Showing papers on "Vinyl alcohol published in 1994"
TL;DR: Polyvinyl alcohols (PVA) of a molecular weight of about 50 000 were applied to the modification of fused silica surfaces for the separation of large charged molecules such as proteins as mentioned in this paper.
Abstract: Poly(vinyl alcohols) (PVA) of a molecular weight of about 50 000 were applied to the modification of fused silica surfaces for the separation of large charged molecules such as proteins. Basic and acidic proteins could be separated in PVA-modified capillaries at highly optimized and analytically suitable performance with regard to efficiency, zone symmetry, and resolution. PVA can be used in the dynamic mode as an additive to the buffer medium or as a water-insoluble permanent coating on the fused silica surfaces which can be achieved by a simple procedure of thermal immobilization
316 citations
TL;DR: In this paper, the first fiber-optic microbial sensor for determination of biochemical oxygen demand (BOD) is described, which consists of layers of an oxygen-sensitive fluorescent material, Tricbosporon cutneum immobilized in poly(vinyl alcohol), and a substrate-Dermeable polycarbonate membrane to retain the yeast cells.
Abstract: We describe the first fiber-optic microbial sensor for determination of biochemical oxygen demand (BOD). The sensing membrane at the tip of the fiber consists of layers of (a) an oxygen-sensitive fluorescent material, (b) Tricbosporon cutneum immobilized in poly(vinyl alcohol), and (c) a substrate-Dermeable polycarbonate membrane to retain the yeast cells. The layers are placed, in this order, on an optically transparent gas-impermeable polyester support. Tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) perchlorate is used as the oxygen indicator. Typical response times are 5-10 min, and the dynamic range is from 0 to 110 mg/L BOD when a glucose/glutamate BOD standard is used
273 citations
TL;DR: In this article, substituted O-methylcelluloaea, 2,3-di-O-methyl-cellulose and 6-O methylcelluloae were used as cellulosic components in blends with poly(ethylene oxide) and poly(vinyl alcohol) (PVA) to investigate the effect of hydrogen bonding in cellulose-synthetic polymer blend systems.
Abstract: Specifically substituted O-methylcelluloaea, 2,3-di-O-methylcellulose and 6-O-methylcelluloae were used as cellulosic components in blends with poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA). Since their hydroxyl groups (OH) form controlled intra- and intermolecular hydrogen bonds, the cellulose derivatives are useful as model compounds to investigate the effect of hydrogen bonding in cellulose-synthetic polymer blend systems. FTIR spectra of the cellulosic-PEO blend films revealed that, while the primary hydroxyl groups at the C-6 position of cellulose interact strongly with ether oxygen in PEO, the secondary hydroxyl groups at the C-2 and C-3 positions show no evidence for polymer-polymer interactions
172 citations
TL;DR: In this article, a polyvinyl alcohol-containing silver nitrate membranes was synthesized and the authors showed high olefin flux and Olefin/paraffin selectivity for this membrane, the effects of water saturation, salt content, total retenate pressure and permeate partial pressure on butene fluxes were investigated.
146 citations
TL;DR: In this article, the structure and compatibility of polyvinyl alcohol-silk fibroin (PVA/SF) blend films were analyzed by DSC, TMA and TGA, x-ray diffractometry, SEM and TEM.
Abstract: The structure and compatibility of poly (vinyl alcohol)-silk fibroin (PVA/SF) blend films were analyzed by DSC, TMA and TGA, x-ray diffractometry, SEM and TEM. DSC curves of PVA/SF blend films showed a major endothermic peak at 220°C, along with a peak at 280°C. These endotherms were assigned to the thermal decomposition of the ordered PVA elements and to the thermal degradation of silk fibroin, respectively. The PVA/SF blends behaved in a manner intermediate to the pure components, as suggested by both contraction-expansion and sample weight retention properties recorded by TMA and TGA measurements
144 citations
TL;DR: The permeability study showed that the water content as well as the mesh size had an influence on the diffusion of low molecular weight glucose and insulin, indicating that diffusion occurs primarily through the water hydrating the polymer network.
