THEORETICAL BASIS OF CHEMICAL TECHNOLOGY
The parameters of the binary energy interaction of the UNIQUAC model of hydrogen isotopic mixtures D2–T2, D2–DT, and DT–T2 are determined. The UNIQUAC model is adequate in relation to experimental data on the coefficient of separation. Due to systematic deviations in the theoretical Sherwood and ideal models, they are not suitable for further calculations of phase equilibrium of isotopic mixtures of hydrogen D2–T2, D2–DT, DT–T2, and D2–DT–T2.
Objectives. Determination of the parameters of the binary energy interaction of the (UNIversal QUAsiChemical) UNIQUAC model on the basis of mathematical processing of experimental literature data on the phase equilibrium of hydrogen isotopic mixtures D2-T2, D2-DT, DT-T2 to calculate the activity coefficients of the components D2, DT, and T2.
Methods. The method of successive approximations was used in junction with the “from stage to stage” method, which consists in calculating a single evaporation process on a theoretical plate.
Results. Equations were written for calculating the activity coefficients of hydrogen isotopes on the basis of the Sherwood theory as applied to binary D2-T2, D2-DT, DT-T2 and ternary D2-DT-T2 hydrogen isotope mixtures. The graphical dependences of the activity coefficients and separation coefficients of mixtures D2-T2, D2-DT, and DT-T2 are compared in the range of the concentration of a highly volatile component from 0 to 100 mol % at atmospheric pressure for three options: ideal mixtures; non-ideal mixtures using the Sherwood theory; non-ideal mixtures on the basis of the UNIQUAC model. The dependences of the separation coefficients a were found to be similar for all binary isotopic mixtures. However, when considering mixtures as ideal, a increases.
According to Sherwood's theory, a remains a practically constant value, which is independent of the composition of the mixture. The UNIQUAC model predicts a decrease in a with an increase in the concentration of a less volatile component in the mixture. The profile of the distribution of hydrogen isotopes D2, DT, and T2 of a three-component mixture D2-DT-T2, along the height of a distillation column operating in a closed mode was calculated for three variants. It was accepted that: pressure along the height of the column is constant and equal to atmospheric 760 mm Hg. Art.; number of theoretical plates 21; concentration of components in the liquid phase on the first plate (stage), in mol %: XD₂ = 65; XDT= 10; XT₂= 25; the accuracy of calculating the composition of the vapor phase is 10-10.
Conclusions. The parameters of the binary energy interaction of the UNIQUAC model of hydrogen isotopic mixtures D2-T2, D2-DT, and DT-T2 are determined. The UNIQUAC model is adequate in relation to experimental data on the coefficient of separation. Due to systematic deviations in the theoretical Sherwood and ideal models, they are not suitable for further calculations of phase equilibrium of isotopic mixtures of hydrogen D2-T2, D2-DT, DT-T2, and D2-DT-T2.
The influence of both the number of processing cycles and pressure arising during pumping dark oil products through a diffuser on the change of fractional composition of oil products was an-alyzed. It has been shown that the gradient of pressure has a greater impact on the increase of the yield of fractions boiling away up to 400°C than the number of cycles. The equation allowing iden-tifying the possible yield of the TIBP–400°C fraction after its cavitation processing under various conditions of the process according to the physicochemical characteristics of the feedstock was proposed.
Objectives. The reduction of the anthropogenic burden on the environment is generally associated with the transition to alternative energy sources. However, some of these have only regional significance, while the effectiveness of others remains doubtful. On this point, innovative processes aimed at increasing the depth of oil refining may be equally important for reducing the carbon footprint. Wave-based technologies such as cavitation may also be included in these processes. Among the various methods for inducing such cavitation phenomena in oil refining, hydrodynamic approaches are especially promising. It has been shown that the treatment effectiveness increases with greater pressure or when augmenting the number of cavitation processing cycles. The aim of this work is to identify the factor (i.e., pressure gradient or number of treatment cycles) having the greatest influence on the change of the characteristics of the oil product.
Methods. Cavitation phenomena were created by pumping dark oil products through a diffuser. The pressure gradient ranged from 20 to 50 MPa, while the number of cavitation processing cycles varied from 1 to 10. The influence of cavitation conditions on the change of fractional composition of petroleum products was analyzed. Target fractions are those having a boiling point up to 400°C.
Results. It is shown that increased pressure generated in the diffuser leads to a linear increase in the yield of desired cuts. The dependence of the yield of these fractions on the number of processing cycles is described by the growth model with saturation. A proposed equation describes the influence of pressure and number of cycles on the yield of the fractions from initial boiling point temperature (TIBP) to 400°C following cavitation processing of dark oil products. Some of the coefficients of this equation have been associated with the physicochemical characteristics of the feedstock.
Conclusions. An equation for predicting the maximum possible yield of the TJBP-400°C fraction as a result of cavitation processing under different conditions of the process is proposed according to the physicochemical characteristics of the feedstock. The prediction error did not exceed 12%. The equation analysis and comparison of energy consumption between different process regimes shows that a higher yield of the target product is achieved by increasing pressure gradient rather than the number of processing cycles.
