Concentration Of PVA Solution Research Articles

Komposit Zeolit-Polivinil Alkohol sebagai Adsorben untuk Menurunkan Kesadahan Air Tanah

Granular zeolite-polyvinyl alcohol (PVA) composites without glutralaldehyde and zeolite-PVA composites with the addition of glutaraldehyde were carried out in this study and used as adsorbents. This study aims to reduce groundwater hardness, determine the optimum zeolite size in composite mixtures, and determine the characterization of functional groups in composites. The stages of the research included: preparation and activation of zeolite with variations in zeolite sizes of 100, 60 and 45 mesh and variations in composition of zeolite-polyvinyl alcohol 1:1; 1:2; 2:1; 2:3 and 3:2. Furthermore, the preparation of PVA solution concentration of 9% and the formation of the composite. The results showed that the optimum size of the zeolite on the composite without glutaraldehyde was 60 mesh with a decrease in hardness of 68% while the ratio of the optimum zeolite-PVA composition was at a ratio of 3:2 with a decrease in hardness of 34 mg/L. The results of Langmuir and Freundlich isotherm analysis showed the presence of chemical bonds because the determination value (R2) of the adsorption isotherm was > 0.9. The results of functional group characterization showed OH- in the zeolite-PVA composite without glutaraldehyde at a wavelength of 3363.01 cm-1 while in the composite with glutaraldehyde at a wavelength of 3345.89 cm-1. The C=C functional group appeared at a wavelength of 1628.73 cm-1 for the zeolite-PVA composite without glutaraldehyde and 1635.86 cm-1 for the composite with glutaraldehyde. At a wavelength of 788.70 cm-1 and 794.40 cm-1, the Si-O symmetric stretching vibrations show in the zeolite structure.

Effect of Electrode Type on Electrospun Membrane Morphology Using Low-Concentration PVA Solutions.

Electrospun polymer nanofiber materials have been studied as basic materials for various applications. Depending on the intended use of the fibers, their morphology can be adjusted by changing the technological parameters, the properties of the spinning solutions, and the combinations of composition. The aim of the research was to evaluate the effect of electrode type, spinning parameters, polymer molecular weight, and solution concentration on membranes morphology. The main priority was to obtain the smallest possible fiber diameters and homogeneous electrospun membranes. As a result, five electrode types were selected, the lowest PVA solution concentration for stable spinning process was detected, spinning parameters for homogenous fibers were obtained, and the morphology of electrospun fiber membranes was analyzed. Viscosity, conductivity, pH, and density were evaluated for PVA polymers with five different molecular weights (30–145 kDa) and three concentration solutions (6, 8, and 10 wt.%). The membrane defects and fiber diameters were compared as a function of molecular weight and electrode type. The minimum concentration of PVA in the solution allowed more additives to be added to the solution, resulting in thinner diameters and a higher concentration of the additive in the membranes. The molecular weight, concentration, and electrode significantly affected the fiber diameters and the overall quality of the membrane.

High Throughput Preparation of Poly(Lactic-Co-Glycolic Acid) Nanoparticles Using Fiber Fluidic Reactor.

Polymeric nanoparticles (NPs) have a variety of biomedical, biotechnology, agricultural and environmental applications. As such, a great need has risen for the fabrication of these NPs in large scales. In this study, we used a high throughput fiber reactor for the preparation of poly(lactic-co-glycolic acid) (PLGA) NPs via nanoprecipitation. The fiber reactor provided a high surface area for the controlled interaction of an organic phase containing the PLGA solution with an aqueous phase, containing poly(vinyl alcohol) (PVA) as a stabilizer. This interaction led to the self-assembly of the polymer into the form of NPs. We studied operational parameters to identify the factors that have the greatest influence on the properties of the resulting PLGA NPs. We found that the concentration of the PLGA solution is the factor that has the greatest effect on NP size, polydispersity index (PDI), and production rate. Increasing PLGA concentration increased NP sizes significantly, while at the same time decreasing the PDI value. The second factor that was found to affect NP properties was the concentration of PVA solution, which resulted in increased NP sizes and decreased production rates. Flowrates of the feed streams also affected NP size to a lesser extent, while changing the operational temperature did not change the product’s features. In general, the results demonstrate that fiber reactors are a suitable method for the large-scale, continuous preparation of polymeric NPs suitable for biomedical applications.

