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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]

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]

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]

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]

The unfilled and filled with aerosil blends of linear polyurethane (PU) and polystyrene (PS) with PU-PS ratio of 70:30, 60:40 and 50:50 wt.% formed in situ have been studied by methods of differential scanning calorimetry and dynamic mechanical analysis. It is shown that introduction the filler in a PU-PS blend of 70:30 wt.% leads to increase of the fraction of an interfacial region and increase of the compatibility of components in a blend. For the filled PU-PS blends of 60:40 and 50:50 wt.% the fraction of an interfacial region decreases and the more separated system is formed. [ABSTRACT FROM AUTHOR]

The graft block copolymer (GBC), based on the functionalized ethylene-vinyl acetate copolymer and monoisocyanateurethane of reactive olygomers of soybean oil, was synthesized. The structure of the copolymer was confirmed by IR-spectroscopy and gel permeation chromatography. Physico-chemical characteristics of the GBC were studied by thermal gravimetric analysis and differential scanning calorimetry. It was found that the obtained GBC has high heat resistance, the glass transition temperature of the copolymer is shifted towards lower temperatures. Efficient use of GBC as compatibilizer for composite materials based on recycled polypropylene and crumb rubber was shown. [ABSTRACT FROM AUTHOR]

Graft block copolymer (GBC) based on functionalized ethylene-vinyl acetate copolymer and macrodiisocyanate based on liquid rubber was synthesized, the structure of GBC was confirmed by IR-spectroscopy. Physico-chemical characteristics of the GBC were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that the GBC has a higher thermal stability compared with the original components, and the glass transition temperature is shifted to lower temperatures. Efficient use of PBS as compatibilizer for composite materials based on recycled polypropylene and crumb rubber was shown. [ABSTRACT FROM AUTHOR]

Epoxy polymers and epoxy-silica composites cured with anhydride in the presence of metal acetylacetonates were investigated by dynamic mechanical analysis, differential scanning calorimetry and scanning electron microscopy. Silica filler in situ formation leads to decrease of concentration of internodal chains and glass transition temperature of composites. Effective crosslink density of polymers depends on curing accelerator and increases in the sequence Ni(acac)2, Co(acac)3, Fe(acac)3, Cr(acac)3. [ABSTRACT FROM AUTHOR]