CHEMISTRY AND TECHNOLOGY OF ORGANIC SUBSTANCES
The revealed differences in the reactivity of the studied sulfocationites (Amberlyst™ 15, Amberlyst™ 70, and TULSION® 66) confirm the well-known theoretical positions, according to which the kinetic pseudo-homogeneous model of the esterification process of hydroxy acids in excess of aliphatic alcohols is based on the law of acting masses and depends on the specific surface area of the catalyst, which for Amberlyst™ 15 is of the greatest importance as compared to Amberlyst™ 70 and TULSION® 66 (m2/g): 53:36:35, respectively.
Objectives. To find an effective way for obtaining triamyl citrate, an environmentally friendly, biodegradable citric acid ester used as a plasticizer for PVC-based polymer compositions.
Methods. The possibilities of heterogeneous catalysis were analyzed using the case study of three commercial samples of macroporous sulfocationites (Amberlyst™ 15, Amberlyst™ 70, and TULSION® 66). Homogeneous catalysis was studied using the example of orthophosphoric acid (H3PO4), while self-catalysis was investigated during esterification of citric acid with amyl alcohol (ROH). The syntheses were carried out under identical conditions: T = 110 °C, the ratio of CA:ROH = 1:5 (mol) amount of catalyst 1 wt % on the reaction mass in a thermostatically controlled reactor of ideal mixing with continuous distillation of the resulting water.
Results. It was found that in all variants (even under self-catalysis conditions), the conversion of citric acid in 180 min reached 94–99%. Triamyl citrate was formed after 9 h with a yield of 90% only when using a homogeneous catalyst (H3PO4) and in the presence of a heterogeneous catalyst sample (Amberlyst ™ 15).
Conclusions. The revealed differences in the reactivity of the studied sulfocationites (Amberlyst™ 15, Amberlyst ™ 70, and TULSION® 66) confirm the well-known theoretical positions, according to which the kinetic pseudo-homogeneous model of the esterification process of hydroxy acids in excess of aliphatic alcohols is based on the law of acting masses and depends on the specific surface area of the catalyst, which for Amberlyst ™ 15 is of the greatest importance as compared to Amberlyst ™ 70 and TULSION® 66 (m2/g): 53:36:35, respectively.
BIOCHEMISTRY AND BIOTECHNOLOGY
The C60/poly-N-vinylpyrrolidone (C60/PVP) complex, representing a mixed-type lactate dehydrogenase inhibitor, was shown to inhibit (lactate dehydrogenase) LDH activity, as well as contributing to a decrease in lactate concentration and an increase in the concentration of pyruvic acid and glucose in blood serum when administered per os to mice. The inhibitory effect of PVP on LDH activity was revealed in both in vivo and in vitro investigations. In vivo, PVP contributes to a decrease in the concentration of lactate in the blood.
Objectives. The study aimed to investigate the biological activity of the C60/poly-N-vinylpyrrolidone (C60/PVP) complex representing a water-soluble fullerene derivative. In vitro and in vivo techniques were used to analyze the effect of the C60/PVP complex on the activity of lactate dehydrogenase (LDH) and evaluate changes in the biochemical parameters of blood serum when per os administered to mice.
Methods. In order to determine the activity of a commercial LDH preparation and study the kinetics of this process, the standard Warburg photometric method was used. To assess the effect of polyvinylpyrrolidone (PVP) and the C60/PVP complex on some biochemical parameters in vivo, a study was conducted on two-month-old male white mongrel mice weighing 20 ± 3 g. Determination of biochemical parameters of blood serum was carried out using a semi-automatic biochemical analyzer according to standard methods.
Results. The effect of the C60/PVP complex on LDH activity was studied along with changes in the biochemical parameters of mouse blood serum characterizing carbohydrate metabolism. As well as increasing the glucose and pyruvic acid content, the C60/PVP complex was found to reduce lactate content and LDH activity in blood serum along with in vitro LDH activity according to the type of mixed inhibition.
Conclusions. The C60/PVP complex and PVP were shown to exhibit biological activity in vitro and in vivo. The C60/PVP complex, representing a mixed-type LDH inhibitor, was shown to inhibit LDH activity, as well as contributing to a decrease in lactate concentration and an increase in the concentration of pyruvic acid and glucose in blood serum when administered per os to mice. The inhibitory effect of PVP on LDH activity was revealed in both in vivo and in vitro investigations. In vivo, PVP contributes to a decrease in the concentration of lactate in the blood. The less pronounced effect of the C60/PVP complex as compared to PVP alone may be due to the fact that C60 molecules are “hidden” in cavities formed in PVP molecules.
SYNTHESIS AND PROCESSING OF POLYMERS AND POLYMERIC COMPOSITES
A comparison of the chemical composition, structure, thermal and rheological characteristics of thermoplastic polyesterurethanes with polyesterurethane solutions widely used for the production of fibrous-porous materials and coatings of Sanpren LQ-E-6 and Vitur R 0112 grades demonstrates their practicability as production materials and coatings having a predetermined structure and a set of properties depending on the requirements and operating conditions of finished products.
