Vol 91, No 7 (2018)

The effect of impurities on the thermal decomposition kinetics of mineral fertilizers based on (NH₄)₂HPO₄ in self-generated atmosphere was studied by the methods of thermogravimetry and differential thermal analysis. Results are presented of isothermal measurements made in the temperature range 100–110°C. An analysis of the experimental data made it possible to suggest reaction models of the decomposition and to reveal a dependence of the activation energy on the degree of decomposition. A strong deviation of the temperature dependence of rate constants from the Arrhenius law was observed. Conclusions were made on the basis of the study about the influence exerted by impurities on the thermal decomposition of mineral fertilizers based on (NH₄)₂HPO₄ in the self-generated atmosphere and reasons for the deviation from the Arrhenius law.

Sorption properties of commercial hematite (α-Fe₂O₃) for divalent copper ions were studied. This was done with a model solution of copper(II) sulfate additionally containing 400 mg L^–1 of sodium sulfate. It was shown that the hematite sample under study is a good sorbent for removal of divalent copper ions from aqueous solutions. The process of Cu²⁺ sorption is described by the Langmuir equation. The parameters of this equation were determined at various pH values of the model solution and compared with similar published parameters for other hematite samples.

Sorption extraction of anionic surfactants NaDDS and NaDBS on freshly formed iron(III) and aluminum(III) hydroxides and on a highly dispersed activated carbon of OU-B brand was experimentally studied. It was shown that NaDDS is the most fully sorbed on Al(OH)₃ and OU-B, whereas on Fe(OH)₃, the maximum sorption is observed for NaDBS. The electroflotation extraction of anionic surfactants and poorly soluble iron(III) and aluminum(III) hydroxides was examined and the influence exerted by the following factors (pH, nature of electrolyte, surfactant concentration) on the degree of extraction of these substances was analyzed. In addition, electroflotation extraction of OU-B in the presence on nonferrous metal hydroxides and surfactants of varied nature from aqueous solutions was performed. The results obtained were used to develop a technological scheme for electroflotation of complex-composition wastewater.

The state of the art in production and consumption of carbon sorbents and the main directions of research in this field are considered. Approaches to preparing sorbents derived from lignin are summarized. The advantages and drawbacks of lignin as a raw material and prospects for the progress in this field are discussed.

Deposition of chromium coatings from an electrolyte based on a deep eutectic solvent (new type of ionic fluids) was studied. The electrolyte used to deposit the coatings contained choline chloride, chromium(III) chloride, and addition of water. It was found that introduction of a certain amount of water makes it possible to raise the electrical conductivity and reduce the viscosity of the electrolyte to values acceptable for its practical application. The manner in which the electrolysis conditions affect the current efficiency for chromium deposition was determined. It was shown that uniform hard chromium coatings with good adhesion to the substrate can be deposited.

Methods for synthesis of N-morpholinoethyl methacrylate were compared. It was shown that the monomer produced by acylation of N-morpholinoethanol with methacrylic acid anhydride or methacryloyl chloride spontaneously polymerizes in storage. The possible reasons for the spontaneous polymerization of N-morpholinoethyl methacrylate produced by the acylation method were considered. The conditions in which a stable-in-storage monomer can be obtained in 86–88% yield by the method of re-esterification of methyl methacrylate with N-morpholinoethanol were determined.

The main applications and ways of utilization of industrial lignins, which are a large-tonnage waste from pulp and hydrolysis plants, are considered. The first group of methods includes nonthermal methods of lignin processing with preservation of the natural polymeric structure of lignin. The second group of methods includes thermal methods for lignin processing with the formation of low- and high-molecular-mass compounds and combustible gas. The largest-tonnage application fields of lignins are building, mining, metallurgical, oil-extracting, and agro industries, and also water treatment.

The possibility of preparing new polyampholyte polymers based on polypropylene glycol fumarate–acrylic acid–dimethylaminoethyl methacrylate terpolymers was demonstrated. The main relationships of radical terpolymerization in dioxane, including binary systems participating in the terpolymerization, were studied. The block lengths, transition probabilities, and Harwood block structure parameter were calculated for the terpolymers from the copolymerization constants for the binary systems. These parameters reflect the arrangement of the macroradicals in the chain. The morphology of the polymer surface was studied by scanning electron microscopy, and the surface pore size was estimated. The influence of organic solvents and pH on the sample swelling was studied, and the isoelectric point (pH 6.00) of the terpolymer was determined.

The influence of carbon microfiber on the physicomechanical, thermophysical, and fireproof characteristics of elastomeric compositions based on ethylene propylene diene rubber is considered. Microfibrous filler contributes to the manifestation of the effect of “micro-reinforcement,” which leads to an increase in the heatprotective properties of the material due to the increase in the strength of coke. The correction of microfibers with a phosphorus-boron-containing oligomer enhances the carbonization of the material, which leads to an increase in the warming-up time of the unheated sample surface by 8–10% and a decrease in the linear combustion rate by 10–15% compared to known analogues.

