Amount Of Polyvinyl Alcohol Research Articles

Development of Mechanical Properties of Cement Paste with Different Addition of Polyvinyl Alcohol

This paper deals with using resonance method for determine the development of the mechanical properties of cement paste with different polyvinyl alcohol content. Main properties which were monitored are the dynamic Young’s modulus and dynamic shear modulus. Those properties were measured during 161 days for better understanding of influence of Polyvinyl Alcohol (PVA) added in the cement paste. Difference between this paper and already published articles is in several parameters. Main difference is that samples in this paper were cured on air, not in water. Moreover was used higher amount of polyvinyl alcohol on modification of cement paste.

Polymer Adsorption on Iron Oxide Nanoparticles for One‐Step Amino‐Functionalized Silica Encapsulation

This paper presents an original method to obtain, in one step, core/shell nanoparticles grafted covalently with polymer and functionalized with amino groups. By combining polyvinyl alcohol (PVA) and silica precursors, we were able to obtain silica‐coated and amino‐functionalized iron oxide nanoparticles (SPIONs) cross‐linked with PVA. We also showed that using silica and amino‐silica precursors together significantly increased the amount of PVA covalently bonded to the SPION surface compared to using only silica precursors. This original and interesting method has high potential for the industrial development of biocompatible functionalized nanoparticles for targeting nanomedicine.

Selective oxidation of n-butanol using gold-palladium supported nanoparticles under base-free conditions.

The base-free selective catalytic oxidation of n-butanol by O2 in an aqueous phase has been studied using Au-Pd bimetallic nanoparticles supported on titania. Au-Pd/TiO2 catalysts were prepared by different methods: wet impregnation, physical mixing, deposition-precipitation and sol immobilisation. The sol immobilisation technique, which used polyvinyl alcohol (PVA) as the stabilizing agent, gave the catalyst with the smallest average particle size and the highest stable activity and selectivity towards butyric acid. Increasing the amount of PVA resulted in a decrease in the size of the nanoparticles. However, it also reduced activity by limiting the accessibility of reactants to the active sites. Heating the catalyst to reflux with water at 90 °C for 1 h was the best method to enhance the surface exposure of the nanoparticles without affecting their size, as determined by TEM, X-ray photoelectron spectroscopy and CO chemisorption analysis. This catalyst was not only active and selective towards butyric acid but was also stable under the operating conditions.

Crystallization behavior of stable urea formaldehyde resin dispersed by polyvinyl alcohol

A series of stable polyvinyl alcohol (PVA) modified urea–formaldehyde (UF) resins have been synthesized by traditional alkaline–acid–alkaline three-step reaction and characterized by Fourier transformation infrared spectrophotometer (FTIR), scanning electronic microscope (SEM), polarization optical microscope (POM) and X-ray diffraction (XRD). In addition, some neat or modified UF resin-impregnated filter papers were prepared and used to test the effects of PVA on the tensile strength and water resistance of the UF resins. The results of formaldehyde titration analysis and viscosity measurement exhibited that when the mass ratio of PVA/U (urea as a fixed value) was increased, the free formaldehyde content of the UF resins was decreased, and the storage stability of the UF resin was improved. Besides, the SEM and POM results showed that the crystallite regions related to the colloidal particle of the UF resin became more uniform by incorporation of proper amount of PVA (with mass ratio of PVA/U around 0.0050). In addition, the result of XRD analysis indicated that the cured neat or PVA-modified UF resin with relatively high mole ratio of formaldehyde to urea has amorphous structure. The results of the mechanical testing showed that PVA can be used to strengthen and toughen the UF resin and the water resistance evaluation indicated that the UF resin modified with more PVA may have lower water resistance.

Optimization of sustained release aceclofenac microspheres using response surface methodology.

