Maksym Iurzhenko

Propriétés électriques, thermomécaniques et de sorption de systèmes hybrides organique-inorganique basés sur des oligomères uréthane et silicates: L'objectif de cette recherche est d'établir des mécanismes de formation de la structure des systèmes hybrides organique-inorganique à base des oligomères uréthane et silicates en fonction de la réactivité de la composant organique, d'identifier l'impact de l'organisation structurelle du OIS obtenue sur leurs propriétés électriques et thermomécaniques, de sorption et de l'activité du capteur. La signification pratique des résultats est la détermination de l'impact de la réactivité composant organique sur la structure des systèmes hybrides polymère organique-inorganique avec la possibilité d'obtenir des matériaux avec des propriétés spéciales prévisibles. Les résultats peuvent être utilisés comme base scientifique pour comprendre l'interconnexion de la structure, les propriétés et les moyens de leur régulation en direction de systèmes hybrides polymère organique-inorganique. La sensibilité très élevée pour les différents types de solvants, qui, combiné avec une haute sélectivité, a été révélé pour les systèmes de synthèse, la possibilité de leur utilisation pratique en tant que matières capteur existe.

Hydrogel materials based on poly(vinyl alcohol) (PVA) and silver nanoparticles are used as wound dressings. However, chemical reducing agents, ultraviolet irradiation, and radiation irradiation are mainly used to reduce silver ions to nanoparticles in hydrogel dressings. In this study, polymeric cryogel materials based on poly(vinyl alcohol), hyaluronic acid (HA), and Ag₂O nanoparticles were synthesized by reducing silver ions with hyaluronic acid followed by freezing and thawing of the samples. Structural features, thermophysical, mechanical, antimicrobial, cytotoxic and genotoxic properties of PVA-Ag-HA polymeric cryogel materials were studied by wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical tests, antimicrobial, cytotoxic and genotoxic studies. Studies of cryogel materials using wide-angle X-ray scattering showed that the PVA-HA composite has a higher degree of crystallinity compared to the pure PVA. It was found that during the formation of samples, silver ions are reduced in the polymer systems PVA-HA-Ag⁺ at T = 85 °C, within 1 h with the formation of Ag₂O nanoparticles. The addition of hyaluronic acid to the composition of PVA cryogel increases the water absorption of the samples, and a decrease in the freezing time and concentration of nanoparticles leads to an increase in the water absorption of PVA-HA cryogel materials. The thermal stability of all the studied samples, except HA, practically does not change up to a temperature of 200 °C. For the studied cryogel materials, the tensile strength increases with increasing freezing time and concentration of Ag₂O nanoparticles up to 0.5 wt %. PVA-HA-Ag₂O cryogel nanocomposites exhibited antimicrobial activity against Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli at silver oxide nanoparticle concentrations of ≥0.05 wt %. The obtained nanocomposites with low concentrations of Ag₂O nanoparticles were not toxic. They did not inhibit the viability of MDCK and L-929 cell cultures at silver oxide nanoparticle concentrations of ≥0.1 wt %. When studying the genotoxic properties of cryogel materials, no mutagenic and clastogenic activity was detected. The obtained materials have potential applications for the creation of dressings for the treatment of wounds of various infectious nature.

Currently, the determination of the molten zone thickness in HDPE pipes during butt fusion welding primarily depends on experimental and numerical methods, leading to high costs and reduced efficiency. In this study, a mathematical (MM) model based on Neumann’s solution for the melting of a semi-infinite region was developed to efficiently predict the average molten zone (AMZ) thickness of HDPE pipes under varying heating temperatures and heating times while incorporating the effects of heat convection. Additionally, a two-dimensional CFD model was constructed using finite element analysis (FEA) to validate the MM model. Welding pressure was not considered in this study. The effects of heating temperature, heating time, and heat convection on the AMZ thickness in HDPE pipes were systematically analyzed. The heating temperature at the heated end of HDPE ranged from 190 °C to 350 °C in 20 °C increments, with a temperature of 28 °C as the ambient and initial setting, and the heating time was set to 180 s for both the MM and CFD models. The results demonstrate a strong correlation between the AMZ thickness predictions from the MM and CFD models. The relative error between the MM and CFD models ranges from 0.280% to 10,830% with heat convection and from −2.398% to 8.992% without heat convection. Additionally, for the MM model, the relative error between cases with and without heat convection ranges from 0.243% to 0.433%, whereas for the CFD model, it varies between 1.751% and 3.189%. These findings confirm the reliability of the MM model developed in this study and indicate that thermal convection has a minimal impact on AMZ thickness prediction for large-diameter, thick-walled HDPE pipes.

