Objectives. To determine the change patterns for the main physical properties of suspensions after their grinding in bead mills, with the prospect of optimizing the preparation technology and extending the results obtained to other dispersed phases.

Methods. The study used the Fraunhofer laser diffraction method to determine particle size. The obtained data on the particle size distribution of suspensions were qualitatively verified by optical microscopy. The Brookfield relative viscosity method was used to evaluate the rheological properties of the resulting suspensions. The density of the resulting suspensions was measured by the hanging method using a calibrated pycnometer.

Results. The dependencies of the change in the particle size distribution after grinding in a bead mill were established. The viscosity of the suspensions was observed to increase following grinding. Common regularities of changes in the density of the considered suspensions were established.

Conclusions. The conducted studies showed that the physical and mechanical properties of suspensions are affected by the type and the filling ratio of the grinding media; the residence time of the suspension in the grinding chamber; the number of grinding operations; mill designs.

Objectives. To evaluate the influence and efficiency of using microwave irradiation on the dichlorocarbenation of polar olefins. To determine the conditions (reaction time and process temperature) under which the maximum yield of target gem-dichlorocyclopropanes is achieved.

Methods. The target compounds were obtained by classical methods of organic synthesis— acetalization of polyols and dichlorocarbenation of unsaturated compounds. The preparation of gem-dichlorocyclopropanes was carried out using the microwave activation method on a Sineo device (microwave system for organic synthesis, made in China). In order to determine the qualitative and quantitative composition of the reaction masses, gas–liquid chromatography (using the Kristall 2000 hardware complex), mass-spectroscopy (using Chromatek-Kristall 5000M device with NIST 2012), and nuclear magnetic resonance spectroscopy (using Bruker AM-500 device with operating frequencies of 500 and 125 MHz) were carried out.

Results. Under microwave irradiation at 25°C for 2 h with the maximum yield (92–98%), the target substituted gem-dichlorocyclopropanes were obtained: 2-(2,2-dichloro-3-methylcyclopropyl)-1,3-dioxolane, 2-(2, 2-dichloro-3-phenylcyclopropyl)-1,3-dioxolane, 8,8-dichloro4-isopropyl-3,5-dioxabicyclooctane, diethyl-2,2-dichloro-3-phenylcyclopropane-1,1-dicarboxylate, and diethyl-2,2-dichloro-3isopropylcyclopropane-1,1-dicarboxylate.

Conclusions. Under the conditions herein proposed, the use of the microwave stimulation method in the dichlorocarbenation of double C=C bonds containing polar substituents allows the reduce the temperature and reaction time to be significantly reduced, and the yield of target gem-dichlorocyclopropanes to be increased.

Objectives. To develop a method to obtain a hydrosol of the salt of chitosan with sulfuric acid—chitosanium sulfate (ChS) hydrosol—and to study the effect of various water-soluble polysaccharides on its stability over time, as well as its resistance to indifferent and non-indifferent electrolytes.

Methods. κ-Carrageenan, sodium alginate (SA), and xanthan were used as polymers which perform the function of colloidal protection for ChS nanoparticles. Capillary viscometry was used to study the viscosity of polymer solutions, their molecular weight, and their adsorption on ChS. The stability of the sols over time and their resistance to indifferent and non-indifferent electrolytes were evaluated photometrically. The hydrosol particle size was determined by means of dynamic light scattering.

Results. On the surface of ChS, κ-carrageenan is adsorbed most strongly over a wide range of concentrations. The graphs of the dependencies of the relative change in the turbidity of sols with the addition of various polysaccharides on their weight concentration at a sol lifetime of 2 days have the shape of curves with a maximum. Sols with the addition of 0.0125% SA and κ-carrageenan in the range of 0.04% have the greatest stability over time. According to dynamic light scattering data, the average particle size of freshly prepared sols with the addition of the polymers to ensure their greatest stability over time are 10.8 nm and 14.6 nm, respectively. For freshly prepared sols without polysaccharides, this size is 24.8 nm. The hydrosol coagulation threshold with an indifferent electrolyte (NaCl) is 9.3 times higher than that with a non-indifferent electrolyte (Na₂SO₄). κ-Carrageenan and SA protect the hydrosol from coagulation with an indifferent electrolyte (NaCl) at all their used amounts. At the same polymer concentrations, no protection from coagulation with a non-indifferent electrolyte (Na₂SO₄) was observed.

