Syntheses and characterization of blend membranes of sodium alginate and poly(vinyl alcohol) for the pervaporation separation of water + isopropanol mixtures

The blend membranes of sodium alginate and poly(vinyl alcohol) have been prepared by physical mixing in different ratios (75, 50, and 25%) of sodium alginate with poly(vinyl alcohol). The membranes were crosslinked with glutaraldehyde and used in the pervaporation separation of water + isopropanol mixtures at 30°C. The crosslinking reaction was confirmed by Fourier transform infrared spectra. Permeation flux increased with an increase in mass % of water in the feed mixture as well as with an increase in the amount of poly(vinyl alcohol) in the blend, but separation selectivity decreased. Diffusion coefficients of water + isopropanol mixtures have been calculated using the Fick's equation from the sorption data. Arrhenius activation parameters were calculated for 10 mass % of water in the feed mixture using the values of flux and diffusion coefficients obtained at 30, 40, and 50°C. The diffusion and pervaporation results have been explained on the basis of solution‐diffusion principles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3642–3651, 2002     

Reaktive träger zur immobilisierung von enzymen auf der grundlage von polyvinylalkohol

On the basis of poly(vinyl alcohol) various reactive carriers for the immobilization of enzymes were synthesized. Starting as well from hydrolyzed beads of crosslinked poly(vinylacetate), as from tubes of poly(vinyl acetate-co-ethylene) which have been coated with poly(vinyl alcohol) resp. from poly(vinyl alcohol) containing synthetic pulp reactive carriers were synthesized by reaction with 2-(3-aminophenyl)-1,3-dioxolane followed by diazotization. Furthermore reactive isothiocyanato groups as well as mixed polymeric disulfides with 2-thiopyridine groups were introduced into gels of poly(vinyl alcohol) which were crosslinked with terephthalaldehyde. The immobilization of enzymes was carried out with papain, trypsin, glucose oxidase, and catalase. The properties of the immobilized enzymes were investigated.     

Mechanochemical synthesis and characterization of poly(vinyl chloride)-block-poly(vinyl alcohol) copolymers by ultrasonic irradiation

Mechanical degradation and mechanochemical reaction in heterogeneous systems of the solid poly(vinyl chloride)-poly(vinyl alcohol) aqueous solutions have been studied by ultrasonic irradiation at 30 °C. The rate of decrease in the viscosity-average degree of polymerization of the degraded poly(vinyl chloride) was much faster than that of the degraded poly(vinyl alcohol). Mechanochemical reaction occurred by free radicals produced from the chain scissions of both polymers by ultrasonic waves. The copolymer was obtained and the molar ratio of the vinyl chloride and the vinyl alcohol units in its copolymer can be determined. In addition, the changes in the composition of the total block copolymer, the unreacted poly(vinyl chloride), and the unreacted poly(vinyl alcohol) were obtained. Received: 1 October 1998/Revised version: 9 January 1999/Accepted: 13 January 1999     

Solution and solid‐state blend compatibility of poly(vinyl alcohol) and poly(methyl methacrylate)

The blend miscibility of poly(vinyl alcohol) and poly(methyl methacrylate) in N,N′‐dimethylformamide solution was investigated by viscosity, density, ultrasonic velocity, refractive index, and UV and fluorescence spectra studies. Differential scanning calorimetry and scanning electron microscopy were used to confirm the blend miscibility in the solid state. Blends were compatible when the concentration of poly(vinyl alcohol) was greater than 60 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2415–2421, 2006     

Miscibility and interaction studies on some aqueous polymer blend solutions by ultrasonic and rheological techniques

The aqueous solutions of poly(ethylene oxide)–polyacrylic acid, poly(vinyl pyrrolidone)–poly(vinyl alcohol), and poly(ethylene oxide)–poly(vinyl alcohol) blends have been studied by ultrasonic, rheological, and viscometric techniques. Extensive investigation over a wide range of concentrations, temperatures, compositions, pH, and shear rates indicate the degree of miscibility, extent of interaction between the polymers, and stoichiometry of the polymer complexes formed by the strong interaction between the polymers in solutions. These investigations indicate the miscibility of poly(ethylene oxide)–polyacrylic acid and poly(ethylene oxide)–poly(vinyl pyrrolidone) blends and the immiscibility of poly(ethylene oxide)–poly(vinyl alcohol) blends in conformity with other reported investigations. © 1994 John Wiley & Sons, Inc.     

