The crystal structure of tetrakis(2,2’-bithiophene-5-yl)silane, C16H10S4Si0.5, has been determined at 293K in the Monoclinic (I2) symmetry. The Si atom has quasi-perfect tetrahedral geometry and bithiophene unit are quasi-planar. Comparison of Si-C bond lengths with literature data indicates an electron donating effect of the terminal thienyl ring on the first C linked to the Si central atom. The study of C-C bond lengths reveals a much more aromatic character for the four thienyl rings directly linked to the Si atom. The molecular packing arrangement shows that each molecule presents eight intermolecular contacts.
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The paper presents the obtaining of zinc and zinc composite coatings using electrochemical TiO2 nanoparticles as well as the determination of the influence of gelatin used as an additive on electrically co-deposited layers. The obtained coatings were studied at the electronic scanning microscope (SEM) for microstructure observation. A distinction was made between the pure zinc electro-deposed layer and the influence of nano-TiO2 on the morphology of zinc nanocomposite layers Zn/nano-TiO2, as well as the determination of the degree of inclusion of nano particles of TiO2 into the zinc matrix. It was confirmed that with the introduction of nano-TiO2, both the roughness of the electro-deposed layer and the micro hardness of the electro-deposed layer significantly increased compared to the micro hardness of the pure zinc electro-deposed layers confirming the existence and beneficial effects of nano-TiO2 in electro-co-deposed nano-composite layers.
The paper focuses on the obtaining of novel nanocomposite hydrogels based on polyacrylamide and layered double hydroxides (LDHs) modified with double bonds. The modification of LDH clay was investigated by FTIR, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses. Mechanical properties of the nanocomposite hydrogels were employed by compression and rheological measurements. The formation of exfoliated and intercalated structures was evidenced in transmission electron microscopy (TEM). Chemical cross-linking of hydrogels using both classical cross-linker and modified clay was an efficient method to improve the mechanical properties of novel nanocomposite hydrogels. These hydrogels with improved mechanical properties could be further tested for biomedical applications such as tissue engineering.
The thermal coefficient of linear expansion, the electrical conductivity and dielectric permittivity of fabric reinforced hybrid composites with filled stratified epoxy matrix were investigated. The measurements of electrical conductivity and dielectric permittivity had been performed, using standard method regarding electrical resistance and electrical capacity. In order to point out the effect of filler and of the spatial distribution of reinforcement layers, the medial layer of fabric was especially prepared by introducing copper wires in the woven. So, the medial layer is made of different types of tows (carbon, aramid, glass). This attempt is made in order to design a composite able to provide information about its state during various loading. The results showed that the fillers did not improve the electrical parameters of epoxy matrix, but they led to reduce the thermal coefficient of linear expansion. The thermal and electrical behavior of hybrid composites varied in dependence of number of carbon layers and fiber orientation.
In this paper, the potential of using ethylene-vinyl acetate (EVA) filled with multi-wall carbon nanotubes (MWCNT) composites for strain sensing was investigated. Stress relaxation experiments were conducted on injection-molded samples, and the stress and electrical resistance were measured in situ during the relaxation process. Based on the experimental results, it was found that the electrical resistance of the EVA/MWCNT composite increases with increasing strain, and exponentially decreases with relaxation time, indicating the capacitive behavior of MWCNTs. The maximum electrical conductivity of 7.35×10-4 S/cm was obtained for the EVA/MWCNT composite with 5 wt.% at 180°C, whereas higher piezo-resistive sensitivity was obtained for the composite with 3 wt.%. The electrical percolation threshold was found to increase from 0.223 wt.% at 140°C to 0.994 wt.% at 180°C.
In this paper we present a comparative study on tensile failure behavior of polymer stiffened composite shell structures, using infrared thermography and finite element analysis through the ABAQUS 6.13 program. The establishment of the distortion of some rectangular shaped specimens was followed. In these specimens a hole with a diameter of 15 mm was applied centrally. By means of infrared thermography, was studied experimentally the variation of the deformations over time, depending on the stress force and the evolution of the thermal field in the crack area. Simulation models of failure behavior have been performed, which have been validated by experimental results.