Preparation of bio-composite hydrogel of hydroxyapatite based using gamma irradiation for artificial bone

The aim of this study is to prepare bio nano-hydroxyapatite based biomaterial for artificial bone using gamma-γ. Preparation of composite hydrogel bio nano-hydroxyapatite based on artificial bone has been carried out via gamma irradiation techniques. The PVA-HAp viscose solutions were prepared using different ratios of HAp (15-30%) with a single PVA solution concentration (20 %) mixed strongly until homogenous. The prepared PVA-HA solution was molded, freeze-thaw to be composites and irradiated using gamma rays (0-20 kGy). The composites were measured its mechanical properties and biodegradation. Surface micrographs of composites were measured using Scanning Electron Microscopy (SEM). The results showed that at optimum conditions (20% PVA-30%,HAp, irradiation dose 20 kGy), the physical appearances of composite more flexible and strong with tensile strength were 1.003 MPa and the elongation at break was 372.33%. With increasing irradiation and HAp content up to 30%, the biodegradation of composite decreased. From SEM measurement the pore sizes of the composite were heterogeneous. PVA-HAp composites prepared using gamma irradiation can be considered as a candidate for biomaterial.

Poly(vinyl butyral)/zeolitic imidazole framework-8/poly(vinyl alcohol) thin-film nanocomposite nanofiltration membrane: synthesis and characterization

Zeolitic imidazole framework-8 (ZIF-8) was synthesized and its structure was investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffractometry methods. Poly(vinyl butyral) (PVB)/ZIF-8 nanocomposite membranes as substrate were prepared with different percentages of ZIF-8 nanoparticles. Then, a thin layer of poly(vinyl alcohol) was created by coating method and cross-linked with glutaraldehyde (GA). As a result, thin-film nanocomposite (TFN) nanofiltration membranes were obtained. The TFN membranes were characterized by SEM, FTIR, atomic force microscopy, and contact angle measurement. The effects of incorporating ZIF-8 on membrane performance were investigated. As amount of ZIF-8 in the substrate was increased, water flux increased due to increasing porosity, and because of increasing hydrophilicity and negative charge of membrane surface fouling decreased. Thereby, the TFN membrane with ZIF-8 at 3% showed the highest water flux and the least fouling because of increasing porosity. As the concentration of PVA solution and GA was increased, the flux decreased and rejection increased. The PVB/(ZIF-8 3%) substrate membrane with PVA (1%) and GA (5%) cured at the temperature of 100 °C for 30 min resulted in the optimum balance of flux and rejection. For TFN membranes prepared under optimum conditions, the average rejection of Congo red dye was 98% and pure water flux was about 195 L/m2 h.

Concentration dependent optical properties of rhodamine B doped poly(vinyl alcohol) solutions

The optical properties, namely refractive index (RI) studies, are reported on a series of pure and doped poly(vinyl alcohol) (PVA) in solution form. The PVA solutions were synthesized with 1, 2, 3, 4, and 5 wt% of PVA in distilled water followed by doping with Rhodamine B in concentrations ranging from 0.05 wt% to 2 wt%. The absorption spectra show an observable shift in the band edge position towards higher wavelength with increase in PVA wt%. When the dopant molecules are added, the curves are drastically modified with the occurrence of new peaks arising at higher doping concentrations along with change in the bandgap. These effects are prominent for all the concentration of PVA solution. The RI does not change much for low doping wt%. but when dopant is added in higher concentrations, it increases slightly reaching a maximum of ∼1.35 at 2 wt%. It is observed that host polymer properties dominate at low doping while a combination of host polymer and dopant dye properties dominate at higher doping concentrations.

Preparation and Dielectric Property of C/SiO<sub>2</sub> Composite via Self-Assembly

In this paper, C/SiO2 bulk composite was prepared via SiO2 microspheres’ self-assembly process combined with heat treatment. SEM and impedance analyzer was used to investigate the microstructure and high-frequency dielectric properties of the composites. The results show that SiO2 microspheres constituted the composite matrix, whose porosity was slightly higher than the densest hexagonal stacking. Sheet carbon distributed in pores formed by SiO2 microspheres. The real and imaginary parts of the dielectric constant of the composite material increased with the content of carbon, but decreased with the frequency. The permittivity of C/SiO2 composite could be adjusted by control the concentration of PVA solution.

