Elastic response of Carbon Black reinforced polyester based composites using micromechanical models: Role of interphase

Carbon-based reinforcements have been widely reported in improving mechanical properties of polymers. However, still few studies exist on the incorporation of the interphase as a result of the interfacial interactions into analytical prediction tools. To better understand the effect of interfacial interphase, this study compares and correlates the experimental mechanical response of polyester based composites filled with carbon black (CB) with the elastic behavior obtained from the micromechanical models. Mold cast composites of polyester reinforced with 0 wt%–10 wt% of CB were fabricated. To determine the length of cooperative rearranging region (CRR) as a measure of the interphase, thermal studies focusing on the variations in the specific heat capacity or the relaxation strength of the composites around the glass transition temperature ( Tg) range were performed using a thermodynamical model. Micromechanical models such as the Halpin-Tsai and Tandon-Weng were used to determine the Young’s modulus with respect to the CB wt% and diameter as well as the interphase thickness and modulus. The results exhibited the sensitivity of the models to the existence of the interphase as a secondary mechanism, which was correlated to the cross-link density and interfacial bonding. The impact results showed the decrease in the impact resistance upon the addition of higher filler loadings ascribed to the destroyed bonding at the interface and CBs agglomeration confirmed by morphological studies. The research results can be further utilized in the explanation of the changes in the elastic response of carbon-based reinforced thermosetting composites emphasizing the key role of interphase.

Influence of Nano Filler (ZrO2) on Optical and Thermal Studies of Potassium Doped Polyethylene Oxide Solid Polymer Electrolytes

Solid polymer electrolyte films made with potassium doped Polyethylene oxide using ZrO2 as nanofiller (70PEO-30KBF4-x ZrO2 where x = 1, 2.5, 5, 7.5, & 10 wt% ­­) were prepared by solution casting technique. Optical and thermal properties of polymer electrolyte films were studied by using Optical absorption and DSC techniques. From Optical absorption spectra, it is observed that fundamental absorption edge is shifted towards the higher wavelength side (range 259- 297 nm) with increase of nano filler (ZrO­2) concentration (1-10 wt %). Optical band gap for all electronic transitions (p=1/2, 2, 2/3 and 1/3) are found to be increased as incorporation of nano filler (ZrO2) which confirms the structural rearrangements takes place in polymer electrolyte films. Optical band gap for indirect allowed transitions (p=1/2) are found to be in the range of 1.93-3.34eV. Decrease in Urbach energy (4.8eV- 1.4eV) is associated with decrease in defect formation in host polymeric matrix (PEO-KBF4) as a result of embedded nano filler (ZrO2). DSC spectra analysis of polymer electrolytes has showed melting temperatures in the range 63.63-73.71°C and highest crystallinity is found to be 85 % (10 wt % ZrO­2). Enthalpy values are elevated with increase in nanofiller composition (ZrO2) in the present polymer electrolyte films.Keywords: PEO based polymer electrolytes, Solid polymer electrolytes, Optical and Thermal studies.

Thermal studies of vacuum panels of cellular structure of a passenger car

Aluminum alloys and composite materials are used in the body structures of modern passenger railway cars, which required the use of new manufacturing technologies: extrusion, pultrusion, etc. The use of new materials and new production technologies is changing the design requirements of passenger rail cars. The use of computer-aided design systems, in particular, SolidWorks Simulation, allows you to optimize the profile of cellular panels used in the construction of the body of a passenger railway car and obtained by extrusion or 3-D printing. Purpose of this work is to optimize the design stage of the enclosing structures of the body of a passenger railway car made of cellular profile panels, which can significantly reduce the heat transfer coefficient of the body walls and their mass, as well as provide the necessary strength conditions. Optimal profile of the vacuum panel, consisting of two rows of hexagonal cells, provides, according to calculations, the value of the specific thermal resistance R = 2.922 (m2 K)/W, which is 16.5% more than that of the existing body structure of a passenger rail car.

