Polyvinyl Alcohol Water Research Articles

Supramolecular adsorption of cyclodextrin/polyvinyl alcohol film for purification of organic wastewater

AbstractInto purified organic wastewater, α-, β-, and γ-cyclodextrin (α-, β-, and γ-CD) were added to polyvinyl alcohol (PVA) with ammonium persulfate as the crosslinker. The CD/PVA composite film with low water solubility and supramolecular adsorption was prepared by solvent evaporation. Fourier transform infrared spectroscopy showed that when CD was successfully added to PVA, the crosslinking process had no effect on -OH, and the structure was stable after soaking in water for 120 h. Solubility experiments showed that the stability of PVA in water was significantly improved. The results of phenolphthalein adsorption showed that the composite film followed the Langmuir isothermal adsorption and the pseudo-second-order kinetics. According to the Langmuir equation, the theoretical maximum adsorption capacities of α-, β- and γ-CD/PVA composite films were 0.41, 2.05, and 2.00 mg/g, respectively. The parameters of the Freundlich equation indicate that the adsorption of the composite film is physical adsorption. The time for α-CD/PVA composite film to reach equilibrium was the shortest, while the longest was for β-CD/PVA composite film. The intraparticle diffusion model showed that the adsorption was mainly affected by the diffusion of the boundary layer, and the diffusion rate limitation of the boundary layer of the high-concentration phenolphthalein solution was more obvious.

Control of formation of viscoelastic droplets and distribution of nano-inclusions in functional deposition for lithium-sulfur batteries.

The electrospray process produces micro/nanodroplets for various applications such as thin and uniform coatings, drug carriers and mass spectrometry. In this paper, we study the spray processes of viscoelastic jets using simulations and experiments. In discretized modeling, the jet is perturbed with axisymmetric instability and the growth of this instability causes the jet to break into droplets. For the experiments, a solution of polyvinyl alcohol in water is sprayed and is visualized using a high-speed camera. The droplet size distribution is studied from simulations with experiments for three spray cases: electrospray, air spray, and air-controlled electrospray. Our simulations and experiments reveal that the electric field is effective in reducing the droplet size, while air flow offers more jet break-ups and thus a larger number of droplets. As a result, air-controlled electrospray where these two driving forces are synergistically combined leads to a larger number of smaller droplets than electrospray or air spray. Finally, we applied three spray processes to obtain a deposition of sulfur/mesoporous carbon/graphene/polymer binder composites as a lithium sulfur battery cathode and demonstrated that air-controlled electrospray leads to a higher capacity and rate capability than other processes, exhibiting 800 mA h g-1 at 0.5C and 600 mA h g-1 at 2C.

Methane hydrate formation in dispersed polyvinyl alcohol cryogel

Kinetics of methane hydrate formation in frozen water solutions (FWS) and polyvinyl alcohol (PVA) cryogel stabilized with hydrophobic silica nanoparticles was first studied. PVA cryogel is a macroporous heterogeneous gel formed at the special conditions of the freezing and subsequent melting processes of the PVA water solution. Such parameters as a rate and a conversion of water to hydrate were investigated for dispersed FWS, PVA cryogel, and dispersed ice at the same thermodynamics conditions using the same equipment. It was found out that the transformation the main part of water contained in FWT and PVA cryogel into hydrate was more than ten times faster than that for dispersed ice. The resistance to hydrate formation/dissociation processes was studied for dispersions of PVA cryogel. Gas hydrate formation and dissociation were carried out at isochoric conditions using temperature cycling. It was shown that cryogels of PVA water solution stabilized with hydrophobic silica nanoparticles were resistant to gas hydrate formation/dissociation processes prompting suggestions that cryogels of PVA water solution might be reused for gas hydrate formation/dissociation multiple times without significantly decrease in the conversion water to hydrate.