Polymeric microspheres containing aceclofenac were prepared by single emulsion (oil-in-water) solvent evaporation method using response surface methodology (RSM). Microspheres were prepared by changing formulation variables such as the amount of Eudragit® RS100 and the amount of polyvinyl alcohol (PVA) by statistical experimental design in order to enhance the encapsulation efficiency (E.E.) of the microspheres. The resultant microspheres were evaluated for their size, morphology, E.E., and in vitro drug release. The amount of Eudragit® RS100 and the amount of PVA were found to be significant factors respectively for determining the E.E. of the microspheres. A linear mathematical model equation fitted to the data was used to predict the E.E. in the optimal region. Optimized formulation of microspheres was prepared using optimal process variables setting in order to evaluate the optimization capability of the models generated according to IV-optimal design. The microspheres showed high E.E. (74.14±0.015% to 85.34±0.011%) and suitably sustained drug release (minimum; 40% to 60%; maximum) over a period of 12h. The optimized microspheres formulation showed E.E. of 84.87±0.005 with small error value (1.39). The low magnitudes of error and the significant value of R(2) in the present investigation prove the high prognostic ability of the design. The absence of interactions between drug and polymers was confirmed by Fourier transform infrared (FTIR) spectroscopy. Differential scanning calorimetry (DSC) and X-ray powder diffractometry (XRPD) revealed the dispersion of drug within microspheres formulation. The microspheres were found to be discrete, spherical with smooth surface. The results demonstrate that these microspheres could be promising delivery system to sustain the drug release and improve the E.E. thus prolong drug action and achieve the highest healing effect with minimal gastrointestinal side effects.

Synthesis and Characterization of Magnetite/Polyvinyl Alcohol Core–Shell Composite Nanoparticles

Magnetite (Fe3O4)/polyvinyl alcohol (PVA) core–shell composite nanoparticles were successfully synthesized using a coprecipitation of ferrous and ferric chloride followed by coating with PVA. The resulting nanoparticles were characterized using X‐ray diffraction, Fourier Transform Infrared Spectroscopy, Transmission Electron Microscopy, X‐ray photo electron spectroscopy, Zeta potential measurements, UV–Vis spectroscopy, Thermogravimetric Analysis, and Vibrating Sample Magnetometry (VSM). The average particle size was 13 nm. The presence of characteristic functional groups of PVA around the core of magnetite nanoparticles was confirmed by FTIR spectroscopy while the amount of PVA (%) bound to it was estimated by TGA analysis. Zeta potential measurements made by dispersing dilute sonicated samples in a Phosphate Buffer Saline (PBS pH 7.4) confirmed that the particles were negatively charged. The stability and retention of the coating material PVA in PBS (pH7.4) over a period of time were substantiated by UV–Vis spectroscopy. Room‐temperature magnetic measurements were made with a VSM which demonstrated the superparamagnetic nature of the particles with higher saturation magnetization of 56.41 emu/g. Furthermore, in vitro cytocompatibility testing of Fe3O4/PVA core–shell composite nanoparticles was carried out on human cervix cancer cells. This confirmed a 97% cell viability with no significant cytotoxicity and thereby substantiated their biocompatibility.

Electrophoretic co-deposition of polyvinyl alcohol (PVA) reinforced alginate–Bioglass® composite coating on stainless steel: Mechanical properties and in-vitro bioactivity assessment

PVA reinforced alginate–bioactive glass (BG) composite coatings were produced on stainless steel by a single step electrophoretic deposition (EPD) process. The present paper discusses the co-deposition mechanism of the three components and presents a summary of the relevant properties of the composite coatings deposited from suspensions with different PVA concentrations. Homogeneous composite coatings with compact microstructure and increased thickness, i.e. as high as 10μm, were observed by scanning electron microscopy (SEM). The surface roughness of coatings with different PVA contents was slightly increased, while a significant increase of water contact angles due to PVA addition was detected and discussed. Improved adhesion strength of coatings containing different amounts of PVA was quantitatively and qualitatively confirmed by pull-off adhesion and cycled bending tests, respectively. In-vitro bioactivity tests were performed in simulated body fluid (SBF) for 0.5, 1, 2, 4, 7, and 14days, respectively. The decomposition rate of the coatings was reduced with PVA content, and rapid hydroxyapatite forming ability of the composite coatings in SBF was confirmed by FTIR and XRD analyses. According to the results of this study, composite alginate–Bioglass® bioactive coatings combined with PVA are proposed as promising candidates for dental and orthopedic applications.