The composite materials with polymeric matrix represent a great realization of chemical engineering. Their applications in all the industrial fields are dictated by their chemical, physical and mechanical properties. In the last 50 years the polymeric composite materials received a large use in the protection and repair work of the surfaces in contact with fluid currents of various natures. The scientific researches followed by the industrial use, show that the polymere films with certain composition and properties have an excellent behavior to chemical, abrasive and cavitation erosions. Because the most stressed machine details subjected to cavitation erosions are the blades, runners and impellers of hydraulic machines as well as the ship propellers, researchers are looking for the best polymers to increase the running time, or for the use in covering the zones with shallow erosions, during the repair work. In this direction is oriented also the present research, performed in the Cavitation Laboratory of the Timisoara Polytechnic University. The obtained cavitation erosion for specimens covered with different polymere films is compared with those realized in identical conditions, but for specimens without protection films. The results show that the films assure some increase in the resistance to cavitation erosion but the tested polymer layers have reduced adherence on the metal surface.
Poly lactic-co-glycolic acid (PLGA) is a biodegradable polymer that has been the focus of intense research due to its potential applications in medical research. Its uses in nanotechnology are underlined by its capability of targeting various cells and delivering active compounds to different human tissues. To date, PLGA nanoparticles are employed in areas such as vaccination therapy, diagnostic imaging procedure and various applications in various anticancer therapies. The aim of the present study is to measure and evaluate different correlations between oxidative stress parameters in spleen and liver following administration of nanoparticles encapsulated with lutein in an animal model. Our results show that acute oral administration of PLGA NPs induces a change in the oxidative stress status in both liver and spleen of rats, but does not induce oxidative stress damage to cell structures such as lipids or proteins.
The memory shape materials seem to be extremely promising materials for medical applications especially as inserts to support the muscular system. In the case of memory shape polymers a supplementary issue is related to their bio-compatibility such as they can be rejected by the organism even their properties are fitting the requirements. Present study started from the hypothesis that mixing the epoxy resin with other polymers some valuable materials could be obtained especially for energy storage. The epoxy resins possess extraordinary properties (relatively to other thermoset polymers) but they also show an excellent stability that generates problems when this type of materials should be neutralized. Epoxy resins also show low water or other liquids absorption due to their low porosity and they cannot be used for energy storage applications when mobility of charge carriers is ensured by liquid phase. A polymer with high porosity used for membrane formation is the polysulfone and, in this regard, tests were performed to analyse the ways to mix an epoxy resin with polysulfone. The idea had generated a study regarding the properties of such a mixture together with the condition that had to be reached to successfully get the mixture. Low-polar solvent solution of polysulfone had been obtained with 1-methyl-2-pyrrolidinone. After compatibility tests, 15 and 20% of this solution was added to the components of the epoxy systems -with the epoxy resin -and formed materials were analysed by mechanical means-compressive and three-point bending - the surprise was that some materials had showed memory shape properties.
The main aim of this study was to investigate a mixture of two poorly water-soluble active pharmaceutical ingredients (APIs): an angiotensin II receptor antagonist (valsartan) and a calcium channel blocker (amlodipine besylate), chosen in a fixed-dose, in order to obtain new polymeric nanoparticles (NPs) for cardiovascular diseases treatment. NPs were prepared via nanoprecipitation method using poly (D,L-lactide-co-glycolide) (PLGA) as matrix and Pluronic F127 as stabilizer. Three formulations were investigated with different ratios of AML:VAL:PLGA (1:16:5, 1:16:7.5 and 1:16:10). Particle size, polydispersity index and zeta-potential analyses were performed to characterize and optimize the formulation. The in vitro drug release study was determined by using a dialysis membrane method under sink conditions. All NPs loaded with both APIs showed nano-size, negative potential, a high homogeneity and a slow drugs release in physiological environment.