Vol 91, No 11 (2018)

Greases based on poly-α-olefin oils of various viscosities, thickened with diureas of various structures, were studied systematically. The influence of the base oil viscosity and/or thickener structure on the physicochemical properties of lubricants was demonstrated. Diurea thickeners differing in the length of the hydrocarbon substituent influence the properties of lubricants prepared with base oils of similar chemical nature but different viscosity in different fashion. The revealed trends were confirmed by rheological studies in a wide range of shear rates. Tribological measurements at loads in the interval 20–80 kgf demonstrated significant dependence of the antiwear properties of ureate lubricants based on low-viscosity poly-α-olefin oils on the thickener structure. This dependence becomes less pronounced in going to higher-molecular-mass oils.

Comparative analysis of the physicochemical properties of styrene solutions of poly(propylene glycol maleate phthalate) with different initial reactant ratio was performed. Increased content of phthalic anhydride in the initial monomer mixture in the synthesis of the unsaturated polyester leads to worse properties of the ready product, poly(propylene glycol maleate phthalate)–styrene copolymer prepared by cold curing. Solutions of poly(propylene glycol maleate phthalate) in styrene with ~30 wt % styrene content exhibit the highest viscosity, allowing the use of the cured product as a structural composite material. The solutions containing ~40 wt % styrene have lower viscosity and are suitable for preparing less hard plastics for general purposes.

Fylolflex oligo(resorsinol phenyl phosphate) with terminal phenyl groups is an effective plasticizer for an epoxy polymer, allowing the development of compounds with enhanced levels of physicomechanical properties, heat resistance, softening point, an flame resistance. Introduction of chromite, a cheap and active filler, into the epoxy polymer in amounts of 0.1 and 100 wt parts enhances the physicochemical and mechanical properties of the composite. Namely, the Vicat softening point increases from 132 to 140–250°С, the degradation onset temperature increases, and the yield of carbonized structures increases from 54 to 68–86 wt %, which leads to a decrease in the release of volatile pyrolysis products into the gas phase and in the combustibility of the epoxy composite.

Effect of hydrogen addition at [C₂H₆]/[H₂] ratios of 10–0.05 on the oxy-cracking of ethane was experimentally studied. It was shown that small additions of hydrogen have nearly no effect on the process rate. With the concentration of added hydrogen increasing at temperatures of up to ~650°C, the contributions from the reactions of oxidation of both hydrogen itself and starting ethane becomes more pronounced, with water, carbon oxides, methane, and ethylene being the main reaction products. With increasing temperature, the influence exerted by small additions of hydrogen on the conversion of ethane and oxygen decreases. Performing the oxidative cracking in hydrogen at temperatures higher than 650°C demonstrated that hydrogen makes the conversion of ethane smaller and the expenditure of oxygen for oxidation of hydrogen grows.

The molecular mechanics method MM+ was used to examine the structure and properties of the inverse water-in-oil emulsion. The energies EMMB of intermolecular interactions between molecules were calculated for 3M + nH₂O systems constituted by molecules of asphaltenes, paraffins, and naphthenes, such as M = C₂₈H₁₉NO, C₁₅H₃₂, and C₁₈H₃₀, which model the structure of oil macrocomponents, and water molecules at n = 0–70. It was shown that the energy EMMB of interaction of H₂O molecules with asphaltene molecules exceeds that with paraffin and naphthene molecules. The values of EMMB were calculated for systems of paraffin and naphthene molecules with H₂O molecules. A mechanism was suggested by which an inverse emulsion is formed. The mechanism is based on the stage that yields cores composed of water molecules, around which asphaltene molecules are coordinated, with molecules of naphthenes and paraffins forming an external layer. A conclusion is made that the molecular mechanics method MM+ can be used to model the structure of a water-in-oil inverse emulsion.

Data on thermodynamic properties of liquid sodium–tin alloys are summarized, analyzed, and compared, and thermodynamic properties of solid phases are estimated. The possibilities of using tin and its alloys and compounds as anode materials for sodium-ion batteries are briefly considered.

The need for micro components/devices in the field of aerospace, automobile and medical is increasing day by day. There are various methods are available for manufacturing of such components/devices. Among the various non-traditional machining techniques, electrochemical micromachining is found to be more suitable due to the reason for its higher material removal rate, good surface quality and accuracy. In this research the microhole machining is performed on the copper inorganic work piece. During the machining, electrolyte has been heated using ultraviolet (UV) rays. L₁₈ orthogonal array (OA) is planned using electrolyte concentration (C_e), machining voltage (V_m), duty cycle (C_d) and electrolyte temperature (T_e). The process parameters are optimized using technique for order of preference by similarity to ideal solution (TOPSIS) and grey relational analysis (GRA). Two optimal parametric combinations are obtained, such as 30 g L^–1, 7 V, 65% and 34°C using TOPSIS and 30 g L^–1, 9 V, 55% and 36°C using GRA. Based on ANOVA the electrolyte concentration shows nearly 65% contributions among the other process parameters. Additionally Scanning electron microscope (SEM) images have been used for the better understanding of roundness of micro-hole.

Thermal treatment of a product formed in the interaction of activated aluminum with water yielded alumina having a specific surface area of 250 m² g^–1, uniform pore size distribution, and average pore size of 7.8 nm. A platinum catalyst on its basis exhibited high activity and stability in propane conversion at a selectivity of propylene formation higher than 90% and suppressed reaction of hydrogenolysis of C–C bonds.