According to statistical data from the National Military Medical Clinical Center for the period from February to May 2022, bone defects in gunshot fractures accounted for 76 % of cases, with defects exceeding 6 cm — classified as critical — found in 28 % of cases. Currently, the "gold standard" for reconstructing critical bone defects is the induced membrane technique, also known as the two-stage Masquelet technique. The most promising substitute for autologous bone is considered to be biphasic bioactive ceramics. In this study, we aimed to evaluate the feasibility of reconstructing critical bone defects resulting from combat trauma using a modified bioactive ceramic-autograft mixture during the second stage of the Masquelet technique, combined with additive manufacturing technologies. The study included a sample of 36 patients with critical bone defects who underwent reconstruction using the Masquelet technique. During the second stage, the defect was filled with a mixture of calcium phosphate ceramics (CPC) and autologous cancellous bone. We analyzed the treatment outcomes of patients with critical bone defects caused by combat-related injuries over the past 2.5 years who received treatment at the Dobrobut Medical Center. The evaluation criteria included pain levels, range of motion, axial load capacity, functional recovery (work capacity), and radiological signs of callus formation, deformities, graft migration, or remodeling. After 12 months of follow-up: Complete functional recovery (clinically and in range of motion) was achieved in 28 (78 %) patients. Partial functional recovery was observed in 7 (17 %) patients. Significant functional impairment requiring additional surgical interventions occurred in 1 (5 %) patient. Conclusions. Based on our experience, the use of a CPC-autograft mixture in the two-stage reconstruction of critical diaphyseal bone defects provides positive treatment outcomes in most clinical cases. The integration of 3D modeling and biodegradable materials enhances the range of possibilities for performing bone grafting procedures and simplifies technical challenges in reconstructive surgery.

Pyroresistive composites based on high-density polyethylene (HDPE) and polyvinyl chloride (PVC) were studied, which contained two types of filler, carbon black (C) or chopped carbon fibers (CC) in an amount of 8 vol.%. It was shown that when an electric voltage is applied to a composite sample, Joule heat is released, which heats the composite to an equilibrium temperature Te. The dependence of the equilibrium temperature on the voltage U is described by the quadratic equation Te = T0 + aU2, and on the electric power P supplied to the sample by the linear equation Te = T0 + b·P, where T0 is the initial temperature, a, b are the coefficients. However, when the voltage is increased above certain values, a deviation from the quadratic law is observed, and the achievable temperature Te is significantly lower than that calculated by the equation. The reason for the deviations is the manifestation of the PTC effect (positive temperature coefficient of resistance), as a result of which an increase in temperature due to an increase in voltage causes thermal expansion of the polymer matrix, which leads to the destruction of the conductive chains of the filler and an increase in the resistance of the sample. A comparison of the curves for composites based on HDPE and PVC demonstrates a significantly higher level of influence of the PTC effect for composites based on PE, and also a higher influence for composites containing carbon fibers compared to carbon black. A comparative calculation of the amount of energy Q required to heat a composite sample to Te and the amount of Joule thermal energy E released in the sample when electrical power is supplied to it showed that the energy Q is 20% of the Joule thermal energy E released in the sample, i.e. the main part of the Joule thermal energy (80%) is dissipated to the environment. The value of the E/Q ratio depends on the intensity of exchange with the environment, as well as on the geometry of the sample. The possibilities of contact welding of plastics using a heating element (HE) made of pyroresistive material are shown. This method demonstrated the maximum adhesive strength of the welded joint, which is comparable to the strength of the welded polymers, both for HDPE and PVC, and is promising for use in various industries.