Bioinspired design and assembly of layered double hydroxide/poly(vinyl alcohol) film with high mechanical performance.

Inspired by the hierarchical structure and excellent mechanical performance of nacre, LDH nanosheets with an appropriate aspect ratio to withstand significant loads and at the same time allow for rupture under the pull-out mode were synthesized as artificial building blocks for the fabrication of nacre-like films. Multilayered PVA/LDH films with a high tensile strength and ductility were prepared for the first time by bottom-up layer-by-layer assembly of pretreated LDH nanosheets and spin-coating of PVA. The weight fraction of inorganic LDH platelets in the hybrid PVA/LDH films (wp) was controlled by changing the concentration of PVA solution applied in the spin-coating process. The resulting films revealed that the PVA/LDH hybrid films were piled close together to form a well-defined stratified structure resembling the brick-and-mortar structure of natural nacre. In the hybrid films, the content of inorganic LDH platelets was comparable to the value in nacre, up to 96.9 wt %. It could be clearly seen that the mechanical performance of the as-prepared PVA/LDH films was greatly improved by increasing the rigid building-block LDHs. The tensile strength of the 2 wt % PVA/LDH hybrid film reached a value of 169.36 MPa, thus exceeding the strength of natural nacre and reaching 4 times that of a pure PVA film. Meanwhile, its elastic modulus was comparable to that of lamellar bone.

Friction of double‐network hydrogels against glass substrate in poly(vinyl alcohol) aqueous solution

AbstractThe frictional coefficient of biological joint cartilage is extremely low. For this, many researchers are looking to develop materials that are similar to those in nature. We prepared a poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate)/polyacrylamide double‐network hydrogel, and tested the friction of the hydrogel in poly(vinyl alcohol) (PVA) aqueous solution, which imitates a biological environment, against glass substrate. Results show that there is a transition sliding velocity in the friction test, which decreases with an increase in PVA solution concentration. At low sliding velocities, the frictional stress exhibits a minimum at a PVA concentration of 2c*, where c* is the overlap concentration. It is assumed that a separation layer of PVA has formed completely at this concentration, the thickness of which is calculated. In addition, the friction of the hydrogel is not sensitive to the normal pressure in PVA aqueous solution. © 2014 Society of Chemical Industry

Al<sub>2</sub>O<sub>3</sub>陶瓷催化剂载体的制备

以氧化铝作为主要原料，利用自制柱塞式挤压模具通过挤压成型法制备φ4 × 10 mm规格的陶瓷催化剂载体。通过对不同原料组成的载体进行表征，研究了各配方对载体性能的影响。在配方中含有高温粘结剂，考察了粘结剂的用量对载体强度的影响。在配方中还含有PVA溶液，考察了PVA用量对载体的造孔效果的影响，从而达到制造最佳催化剂陶瓷载体的目的。 Ceramic catalyst support, with size of 4 × 10 mm, was prepared by plunger extrusion molding using Al2O3 powder as main material. Effects of the composition on the characteristics of the support with different components were investigated. In order to improve the strength of the support, high-temperature adhesive was added in sample. Effect of the concentration of PVA solution on the pore-forming effect of the support was also investigated. The best composition of the support was finally found by investigation.

Optimization of electrospinning process using intelligent control systems

This study describes the application of intelligent control systems in electrospinning engineering as well as to use these approaches for optimizing processing conditions. A multi-objective optimization method based on gene algorithm GA has been proposed for the design and control of electrospinning process. The processing parameters including Polyvinyl alcohol PVA solution concentration, applied voltage, spinning distance and volume flow rate were used as design variables and were mathematically related with the electrospun fiber properties fiber diameter and its distribution using gene expression programming GEP technique. Nonlinear mathematical functions were derived based on the processing parameters. Afterward, using a multi-objective optimization technique based on gene algorithm, optimal conditions were found in such a way that, mean electrospun fiber diameter and its distribution to be minimized.

Electrospraying Fabrication and Characterization of Low Molecular Weight Poly(vinyl alcohol)/Silver Composite Nanospheres for Antibacterial Applications

Low molecular weight poly(vinyl alcohol) (LMW-PVA)/silver (Ag) composite nanospheres were prepared using an electrospraying technique by controlling the concentration of PVA solution. Since PVA is water-soluble and biocompatible, it is one of the best polymers for preparation of antibacterial materials. The composite nanospheres were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and antibacterial activity measurement. The LMW-PVA/Ag composite nanospheres had ∼350 nm average diameter and showed powerful antibacterial ability.