Total reflection X-ray fluorescence used to distinguish mechanically separated from non-mechanically separated meat

This paper presents the successful application of total reflection X-ray fluorescence spectroscopy (TXRF) for the identification of products obtained from mechanically separated meat (MSM), a very important issue for food quality and safety. According to the European Food Safety Authority, one of the most important parameters to distinguish MSM is the content of Ca. Consequently, the development of reliable and cost-effective analytical tools is very important to monitor the chemical composition of these foods.In this study, we have developed an analytical method for elemental analysis of meat samples based on total reflection X-ray fluorescence. A simple sample preparation by suspending the grinded meat sample in a solution of diluted Triton X-100 and polyvinyl alcohol in water showed to be the best for this kind of samples. Fresh chicken meat, chicken meat with different percentage of MSM, pure MSM and meat products prepared with MSM were analyzed. The content of K, Ca, Fe, Cu and Zn was determined. Results show that Ca, but also K and Fe are significant markers to distinguish MSM from fresh meat. A limit of 40% MSM for differentiation was achieved by applying principal component analysis. The method accuracy was evaluated comparing the obtained results with those obtained after acidic digestion and ICP-MS analysis.

Size control synthesis and amperometric sensing activity of Palladium nanoparticles for Glucose detection

Size controlled synthesis of palladium nanoparticles of varying average diameter ranging from 8.1 to 21.3 nm, was executed by controlling the time of reflux of the facile reduction of PdCl2 in a single pot using citric acid as reducing agent in presence of the steric stabilizer poly vinyl alcohol in water. The as synthesized nanomaterials were analysed by different microscopic techniques and utilized for the construction of a few anode-catalysts for biosensing of glucose. The catalytic activity of the anodes was characterized by cyclic voltammetry and chronoamperometry in different glucose solutions of varying concentration in 0.1M aqueous alkali. The maximum sensitivity is 66.2 µA cm-2 mM-1 found at the potential of 0.1V with respect to HgO/Hg electrode, for the particles having optimum crystallite-diameter of 12nm obtained from the solution having reflux time of 1.5 hour. The lowest limit (8.33 µM) and long linear range of detection (8.33 to 166 µM) are also important parameters of the best sensor studied. The results seem to help a better understanding and improvement of Palladium-based amperometric glucose sensor.

Molecular Association Studies on Polyvinyl Alcohol at Different Concentrations

Ultrasonic velocities, densities, and viscosities have been measured for the solution of polyvinyl alcohol in water at concentration range of 0.3% to 1% at temperature 35°C. Ultrasonic velocities have been measured using variable path ultrasonic interferometer at 1 MHz frequency. The acoustical parameters like adiabatic compressibility, acoustic impedance, intermolecular free length, and relaxation time have been calculated by using above‐mentioned values of ultrasonic velocities, densities, and viscosities. The variation of these acoustical parameters is explained in terms of solute‐solvent interaction in a polymer solution.

MODIFIED ADHESIVE COMPOSITIONS BASED ON POLYVINYL ALCOHOL

The use of water soluble adhesives of both natural and synthetic origin, unlike adhesives on organic basis, contributes to solving problems of environmental protection and improvement of sanitary conditions. Therefore the purpose of the research is to make modifications of soluble polyvinyl alcohol adhesive compositions of various applications and forms of origin and evaluate their influence on technological and operational properties of adhesives. The research has the following results. Firstly, the authors have conducted the modification of polyvinyl alcohol water compositions by low-molecular (montmorillonite, wollastonite, phosphate acid) and high-macromolecular (starch) additives to improve technological and operational properties of the compositions. The viscosity of the composition was measured on Brookfield viscometer of type "DV-I". Cryo-processing (freezing) of the samples was carried applying a device for climatic testing "Kimura" KT70068. Adhesion was estimated by tensile strength during shear of glued wooden plates. Then, the influence of modifying additives on the properties of water-soluble adhesive compositions was determined. High-technological filled compositions based on polyvinyl alcohol, which are marked with improved working characteristics, particularly frost resistance were developed. Above mentioned compositions are stable for at least 4 cycles of "freezing – unfreezing" until the temperature –25 °C without significant viscosity change. This confirms the positive plasticizing impact of phosphoric acid on frost-resistance of the water-containing polyvinyl alcohol compositions. Adding of modified soluble starch to the compositions can regulate the technological characteristics of adhesives. It was made possible to reduce the content of polyvinyl alcohol in compositions without worsening of their adhesive properties. Adding the small quantities of mineral (nano) fillers in composition improves their adhesive properties without significant technological changes. The developed compositions are recommended for the glue production, which can be transported, stored and applied in the winter season.