Preparation of Al2O3 dense films using sol derived from Al(NO3)3·9H2O

A new sol–gel route has been applied to prepare Al2O3 dense films using Al(NO3)3·9H2O as a raw material and acetylacetone (AcAc) as a chelating agent. The research results show that AcAc and aluminium form a complex compound in the solution, which makes the sol very stable. A small amount of polyvinyl alcohol (PVA) is added to the mixture solution as an anticracking agent. PVA not only decreases effectively the surface tension of the sol but also mitigates the decomposition of the gel films during calcination. The thin films fabricated by spin coating method after sintering at 650°C for 2 h are amorphous. Atomic force microscope and field emission scanning electron microscope images of the films reveal a crack free surface and a dense cross-section. The dielectric films have a low leakage current density in an electric field. To sum up, this new sol–gel route provides a great promising method using cheap inorganic salt Al(NO3)3·9H2O to synthesise the dense alumina thin films.

Visible light photocatalysis and electron emission from porous hollow spherical BiVO4 nanostructures synthesized by a novel route

Hollow spheres of BiVO4, made of pyramid like nanocrystals have been synthesized in an aqueous medium through a precursor solution mediated growth method with appropriate amount of polyvinyl alcohol (PVA). It was found that concentration of PVA in the precursor solution played a crucial role in determining the morphology of the product. Hollow spherical BiVO4 was formed with PVA concentration of 64mg/mL in the precursor solution while with 32mg/mL PVA concentration mixed morphology of hollow spherical and cubical structure was formed. Without adding PVA, only cubical (bulk like) BiVO4 powder was obtained. The structures have been characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), Fourier-transformed infrared (FTIR) spectroscopy, UV–Vis spectroscopy, thermogravimetry analysis (TGA) and differential thermal analysis (DTA). As-prepared hollow spherical BiVO4 samples were having monoclinic structure with energy band gap 2.42eV. The hollow spherical BiVO4 exhibited excellent visible-light-driven photocatalytic efficiency for degrading N,N,N′,N′-tetraethylated rhodamine (RhB) organic dye, which was nearly 13 times efficient than that of the samples prepared by the same method but without PVA in the precursor solution. After five recycles, the hollow spherical BiVO4 catalyst did not exhibit any significant loss of photocatalytic activity, confirming the photocatalyst is essentially stable. The BiVO4 hollow spheres also exhibited electron field emission indicating that BiVO4 with tailored morphology can be used as a multi-functional material.

Effect of viscosity of polyvinyl alcohol solution on morphology of the electrospun mullite nanofibres

Mullite nanofibres with diameters of 85–110nm were obtained by electrospinning of solutions containing different amounts of polyvinyl alcohol (PVA, as the template) ranging from 0wt% to 10wt%, which were added to the sol, and sintered at different temperatures. The sol was prepared by the sol–gel method, using aluminium isopropoxide (AIP), hydrated aluminium nitrate (AN) and tetraethylorthosilicate (TEOS) as the precursors. The details of crystal development, microstructure and thermal decomposition behaviour of the electrospun nanofibres were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and simultaneous thermal analysis (STA). The optimal content of 6wt% of PVA in the electrospinning polymeric solutions was found to be the suitable viscosity for the electrospinning and ultimately resulted in the formation of the most pure and uniform mullite nanofibres.

Nanometric particle size and phase controlled synthesis and characterization of γ-Fe2O3 or (α + γ)-Fe2O3 by a modified sol-gel method

Fe2O3 nanoparticles with sizes ranging from 15 to 53 nm were synthesized by a modified sol-gel method. Maghemite particles as well as particles with admixture of maghemite and hematite were obtained and characterized by XRD, FTIR, UV-Vis photoacoustic and Mössbauer spectroscopy, TEM, and magnetic measurements. The size and hematite/maghemite ratio of the nanoparticles were controlled by changing the Fe:PVA (poly (vinyl alcohol)) monomeric unit ratio used in the medium reaction (1:6, 1:12, 1:18, and 1:24). The average size of the nanoparticles decreases, and the maghemite content increases with increasing PVA amount until 1:18 ratio. The maghemite and hematite nanoparticles showed cubic and hexagonal morphology, respectively. Direct band gap energy were 1.77 and 1.91 eV for A6 and A18 samples. Zero-field-cooling–field-cooling curves show that samples present superparamagnetic behavior. Maghemite-hematite phase transition and hematite Néel transition were observed near 700 K and 1015 K, respectively. Magnetization of the particles increases consistently with the increase in the amount of PVA used in the synthesis. Mössbauer spectra were adjusted with a hematite sextet and maghemite distribution for A6, A12, and A24 and with maghemite distribution for A18, in agreement with XRD results.

