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The phase transition temperatures for amorphous metals based on aluminum Al87(Ni,Fe)8(REM)5 system were determined by differential scanning calorimetry (DSC). The mechanisms of formation and growth of nanocrystals in an amorphous matrix were predicted using kinetic models (Matusita model). It was found that after annealing at the temperature of stable nanocrystalline growth, an X-ray amorphous structure with a volume fraction of disordered nanocrystalline phases of solid state of Al(X), GdFe2, AlFe2Ni, GdFe2 for the amorphous metal alloy (AMA) Al87Y4Gd1Ni4Fe4 alloy and microcrystalline phases of solid state of Al(X), GdFe2 AlFe2Ni for the Al87Gd5Ni4Fe4 alloy are formed, which significantly affects the mechanical properties of the Al87(Ni,Fe)8(REM)5 system. The effect of annealing on the mechanical properties of amorphous aluminum-based alloys was investigated using Oliver-Pharr and Young's modulus methods it was found that thermal modification of AMAs: Al87Gd5Ni4Fe4 as a result of heat treatment of AMAs from 5 to 15 min., the microhardness increases from 0.20 GPa to 2.75 GPa, and when heat treated for 60 min at a temperatures of T3 = 645±5 K, 647±5 K, it decreases to 0.35 GPa and 0.45 GPa, respectively.

In order to compare the kinetic characteristics of the heat treatment of starches and solve the question of what has a greater influence on the processes of their dextrinization, the chemical composition or their botanical origin, we carried out research by using methods of thermogravimetry and differential scanning calorimetry. It was shown for the first time that there is a process with heat absorption at 130°C in the temperature range of 25-200°C, in addition to the stages of dehydration of starches, which is not accompanied by a decrease in weight. This endoeffect is well explained by the melting process of the low-molecular amylose fraction of starches. In contrast to literature data, it was also established that the stage of starch decomposition in the temperature range of 200-350°C should be considered as a set of three consecutive processes. It was established that the activation energies of dehydration processes of pre-dehydrated starches are equal to 60 kJ mol-1. The average activation energy aor the stages of destruction of starches is 400-500 kJ mol-1. Such values of the activation energy of starch destruction processes are explained by the presence in their composition of a number of semicrystalline subcomponents characterized by different thermal stability. When comparing the values of the activation energies of the dehydration and dextrinization processes of the investigated starches, a linear correlation was established for the first time, which testifies to the uniformity of such processes and their independence from the botanical origin of the starches. [ABSTRACT FROM AUTHOR]

Background: Intercomponent drug interactions could play important role for drug release, membrane permeability and membranotropic action. Therefore, newly developed drugs need for checking their biopharmaceutical characteristics. A new analgetic drug based on paracetamol (Actimask® Acetaminoprofen) and a hepatoprotector N-acetyl-D-glucosamine has been developed, with increased safety and potentiation of the analgesic effect (Ruban O., 2022). Multibilayer lipid membranes were chosen as promising testing medium due to their proved appropriation and sensitivity for study multi-compound drug-membrane interactions. It is the basis for a kinetic approach allowing elucidation of biopharmaceutical interactions in model membrane medium. Objectives: Revealing changes of paracetamol release and membrane penetration in the new paracetamol-glucosamine analgetic drug as well as estimation the rationale of the approach developed to trace biopharmaceutical interactions in model membrane medium. Materials and Methods: L-a-dimyristoyl phosphatidylcholine (DMPC) multibilayer membrane was used as a model biomimetic testing medium. Differential scanning calorimetry (DSC) was applicated to trace kinetics of drug-membrane interactions. Results: Gelatin as a part of Actimask® increased the characteristic time of paracetamol diffusion about threefold, but it had no pronounced effect on the equilibrium paracetamol penetration into the membrane. Sole glucosamine manifested no membranotropic effect under the experimental conditions, however, in combination with gelatin, it sufficiently reduced equilibrium paracetamol penetration while paracetamol diffusion remained within the experimental error. The full drug formulation increased membrantoropic effect by 34 % in compared with sole paracetamol. Conclusions: Glucosamine and gelatin can affect both kinetic and equilibrium parameters of paracetamol-membrane interactions, while the full set of the drug components is able to increase the effect which correlates well with the previously established enhancement of analgetic effect of the drugs. The approach developed allows accurate tracing of drug release and membrane penetration depending on a set of drug components. Generally, the results obtained prove the rationale of applying the approach to pre-clinical drug examination.