A study of heat transfer in power law nanofluid

The purpose of this paper is to study the effects of nanoparticles on mixed convection flow of power law fluid. The shear thinning fluid is considered as base fluid. The nanoparticles of copper for nanofluid are taken into account. To analysis the flow and temperature behavior, various mass concentrations of polyvinyl alcohol in water, different sizes and concentrations of nanoparticles are used. The effects of nanoparticle concentrations on shear stress, heat flux and thermal resistance are also presented.

Fabrication of PVA Fibers Loaded with Fe<sub>3</sub>O<sub>4</sub> Nano Particles Using Electrospinner

It has been studied the fabrication of a sheet made of polyvinyl alcohol (PVA) fibers loaded with Fe3O4 nanomagnetic materials using an electrospinning technique. The solution for the electrospinner was prepared by stirring nano powder of Fe3O4 with a solution of 10% PVA in water at room temperature. The electrospinning process was done under fixed of 15 kV DC voltage, using 12 cm distance between the electrodes, and using a syringe needle having a diameter of 0.4 mm. The morphology of fibers was tested using scanning electron microscope (SEM), while the size of particles was tested using transmission electron microscope (TEM). Moreover, the crystallinity of fibers was tested using Laue and x-ray diffraction, while the magnetic moment was tested using a vibrating sample magnetometer (VSM). The result shows that the PVA sheet composing of fibers having a diameter in the range of 130 mm to 250 mm, accommodating Fe3O4 nano particles in the range of 15 mm to 25 mm, indicating a partial superparamagnetic property.

Mechanical Property Variations of Handsheets by Mixing Ratios of Sw-BKP, Hw-BKP, and PVA Fibers

In order to improve the strength of paper, mixing ratio of Sw-BKP and Hw-BKP and PVA (polyvinyl alcohol) fibers dosage were investigated. When the Sw-BKP fraction was increased, strength properties were increased because of average fibers length increased. When PVA fraction increased, paper strength was increased, but there was dissolution of PVA in water. The reason for improving handsheet strength that contained PVA was due to increased bonding action between the fibers by the PVA. The addition of PVA to kraft pulp would be helpful for packaging paper materials to increase strength and fracture toughness.

Fabricating Polyvinyl Alcohol Fibers with Evenly Distributed Nano Silver

Fabrication of polyvinyl alcohol (PVA) fibers loaded with evenly distributed nanosilver has been sucessfully done using electrospinner. The electrospinner is set at 15 kV DC voltage with distance between electrodes 13 cm, using a syringe hole diameter 0,5 mm. The feeding solution for the electrospinning was prepared by directly mixing the solution of PVA in water with a stable colloid of nanosilver at room temperature. The fibers morphology was characterized using scanning electron microscope. The optical property was tested using spectrometer. The distribution of silver nanoparticles in the fibers was tested using transmission electron microscope. The result indicates that the fibers still showing plasmonic property of silver having peak at 410 nm with no crystaline changes. The diameter of fibers loaded with nanosilver are smaller compared to that of the ones without nanosilver.The distribution of nanosilver in fibers made of PVA and the ones made of PVA and chitosan are compared and discussed.