Research on Miniature Thermoplastic Processing of Polyvinyl Alcohol Based Nanocomposites

This paper discusses the synthesis and preparation of polyvinyl alcohol based nanocomposites through the use of miniature thermoplastics processing technology. It studies the influence of different process conditions, the amount of raw materials and water on the processing performance, tensile strength and elongation at break of polyvinyl alcohol based nanocomposites. Studies have shown that using two miniature thermoplastic processes does not have much influence on the mechanical properties of polyvinyl alcohol based nanocomposites, different amount of polyvinyl alcohol will lead to enhancement of the tensile strength of the polyvinyl alcohol based nanocomposites system by the increasing amount of glycerin, and the water content has a great influence on the performance of polyvinyl alcohol based nanocomposites. To this end, according to the analysis of experimental results, it can obtain preparation conditions and influencing factors of polyvinyl alcohol based nanocomposites with the miniature thermoplastic processing conditions, and provide a new theoretical method and means for nanocomposites.

Control on the porosity of disk-like hematite particles prepared from a forced hydrolysis reaction using polyvinyl alcohol

The effects of polyvinyl alcohol (PVA) molecules on the porosity of disk-like hematite particles produced from the forced hydrolysis reaction using two kinds of PVA molecules with a well-defined molecular weight and a high degree of saponification (PVA-105 and PVA-124) were investigated. It is evident from TEM and field-emission scanning electron microscope (FE-SEM) measurements that a fraction of particles lost their spherical habit and acquired a disk-like shape by the addition of small amounts of both PVA molecules, though no difference in the particle size between the two PVA systems was observed. FE-SEM images of the particles revealed that the disk-like hematite particles are made up of small cluster particles with a diameter of approx. 5–10 nm. The disk-like particles produced a rather lower concentration for PVA-124 with a higher molecular weight than that for PVA-105 with a lower molecular weight. This fact was due to the large number of hydroxy groups in PVA-124 molecules than in PVA-105; hydroxy groups act as adsorption sites onto polynuclear (PN) primary particles and cause pronounced effects on the formation and structure of particles during the aggregation of PN particles. It was clarified from N2 adsorption measurements at 77 K that the porosity of the hematite particles can be controlled from microporous to mesoporous by changing the concentrations of PVA-105 and PVA-124, as was classified into three groups, i.e., groups 1, 2, and 3. The control particles produced without PVA molecules, classified into group 1, showed type IV adsorption isotherms, and only the voids produced between spherical particles were detected as mesopores. On the other hand, the particles produced with small amounts of PVA produced micropores as classified in group 2. In this group, the particles produced uniform micropores after being outgassed at 100–200 °C. The hematite particles produced with high concentrations of PVAs were classified into group 3. In this group, the particles after being outgassed at lower temperature produced micropores with diameters between 0.6 and 2.0 nm, though the micropores in the particles changed to mesopores after outgassing at 300 °C. This mesopore formation was attributed to the elimination of the PVA-adsorbed layer by evacuation at 300 °C, i.e., the large voids residing in the disk-like hematite particles make the particles mesoporous. This mesopore formation was further confirmed by adsorption experiments of C6H6(benzene) and CCl4 molecules at 298 K.