Ultrasonic attenuation and mobility in polymer solutions and dispersions. Poly(vinyl alcohol) and poly(vinyl acetate)

Summary To obtain informations about molecular processes, poly(vinyl alcohol) solutions and poly(vinyl acetate) solutions and dispersions have been studied by ultrasonic methods in the frequency range from 200 kHz to 150 MHz. The measured excess attenuations are qualitatively discussed in terms of cooperative and local mode motions of the macromolecules. In poly(vinyl alcohol) solutions with different residual vinyl acetate content a mixing of normal and local mode motions has been observed. In poly(vinyl acetate)/toluene solution two discrete relaxation processes have been detected which are probably related to a local mode and a coupling of local and normal mode motions, respectively. The frequency-temperature dependence of the absorption maximum of the poly(vinyl acetate) dispersion follows the WLF relation.     

Crosslinking of cotton in the presence of poly(vinyl alcohol). Analysis and composition of products

The spectrophotometric method developed by Finley for the determination of poly(vinyl alcohol) in paper coatings has been adapted for analysis of cotton fabrics crosslinked with finishes containing a poly(vinyl alcohol) additive. The effect of time and pH of hydrolysis on the analysis, and the dependency of the durability of the poly(vinyl alcohol) on the crosslinking agent are established. Evidence of chemical attachment to the cellulose of the cotton fiber through the crosslinking agent is offered.     

Grafting of ethyl α-cyanacrylate on poly(vinyl alcohol)

Because hydrophilic copolymers containing cyanacrylate elements should be useful as components of adhesives in surgery, the conditions of grafting of ethyl α-cyanacrylate on poly(vinyl alcohol) were studied. Two anthraquinone derivatives were applied as sensitizers in UV-initiated grafting; 2,6-disulfoanthraquinone sodium salt proved to be especially efficient. IR spectra and derivatograms of poly(vinyl alcohol-g-ethyl α-cyanacrylate) are described.     

Swelling effect of semicrystalline poly(vinyl alcohol) in hydrogen peroxide

The effect of hydrogen peroxide on the physicochemical properties of semicrystalline poly(vinyl alcohol) (PVA) has been investigated. Significant and irreversible increases in equilibrium water swelling, dissolved oxygen permeability, and surface wettability have been observed in PVA samples treated with concentrated hydrogen peroxide. Based on the small amount of carbonyl content detected and the crystallinity reduction in hydrogen-peroxide-treated poly(vinyl alcohol) samples, a mechanism involving a combination of hydrogen-peroxide-induced oxidative chain scission and dissolution of crystalline regions in poly(vinyl alcohol) is proposed for the observed swelling kinetics and associated changes in polymer properties.     

The hydration of reactive cement-in-polymer dispersions studied by nuclear magnetic resonance

The behaviour of two novel cement-in-polymer (c/p) dispersions, namely cement-in-poly(vinyl acetate) and cement-in-poly(vinyl alcohol) upon exposure to water at room temperature was investigated by a combination of various NMR methods. The swelling, cracking, and the water ingress were monitored non-destructively using ¹H single point imaging. The hydration of the cement matrix was investigated using ²⁹Si NMR whilst ¹³C CPMAS NMR spectra allowed the quantification of the kinetics of the hydrolysis reaction of poly(vinyl acetate) into poly(vinyl alcohol). The polymer controls the rate of water ingress and swelling which in turn determines the behaviour of the c/p dispersions upon exposure to water. For the cement-in-poly(vinyl alcohol), the rates of water ingress and swelling are much faster than the hydration of the clinker whilst for the cement-in-poly(vinyl acetate) the slow rates of the two processes allow the formation of a cementious matrix which assures the stability of the sample.     

