جستجوی مقالات مرتبط با کلیدواژه « poly(vinyl alcohol) » در نشریات گروه « شیمی »

In the present work, different concentrations of citrate (reducing agent) were used to reduce the silver precursor, and Poly Vinyl Alcohol (PVA) was used as a capping agent. The electrochemical performance of the synthesized multivalent silver oxide (AgxO)/PVA nanocomposite has been carefully examined. The well-crystalline, spherical, and aggregate-free AgxO/PVA nanocomposite was synthesized. The present findings were strengthened by structural, elemental, and morphological studies. The AgxO/PVA nanocomposite showed Surface Plasmon Resonance (SPR) and defect-related band gap mechanisms. The two oxidoreduction peaks in the cyclic voltammogram were observed for the graphite electrode coated with the as-prepared samples. The AgxO/PVA-loaded electrodes showed a maximum specific capacitance of 269 Fg-1 at a scan rate of 10 mVs-1. It was observed that the citrate can be used to produce silver oxide nanoparticles and to improve the electrochemical functionality of the silver oxide nanoparticles blended with PVA. There are potential uses for this type of nanocomposite-coated electrode in supercapacitors and high-performance energy storage systems.

In the present work nanocomposite thin films have been prepared from poly(vinyl alcohol) (PVA) mixed with carbon nanotube (CNT) and carbon nano particles (CN) by casted method. The aim of this work produce texture of PVA with CNT and CN, the effect of CNT and CN content in thin films nanocomposite were measured by utilizing reflectance and absorbance data. The contents of CNT and CN reinforcement in the PVA matrix increase the optical properties such as reflectance, absorption coefficient, refractive index, extinction factor. But the transmittance and reflectance of thin films nanocomposite (PVA-0.05CNT, PVA-0.05CN, and PVA-0.025CNT-0.025CN) decreased, on anther hand the conductivity and dielectric constant were increased. The direct allowed transition of energy gap decreased from 4.0 eV to 2.9 eV, the indirect allowed transition of energy gap decreased from 4.4 eV to 2.8 eV, respectively. Urbach energy was increased from 1.238 eV to 2.711 eV after added the CNT and CN to PVA texture. The scanning electron microscope was used to evaluate the particle sizes of CNT and CN after preparation from the experimental method, which used in the PVA lattice to constitute the thin films nanocomposite (PVA-0.05CNT, PVA-0.05CN, and PVA-0.025CNT-0.025CN). The AFM test used to exhibit the roughness.

In this work, we demonstrate water-based corrosion inhibition properties of engineered sulfonated polyaniline molecules on poly(vinyl alcohol), PANI-PVA, for mild steel. The corrosion-inhibition performances were evaluated using potentiodynamic polarization in a salty corrosive 3 % NaCl solution. The anti-corrosion coating based on these composite materials displays barrier properties against corrosion-causing agents and shows a corrosion protection efficiency of 84.39 %, compared with uncoated. The material showed a lower value of corrosion current (Icorr) which is 2.56 μA/cm2 and a positive shift in corrosion potential (Ecorr), -0.426 V, in comparison with uncoated steel. Open Circuit Potential (OCP) Studies and electrochemical impedance (EIS) were also carried out to check the corrosion protection ability of the material. OCP studies, Nyquist plot, and Bode plots showed that the synthesized PANI-PVA possess a corrosion protection ability on mild steel against the corrosive species.

Dehydration of alcohols has attracted a great deal of attention owing to its wide application in ‎several medical, pharmaceutical and chemical industries. High separation efficiency, low energy ‎consumption, simplicity and minimum contamination are the main characteristics which make ‎pervaporation (PV) a promising method in the area of alcohol dehydration to provide extremely ‎pure alcohols. Due to their permselectivity and high processability, polymers are the main ‎materials for PV membranes. For this purpose, poly(vinyl alcohol) (PVA) is the most commonly ‎used polymer because of its desired hydrophilicity, flexibility, good film-forming ability and low ‎cost. However, excessive swelling is the main challenge in fabrication of PVA membranes for ‎dehydration application; to overcome this disadvantage, various attempts have been made to ‎modify PVA membranes for separation of water and alcohols. In this paper, various ‎modifications and developments that have been made to improve the PV performance of PVA-‎based membranes for separation of water and alcohols have been reviewed.‎

In the present work, BaCe0.85Yb0.15O3-δ mixed metal oxide nanoparticles supplying strong acid sites and good hydrophilic nature were used for the first time to build organic-inorganic proton exchange membranes. Poly(vinyl alcohol) - BaCe0.85Yb0.15O3-δ (PVAYb) nanocomposite membranes were fabricated. Different analyses such as Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX) spectroscopy, Fourier Transform Infra-Red (FT-IR) spectroscopy, and ThermoGravimetry Analysis (TGA) were used to characterize and study the structural properties of the obtained membranes. SEM and EDX analyses exhibited a homogenous dispersion of the nanoparticles in the nanocomposite membrane.  It was found that PVAYb1.5 had a better elemental distribution compared to PVAYb2.5 composite membrane. PVAYb nanocomposite membrane containing 1.5 wt.% of BaCe0.85Yb0.15O3-δ nanoparticles displayed a high proton conductivity value (64 mS/cm) at 70 °C operation temperature. The peak power density of 29 mW/cm2 was obtained with a peak current density of 210 mA / cm2 for as-prepared Proton Exchange Membrane Fuel Cell (PEMFC) equipped with PPYb1.5 nanocomposite membrane at 70 °C.