Conclusions. A method was developed to obtain ChS hydrosol with a positive particle charge. The stability of ChS sols over time was studied both without and with the addition of SA, κ-carrageenan, and xanthan. Sol coagulation thresholds with indifferent and non-indifferent electrolytes, as well as the protective numbers for κ-carrageenan and SA against the coagulation of hydrosols with these electrolytes, were established. The mechanism of stability of sols at certain concentrations of water-soluble polysaccharides was explained using data on the adsorption of these polysaccharides on the surface of chitosan treated with a solution of sulfuric acid. Based on the results of the work, it can be concluded that SA and κ-carrageenan can be used for the efficient stabilization of ChS hydrosols over time and for the colloidal protection of ChS from coagulation with sodium chloride.

Objectives. To develop a new method to determine amino acids in drugs by means of reverse-phase high-performance chromatography (RP HPLC) with pre-column derivatization using phenyl isothiocyanate (PITC) and one-pot sample preparation.

Methods. The initial standard solutions of amino acids were prepared by weighing, followed by dissolution in water. Working solutions were then prepared: standard, test, and blank, by dilution in 20 mM hydrochloric acid. Further sample preparation was carried out in Safe-lock polypropylene tubes (Eppendorf) in a reaction buff containing mobile phase A, acetonitrile, and triethylamine in a ratio of 85 : 10 : 5, labeled with a 5% PITC solution in acetonitrile. After thorough mixing for 3–5 min on a vortex, the tubes were kept in a solid-state thermostat with a thermally insulating lid for 2 h. The samples were then cooled for 10 min, centrifuged for 1 min at 13000 rpm, the supernatant was transferred into vials, and the mixture of amino acids was separated by RP HPLC using hydrophobic silica gel with grafted C18 groups as a stationary phase. The quantitative determination of amino acid derivatives was carried out using a diode array detector.

Results. A new method for the separation and determination of amino acids in medicinal preparations was developed and validated. Simple one-pot sample preparation using available reagents and equipment enabled studies to be carried out without using commercial kits, for example, the AccQ·Tag Ultra Derivatization Kit, USA. Using the analysis of mixtures of histidine and glycine as an example, it was shown that when using two mobile phases, an acceptable separation of amino acid derivatives in a gradient mode can be achieved for 20 min at a flow rate of 1.0 mL/min. The samples prepared according to the new method demonstrated a high level of stability in use and storage. A composition of mobile phases A and B consisting of 10 mM acetate buffer pH 3.5 and 80% acetonitrile solution was proposed. Validation of the method hereby developed in the analysis of the drug Innonafactor®, containing glycine and histidine as excipients, demonstrated high convergence of the results of the quantitative determination of these amino acids.

Conclusions. The new method to determine amino acids in medicinal preparations by RP HPLC with PITC pre-column derivatization has a wide range of applications, has a number of advantages when compared to imported commercial kits for the determination of amino acids. These include: lower cost of reagents and materials, high accuracy and repeatability. Thus, it can be recommended for use in quality control laboratories of pharmaceutical enterprises.

Objectives. To compare the properties of rubber compounds and rubbers based on natural rubber RSS1 and synthetic isoprene rubbers obtained using Ti, Nd, Gd catalysts, both when used individually in the formulation of rubber compounds and when synthetic analogues partially replace natural rubber.

Methods. Rubber compounds were prepared using a laboratory roll and a 100 cm³ rubber mixer. For rubber compounds, the following factors were determined: Mooney viscosity, cohesive strength, and vulcanization characteristics. For rubbers, the following factors were determined: physical and mechanical parameters, Shore A hardness, rebound resilience, and volume loss upon abrasion.

Results. Based on the results of the rubber compound tests, the study showed that compounds based on all the synthetic polyisoprenes studied are significantly inferior to compounds based on natural rubber in terms of cohesive strength. The partial replacement of natural rubber with synthetic rubber (regardless of the type of catalytic system) leads to a significant decrease in the cohesive strength of the blends. Despite the differences observed in the properties of the rubber compounds, the results of the rubbers based on individual rubbers do not manifest significant differences.