This study developed a technical task associated with the formation of welded joints based on biodegradable polymers and their subsequent physicochemical characterization. The primary objective was to establish the effect of the welding process and modification of natural poly(3-hydroxybutyrate) (PHB) with N,N-dibutylundecenoylamide (DBUA) as a plasticizing agent on the structure and properties of PHB-based biopolymer materials as well as the process and structure of welded joints formation using ultrasonic welding technique. The weldability of biodegradable layers based on PHB and PHB/DBUA mixture was ultrasonically welded and optimized using a standard Branson press-type installation. The effect of the DBUA plasticizer and welding process on the structure of PHB-based biodegradable material was investigated using scanning electron microscopy, X-ray diffraction, FT-IR spectroscopy, differential scanning calorimetry, and thermomechanical analysis. The results confirmed that the DBUA acted as an effective plasticizer of PHB, contributing to lower crystallinity of the PHB/DBUA mixture (63%) in relation to the crystallinity degree of pure PHB film (69%). Ultrasonic welding resulted in an additional increase (approximately 8.5%) in the degree of crystallinity in the PHB/DBUA in relation to the initial PHB/DBUA mixture. The significant shift toward lower temperatures of the crystallization and melting peaks of PHB modified with DBUA were observed using DSC concerning pure PHB. The melt crystallization process of PHB was affected by welding treatment, and a shift toward higher temperature was observed compared with the unwelded PHB/DBUA sample. The butt-welded joints of biodegradable PHB/DBUA materials made using the ultrasonic method tested for tensile strength have damaged the area immediately outside the joining surface.

The paper presents the results of complex studies of the influence of mixtures of hydrogen gas with natural gas in the ratios of 10%Н₂/90%СН₄ and 20%Н₂/80%СН₄ on the operational and thermophysical characteristics of PE-80 polyethylene pipes and their material Research was conducted on an experimental stand, the diagram of which is attached. The results of comprehensive strength and thermophysical studies of the material of PE-80 polyethylene pipes, which were previously operated in the current gas distribution networks of Ukraine for 15 years, after 6 months of hydrogen exposure, are presented. In order to indicate possible changes in the properties of the material, the same complex of studies was carried out before hydrogen exposure of the samples. The influence of gas mixtures on the thermophysical properties of polyethylene pipes has been established, which is manifested in the reduction of the size of polyethylene crystallites and their orderliness in the volume of pipe walls under the influence of gas mixtures. At the same time, the appearance of crystallites of a new shape was found on the surface of the inner wall of the pipes. It is assumed that this may be caused by the competing action of methane and hydrogen molecules. In the course of conducting hydraulic tests on the resistance of pipes to internal pressure and mechanical studies on uniaxial tension, it was determined that all pipe samples, according to their strength characteristics, meet the requirements of regulatory documents issued for polyethylene pipes used for natural gas transportation. The relationship between the concentration of hydrogen in the mixture and the degree of its influence on the strength characteristics of the samples was established. No changes in the chemical structure of the material of polyethylene pipes were detected. It should be noted that the given results are only the beginning of a more detailed study, during which it is also planned to investigate the effect of hydrogen mixtures on technical polyethylenes after 12 and 24 months of hydrogen exposure. Bibl. 17, Fig. 11, Tab. 2.

Infectious diseases caused by viruses and microorganisms continue to be one of the biggest health problems worldwide, despite the rapid progress in the creation of drugs and the development of pharmaceutical technologies. The risk of complications and the spread of infections in society remains high. Scientific research and the fight against viral infections, in particular with a large group of respiratory diseases caused by viruses, such as influenza viruses, parainfluenza viruses, respiratory sensitivities, adenoviruses, rhinoviruses, coronaviruses, etc., occupy an important place in modern medicine. Due to the nature, characteristics and biological and physical properties of viruses, the issues of combating them are very acute. Microorganisms resistant to many antimicrobial agents are also developing (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, etc.). Therefore, today there is an urgent need for new materials with a higher antiviral and bactericidal effect, less toxicity for humans and the environment (ecology, medicine and food industry). Silver-containing biomaterials in various forms (powders, films, solutions, products formed by 3D printing technology) with effective antimicrobial and antiviral effects have been developed. The materials are made on the basis of polyelectrolyte complexes of polysaccharides (pectin – chitosan, pectin – cationic starch, carboxymethylcellulose – cationic β-cyclodextrin, anionic starch – cationic starch) and polylactide biopolymer. Silver nanoparticles in the composition of composites were formed in environmentally friendly ways: by reduction silver ions with extracts of natural substances (green tea, mint, propolis, pectin), by methods of thermochemical reduction or cathodic sputtering of silver nanoparticles from silver foil onto the surface of the film. The structure, morphology, obtained materials and their antimicrobial, antiviral and cytotoxic properties were studied. The relationship between the structure and morphology and the protective properties of the obtained materials was studied.