Effect Of Polyvinyl Alcohol Concentration Research Articles

Preparation and Study of Polyvinyl Alcohol Gel Structures with Acrylamide and 2-Acrylamido-2-methyl-1-propanesulfonic Acid for Application in Saline Oil Reservoirs for Profile Modification.

Polymer gels can be effectively applied to plug fractured reservoirs and carbonate cave strata. Herein, polyvinyl alcohol (PVA), acrylamide, and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were used as raw materials to prepare interpenetrating three-dimensional network polymer gels using formation saltwater in the Tahe oilfield (Tarim Basin, NW China) as a solvent. The effect of AMPS concentration on the gelation properties of PVA in high-temperature formation saltwater was analyzed. Further, the effect of PVA concentration on the strength and viscoelastic properties of polymer gel was studied. The polymer gel could retain stable continuous entanglement at 130 °C and exhibited satisfactory thermal stability. Continuous step oscillation frequency tests showed that it exhibited an excellent self-healing performance. Scanning electron microscopy images of the simulated core by gel plugging showed that the polymer gel could firmly fill the porous media, indicating that the polymer gel exhibits excellent application prospects in oil and gas reservoirs under high-temperature and high-salinity conditions.

Effect of polyvinyl alcohol concentration on biomedical application of chitosan/bioactive glass composite coated on AZ91D magnesium alloy

The aim of this work is to improve the biomedical properties of AZ91D magnesium by coating it with polyvinyl alcohol (PVA), bioactive glass (BG), and natural chitosan (CH), using the electrophoretic deposition (EPD) method with different PVA concentrations (15%, 20%, and 25%). The composites were characterized by X-ray diffraction (XRD), furrier infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), which showed uniformity on the surface. Bio-corrosion activities were investigated by polarization tests in phosphate buffer saline (PBS) solution, which indicated that a composite with 15% PVA has lower corrosion resistance than base metal due to the weakness of the composite coating and applied current in the EPD process. The higher corrosion resistance was observed in the 25% PVA concentration due to the presence of a higher amount of PVA in the applied composite (which induces a denser and thicker composite coating). An in vitro bioactivity test was performed in PBS solution, which showed that more hydroxyapatite was formed on the surface by increasing PVA concentration. Furthermore, adhesive analysis of composite coatings indicates that by increasing the PVA concentration in composites, more adhesivity is obtained (5%, 12%, and 30%, respectively).

Preparation and characterization of PVA thin-film composite membrane for pervaporation dehydration of ethanol solution

These days, ethanol fuel has been widely consumed worldwide to replace gasoline due to its possible environmental and long-term economic advantages. In detail, the ethanol fuel (purity ≥ 99.5 wt%) has been produced by traditional separation processes such as azeotropic distillation or molecular sieve adsorption, which excessively employs energy and capital cost. The pervaporation has already been considered as an effective alternative to conventional methods because of its high separation efficiency and low power consumption. Pervaporation separation of ethanol/water solution using hydrophilic membranes has been extensively studied owing to their superior perm-selectivity. In this present work, the polyvinyl alcohol thin-film composite membrane is prepared by casting a thin crosslinked polyvinyl alcohol (PVA) film on the polyacrylonitrile (PAN) porous substrate. The effect of PVA concentration on the pervaporation performance of the fabricated membrane is studied. The physicochemical properties of the prepared membrane are characterized using FTIR, SEM images, and contact angle measurements. The separation performance in terms of permeation flux and selectivity is simultaneously evaluated through a pervaporation dehydration of ethanol/water mixture of 80/20 wt.% at 60°C. The results show that the increase in PVA concentration leads to the decline in the hydrophilicity and the growth of the thickness and swelling degree of the membrane. Therefore, the selectivity of the membrane is found to improve significantly, while the permeation flux decreased with the PVA concentration ranging from 2.5 to 15 wt.%. Based on the results, the PVA membrane prepared from the 10 wt.% concentration is likely to provide high separation performance.

The Effect of Polyvinyl Alcohol Concentration on the Growth Kinetics of KTiOPO4 Nanoparticles Synthesized by the Co-precipitation Method

KTiOPO4 nanoparticles are known as the best candidate to utilize for second-harmonic generation in multiphoton microscopes and bio labels. Size and shape are important and effective parameters to control the properties of nanoparticles. In this paper, we will investigate the role of capping agent concentration on the size and shape control of KTP nanoparticles. We synthesized KTP nanoparticles by the co-precipitation method. Polyvinyl alcohol with different mole ratios to titanium ion (1:3, 1:2, 1:1) was used as a capping agent. Products were examined by X-ray diffraction patterns and scanning electron microscopy analyses. X-ray diffraction patterns confirmed the formation of the KTP structure. The biggest (56.36nm) and smallest (39.42nm) grain size were obtained by 1:3 and 1:1 mole ratios of capping agent, respectively. Dumbly, spherical and polyhedral forms of KTP nanoparticles were observed by the change in capping agent mole ratio. The narrowest size distribution of KTiOPO4 nanoparticles was obtained at 1:1 mole ratio of capping agent. Doi: 10.28991/HIJ-2020-01-04-06 Full Text: PDF

