Vol 92, No 9 (2019)

Classes of styrene–diene copolymers used as thickenining (viscosity) additives to lubricating oils are considered. Specific features of the synthesis and hydrogenation of such copolymers are discussed. The main requirements to thickening additives and the molecular structure–property relationships for the thickening power and viscosity index, mechanical stability, ability to disperse carbon black particles, heat resistance, and low-temperature properties are analyzed. The main producers of thickening additives based on hydrogenated stryrene–diene copolymers are presented.

Curing of Bisphenol A diglycidyl ether with methylendic anhydride under the action of imidazole-type catalysts was studied by differential scanning calorimetry and IR spectroscopy. The curing system with the optimum catalyst content was chosen. Heat-resistant polymers and composites with high values of the glass transition point, elastic modulus, and tensile, compression, and bending strength were prepared from epoxy resins of various functionalities.

The kinetics of formation of carbonyl groups in naturally aged polyethylene films under the action of ⁶⁰Co γ-radiation was studied, and the specific power consumption in the process was determined. The radiationstimulated oxidation of the aged films (in contrast to model freshly prepared samples) is a self-accelerating process occurring by at least two mechanisms. One of them is a chain process, and the other, most probably, involves the reaction of oxygen with the trans-vinylene unsaturated moieties initially localized in the crystalline phase of polyethylene. On the whole, the aged polymer materials exhibit increased tendency to oxidation under irradiation, which restricts the use of items based on them under the conditions of the action of high-energy radiation.

The effect exerted by organometallic iron complexes (ferrocene, tricarbonyl cyclooctatetraene iron, and dimer cyclopentadienyldicarbonyl iron) on the benzoyl peroxide initiated homo- and copolymerization of methyl methacrylate and n-butyl methacrylate was studied. The ligand surrounding in the organometallic complexes influences the shape of the kinetic curves of the methyl methacrylate and n-butyl methacrylate polymerization. In the presence of organometallic iron complexes, the copolymerization constants are close to unity. That is, the azeotropic copolymerization occurs, with the copolymer composition equal to the composition of the monomer mixture and with the random distribution of monomeric units in the copolymer chain. On the other hand, the presence of metallocenes influences the microstructure and molecular-mass characteristics of the copolymers. These changes are due to the formation of macromolecules with the participation of both free radicals and coordination-active polymerization sites formed in the presence of organometallic complexes.

Studies were carried out to reduce the leakage current of high-voltage ZnO varistor ceramics by varying Sb₂O₃ and NiO content in a ZnO-Bi₂O₃-Sb₂O₃-Al₂O₃-Co₃O₄-NiO. It was found that the ceramic composition (wt %): ZnO 80, Bi₂O₃ 5.83, Sb₂O₃ 2.62, A1₂O₃ 4.66, Co₂O₃ 3.80, NiO 3.09, has a minimum leakage current density I_out ≤ 0.1 μA cm^-2, breakdown voltage U_b = 4.1kV mm^-1, nonlinearity coefficient α = 65. The resulting ceramics are promising for the production of varistors with high stability of performance.

Stability constants of zinc and cobalt(II) complexes with Taurine were determined at 25°C and ionic strengths of 0.5, 1.0, and 1.5 (KNO₃). The thermodynamic stability constants were calculated. The processes in which zinc-cobalt alloys are electrodeposited onto 08kp steel from electrolytes with addition of Taurine and the physicochemical properties of the coatings were examined. It was shown that the ratio between the alloy components affect the chemical composition and microstructure of the coatings. The most homogeneous and finely crystalline structure is observed for zinc-cobalt alloy coatings obtained at a cathode current density of 1 A dm⁻² from an electrolyte with zinc concentration twice that of cobalt. At these concentration conditions, zinc-cobalt alloy coatings with 15.1 at % Co were obtained. The kinetic patterns of deposition of zinc-cobalt alloys at temperatures of 25 and 50°C were demonstrated. A relationship between the chemical composition, microstructure, and corrosion rate of the zinc-cobalt coatings obtained was determined.