Mechanically activated dehydrochlorination of polyvinyl chloride in the presence of lithium, potassium, and calcium hydroxides was studied. Short joint mechanical treatment of polyvinyl chloride with the above bases in a high-energy centrifugal planetary mill for 5–10 min ensures the formation of polymers with a conjugated double bond system (polyvinylenes). Their subsequent heat treatment at temperatures of up to 400°С yields amorphous carbon structures. Activation of the resulting material in a CO₂ medium at 850°С results in the formation of a micro-, mesoporous carbon material with the prevalent mesopore volume. The results obtained can serve as a basis for the development of technologically acceptable procedures for polyvinyl chloride waste processing to obtain demanded carbon materials without dioxin formation.

Dissolution of nepheline-containing raw materials was studied in relation to the concentrations of dry formulation and aqueous acid solutions. The conditions in which a low-concentration composite coagulant‒flocculant can be obtained on the basis of a nepheline concentrate were determined. These conditions make it possible to synthesize the composite reagent in conventional reagent facilities of wastewater-treatment stations and, simultaneously, to take technological measures for improving the quality of purified water, with the secondary contamination of water by compounds of aluminum minimized.

Magnetic sorbent MNP@CNT was synthesized on the basis of magnetic nanoparticles of magnetite (MNPs) and carbon nanotubes (CNTs). The sorbent was studied in extraction of toxic elements from aqueous media and its synthesis conditions were optimized. Isotherms of sorption of the metal ions under study from aqueous solutions were plotted in relation to their concentrations and solution pH values. The optimal conditions for extraction of Pb(II), Cr(III), and Bi(III) at pH 6 and Cd(II) at pH 4.5–5.0 were found. It was shown that the sorption capacity of the MNP@CNT sorbent for the elements under study is comparable with the capacity of carbon nanotubes, being 4.0, 3.8, 3.5, and 3.5 mg g^–1 for Bi(III), Pb(II), Ct(III), and Cd(II), respectively. An important advantage of the magnetic composite sorbent over carbon nanotubes is the simple separation of the liquid and solid phases, compared with the conventional column variation of the solid-phase extraction. The resulting composite magnetic sorbent can be used both for analytical purposes, to preliminarily concentrate impurities, and for purification of various technological media and water basins in the environment to remove toxic elements.

A series of porous coordination polymers of Zn-oxac-ATaz (oxac: oxalic acid and ATaz: 3-amino,1,2,4- triazole), Zn-oxac-Taz (Taz: 1,2,4-triazole), and combination of ATaz–Taz ligand with 0.5 molar ratio X of Zn-oxac-Taz/ATaz were synthesized under magnetic fields. There is no even significant XRD pattern change of Zn-oxac-Taz 6T but there are noticeable changes in the morphology of irregular agglomerates at zero field to rectangular-prism crystals with smooth surfaces. Compared to the zero field, it is obvious that magnetic fields also bring significance morphology and crystal orientation change of Zn-oxac-ATaz 4T and Zn-oxac-Taz/ATaz 4T with growth to prolong rectangular morphology. Zn-oxac-Taz/ATaz 0T adsorbed more CO₂ (135 mg g^–1) at 303 K after heating in a vacuum at 333K for 12 h. It is suggested that the integration effects of pore space and amine group presences inside the frameworks induce to enhance carbon dioxide adsorption amount. Furthermore, due to magnetic fields the CO₂ adsorption by Zn-oxac-Taz/ATaz 4T also increases to 155.46 mg g^–1 and Langmuir surface areas developed is 467 m² g^–1. Magnetic fields cause interesting phenomena observed in XRD pattern and through morphological changes inducing the enhancement carbon dioxide (CO₂) capture in these porous coordination series.

A promising method based on solution combustion was considered for preparing a catalyst for the synthesis of nanofibrous carbon and hydrogen. The temperature profile of the hexamethylenetetramine combustion front in the bulk of the catalyst precursor is presented on the basis of process imaging. Catalyst samples were tested in a quartz tubular reactor at a temperature of 550°С and a pressure of 1 atm with methane as reaction medium. The influence exerted by the procedure for introducing hexamethylenetetramine into the nitrate base of the catalyst on the performance of the catalyst precursor in synthesis of nanofibrous carbon was studied. The catalyst was obtained as solid foam-like agglomerate (mean size of NiO particles 13.8–35.2 nm).

Dynamic and isothermal thermogravimetry were used to examine under atmospheric pressure the migration of a nitrate ester plasticizer from samples of K-1 model formulation simulating the solid rocket propellant of the NEPE type into the ambient environment (argon). The mass evaporation rate of the plasticizer from the sample surface and the loss of its mass in the stage of migration limited by the diffusion rate were estimated. The diffusion coefficients of the plasticizer were determined at temperatures of 55 to 100°C.

The purpose of the current study is to optimize the batch reactor performance model using multiple regression analysis for saponification of ethyl acetate by sodium hydroxide. Reaction temperature, reactor volume, agitation rate and reactants initial concentration were the main parameters examined including their interaction effect. Selected process response was the reaction conversion with respect of NaOH. Regression analysis was used to screen out the insignificant factors and the reaction temperature and volume were found to have insignificant effect on the response at the 5% selected significance level (α = 0.05). As a result of multiple regression analysis, agitation rate and reactants concentration were found to be significant operating parameters. The dependence of reaction conversion (response) on agitation rate and concentration was explained by a second order polynomial model and it was concluded that regression model with second order polynomial was good enough to fit the experimental data. The maximum conversion (99.5%) was obtained under optimum operating conditions of agitation rate (70 rpm) and reactants concentration (0.05 M) as evident from surface contours.