Organic–inorganic hybrid materials are synthesized on the base of anhydride-cured epoxyurethane polymer matrix with an ultra-low content of poly(titanium oxide) nanoparticles (0.005 and 0.020 wt.% for TiO2) obtained in situ by the sol–gel method in polyoxypropylene glycol medium. The structure of the formed optically transparent samples was confirmed by the methods of optical microscopy and wide-angle x-ray scattering. As shown, TiO2 reveals itself as an amorphous phase and does not form aggregates of large size (>200 nm). The behaviour of the neat epoxyurethane and of titanium-containing ones is studied under artificially accelerated weathering conditions in a climate chamber. The changes in the properties of films after exposure to UV radiation, elevated temperature and relative humidity are investigated by the methods of IR spectroscopy, hydrostatic weighting, differential scanning calorimetry, thermogravimetric analysis, and spectrophotometry. As found, under the influence of such climatic factors, the chemical structure of the samples changes insignificantly that proves their atmospheric stability. The increase in density and initial temperatures of thermal decomposition as well as the decrease in the increment of heat capacity (ΔCp ) of epoxyurethanes indicate the proceeding of cross-linking reactions via condensation of hydroxyl groups in the conditions of the climate chamber, which lead to the formation of a denser structure. After accelerated weathering test, the optical transmission coefficient of all the samples diminishes slightly, but the loss of transparency decreases with increasing content of poly(titanium oxide) (18.2% for the neat epoxyurethane polymer and 11.6% for the sample with 0.020 wt.% TiO2). In general, modified epoxyurethanes have a higher resistance to degradation compared to the unmodified ones that is an evidence of the exhibiting of the UV-shielding properties of TiO2 and the simultaneous absence of its photocatalytic activity, which, on the contrary, would provoke the destruction of the polymer matrix under UVirradiation. [ABSTRACT FROM AUTHOR]

Thermoplastic film materials with a structure of pseudo-interpenetrating polymer networks (pseudo-IPNs) were created on the basis of natural semi-crystalline poly-3-hydroxybutyrate (PHB) and natural rubber (NR), the content of the NR was varied from 2 to 40 wt.%. Using the methods of Fourier Transform Infra-Red (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), structureproperties relationships were studied for PHB/NR thermoplastic pseudo-IPNs at different ratios of the components. Significant non-additive increase in mechanical characteristics compared to the individual PHB was found for PHB/NR pseudo-IPNs samples with a low content (up to 15 wt.%) of NR. For the sample with a content of 5 wt.% NR, the greatest increase (~18.4%) in strength at break was fixed (σb ≈ 22.5 MPa); for a sample with a content of 10 wt.% NR, the largest increase (~ 215%) in elongation at break (εb ≈ 48.8%) was observed. By FTIR spectroscopy, it was found that certain changes in the crystal structure of the PHB matrix occurred in the samples of pseudo-IPNs at increasing the NR content; however, no changes in the chemical structure of the components were detected. The SEM method revealed spherical domains of the dispersed elastomeric NR phase distributed in the PHB matrix in the samples of PHB/NR pseudo-IPNs. These observations evidence the microphase separation of the system components due to their thermodynamic incompatibility. It is worth to note that the sizes of the domains of the dispersed elastomeric phase naturally increased from ~10-20 μm for pseudo-IPNs PHB/NR = 85/15 wt.%, up to ~ 100 μm for PHB/NR = 60/40 wt.%. Using TGA method, it is established that PHB/NR pseudo-IPNs samples are characterized by high resistance to thermo-oxidative destruction, which non-additively increases with increasing the NR content. Destruction of PHB/NR pseudo-IPNs samples occur in two main stages: at I stage (Td ~ 240-285 °С) the main weight loss of the samples is occurred due to the destruction of macromolecules of the PHB matrix; at II stage (Td ~ 320-380 °С) the oxidative destruction of NR component takes place. Calculations have shown that with increasing the NR content, the maximum rate of thermo-oxidative destruction of pseudo-IPNs samples decreases compared to the individual PHB by 5-52 % with increasing the NR content from 2 to 40 wt.%. Therefore, it means that their resistance to thermo-oxidative destruction increases. The results obtained by DSC method have shown that the introduction of NR and changes of the components ratio significantly and nonadditively affect all the thermophysical characteristics of the samples studied. This indicates a significant restructuring of the microphase (amorphous and crystalline) structure of pseudo-IPNs synthesized due to the interpenetration of the components into the microphases of each other and the formation of mixed PHB/NR microphases with different ratios of the components. [ABSTRACT FROM AUTHOR]