In this study, the irradiated ultra-high molecular weight polyethylene (UHMWPE) components doping with graphene oxide (GO) were immersed in simulated body fluid (SBF) environment at 37°C for 6 months, and their surface properties were studied by ball indentation, scratch, and wetting tests. The results show that both the irradiation cross-linking treatment and the addition of 0.5 wt % GO can increase the indentation hardness and scratching coefficient of the surface of UHMWPE composites, and wettability of it becomes better. After soaking in SBF, the ball indentation and scratch coefficient of irradiated GO/UHMWPE nanocomposites decreased by 12.4 and 10.0%, respectively. Which may due to a swelling action and the oxidative degradation occurred on the surface of GO/UHMWPE nanocomposites. However, irradiation cross-linking and filling with GO can prevent the macromolecules from penetrating into UHMWPE base material and materials, thereby reducing the rate of swelling and oxidative degradation.

Reaction of N-tert-butyl-2-benzothiazolylsulfenamide with trimethylolpropane triglycidyl ether was performed, and the product was characterized and studied as an additive to rubber. Interaction of this additive with rubber was studied by the method of equilibrium swelling. The additive was found to increase the amount of cross-links in the polymer matrix and to improve the process characteristics of rubber stocks with silica, decreasing their viscosity and vulcanization time and enhancing the resistance to scorching. The use of this additive allows preparation of vulcanized rubbers with higher modulus, compared to the rubbers modified with the product of the reaction of methacrylic acid with trimethylolpropane triglycidyl ether.

Novel water-based biodegradable polyurethane dispersions with an aim to develop environmentally friendly materials, including medicine, various industries, have been prepared in this study. Biodegradable ionic polyurethanes (IPU) were synthesized based on polyols from renewable resources, such as castor oil (CO), in the presence of a polyester polyol and polyethylene glycol (PEG) with hydrophilic property and 1,6-hexamethylene diisocyanate. 1,4-Butanediol and dibutyltin dilaurate, were used as a chain extender and catalyst, respectively. The comprehensive investigations of the structure and properties of five types of synthesized polyurethanes demonstrated biodegradability relationship of these polyurethanes with their structure and composition. In this research effects of different types and content of polyols on biodegradability and physico mechanical properties of prepared PUDs were investigated. The structure, properties and physico mechanical and application behavior of mentioned materials were characterized by ¹H NMR, FTIR spectroscopy, thermogravimetric analysis (TG/DTG) and dynamic mechanical thermal analysis (DMTA). The adhesion properties were measured by pull off test as well. Particle size was measured by dynamic light scattering (DLS) methods. The biodegradability of prepared polyurethane dispersions was confirmed by water uptake, hydrolytic and enzymatic degradation in phosphate buffer saline (PBS) with lipase enzyme in PBS. Results showed that by the incorporation of natural components into the polymer chain, adjusting of hydrophilic and hydrolytic liability properties of soft segments and especial relevant designs, useful polyurethane can be synthesized with desirable property of biodegradability and dispersion stability. Except for one sample, other samples were decomposed totally in enzymatic media.

Carbon nanomaterials (fullerite, detonation nanodiamonds, Taunit, fullerenol, fullerene-containing black) were decorated with platinum group metal nanoparticles in situ in one step by low-temperature combustion (~250–270°С) of a powdered mixture of platinum metal acetylacetonate [Pt-M(асас)_n, Pt-М = Pt(II), Pd(II), Rh(III), Ir(III), acac = CH₃COCHCOCH₃, n is the oxidation state of Pt-М] with carbon nanomaterials in air. As shown by thermal analysis, the process is based on thermal oxidative degradation of the organometallic complex, catalyzed by carbon nanomaterials, with oxidation (combustion) of the organic moiety and release of the metal into the condensed phase. The thermal process in an open system occurs in the glowing mode (210–250°С); the size of the nanoparticles formed is 7–30 nm. Under the conditions restricting the air access to the reaction mixture and free outflow of gaseous products formed by oxidation of acac ligands, the nanoparticle size decreases to 3–10 nm. The particle size depends on the metal amount in the initial powder mixture and on the support morphology.

Nitration of α-, β-, and γ-cyclodextrins with nitric acid of various concentrations was studied. The nitration occurs similarly for all the three cyclodextrins studied. The influence of the reaction conditions on the degree of substitution of hydroxy groups in cyclodextrin by nitrate groups was examined. The composition and degree of substitution of the nitration products depend not only on the nitric acid concentration, but also on the molar ratio of HNO₃ to OH groups. The results obtained allow optimization of the procedure for preparing cyclodextrin nitrates with definite topology of substitution of cyclodextrin hydroxy groups.