Physically crosslinked poly(vinyl alcohol) hydrogels with magnetic field controlled modulus

Physically cross-linked isotropic and anisotropic poly(vinyl alcohol) (PVA) hydrogels containing micron-sized carbonyl iron particles were prepared through a cyclic freezing–thawing process. The PVA hydrogel can respond to a magnetic field and shows a magnetorheological (MR) effect, i.e., the modulus of the PVA hydrogel can be adjusted under a magnetic field. The chain-like structures of carbonyl iron are formed in the PVA hydrogel after orientation under a magnetic field of 1.5 T. Also some magnetic field induced oriented pores with a tunable diameter are observed in the dried PVA gel. The MR effect can be adjusted by changing the carbonyl iron content, the initial concentration of PVA solution and test frequency. The formation of aligned chain-like structures of carbonyl iron in the anisotropic PVA MR hydrogel improves the compression properties and the MR effect. At a carbonyl iron content of 70 wt%, the maximum absolute and relative MR effect of anisotropic PVA MR hydrogels are ∼1.24 MPa and ∼230%, respectively. The PVA hydrogels with good MR effects and moderate mechanical strength have potential applications in artificial muscle, soft actuators and drug release.

Preparation of Low Molecular Weight Polyvinyl alcohol)/Montmorillonite Composite Nanoparticles Using an Electrospraying Technique

Composite nanoparticles composed of low molecular weight poly(vinyl alcohol) (LMW-PVA) and montmorillonite (MMT) were prepared using the electrospraying technique by regulating PVA solution concentration. Field-emission type scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, reflection type X-ray diffraction and thermal gravimetric analysis were utilized to characterize the LMW-PVA/MMT composite nanoparticles morphology and properties. MMT platelets were exfoliated and well distributed within the composite nanoparticles. It was also found that the thermal stability was enhanced by the addition of MMT.

Electrospun poly(vinyl alcohol) nanofibers: effects of degree of hydrolysis and enhanced water stability

The effects of the degree of hydrolysis (DH) of poly(vinyl alcohol) (PVA) on electrospinning and water resistance of electrospun PVA/poly(acrylic acid) (PAA) composite fibers were explored. At a constant concentration of PVA solution (∼8wt%), the average diameter of electrospun PVA fibers increased with increasing DH. The water resistance of heat-treated PVA/ PAA composite fibers was dramatically enhanced, and was also affected by PAA weight fractions (φPAA) in PVA/PAA blend solutions.

Preparation and characterization of high‐molecular‐weight atactic poly(vinyl alcohol)/sodium alginate/silver nanocomposite by electrospinning

AbstractHigh‐molecular‐weight poly(vinyl alcohol) (PVA)/sodium alginate (SA)/ silver nanocomposite was successfully prepared via electrospinning technique. Water‐based colloidal silver in a PVA/SA blend solution was directly mixing without any chemical and structural modifications into PVA/SA matrix to form an organic‐metallic nanocomposite. The effect of the addition of silver colloidal solution on the PVA/SA/silver nanocomposite was investigated through a series of experiments varying molecular weight of PVA and electrospinning processing parameters such as concentration of PVA solution, PVA/SA blend ratio, applied voltage, and tip‐to‐collector distance. In the case of PVA with number‐average degree of polymerization of 1700, by increasing the amount of SA in spinning solution, the morphology was changed from fine uniform fiber to beaded fiber or bead‐on‐string fiber structure. Increase of the amount of silver colloidal solution resulted in higher charge density on the surface of ejected jet during spinning, thus more electric charges carried by the electrospinning jet. As the charge density increased, the diameter of the nanocomposites became smaller. Transmission electron microscopy images showed that the dense silver nanoparticles were well separately dispersed in PVA/SA matrix. Energy‐disperse X‐ray analysis indicated that carbon, oxygen, natrium, and silver were the principle element of PVA/SA/silver nanocomposite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1916–1926, 2009

Improvement of Hydrophobic Properties of the Electrospun PVA Fabrics by SF<sub>6</sub> Plasma Treatment