Conclusions. The study demonstrated the influence of defects (oligomers, gel, low molecular weight fractions, branches, and 3,4-units) in the structure of synthetic polyisoprenes on the cohesive strength index of rubber compounds based on them, in which the number of 3,4-units plays a decisive role. The study also showed the potential of studying synthetic polyisoprenes as analogues of natural rubber in formulations of rubber compounds in the aims of resolving the problem of import substitution in the tire and rubber goods industry.

Objectives. The aim of the study was to confirm the compliance of the mechanical and thermophysical properties of titanate-zirconate mineral-like matrices intended for immobilization of the rare-earth-actinide fraction of high-level waste (HLW) with pyrochlore structures (Nd₂ZrTiO₇) and orthorhombic titanate of rare earth elements (Nd₄Ti₉O₂₄+TiO₂) with the Russian requirements for the final forms of radioactive waste sent for disposal. With regard to fractionated radioactive waste, this type of matrix is preferable when compared with conservative aluminophosphate and borosilicate glasses. This is due to larger capacity, and a better level of chemical, thermal, and radiation resistance.

Methods. The synthesis of mineral-like matrices was carried out by remelting a granular precursor consisting of mineral-forming metal oxides and a solution imitating the rare earth-actinide fraction of HLW in an induction furnace with a cold crucible. The thermal diffusivity was determined by the laser flash method. The heat capacity of the matrix samples was measured by differential scanning calorimetry. Ultimate flexural and compressive strengths were determined using universal test machines. The elastic moduli (Young’s) were measured by the acoustic method. The temperature coefficients of linear expansion were determined using a high-temperature dilatometer.

Results. The ultimate strength of the matrices (Nd₂ZrTiO₇) and (Nd₄Ti₉O₂₄+TiO₂) was found to be 150–179 and 20.6–57.8 MPa in compression and bending respectively. Young’s moduli vary from 3.7 ∙ 10⁷ to 2.15 ∙ 10⁸ kN/m². With an increase in temperature from 50 to 500°C, the values of thermal conductivity have a pronounced tendency to decrease from 1.71 to 0.91 W/(m∙K). The temperature coefficients of linear expansion increase from 6.96 ∙ 10⁻⁶ to 1.01 ∙ 10⁻⁵ K⁻¹ in the same temperature range.

Conclusions. Comprehensive studies of titanate-zirconate mineral-like matrices show that their mechanical and thermal properties in certain cases significantly exceed the minimum requirements of regulatory documentation for the final forms of HLW.

Objectives. To calculate the effect of leakage of volatile synthesis products on silicon carbide yield in an electrothermal fluidized bed reactor, as well as to develop a general model of the synthesis of finely divided silicon carbide. This will be achieved by particularizing a mathematical model of leakage of volatile products of chemical reactions from the reaction volume of the reactor with the fluidizing inert gas.

Methods. As a method to produce silicon carbide, synthesis in an electrothermal fluidized bed was studied. The model of leakage of volatile products was validated by comparing the calculation results with existing experimental data on the SiC synthesis in a hightemperature fluidized bed reactor. The comparison parameters were: mass yield of silicon carbide, and the total synthesis time in a reactor with batch loading of silicon dioxide into the reaction volume.

Results. The value of the parameter p in the general model of SiC synthesis in a fluidized bed was established. The parameter p is equal to the ratio of the number of carbon-containing particles involved in the formation of SiO, to the total number of silicon dioxide particles. It also characterizes the composition of stable complexes of particles of the charge at various operating temperatures of the fluidized bed. The discrepancy between the calculated and experimental values of the masses of the synthesized silicon carbide was shown not to exceed 15.5% at a high temperature of the fluidized bed (T = 1800°C) and decreases with a decrease in the operating temperature to 4.7% at T = 1450°C.

Conclusions. The general computational model for silicon carbide synthesis with a built-in procedure for calculating the leakage of volatile products of chemical reactions enables the variants of SiC production in electrothermal fluidized bed reactors to be analyzed. In this case, it is important to establish an energy-efficient working cycle without preliminary expensive experimental studies.