Eccentric Loading of Fluorogen with Aggregation‐Induced Emission in PLGA Matrix Increases Nanoparticle Fluorescence Quantum Yield for Targeted Cellular Imaging

A simple strategy is developed to prepare eccentrically or homogeneously loaded nanoparticles (NPs) using poly (DL-lactide-co-glycolide) (PLGA) as the encapsulation matrix in the presence of different amounts of polyvinyl alcohol (PVA) as the emulsifier. Using 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl)-phenyl)amino)-phenyl)-fumaronitrile (TPETPAFN), a fluorogen with aggregation-induced emission (AIE) characteristics, as an example, the eccentrically loaded PLGA NPs show increased fluorescence quantum yields (QYs) as compared to the homogeneously loaded ones. Field emission transmission electron microscopy and fluorescence lifetime measurements reveal that the higher QY of the eccentrically loaded NPs is due to the more compact aggregation of AIE fluorogens that restricts intramolecular rotations of phenyl rings, which is able to more effectively block the non-radiative decay pathways. The eccentrically loaded NPs show far red/near infrared emission with a high fluorescence QY of 34% in aqueous media. In addition, by using poly([lactide-co-glycolide]-b-folate [ethylene glycol]) (PLGA-PEG-folate) as the co-encapsulation matrix, the obtained NPs are born with surface folic acid groups, which are successfully applied for targeted cellular imaging with good photostability and low cytotoxicity. Moreover, the developed strategy is also demonstrated for inorganic-component eccentrically or homogeneously loaded PLGA NPs, which facilitates the synthesis of polymer NPs with controlled internal architectures.

Poly(vinyl alcohol) Membrane with Surface Immobilized β-Cyclodextrin Synthesis via Glutaraldehyde

A novel cyclodextrin (CD) grafted polyvinyl alcohol (PVA) material has been synthesized. Beta-cyclodextrin (βCD) is chemically grafted into PVA via glutaraldehyde (GA) in acidic medium (HCl). The reaction mechanism and the membrane surface grafting are confirmed by Fourier Transform Infrared Spectroscopy (FTIR), modulus of elasticity and contact angle determination. An amount of PVA and βCD are dissolved in a pH 3 HCl solution at 90oC with continuous stirring. Glutaraldehyde was slowly added into the clear solution to effect grafting and crosslinking between the PVA and βCD. It was cooled and allowed to stand overnight to eliminate bubbles formed. The clear PVA-GA-βCD material is casted on a glass plate to form membranes which are peeled off after subsequent drying. The grafted and crosslinked membrane showed peaks in the IR spectra confirming the chemical bonding between PVA, GA and βCD. PVA-GA-βCD membrane is 6% stronger than the physically blended membrane as shown by the increase of its modulus of elasticity. Likewise, a reduction in the hydrophilicity is observed by the newly synthesized membrane as shown by the increase of the membrane’s contact angle.This newly developed material with immobilized βCD may significantly improve the performance of PVA-CD pervaporation membranes by reducing the phase separation phenomenon due to agglomeration of CD in high concentrations as well as preventing βCD from dissolving in aqueous feed. Moreover, this may open new perspective for the development of high performance nanofibers and other nanomaterialssuch as drug delivery system materials and inclusion complexes.

Preparation and Characterization of Diatomite-Based Porous Ceramics

Diatomite-based porous ceramics were prepared by hand compression molding under low temperature sintering, using diatomite as raw material, sodium carbonate and polyvinyl alcohol (PVA) as additives. The effects of sintering temperature, addition amount of sodium carbonate and PVA on the properties of porous ceramics were discussed. The prepared porous ceramics were characterized by mercury porosimeter, XRD, SEM and FTIR. And the adsorption of methyl orange by porous ceramics was investigated. The results show that the performances of porous ceramics, such as porosity and crushing strength, change with the addition amount of sodium carbonate and PVA, also the sintering temperature. The optimum formula for preparing porous ceramics used as carrier and filter simultaneously consists of 100 portions of calcined diatomite, 10 portions of sodium carbonate, 150 portions of water, PVA and polyacrylamide (PAM) solution[m(H2O):m(PVA):m(PAM)=1000:4:4]. When sintered at 900°C, the porosity, crushing strength, average pore diameter and specific surface area of prepared porous ceramics are 71.74%, 4.535MPa, 10.023μm and 230m2/g, respectively. The prepared porous ceramics are composed of tetragonal cristobalite. And the decoloration conversion for methyl orange of prepared porous ceramics can reach 40.43% in 90 min.