Electrospun fabrics, prepared from 5, 7 and 10%w/v were Poly(vinyl alcohol) (PVA) solutions successfully prepared. The electrospinning condition was 15 kV, distance 15 cm, flow rate of 1 ml/hr and spinning time of 5 hours. Physical properties of electrospun PVA fabrics were analysed by SEM, FE-SEM and contact angle measurement.The contact angle of the electrospun PVA fabrics was 54.5°, characterizing the hydrophilicity of the fabrics. Hydrophobic properties of the electrospun PVA fabrics were improved by plasma treatment using radio frequency inductively coupled plasma (RF-ICP). RF-ICP plasma treatment of the electrospun PVA fabrics were carried out sulphurhexafluorene (SF6) gas with pressure of 0.5 Torr, RF power of 30W and treating time of 30, 60, 90 and 120 seconds. Effects of the PVA solution concentration and plasma treating time on hydrophobicity of the electrospun PVA fabrics were determined by contact angle that result of contact angle of treated fabrics increased when treated time increased and they decreased when concentration of fabrics increased.

Hybrid Bioactive Glass-Polyvinyl Alcohol Prepared by Sol-Gel

Bioactive glasses are materials that have been used for the repair and reconstruction of diseased bone tissues, as they exhibit direct bonding with human bone tissues. However, bioactive glasses have low mechanical properties compared to cortical and cancellous bone. On the other hand, composite materials of biodegradable polymers with inorganic bioactive glasses are of particular interest to engineered scaffolds because they often show an excellent balance between strength and toughness and usually improved characteristics compared to their individual components. Composite bioactive glass-polyvinyl alcohol foams for use as scaffolds in tissue engineering were previously developed using the sol-gel route. The goal of this work was the synthesis of composite foams modified with higher amounts of PVA. Samples were characterized by morphological and chemical analysis. The mechanical behavior of the obtained materials was also investigated. The degree of hydrolysis of PVA, concentration of PVA solution and different PVA-bioactive glass composition ratios affect the synthesis procedure. Foams with up to 80 wt% polymer content were obtained. The hybrid scaffolds obtained exhibited macroporous structure with pore size varying from 50 to 600 µm and improved mechanical properties.

Mechanical properties of nanohydroxyapatite reinforced poly(vinyl alcohol) gel composites as biomaterial

Nanohydroxyapatite reinforced poly(vinyl alcohol) gel (nano-HA/PVA gel) composites has been proposed as a promising biomaterial, especially used as an articular cartilage repair biomaterial. In this paper, nano-HA/PVA gel composites were prepared from mixing nano-HA particles modified by silicon coupling agent, with physiological saline solution (PSS) of PVA by freezing-thawing method. The effects of various factors on the mechanical properties of nano-HA/PVA gel composites were evaluated. It was shown that the mechanical behavior of nano-HA/PVA gel composites was similar to that of natural articular cartilage, which held special viscoelastic characteristics. The tensile strength and tensile modulus of the composites improved correspondingly with the increase of freezing-thawing times and concentration of PVA solution. The more concentration of PVA solution, the higher influence degree of concentration on the tensile strength of composites is. The tensile strength and tensile modulus of nano-HA/PVA hydrogel composites increased first and then decreased with the rising nano-HA content of the composites. The tensile modulus of the composites improved remarkably with the increase of elongation ratio.

Preparation and properties of metal-PVA composite hydrophilic ultrafiltration membranes

Metal-polyvinyl alcohol (PVA) composite ultrafiltration membranes were prepared by coating a certain concentration of PVA solution on metallic fiber sintered membranes. The effects of preparation conditions, such as the coating solution concentration, sequence and times of coating, and heat-treatment on the properties of the composite membranes were studied. The results show that the hole diameter of the composite membrane decreases with the increases of the concentration of PVA, the hole diameter of composite membrane is different when the sequence of coating is different. When the higher concentration of PVA solution is used to coat the metallic membrane for the first time and the other smaller one for the second time, the hole diameter of the composite membrane is relatively small, compared with that of the composite membrane made by the smaller concentration of PVA solution for the first time and the other higher one for the second time. The holes of the composite membrane contract and the stability of the membrane is improved by heat treatment. When metal-PVA composite hydrophilic membranes are used to treat the oil/water emulsion with the concentration of 1000 mg·L−1, the retention is from 80% to 90%, and the permeate flux is from 15 L·m−2·h−1 to 40 L·m−2·h−1 at pressure of 0.2 to 0.3 MPa.