In this work, the effect of ultrasonic dispersion time on the structural and thermophysical properties of nanocomposites was studied. Model systems were made based on polyethylene glycol and montmorillonite. All samples had the same composition and filler content (5% by weight), the ultrasonic treatment time was from 5 to 12 minutes. The methods of wide-angle X-ray scattering and differential scanning calorimetry were used to establish the dependence of the properties of the systems on the dispersion time. Data analysis of the obtained results showed that the variation of ultrasonic dispersion time significantly affects the properties of polymer nanocomposites. As the mixing time increases, the interplanar distance of montmorillonite increases, which indicates an increase in the degree of intercalation of the polymer matrix. At the same time, the crystallinity of the nanocomposite decreases, which corresponds to the increase in the area of the polymer/filler boundary layer. The melting temperature of the nanocomposite increases with increasing dispersion time. This trend is a consequence of the complication of the thermal movement of polymer molecules due to the presence of a developed surface of the filler. It is shown that with an increase in the sonication time, the part of the immobilized amorphous fraction of the polymer increases. This is explained by the fact that the polymer intercalated in the interlayer space of montmorillonite loses its ability to cooperative movement, that is, to glass transition. It was established that the maximum improvement of system properties is observed at a dispersion time of 10 min. In this state, the montmorillonite particles are most stratified, which leads to the maximum increase in the area of the boundary layer. During further mixing, processes of aggregation of montmorillonite particles and destruction of polymer molecules occur, which leads to the loss of the desired properties of the nanocomposite. Finding the optimal mixing time of a polymer nanocomposite makes it possible to obtain the desired properties of systems with a defined composition. [ABSTRACT FROM AUTHOR]

We have synthesized large scale, thin, transparent graphene oxide (GO) flakes by Hummer’s method and investigated their suitability for fabrication of transparent nanocomposites. The GO flakes were comprehensively characterized by X-ray diffraction, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), Raman spectroscopy and Differential Scanning Calorimetry (DSC). X-ray diffraction displayed the peak of graphene oxide at 9°degree, which is characteristic peak of GO in agreement with the literature results. Scanning Electron Microscopy images revealed that thin, transparent, flake form GO with 14,8 µm lateral size and 0,31µm thickness were synthesized. The comparison with literature results show that for the first time, our group could synthesize large scale, thin and more transparent GO flakes by simple Hummer’s method using simple dispersed graphite. EDX measurements indicate the formation of layered structure with oxygen containing functional groups. The intensity ratio between D and G peaks in the Raman spectra proves that less defective GO flakes have been synthesized. The solution ability of the synthesized material indicate that high quality GO flakes were synthesized, which make them effective soluble material due to oxygen containing groups formed on the graphene plane during synthesis process.DSC results shows that these flakes are thermally stable till 200°C. Due to high solubility properties, large scale and transparency they can be very useful in fabrication of high optical transparent nanocompoties for replacement indium tin oxide transparent conductors in solar panels, biomedical applications and microwave absorbers for electromagnetic interference (EMI) environmental protection.

The article is devoted to the development and research of the structure and properties of polyurethane foam (PUF) composite materials with the antibacterial enzyme lysozyme. A series of PUF composite materials with lysozyme of various concentrations (1, 3 and 5 wt %) were obtained. It is established that the immobilization of lysozyme occurs due to intermolecular hydrogen bonds by the method of IR spectroscopy. According to the results of physical-mechanical tests the adhesive strength of polyurethane foam compositions with lysozyme is in the range of 0,82–1,16 MPa. Th e introduction of lysozyme into the composition of polyurethane foams and an increase its amount causes a decrease in the values of adhesion strength by 18,1– 29,3 %. According to differential scanning calorimetry the tested systems are single-phase with a glass transition temperature in the range of -49,20 to -49,86°C. The introduction of lysozyme into the composition causes an increase heating capacity at the glass transition, which can be associated with a decrease of the packing density of macrochains resulting in an increase in free volume, which leads to an increase molecular mobility. According to the results of the analysis of transmission optical microscopy micrographs the studied PUF have a microporous structure, which depends on the content of filler in their composition. It was found that the presence of lysozyme in the composition of composite materials leads to a decrease in the percentage of porosity, an increase in the number of pores with a diameter of up to 300 μm, which is 76,7–82,4 % (while for PUF – 69,5 %) and the absence of pores with a diameter larger than 990 μm. Thermogravimetric characteristics indicate the heat resistance of the synthesized PUF to a temperature of 179,95°C, which allows dry sterilization of samples without changing their characteristics. PUF composite materials with lysozyme are promising materials that can be used in medical practice as polymer compositions for the treatment of wounds and burns. [ABSTRACT FROM AUTHOR]