The present work was aimed to examine the effects of incorporation of each of two different types of nanoclay, i.e. Cloisite Na and Cloisite 30B, into PVA foam on cellular morphology and water absorption capacity. Foam samples containing 0.0-10.0 wt% of each of the two types of nanoclay alone were prepared using mechanical foaming. Accordingly, PVA/organoclay/water suspensions were prepared first. Then other agents, i.e. catalyst, surfactant and crosslinking agent were added, respectively, to each of the prepared suspensions rendering primary froths, which were converted to final foam samples at room temperature during a period of 24 h. State of clay dispersion in the polymer matrix and cellular morphology of the prepared foam samples were examined using X-Ray Diffraction (XRD) technique and Field Emission Scanning Electron Microscopy (FESEM), respectively. Also, dry foam density and water absorption of the foam samples were measured gravimetrically. XRD patterns revealed the existence of intercalated and exfoliated structures in the PVA/Cloisite 30B and the PVA/Cloisite Na foam samples, respectively. FESEM images demonstrated open-cell morphology for all the samples but the extent of cell wall rupture was more significant in the case of PVA/nanoclay foam samples. In addition, water absorption capacity of the PVA foam was shown to be decreased by the incorporation of either of the two types of nanoclay, which was explained in terms of the lower total pore volume in the PVA/nanoclay foam samples than in the neat PVA foam sample. Finally, the obtained results were explained in terms of the effects of the nanoparticles on the elevation of the rate of the drainage in the crosslinking PVA solution before the stabilization of the cellular structure.

Poly(Vinyl Alcohol) (PVA) films were prepared with AlCl3·6H2O/glycerin and AlCl3·6H2O/poly glycerin as two kinds of complex plasticizer. The micromorphology of pure PVA film and PVA films plasticized with complex plasticizer was observed by Scanning Electron Microscope (SEM). The interaction between complex plasticizer and PVA molecules was investigated by Fourier Transform Infrared (FT-IR) spectroscopy. The influence of complex plasticizer on crystalline, thermal and mechanical properties of PVA films was studied by X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), ThermoGravimetric Analysis (TGA), and tensile tests, respectively. The results showed that both AlCl3·6H2O/glycerin and AlCl3·6H2O/poly glycerin complex plasticizers could interact with PVA molecular and then effectively destroy the crystals of PVA. PVA films plasticized with AlCl3·6H2O/glycerin, and AlCl3·6H2O/poly glycerin complex plasticizers became soft and ductile, with lower tensile strength and higher elongation at break compared with pure PVA films. This is an important cause of plasticization of AlCl3·6H2O /glycerin and AlCl3·6H2O /poly glycerin on PVA films.

Al(OH)3 nanoparticles were synthesized by a simple precipitation reaction. The effect of various amines like ethylene diamine, propylene diamine, triethylenetetramine and tetraethylenepentamine as precipitating agents on the morphology of Al(OH)3 nanostructures was investigated. The influence of Al(OH)3 nanoparticles on the flame retardancy of the poly vinyl alcohol (PVA) matrix was studied using UL-94. Nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Flame retardancy of the nanocomposites enhanced in the presence of Al(OH)3 nanostructures. This improvement of nanocomposites is due to the endothermic decomposition of Al(OH)3 and release of water which dilutes combustible gases.

Nanofibrous scaffolds produced by electrospinning have attracted much attention, recently. Aligned and random nanofibrous scaffolds of poly (vinyl alcohol) (PVA), poly (ε-caprolactone) (PCL) and nanohydroxyapatite (nHA) were fabricated by electrospinning method in this study. The composite nanofibrous scaffolds were subjected to detailed analysis. Morphological investigations revealed that the prepared nanofibers have uniform morphology and the average fiber diameters of aligned and random scaffolds were 135.5 and 290 nm, respectively. The obtained scaffolds have a porous structure with porosity of 88 and 76 % for random and aligned nanofibers, respectively. Furthermore, FTIR analysis demonstrated that there were strong intramolecular interactions between the molecules of PVA/PCL/nHA. On the other hand, mechanical characterizations show that aligning the nanofibers, could significantly improve the rigidity of the resultant biocomposite nanofibrous scaffolds. The results indicate that aligned scaffolds are suitable for tissue engineering applications.