Characterization of poly(vinyl alcohol—acetate) by C n.m.r. and thermal analyses

Commercial poly(vinyl alcohol—acetate) copolymers were characterized by ¹³C n.m.r. spectroscopy in D₂O at 100.6 MHz and by differential scanning calorimetric measurements. N.m.r. spectra can be used for quantitative measurements of tacticity, vinyl alcohol—vinyl acetate composition, non-hydrolyzable branch content and blockiness of vinyl acetate residues. Conventional quality control tests for poly(vinyl alcohols) are recognized to be inadequate to account for all the important properties of these polymers. They have been augmented by thermal analyses for estimations of blockiness of alcohol and acetate residues. The crystal melting points of commercial poly(vinyl alcohols) vary significantly with thermal history of the samples. A standardized thermal procedure was used with observed melting temperatures to estimate either the degree of hydrolysis or the overall blockiness of the polymer. The equations used are based on theory but the procedures used industrially should best be regarded as semi-empirical because equilibrium melting points are not normally measured.     

Surface free energy analysis of poly(vinyl alcohol) films having various molecular parameters

The molecular parameters of poly(vinyl alcohol) have enormous effects on its physical and chemical properties. Therefore, the surface characteristics of poly(vinyl alcohol) films are also determined by the molecular parameters. In this study, the dependence of the surface free energy on the molecular weight, degree of saponification, and stereoregularity of poly(vinyl alcohol) films has been evaluated with contact‐angle measurements. The surface free energy of poly(vinyl alcohol) films increases with decreases in the syndiotactic dyad content, molecular weight, and degree of saponification. The polar component of the surface energy is not affected by the deviation of the molecular weight and degree of saponification very much. However, it decreases with increases in the syndiotactic dyad content and ranges from 11.64 to 4.35 dyn/cm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Role of 1,10‐phenanthroline and ortho phosphoric acid on graft polymerization of vinyl monomers from poly (vinyl alcohol) in the presence of Fenton's reagent

The effect and role of 1,10‐phenanthroline (o‐phen) and ortho phosphoric acid on graft polymerization of vinyl monomers from poly (vinyl alcohol) (PVA) in the presence of Fenton's reagent have been studied. Reaction conditions were optimized. Fourier transform infrared (FT‐IR) spectra were used for confirmation of grafting. A probable mechanism of grafting to elucidate the role of phenanthroline and phosphoric has been suggested. Thermal properties of the grafted polymer were studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2335–2339, 2005     

Electrospinning of chitosan/poly(vinyl alcohol)/acrylic acid aqueous solutions

Chitosan bicomponent fibers were prepared via the electrospinning of chitosan/poly(vinyl alcohol)/acrylic acid aqueous solutions with different concentrations. With a 4% acrylic acid aqueous solution, when the chitosan/poly(vinyl alcohol) mass ratios were lower than 80/20, electrospinning nanofibers could be obtained. With a 90% acrylic acid aqueous solution, when the chitosan/poly(vinyl alcohol) mass ratios were less than 95/5, good nanofibers could be electrospun. The average diameter of the nanofibers gradually decreased, and its distribution became narrower as the poly(vinyl alcohol) concentration increased. Chitosan/poly(vinyl alcohol)/acrylic acid aqueous solutions could be electrospun at various concentrations by the adjustment of the chitosan and poly(vinyl alcohol) concentrations. The effects of the viscosity and conductivity of the blend solution on the morphologies of the fiber mats were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5692–5697, 2006     

Physicochemical characterization of hydrogels based on polyvinyl alcohol–vinyl acetate blends