Polymer systems containing nanoparticles are new class of polymer composite materials. Polymer matrix filling influences on network polymer structure forming mechanism. The filler influence appears in formation features of the network structure both near the filler surface and in polymer matrix volume. Polymer solid surface (filler, substrate, etc.) interaction results in polymer chains movement restriction, that in fact is equivalent of additional polymer network physical knots formation. The polymer - filler interface presence may lead to both increasing of physical polymer knots average amount and decreasing it because of decreasing the polymer-polymer type physical bonds amount. This in turn determines strength of the polymer composite value. Polyurethane composite filled with different type of gypsum has been studied. The semi-aquatic gypsum (water suspension and dry powder) and two-aquatic gypsum water suspension were used as the filler. The polyurethane oligomer was used as reactive polymer matrix. Thermal-and-physical properties of polymer composites were studied by differential scanning calorimetry. It is found that the semi-aquatic gypsum does not transform in two-aquatic gypsum within polymer matrix during observation time. Evidently, the first - the polymer matrix doesn't have continues pores and the second - the polymer matrix forms dense surface layer that hinders the diffusion of water vapor to the filler. Obtained polymer compositions glass temperature shows weak dependence on gypsum concentration and method of gypsum filling, but shows strong dependence on heating multiplicity. Polymer composition change in heat capacity upon glass transition value ΔCp decreases with filler concentration increases and strongly depends on filling process. To obtain stable material properties the annealing of internal strength is needed to carry out. [ABSTRACT FROM AUTHOR]

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The dependence of crystallization of thermoplastic polymers on the conditions of introduction and the nature of the distribution of the filler in the production of nanocomposites is an extremely important characteristic. However, due to the low concentration of concentration series, some effects of the influence of the nanofiller on the mechanisms of crystallization remain unexplored. Therefore, the purpose of this work was to study the influence of the filler on the mechanisms of crystallization and the growth of crystals in the overcooled melt nanocomposite. To study the kinetics of crystallization of nanocomposites, systems based on polypropylene (PP) and pyrogenic aerosil, which specific surface was 175 m2/g, and an outer diameter of ≈ 40 nm, were used. The samples were made by mixing in a melt at a temperature of 200 °C using an extruder. The content of the filler was (0,2 ÷ 1,0) wt. % The kinetics of nonisothermal crystallization was studied using crystallization exotherm, which was obtained by differential scanning calorimetry. As a result of this work, the influence of the filler on the mechanisms of crystallization and the growth of crystals in the overcooled melt of nanocomposite polypropylene-aerosil was studied. The analysis of the parameters of crystallization obtained from the dependences of the rate of cooling of samples from the areas under the crystallization exotherms showed an increase in the barrier of crystallization of the lamellar crystallization of the PP in the volume between adjacent nanoparticles of an infinite nanocomposite cluster, which corresponds to a strong restriction to transport of PP segments across the melt/lamellar crystal interface. The exotherm of crystallization for the non-filled PP was analyzed in the framework of the standard Kolmogorov-Avrami equation. From the kinetics of crystallization for a system containing 1% of the aerosil, the assumption, based on the superposition of the contributions of the initial (unimpeded) and the secondary (limited) mechanisms of crystallization, respectively, is confirmed. The obtained results confirm the coexistence in the overcooled melt PP of a nanocomposite of the initial mechanism of crystallization, characteristic of the unpolished PP, and of essentially other areas of crystallization. For composites based on PP filled with aerosil, at 0,2 % the mechanism of a strained matrix is realized, at 1 % a three-dimensional mechanism is realized. [ABSTRACT FROM AUTHOR]