Possibility of creating superacid catalysts on the basis of sulfated hydrosilicate nanoscrolls with halloysite structure and catalytic activity of the resulting materials in the model reaction of hexene-1 oligomerization were studied. The sulfation was performed with sulfuric acid solutions at concentrations of 0.25–1 M. The number of acid centers on the surface of the scrolls decreases with increase of the scid concentration, most probably due to the selective dissolution of the aluminum oxide sheet. In this case, the composition of the reaction products also changes, with the content of hexene-1 isomers increasing as compared with the oligomers. It was possible to obtain, at the lower boundary of the concentration range, an increased content of heavy fractions in the oligomerization products.

Surface activation of carbon materials produced by chemical vapor deposition onto a nickel plate is described. The products of pyrolysis of a gas mixture composed of propane, butane, and isobutane were for the most part nanofibers. This material was used as the active mass for electrodes of supercapacitors. The elec¬trodes were activated with a potassium hydroxide (KOH) at temperatures of 700 and 800°C in the atmosphere of argon. The activation efficiency was evaluated by the capacitance of supercapacitor cells by measurement of the electrochemical properties based on activated and unactivated materials. The salt 1.1-dimethylpyrrolidinium tetrafluoroborate (DMP) in acetonitrile (AN) was used as an electrolyte. The specific surface area of the electrodes was determined from adsorption data. It was shown that the specific surface areas of non-activated samples and samples activated at 700 and 800°C were 190, 338, and 586 m² g^-1, respectively. The specific capacitance of the samples also became higher with increasing specific surface area.

Theoretical analysis was made on the composition and thermodynamic parameters of combustion products of 2,2'-bis(bicyclo[2.2.1]heptane) in oxygen in a wide range of temperatures and pressures. 2,2'-Bis(bicyclo[2.2.1]heptane) can potentially be used as a fuel component in combustion chambers of liquid rocket engines for the first-stage launch vehicles. The average molar mass of approximately 26 amu., obtained for products formed in combustion of 2,2'-bis(bicyclo[2.2.1]heptane) in oxygen is close to similar values for methane in oxygen, whereas its density is more than twice the density of liquid methane. This circumstance makes it possible to hope that the mass of storage tanks can be made smaller if 2,2'-bis(bicyclo[2.2.1]heptane) is used for rockets, compared with the mass of storage tanks containing an equivalent amount of methane. The results obtained can be used to calculate nozzle profiles and combustion chamber parameters of a liquid jet propulsion engines.

In this study, oxidation of a model fuel, benzothiophene (BT) in n-decane, using polyoxometalate catalyst with Keggin structure has been investigated. The solid product evaluation was performed using gel permeation chromatography (GPC), thermal gravimetric analysis (TGA)/(DSC) differential scanning calorimeter, FTIR, proton and carbon nuclear magnetic resonance (¹H + ¹³C NMR) spectrums, elementary (C, H, N and S) analyses. The results showed that the solid product was a polymer with a weighted average molecular weight (Mw) of 183030. In addition, the polymer was found to be sticky, branched and cross-linked. Moreover, for the first time, the role of the different solvents in the formation of the polymer was studied. It was revealed that the solvent intermolecular force plays an important role in polymerization so that the solvent with stronger molecular force did not participant in the polymerization. Ultimately gas chromatography-flame ionization detector (GC-FID) analysis showed the amount of desulfurization was about 81%.

In this report, catalysts of Au nanoparticles on different supports (Au/ZrO₂, Au/C, Au/Al₂O₃, Au/SiO₂, Au/TiO₂, Au/MgO) were fabricated by co-precipitation and impregnation methods to determine the role of Au over oxides. The crystal structure and phase composition of catalyst samples before and after test reactions were investigated by X-ray diffraction technique, X-ray photoelectron spectroscopy and transmission electron microscopy. The catalytic activity was tested on the hydrogenation reaction of levulinic acid (LA) into γ-valerolactone (GVL) using formic acid (FA) as a hydrogen source. In all tested samples, Au/ZrO₂-D (was fabricated by co-precipitation method) gave the best GVL yield of 85.0% with very low amount of catalyst loading (catalyst/reactant 1 wt). The existent of Au³⁺ in the catalyst system may be the main factor to improve the yield of GVL formation.