Objectives. To study the structure and properties of solutions of thermoplastic poly(ether urethane)s (PEUs) to inform their potential use in the production of fibrous-porous polymer composite materials with a given structure and set of performance properties depending on the field of practical application.
Methods. The composition of PEUs was studied by attenuated total reflection infrared (ATR-IR) spectroscopy using a program for correcting the spectra on an IR Fourier spectrophotometer, as well by differential scanning calorimetry (DSC) using a heat flow calorimeter. The viscosity of PEU solutions was determined on a rotational viscometer.
Results. The chemical composition of PEUs and the nature of the formation of hydrogen bonds were studied. An analysis of the spectra demonstrates the almost complete identity of the PEUs synthesized from the same 4,4'-diphenylmethane diisocyanate. In the studied PEUs of the Vitur and Desmopan® brands, as well as Sanpren, pronounced absorption bands characteristic of urethane groups involved in the formation of hydrogen bonds are visible in the region from 1702 to 1730 cm−1. The temperature transitions and thermal stability of the investigated PEUs were determined by DSC. The influence of the ratio of rigid and flexible blocks, as well as the nature of hydrogen bonds on the melting temperatures of polymers, was shown. Analysis of the DSC curves demonstrated all the studied PEUs to have high melting points ranging from 159 to 215°C. From the studied temperature dependences of the structural viscosity of thermoplastic PEUs solutions, all solutions were established to have a minimum viscosity anomaly; the value of the logarithm of viscosity depends on the chemical composition and structure of the initial PEUs. It is shown that the viscosity anomaly of PEU solutions can be reduced with increasing temperature.
Conclusions. A comparison of the chemical composition, structure, thermal and rheological characteristics of thermoplastic PEUs with PEU solutions widely used for the production of fibrous-porous materials and coatings of Sanpren LQ-E-6 and Vitur R 0112 grades demonstrates their practicability as production materials and coatings having a predetermined structure and a set of properties depending on the requirements and operating conditions of finished products.
This paper is a review of modern materials based on biodegradable polymers used in modern conditions as bone implants as well as the paper analyzes scientific areas in which the development of implants is carried out taking into account the basic properties of the materials from which they are made.
Objectives. To discuss the main problems and prospects of creating modern osteoplastic materials based on polymer compositions used for bone surgery.
Methods. This review summarizes the research works devoted to the creation of materials used for bone implants and issues involved in their practical testing, as well as analyzes and synthesizes data of scientific articles on the following topics: rationale for the use of biodegradable materials in bone surgery; biodegradation and bioreparation bone graft processes; requirements for degradable polymer composite materials (PCMs) for biomedical applications; overview of polymeric materials suitable for use in implant practice; impact of modifications of the PCM on the structure and biological activity of the material in biological media; effect of exhaust and heat treatment on the molecular structure of polyalkanoates.
Results. The most promising biodegradable resorbable materials for reparative bone surgery to date are compared. The requirements for these types of materials are formulated and a rationale for their use is provided that takes into account the advantages over traditional metal and ceramic implants. The features of the kinetics and mechanism of biodegradation of implants in their interaction with the bone biological environment of the body from the moment of implant insertion to complete wound healing are considered. As a result of the analysis, factors that may affect the activity of implant decomposition and methods of adjusting the decomposition rate and mechanical characteristics of the material, such as chemical functionalization, the creation of block copolymers, the inclusion of fibers and mineral fillers in the composite, as well as heat treatment and extraction of the composite at the manufacturing stage, were identified. Among the main factors, the influence of the structure of the composite material on its biological activity during interaction with biological media was evaluated. Of polymer materials, the main attention is paid to the most common biodegradable polymers widely used in medicine: polyhydroxybutyrate (PHB) of microbiological origin, polylactide (PLA) and other polymers based on polylactic acid, polycaprolactone (PCL). The effect of their modification by such additives as hydroxyapatite (HAP), chitin and chitosan, and beta-tricalcium phosphate (β-TCF) is considered. Materials based on PHB are concluded as the most promising due to their complete biodegradability to non-toxic products (carbon dioxide and water) and good biocompatibility. Nevertheless, existing compositions based on PHB are not without disadvantages, which include fragility, low elasticity, unstable behavior under high-temperature exposure during processing, implant molding, sterilization, etc., which requires improvement both in terms of polymer modification and in terms of composition of compositions.
Conclusions. The review considers approaches to achieving the properties of materials required for perfect implants. The main requirements for implants are optimization of the time of resorption of the osteoplastic matrix, facilitating the resorption of the osteoplastic matrix synchronized in time with the process of bone regeneration. To achieve these requirements, it is necessary to apply technologies that include modification of polymer composite materials by affecting the chemical composition and structure; introduction of fillers; use of chemical functionalization, orientation extraction, heat treatment. The success of using bone materials based on biodegradable polymers is based on an accurate understanding of the mechanism of action of various components of the implant composition and strict compliance with the tightening regulatory requirements of implantation technology.
ISSN 2686-7575 (Online)