Application of ionic liquids as a catalyst in the synthesis of polyvinyl butyral (PVB) polymer

Abstract Polyvinyl butyral (PVB) polymer was successfully synthesized using ionic liquid (IL) catalyst. The synthesis of PVB was achieved by acetalization of polyvinyl alcohol (PVA) and butyraldehyde (BA) in the presence of [HMIM] + HSO 4 − IL catalyst. The FT-IR, 1 H NMR, DSC, GPC and SEM characterizations were used to analyze the structure and properties of PVB. The effects of the concentration of PVA in water and the number of reuse cycles on the acetalization degree were investigated. The results indicated that the maximum acetalization degree of PVB obtained using [HMIM] + HSO 4 − IL catalyst was up to 72%. The comparison of the commercial PVB and the PVB obtained using [HMIM] + HSO 4 − IL catalyst showed that the self-made PVB has a larger molecular weight, higher viscosity, and higher acetalization degree than the commercial PVB.

Dissolution behavior of poly vinyl alcohol in water and its effect on the physical morphologies of PLGA scaffolds

Presented are data from a study of the aqueous properties of Poly Vinyl Alcohol (PVA), a well studied emulsifying agent, used in the preparation of biodegradeable Poly (DL-Lactide-Co-Glycolide) (PLGA) scaffolds/microparticles in water. How these properties affect the physical morphologies of PLGA scaffolds/microparticles produced from the various PVA solutions at different concentrations via the water emulsion synthetic method were also evaluated. UV-Visible absorbance measurements showed a quantitative correlation between the estimated concentrations of PVA used in solution preparations and the actual concentrations in solution. The physical appearance/morphologies of the PLGA scaffolds produced from the different PVA solutions were the same irrespective of the concentration used.

Study on Treatment of Polyvinyl Alcohol in Water by Ozone Catalytic Ozonation

The paper has studied the degradation effect of the polyvinyl alcohol in the Ozone catalytic oxidation oxygenated water, include three kind of catalyst of Fe2+, Mn2+, Cu2+. The results as below, the degradation effect of the polyvinyl alcohol by Ozone catalytic oxidation is higher than ozone alone obviously, and it is related with the concentration of catalyst, the degradation effect will increase with the increase of concentration of Fe2+, and to the maximum value, the degradation is 85%; it will decrease with the increase of concentration of Mn2+, the optimum content is about 5mg/L, the degradation rate is 85%; when Cu2+ is added, the degradation rate is 53% in 35mg/L, and the degradation of other contents is not obvious. When the content of three kinds of catalyst are all 35mg/L and the reaction time is 3h, the sort of degradation effect is Fe2+>Cu2+>Mn2+.

Highly porous open cell Ti-foam using NaCl as temporary space holder through powder metallurgy route

Open cell Titanium-foam (Ti-foam) with varying porosities (65–80%) was prepared using sodium chloride (NaCl) particles as space holder through powder metallurgy route. In order to ensure sufficient handling strength in cold compacted pallets, 2wt.% polyvinyl alcohol (PVA) solutions (5wt.% PVA in water) was mixed with the mixture of Ti and NaCl powders prior to cold compaction. After sintering, NaCl salt was removed by dissolving it in hot water. Detailed Energy dispersive X-ray (EDX) analysis and X-ray diffraction studies of the prepared Ti-foams were conducted to examine any physical and chemical changes in the phase constituents. The micro-architectural characteristics, density vis-a-vis porosity, and compressive deformation behavior of the synthesized foams were evaluated to examine their suitability as biomaterial and engineering applications.