Hydrogels made of polyvinyl alcohol–vinyl acetate and its blends with water soluble polymer were studied in terms of swelling behavior, microstructure, and dynamic mechanical properties. Hydrogels prepared by blending polyvinyl alcohol–vinyl acetate with either polyacrylic acid or poly(4‐vinyl pyridine) exhibited a strong pH dependency. When poly(vinyl pyrrolidone) was used for blending, an unusual pH dependency was observed. An increase in the equilibrium water content in all systems resulted in an increase in the freezable water as determined by DSC. Critical point drying led to a striated surface on polyacrylic acid–polyvinyl alcohol–vinyl acetate hydrogels, whereas a porous structure was observed on the freeze‐dried poly(vinyl pyrrolidone)–polyvinyl alcohol–vinyl acetate gels. Hydrogels with elevated storage modulus were obtained when either polyvinyl alcohol–vinyl acetate alone or polyacrylic acid–polyvinyl alcohol–vinyl acetate blends were thermally treated at high temperatures (i.e., 150°C). Low storage modulus was observed for both poly(vinyl pyrrolidone) and poly(4‐vinyl pyridine)‐containing hydrogels. Temperature dependency of storage modulus from 20 to 60°C was observed only for poly(4‐vinyl pyridine)–polyvinyl alcohol–vinyl acetate hydrogels. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3578–3590, 2001     

Studies on the preparation and properties of conductive polymers. IX. Using photographic developer to prepare metallized conductive polymer films

Poly(vinyl alcohol) metal chelate solutions were prepared by mixing silver nitrate with solutions of poly(vinyl alchol), and films wee prepared from these solutions. These poly(vinyl alcohol) metal chelate films were reduced by photographic developer. The silver ions in poly(vinyl alcohol) films were reduced to silver on the surface, and conductive polymer films were obtained. © 1996 John Wiley & Sons, Inc.     

New Types of Ecologically Safe Flame Retardant Polymer Systems

Abstract

New types of ecologically safe flame retardant composition based on poly(vinyl)alcohol and poly(vinyl)alcohol oxidized by KMnO₄ (polymer-organic char formers) were proposed for nylon 6,6. These systems can promote the formation of char by intermolecular crosslinking (“synergetic carbonization”). The Cone Calorimeter tests indicated the improvement of fire retardant properties for the compositions of nylon 6,6 with poly(vinyl)alcohol and poly(vinyl)alcohol oxidized by KMnO₄ in comparison with pure nylon 6,6.     

Preparation of Poly(Vinyl Alcohol) Nanocomposite Films Reinforced with Poly(Amide–Imide)/CuO Having N-trimellitylimido-L-valine Linkages for the Improvement of Mechanical and Thermal Properties

In this investigation, nanocomposite films were fabricated by dispersion of poly(amide–imide)/CuO nanocomposites as nanofiller in the poly(vinyl alcohol) matrix via an ultrasonic process. The nanofiller was prepared and mixed with PVA matrix. After dispersion of nanofiller into the poly(vinyl alcohol), the mechanical properties of the nanocomposites were improved. For example, the addition of 6 wt% nanofiller into the poly(vinyl alcohol) matrix enhanced the tensile modulus by 39%. The residual weight at 800°C was 7% for pure poly(vinyl alcohol) while the nanocomposites illustrated 12–19% residue at this temperature.     

Separation of benzene/cyclohexane by pervaporation through chelate poly(vinyl alcohol)/poly(allyl amine) blend membrane

Summary Chelate poly(vinyl alcohol)/poly(allyl amine) blend membrane was prepared and used for the separation of benzene/cyclohexane mixture by pervaporation processes. The coordination of benzene in the feed with cobalt in the membrane plays a major role in the separation of the mixture. Chelate poly(vinyl alcohol)/poly(allyl amine) blend membrane showed a preferential sorption toward benzene and was found to be more effective for permeating benzene in the benzene/cyclohexane mixture than an original Schiff base poly(vinyl alcohol)/poly(allyl amine) membrane.     

溶液共混法制备高强度淀粉基完全生物降解塑料薄膜

利用一步溶液共混法，将预糊化的淀粉糊与PvA溶液共混，用乙二醛进行交联，制备淀粉／聚乙烯醇（PVA）完全生物降解塑料薄膜。研究不同乙二醛和甘油的用量对薄膜性能的影响。薄膜的力学性能、热性能和微观形态表征表明，淀粉／PvA体系具有较好的相容性和较高的力学性能，薄膜的拉伸强度和断裂伸长率分别可达到28．52MPa和307．5％。