THERMAL STUDIES OF POROUS ALUMINUM OXIDE MEMBRANES

Изучение оптических свойств наноразмерных мембран пористого анодного оксида алюминия позволяет значительно расширить области применения данного материала. В работе представлены результаты тепловизионных исследований мембран пористого анодного оксида алюминия с различными структурными параметрами. Построены профили распределения температуры для мембран, полученных в различных электролитах на основе серной, щавелевой и ортофосфорной кислотах. Установлено, что экранирование ИК излучения сильнее (примерно на 30%) проявляется у мембран с меньшим диаметром пор d ≈ 20 нм по сравнению с мембранами, у которых d ≈ 200 нм. Это связано с рассеиванием теплового излучения на неоднородностях структуры, которых значительно больше в мембранах пористого анодного оксида алюминия, полученных на серной кислоте. В качестве источников неоднородности выступают поры малого диаметра, недотравленные области и дефекты. Также, за счет повышенной активности серной кислоты по сравнению с другими используемыми кислотами большее количество анионов встраивается в структуру образца. Study of optical properties of nanoscale membranes of porous anodic alumina can significantly expand the scope of this material. The paper presents the results of thermal imaging studies of porous anodic alumina membranes with various structural parameters. Temperature distribution profiles for membranes obtained in various electrolytes based on sulfuric, oxalic and orthophosphoric acids have been constructed. It was found that the shielding of IR radiation is more pronounced (approximately 30 %) in membranes with a smaller pore diameter d ≈ 20 nm compared to membranes with a larger pore diameter d ≈ 200 nm. This is due to the scattering of thermal radiation on structural inhomogeneities, which are much higher in porous anodic alumina membranes obtained with sulfuric acid. Small-diameter pores, under-etched areas and defects act as sources of inhomogeneity. Also, due to the increased activity of sulfuric acid in comparison with other acids used, more anions are incorporated into the structure of the sample.

Development, characterization, and in vitro evaluation of adhesive fibrous mat for mucosal propranolol delivery

This research focuses on the synthesis and adhesive properties of mucoadhesive mats, prepared with poly(vinylic alcohol) as a base polymer for the oromucosal release of propranolol (PRO) by the electrospinning technique. The nanofibers mats were evaluated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry; in vitro drug entrapment efficiency, degradation time, and adhesion studies were performed. SEM images of the electrospun mats show the correct formation of fibers with a variable diameter and porosity. Thermal studies indicate excellent thermal stability of the scaffolds, The fibrous mats loaded with 10% of the drug exhibit the best thermal stability with decomposition after 450°C. In vitro studies indicate a drug content of 88% loaded in the mats. In the cytotoxicity test, loaded mat presents cell proliferations of 97% and 88% for drug concentrations of 10% an 15%, respectively. To conclude, the formed electrospun adhesive mats exhibited excellent thermal stability, adhesive properties, and drug entrapment efficiency, promising features for a successful drug topical release system on mucosal tissue in the oral cavity.

Synthesis and Spectroscopic Analyses of New Polycarbonates Based on Bisphenol A-Free Components

This paper discusses a new synthesis of bisphenol A-free polycarbonates based on four aliphatic-aromatic systems. In the first stage, different types of monomers (with/without sulfur) derived from diphenylmethane were synthesized. Then, new polycarbonates were prepared in the reactions with diphenyl carbonate (DPC) by transesterification and polycondensation reactions. Three different catalysts (zinc acetate, 4-(dimethylamino)pyridine and benzyltriethylammonium chloride) were tested. The structures of the compounds were confirmed by Nuclear Molecular Resonance spectroscopy (NMR) in each stage. The chemical structures of the obtained polycarbonates were verified by means of Attenuated Total Reflectance Fourier Transform infrared spectroscopy (ATR-FTIR). The presence of a carbonyl group in the infrared spectrum confirmed polycarbonate formation. Thermal studies by differential scanning calorimetry (DSC) were carried out to determine the melting temperatures of the monomers. A gel permeation chromatography analysis (GPC) of the polycarbonates was performed in order to investigate their molar masses. Thermal analysis proved the purity of the obtained monomers; the curves showed a characteristic signal of melting. The obtained polycarbonates were characterized as having high resistance to organic solvents, including tetrahydrofuran. The GPC analysis proved their relatively large molar masses and their low dispersity.