Polymer reinforcement using liquid-exfoliated boron nitride nanosheets

We have exfoliated hexagonal boron nitride by ultrasonication in solutions of polyvinylalcohol in water. The resultant nanosheets are sterically stabilised by adsorbed polymer chains. Centrifugation-based size-selection was used to give dispersions of nanosheets with aspect ratio (length/thickness) of ∼1400. Such dispersions can be used to produce polyvinylalcohol-BN composite films. Helium ion microscopy of fracture surfaces shows the nanosheets to be well dispersed and the composites to fail by pull-out. We find both modulus, Y, and strength, σ(B), of these composites to increase linearly with volume fraction, V(f), up to V(f)∼ 0.1 vol% BN before falling off. The rates of increase are extremely high; dY/dV(f) = 670 GPa and dσ(B)/dV(f) = 47 GPa. The former value matches theory based on continuum mechanics while the latter value is consistent with remarkably high polymer-filler interfacial strength. However, because the mechanical properties increase over such a narrow volume fraction range, the maximum values of both modulus and strength are only ∼40% higher than the pure polymer. This phenomenon has also been observed for graphene-filled composites and represents a serious hurdle to the production of high performance polymer-nanosheet composites.

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.

Surface Acoustic Wave Humidity Sensors Based on Graphene Oxide Thin Films Deposited with the Surface Acoustic Wave Atomizer

Submicron-thick films of graphene oxide and polyvinyl alcohol (PVA) were deposited onto the surface of 160 MHz quartz surface acoustic wave (SAW) delay lines, and manufactured devices were used as humidity sensors. Films were obtained by consecutive atomization of 0.35 μl droplets of 0.33 mg/ml graphene oxide water suspension or 5.00 mg/ml PVA water solution using 25 MHz SAW atomizers. During measurements authors did not observe additional attenuation of the surface acoustic wave propagating along the surface of the sensors, which confirms that deposited films have low thickness and good uniformity. It was shown that SAW quartz humidity sensors with graphene oxide films, PVA thin films and uncoated surface have sensitivity of 1.54 kHz/%RH, 0.47 kHz/%RH and 0.13 kHz/%RH respectively. Sensors with graphene oxide thin films showed the best sensitivity and dynamic response. It was concluded that they can be used as sensitive coatings in humidity sensors for industrial environment.

Preparing poly (caprolactone) micro-particles through solvent-induced phase separation

Poly (caprolactone) (PCL) micro-particles with the size distribution from 1 to 100μm were prepared through solvent-induced phase separation, in which polyvinyl-alcohol (PVA) was used as the matrix-forming polymer to stabilize PCL micro-particles. The cloud point data of PCL–acetone–water was determined by the titration method. PCL–acetone and PVA–water solutions, PCL–PVA gel, and PCL micro-particles suspension were recorded by a digital camera. The morphology of PCL–PVA suspension and PCL micro-particles were observed by optical microscopy and scanning electron microscopy, respectively. The size distribution of PCL micro-particles was investigated by a particle size analyzer. Results from a differential scanning calorimeter indicated that the main interaction between PCL and PVA was mediated through hydrogen bonding.

高吸水性高岭土/聚乙烯醇复合材料的制备及表征<sup>*</sup>

将高岭土与聚乙烯醇以一定的比例在水中共混，得到高岭土/聚乙烯醇有机–无机复合材料，并利用电导率仪测量溶液电导率。将戊二醛以一定的比例与复合材料混合均匀后在室温下自然成膜。研究戊二醛的用量对膜的溶胀性、吸水性、拉伸强度和断后伸长率的影响。结果表明：戊二醛的添加量为10%时，溶胀率和吸水率最大。随交联剂用量增加，复合膜的抗拉强度增强，断后伸长率下降。 A series of kaolin/PVA organic-inorganic compound material were successfully prepared via mixing certain proportion of kaolin and polyvinyl alcohol in water. The electrical conductivity of solution of the resulting polymers was characterized by electrical conductivity meter. A series of film material were prepared via mixing certain proportion of glutaraldehyde and the compound material evenly and naturally form film at room temperature. The effect of the dosage of glutaraldehyde on swelling, water absorption, tensile strength and the percentage elongation after fracture was explored. The results showed that the water absorption and the swelling rate were the largest when glutaraldehyde addition was 10%. The tensile strength of the composite membrane enhanced, and the percentage elongation after fracture declined with increasing the dosage of cross-linking agent.