiO2 and Fe2O3 were investigated by infrared spectroscopy. It was found that the adsorption interaction between EHEC and a surface of oxides is accompanied by conformation transformations of the adsorbed molecules of EHEC. The means by which macromolecules bind with active centers on a surface of metal oxides and the influence of the oxides’ nature on the EHEC macromolecule conformation transformations determining the structure of the adsorption layer upon adsorption were established.

This work describes a new class of macromolecular compounds, i.e., acrylic acid and isobornyl acrylate gradient block copolymers synthesized by controlled radical polymerization. A series of these gradient block copolymers was compared with acrylic acid and isobornyl acrylate block copolymers with similar compositions to demonstrate the effect of copolymer molecular architecture and the intense mechanical effect on their surface interactions with particles of different nature in aqueous dispersion systems. The method of electrokinetic sonic amplitude revealed the architectural effect of macromolecules to their surface interaction the particles at various concentrations of polymer and calculated the parameters of polymer adsorption layers. The surface interaction models were suggested for macromolecules of block and gradient block copolymers of various compositions with hydrophilic and hydrophobic particles and the copolymer architecture was proven to determine the nanostructure of polymer adsorption layers on interface. The nanostructural differences were suggested and confirmed in the interaction of block and gradient block copolymers with interface of different nature.

The adsorption of hydrophilic ethylhydroxyethylcellulose (EHEC) polymer on the surface of TiO2 and Fe2O3 inorganic pigments under the action of intense mechanical actions was studied by infrared spectroscopy. Mechanoactivation methods included ultrasonic action and mechanical treatment at sonic frequencies. Intense action on TiO2 and Fe2O3 aqueous disperse systems activated the surface of inorganic oxides and intensified the adsorption of the polymer. It also caused the formation of adsorption-solvation EHEC layers with increased densities, which determined the sedimentation stability of disperse systems.

With a precision Haake RS1 rheometer, it is first found that at extremely low rates of shear (\( \dot \varepsilon \) ≤ 10−3 to 10−4 s−1 or lower), in nanodisperse systems based on highly dispersed aerosil or aerosil-bentonite compositions, with an increase in the shear rate, a non-Newtonian flow is observed. It is accompanied with a continuous growth of the effective viscosity of the dispersions ηeff, till the yield point P ≈ Pk is reached. At P ≥ Pk, the effective viscosity decreases abruptly; the structure decomposes via an aggregate mechanism. Earlier it was believed, that each viscosity level there corresponds to a combination of the full destruction of structural bonds and their partial restoring up to the equilibrium level determined by ηeff. In addition, the structured dispersed system flow remains Newtonian unless the static yield point has been overcome; it corresponds to the largest viscosity of a virtually undestructed system. Using a special procedure, SEM-imaging of the structure of the bentonite-suspension, as well as the bentonite added with minor amounts of aerosil, was carried out in water-ethanol medium. Photomicrographs of structure of the studied nanodisperse systems subject to shearing were obtained. The active filler (aerosil) particles distribution in the model system structure is studied. A procedure of studying the thixotropic properties of the structured nanodisperse systems in dynamic conditions is developed. The complex modeling of the structured nanodisperse system spreading over the scaled physical model, as well as special conditions of rheological tests in the Haake RS1 rotational rheometer cell, made us detecting a correlation between the spreading macroscopic factors and microscopic factors of the rheological behavior of the nanodisperse systems structure in dynamic conditions.

The main rules governing the redistribution of microparticles in disperse systems were revealed by computer simulation. These rules predetermine the character and properties of the structure being formed, which opens up the possibility to control the properties of disperse materials, including sorbents and catalysts based on high-dispersity solid phases.

The formation of the structure of sorbents and catalysts on the basis of high-dispersity solid phases under dynamic conditions was considered. The rheokinetic changes in contact interactions and rheological properties of high-dispersity component compositions under the conditions of continuous shear combined with oscillations were analyzed in terms of the new direction in physical chemistry of disperse systems, physicochemical dynamics. The reasons for and conditions of attaining maximum system uniformity were substantiated.

The influence of the vibrowave action on the properties of some disperse systems used in the textile industry has been considered. It has been noted that excitation of nonlinear oscillation in the audio band under resonant conditions leads to an increase in the degree of dispersion of distributed systems and an increase in their colloid stability.

The conditions of disintegration of structured formations occurring in disperse systems of the solid-dispersed-phase-liquid-dispersion-medium type, increasing their effective viscosity and inhibiting the attainment of a high fluidity by the dispersions, have been investigated. The role of inertial effects in attainment of the isotropic dynamic state by S/L disperse systems, when external vibration action is applied to them, has been studied. It has been shown in what manner the presence of particles of different mass (and consequently inertia) in the system leads to a disintegration of the structure under the action of dispersion-medium oscillations.

This paper reports on the results of rheological investigations into the kinetics of gelation of the sol-gel systems based on a water-alcohol solution of tetraethoxysilane (TEOS) modified by a number of metal salts and organic polyhydroxyl compounds, such as glycerol, poly(ethylene glycol) (PEG-300), and hyperbranched aliphatic complex polyol polyethers (HBP-49, HBP-64). It is demonstrated that, at a dispersed phase concentration of approximately 10 wt %, water-ethanol sol-gel systems containing 2–4 g/l of high-molecular additives possess a shear strength and are characterized by anomalous properties in their flow. The gelation time of sols in the presence of organic additives is affected by the ratio between the numbers of OH− hydrophilic and CH3 hydrophobic groups in the polymer molecule, the concentration of the introduced additive, and the electrolyte multivalence. The presence of metal salts enhances the structuring effect of polymers.