Structural and magnetic properties of cobalt ferrites synthesized using sol-gel techniques

Cobalt ferrite (CoFe2O4) was synthesized using sol-gel techniques from cobalt nitrate: iron nitrate: polyvinyl alcohol (PVA) gel in a ratio of 1:2:12. Variations in the amount of PVA in water (5 %, 10 % and 15 %) influenced the crystallite size and phases of the ferrite products, which in turn controlled their magnetic properties. X-ray diffraction studies indicated single phase CoFe2O4 with larger crystallite size and with the hysteresis loops displaying an increase in both coercive field and squareness as the PVA content was increased. Differential scanning calorimetry (DSC) showed that desorption of water and combustion of excess gel were clearly observed in CoFe2O4 prepared from 10 % and 15 % PVA in water. In the case of 5 % PVA in water, two other ratios of cobalt nitrate: iron nitrate: PVA solution were also tested and it was found that the 1:2:10 ratio led to the smallest coercive field and squareness.

Temperature effects on the adsorption of polyvinyl alcohol on silica

Abstract The influence of temperature on the adsorption of polyvinyl alcohol (PVA) on a silica surface was studied from 15–35°C. The structure of the polymer adsorption layer was determined from spectrophotometric, viscosity and thermogravimetric measurements. The amount of PVA adsorbed, macromolecules’ conformation in solution, thickness of the polymer adsorption layer, and changes in the heating curve of SiO2 with adsorbed polymer were determined. Temperature influences the PVA chain conformation in solution and the structure of the polymer adsorption layer. A temperature rise causes relaxation of polymer coils which results in an increase in the linear dimensions of PVA chains in the solution, the creation of a thicker adsorption layer, and an increase in polymer adsorbed. Polymer adsorption on the silica surface also causes changes in the heating curve of these systems. The mass losses due to heating are smallest for the systems obtained at 15°C because the least polymer is adsorbed at this temperature.

The Gelation Study of Silk Fibroin for Biomedical Application

Silks are the biomaterials that have been used for a century. Most of them are related to the biomedical applications especially silk fibroin. Since the gelation process of silk fibroin was affected by many factors for example the concentration of silk fibroin protein, pH, temperature and cross-linking agent. These factors also influence on the mechanical properties of the silk gel. This study is then focused on making silk fibroin gel by using poly vinyl alcohol (PVA) as a cross-linking agent and physical induced by ultrasonic. The structure of SF/PVA gel was examined by Fourier Transform Infrared (FT-IR). The two main effects of ultrasonic and PVA to the silk fibroin gelation are the gelation time and the gel structure. The more ultrasonic power and PVA amount can make the silk fibroin solution becomes a gel faster. For the gel structure, both ultrasonic and PVA affect to the Amide I and Amide II structure which lead to the gel characteristic used as a wound dressing in the future.

Taste masked lipid pellets with enhanced release of hydrophobic active ingredient

Solid lipid extrusion is a suitable technique to produce oral dosage forms with improved taste properties. The design of a lipid formulation for poorly water soluble drugs is a challenge because of the poor dissolution and potential bioavailability problems. In this study, solid lipid extrusion at room temperature was applied for the formulation development of the BCS Class II drug NXP 1210. Powdered hard fat (Witocan® 42/44 mikrofein), glycerol distearate (Precirol® ato 5) and glycerol trimyristate (Dynasan® 114) were investigated as lipid binders. Different amounts of polyvinylalcohol (PVA)–polyethyleneglycol (PEG)-graft copolymer (Kollicoat® IR) and crospovidone (Polyplasdone® Xl-10) were scrutinized as solubilizers. The dissolution profiles depicted a short lag time (about 2min) and then fast and complete dissolution of NXP 1210 by increasing the amount of crospovidone. The initial release was more delayed with an increased amount of PVA–PEG-graft copolymer. Dissolution rate could also be influenced by changing the lipid binder from pure hard fat into a mixture of hard fat, glycerol distearate and glycerol trimyristate. The formulations are feasible for taste-masked granules or pellets containing poorly soluble drugs.