Thin Film Composite Membrane from PSF/Chitosan/PEG: Effect of PVA Concentration on the Removal of Mercury and Antifouling Properties

In this study, a thin film composite membrane was synthesized by coating a layer of hybrid membrane formulated from a blend of polyethylene glycol (PEG), chitosan and polyvinyl alcohol (PVA), cross linked with tetraethylorthosilicate on a polysulfone support membrane. The aim of this experiment is to study the effect of varying the PVA concentrations on the performance of the TFC membranes on the removal of mercury and to determine their antifouling behaviour. Four different concentrations of PVA were selected; 2 wt.%, 3 wt.%, 5 wt.% and 6 wt.%. Results showed that the increase concentration of PVA leads to good removal of mercury ions, and good antifouling properties which was portrayed through high FRR and RFR respectively, and low IFR. The suitable concentration of PVA was found at 3 wt. %, where it has yield TFC membrane that able to remove all the mercury ions from the solution even after 30 minutes filtration time with sufficient amount of flux as compared to other membranes. It also portrays good anti fouling behaviour due to low IFR and average value of RFR (66%). Therefore, this study concludes that the fabricated thin film composite membrane suitable to be used in membrane filtration for heavy metal removal.

Effect of PVA Concentration on Structure and Performance of Precipitated Iron-Based Catalyst for Fischer-Tropsch Synthesis

Fe2O3 catalysts were prepared by co-precipitation method with the assistance of polyvinyl alcohol (PVA) for Fischer-Tropsch synthesis. Effects of PVA concentration on structure and performance of the catalyst were investigated in a fixed reactor at 230-310 °C, 1.5 MPa, 2000 h-1, and syngas H2/CO = 2.0. The catalysts were characterized by N2 adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), H2 or CO temperature-programmed reduction (TPR) and H2 temperature-programmed desorption (H2-TPD), Fourier transform infrared (FTIR) spectra and thermogravimetric analysis (TGA). It was found that there was strong interaction between Fe and PVA, which controlled the structure of the catalyst. Among the catalysts investigated, the catalyst prepared with 15 wt.% PVA exhibited better catalytic performance due to the dispersion of iron oxides and the formation of the more active phase on the catalyst. Meanwhile, this catalyst showed the high selectivity to heavy hydrocarbons and satisfactory thermal stability.

Optimization of Solvent System and Polymer Concentration for Synthesis of Polyvinyl Alcohol (PVA) Fiber Using Rotary Forcespinning Technique

Rotary forcespinning is one of techniques used for fabrication of polymer fiber. In this paper optimization of several parameters for synthesis of Polyvinyl Alcohol (PVA) fiber using rotary forcespinning technique was described. In order to obtain PVA fiber with smallest diameter the optimization parameters of solvent system and polymer concentration were performed. The results show that PVA dissolved in water as a single solvent produced fiber with high wettability. A mixture of water and ethanol as a solvent system was developed with variation in ethanol content. The effects of ethanol content on fiber diameter were investigated. Rotary forcespinning using solvent with ethanol content below 30% resulted in PVA fiber with high wettability, while solvent ethanol content of more than 70% was unable to dissolve PVA completely. The effect of PVA concentration on the fiber morphology was investigated by adjusting PVA concentration in the range of 9 to 13 weight %. The diameter of the PVA fiber was uniform and could be controlled by adjusting the PVA concentration.

Preparation and applications of poly vinyl alcohol (PVA) modified cellulose acetate (CA) membranes for forward osmosis (FO) processes

Polyvinyl alcohol (PVA)-coated cellulose acetate (CA)-based flat-sheet membranes have been fabricated and tested in the forward osmosis (FO) process. PVA was used as a surface modifying agent. CA membranes prepared by conventional immersion precipitation were treated in an aqueous solution of PVA and tested water flux and salt rejection. The effects of PVA concentration, treatment time on the hydrophilicity of membrane surface, water permeability, and salt retention property of the membrane were estimated. The modified membrane was characterized by X-ray photoelectron spectroscopy and contact angle measurement. A hydrophilicity of membrane surface was observed in longer modification times and the higher PVA solution concentration accounted for a attaching of the PVA chains by glutaraldehyde as cross-linking agent. The best condition of salt rejection and permeability performance was obtained by using 1 wt% PVA solution and treatment time of 2 min. In the FO process, modified CA membrane exhibited water flux 20% higher than unmodified CA membrane without salt leakage. This result indicated that PVA coating improved water flux performance for FO processes.