This paper analyzes the processes of structure formation of disperse systems under dynamic and static conditions in terms of synergetics and the theory of catastrophes. The efficiency of using these methodological approaches together with adopted instrumental methods of investigating the properties of structured dispersions is shown.

In this work, it was detected for the first time that, in the range that was previously deemed to be the range of the Newtonian viscosity η 0 , systems with lyophobic interactions of particles are characterized by a nonlinear dependence of the viscosity on the shear stress with an increase in the shear rates in the range 0 ≤ ≤ 10 –3 s –1 . The viscosity increases until the yield strength P k , after which an avalanche-like breakup of the structure starts. A specific feature of the flow of the considered structured dispersions in the range P < P k is that the viscosity increases in a sawtooth manner, which is typical of breakup of the structure into aggregates of particles with subsequent restoration and strengthening. This phenomenon can be explained by an increase in the probability of contacts between particles and aggregates of particles at lyophobic parts of the surface (if there is a lyophobic‐lyophilic mosaic pattern [5]). In this work, we studied suspensions of modified (methylated) nanodisperse Aerosil in mineral oil with concentrations of 2‐7 wt %. The total flow curves of the studied suspensions under quasi-equilibrium conditions were recorded with a Haake RS1 rotational rheometer in a controlled stress mode where the shear stress was specified discretely and the shear rate was controlled. Reaching of a quasi-equilibrium state at each point was detected by the device automatically once the amplitude of oscillations of a parameter being measured reached 1% of the mean. Great attention was paid to studying the behavior of structured nanodisperse systems in the range of extremely low shear rates e ˙ (on the order of 10 –6 s –1 ). Detailed data were obtained on the structural‐rheological properties of suspensions in the highest viscosity range characterizing the virtually unbroken structure of the system.

A relation is obtained to describe the effect of the volume content of particles on the effective viscosity of a concentrated monodisperse suspension of spherical particles in a medium which can be regarded as a power-law fluid. It is shown that this effect becomes weaker as the nonlinearity of the medium increases. The analysis is performed on the basis of the proposition that the deciding role is played by the lubricant action of thin interlayers of the medium between the surfaces of the particles. These results are used to calculate the viscosity of a bidisperse suspension containing a highly dispersed colloidal fraction and a coarsely dispersed fraction (filler). The viscosity is calculated as a function of the ratio of the two fractions. The calculated results are compared with experimental data for model systems.

A method was developed to determine contact interactions in high-disperse powders under dynamic conditions of total destruction of powder structure by vibrations. A Theological model was proposed and analyzed which describes the processes of fluidization and vibroboiling of a disperse system and relates the macro-rheological characteristics of a pseudofluid to contact interactions of particles. The experimental studies of a series of high-disperse powders have confirmed the theoretical results, so that contact forces within high-disperse powders can be determined under dynamic conditions. These dynamic interaction forces were found to be several orders greater than static ones, the latter having been measured in shearing and tearing tests of a powder layer and by direct measurements of interactions of individual particles. Interactions in a mixture of powders were shown to change both qualitatively and quantitatively under dynamic conditions, showing that the dynamic tests were necessary. The sta...

High-concentrated disperse systems, especially those including solid particles, are now becoming of considerable importance in technological applications. Although such systems are very diverse in chemical composition and physical properties, they can be considered in a general way due to two characteristic features: developed interphase surface and high concentration of disperse phases in liquid dispersion media

Highly dispersed powders having a well developed interphase surface belong to the class of difficult-to-mix free-flowing materials. Different types of mixers are being used for mixing them [i]. However, most of them fail to ensure a high degree of homogeneity (uniformity) during the mixing process because of the difficulties in attaining the maximum possible (limiting) destruction of the structure of the material. In view of this, effective realization of the mass transfer processes becomes impossible under the conditions of continuous movement (displacement/shear) since the structure of the material is not fragmented into individual particles and discontinuous localized layers of the dispersed systems (zones) or blocks (particle aggregates) form [2]. Complete and uniform distribution of various phases in the macro and micro-volumes of the system (i.e., attainment of the limiting homogeneity) is possible only when the maximum possible (limiting) destruction of the structure of the entire dispersed system and all the particle aggregates of the solid phase occurs and their complete separation is ensured.

The process of vibrational dosing of highly dispersed powders was studied. It was shown that in order to improve the effectiveness of this process, it is necessary to control the rheological properties of the powders.

1. Vibroactivation and pregrinding of cement (especially in high-fill systems with low W/C ratio) enable us to create homogeneous, finely-crystalline, finely-capillary concrete. 2. The structure-forming role of quartz microfiller in adhesive appears in the growth of the specific surface of the pore capillaries and the proportion of fine pores. 3. As more quartz is added up to the optimal quantity, the structure of the adhesive improves. Above this limit the proportion of coarse pores begins to increase, together with the overall porosity, owing to excess of water for the case W/S=const, or owing to incomplete compaction at constant water-cement ratio. For the compositions investigated (W/S=const) the best amount of added quartz is 20–30%. 4. Vibroactivation of high-fill systems based on finely-ground cement and the addition of quartz microfiller up to 40% secure high water-imperviousness of colloidal cement adhesive and solutions based on it. 5. The experimental data on the pore structure and water imperviousness show that CCA and CCS can be successfully used as waterproofing materials.