Effect of polyvinyl alcohol concentration on the ZnS nanoparticles and wet chemical synthesis of wurtzite ZnS nanoparticles

ZnS is one of the most important semiconducting materials, and this paper discusses the wet chemical synthesis of ZnS nanoparticles in cubic and hexagonal structures. The effect of polyvinyl alcohol concentration on the ZnS particle formation is studied, and ZnS nanocrystals smaller than the Bohr exciton radius have been prepared using the capping agent polyvinyl alcohol. ZnS nanocrystals of about 1.54 nm have been prepared, and their optical absorption shows interband transitions. It is found that the polyvinyl alcohol concentration has a tremendous effect on the particle growth, since particle sizes were varied with the concentration of polyvinyl alcohol. The important result is that the strain was seen negative due to the contraction of the particles. The important finding of this experiment is that the preparation of the hexagonal ZnS nanoparticles is possible at lower temperature when a particular concentration of trisodium citrate and polyvinyl alcohol is used simultaneously with the ZnS precursors.

Effect of Polyvinyl Alcohol Concentration in Spinning Dope on Diameter, Beads and HHS of Produced Nanofibers

In this study it was aimed to produce nano fibers of poly vinyl alcohol PVA polymer via electrospinning ES method and to investigate the role of PVA concentration in the spinning dope on diameter, beads and HHS of produced fibers. Spinning dopes with different concentrations of PVA at rang of 5 to 20% (wt/wt on weight of solution) prepared. The requisite voltage for ES (30 kv) was supplied by a DC high voltage power supply and for collecting the fibers a grounded aluminum foil target placed 17 cm below the tip of capillary tube (spinning nozzle). The results showed that spinning dopes with PVA concentration between 8 to 12% (wt/wt) are capable of producing PVA fibers, but those below 8% (wt/wt) concentrations because of low viscosity formed droplets known as electrospray effect. Electrospinning suppressed at spinning dope concentrations above 12% (wt/wt) due to high viscosity of dope. According to the SEM photographs of electrospun PVA fibers it revealed that in higher concentrations produced nanofibers have larger diameter with less beads and HHS in compare with lower concentrations.

Fundamental studies on the intermediate layer of a bipolar membrane Part IV. Effect of polyvinyl alcohol (PVA) on water dissociation at the interface of a bipolar membrane

This paper investigates the effect of polyvinyl alcohol (PVA) as the intermediate layer of bipolar membranes on water dissociation. The bipolar membranes are prepared by coating a solution of sulfonated polyphenylene oxide (SPPO) on the anion exchange layers, which had been immersed in PVA aqueous solutions with different concentrations in advance. The experimental results show that the effect of PVA on water dissociation is significantly affected by its concentration: at low concentration range PVA solution catalyzes water dissociation and at high concentration range PVA solution shows a retardant effect. The phenomenon is different from the situation where polyethylene glycol (PEG) is used as the intermediate layer. Based on the adsorption data and the measurements of X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy, it is found that (1) the effect of PVA concentration on water dissociation can be explained by the competition and compromise of two effects—the catalytic and hydrophilic effect of the PVA molecule and the steric effect of the enlargement of junction thickness; (2) the reason that at high concentration range PVA and PEG show different effects on water dissociation is that the junction thickness is enlarged excessively by PVA, which is based on the intrinsic characteristics of PVA molecules.

Effects of PVA concentration and ribbon immersion time on the interfacial shear strength of amorphous metallic ribbon/polypropylene composites

AbstractThe effect of PVA (polyvinyl alcohol) concentration and the immersion time of the Fe40Ni40B20 ribbon was studied in terms of interfacial shear strength. First, the PVA concentration was constant at 9 wt% while the immersion time of the ribbon is the solution was changed form 20 to 200 h. Second., the immersion time was constant at 144 h while the concentration of the PVA was changed form 1 to 12 wt%. The interfacial shear strength improved only slightly by increasing the immersion time from 20 h (0.55 ± 0.09 MPa) to 100 h (0.86 ± 0.12 MPa). The interfacial shear strength increased sharply form 0.86 ± 0.12 MPa at 100 h of immersion time to 3.02 ± 0.66 MPa at 144 h of immersion time. After 144 h of immersion, the interfacial shear strength almost leveled off (2.97 ± 0.26 MPa) at 200 h of immersion. The surface of the polypropylene (PP) after pullout and just before the ribbon fracture was studied with a scanning electron microscope (SEM). The low interfacial shear strength of composites immersed for less than 100 h is related ot the insufficient coating on the ribbon and a lack of the well developed interfacial zone. This is manifested by the presence of circumferential bands and impression from rough marking of the ribbon contact side left on the PP surface. The presence of parabolic markings and growth of spherulites on the PP surface may explain the higher interfacial shear strength observed at longer immersion times in the PVA, which suggests the existence of the well developed interfacial zone between ribbon and the PP matrix. The effect of PVA concentration on interfacial shear strength is almost similar to the effect of immersion time.