137 citations
TL;DR: In this article, the structure of polyvinyl alcohol (PVA) gels formed in a mixture of deuterated DMSO and heavy water at 23°C has been investigated.
Abstract: The structure of poly(vinyl alcohol) (PVA) gels formed in a mixture of deuterated DMSO and heavy water at 23°C has been investigated. It was directly confirmed from the wide-angle neutron scattering measurements that cross-linking points or junction points in the gels are crystallites. In the small-angle scattering measurements, it was found that the scattering intensity I(Q) decreases with Q according to the -4th power law (Porod's law) in the Q range above 0.05 A -1 where Q=4π sin θ/λ (2θ and λ are scattering angle and wavelength of neutron, respectively), suggesting that the surface of the crystallites has a clear boundary
101 citations
TL;DR: In this article, the authors used response surface models to show how the ultimate tensile strength and percent elongation at break of solution-cast films vary with relative amounts of starch, poly(vinyl alcohol) (PVA), poly(ethylene-co-acrylic acid) (EAA) and glycerol in the formulation.
96 citations
TL;DR: In this article, the DMSO/H2O = 80/20 (w/w) mixture and methanol were found to be the best solvent for the spinning dope and the coagulant, respectively, to give PVA fiber with the highest drawability.
Abstract: Gel spinning of poly(vinyl alcohol) (PVA) was attempted from the PVA dope prepared from the mixture of dimethyl sulfoxide (DMSO) and water. The DMSO/H2O = 80/20 (w/w) mixture and methanol were found to be the best solvent for the spinning dope and the coagulant, respectively, to give PVA fiber with the highest drawability. PVA fiber with the highest strength and Young's modulus were obtained from the undrawn gel fibers when subjected to hot two-stage drawing under conditions such as to produce maximum drawability. Furthermore, higher draw ratios of PVA fiber were attained at 6 wt % dope by lowering the coagulating temperature of methanol. In the present work, the highest tensile strength (2.8 GPa) and the highest Young's modulus (64 GPa) were realized, when the spinning dope was prepared from PVA with DP of 5,000 and the DMSO/H2O (80/20) mixed solvent to have the PVA concentration of 6 wt %, the coagulating temperature of methanol was −20°C, and the two-stage drawing was carried out at 160 (first) and 200°C (second). The PVA fiber prepared under this gel spinning condition could be elongated to 45 times draw ratio. The very high drawability of PVA fibers obtained from the DMSO/H2O (80/20) mixture dope was ascribed to the ability of the DMSO/H2O mixture to promote gelation. © 1994 John Wiley & Sons, Inc.
85 citations
TL;DR: In this article, a polyvinyl alcohol/cyclodextrin (PVA/CD) membrane was used in the pervaporation of ethanol/water mixtures, which increased the water selectivity of the water/ethanol, especially at lower (
82 citations
TL;DR: In this paper, homogeneous poly(acrylic acid) with poly(vinyl alcohol) blend membranes were evaluated for the selective separation of alcohols from toluene by pervaporation.
TL;DR: In this article, an interpenetrating hydrogel network based on polyvinyl alcohol (PVA) and 2-hydroxyethyl methacrylate has been synthesized.
Patent•
11 Jan 1994TL;DR: In this paper, an improved papermaking process was developed to enhance the properties of the resultant paper or paper-type products, which involves adding a polyvinyl alcohol/vinylamine copolymer along with a crosslinking agent at the dry end step of a conventional paper-making process.
Abstract: An improved papermaking process has been developed to enhance the properties of the resultant paper or paper-type products. The process involves adding a polyvinyl alcohol/vinylamine copolymer along with a crosslinking agent at the dry end step of a conventional papermaking process. Improvements in the properties of the resultant paper products are observed, especially at low levels of copolymer addition.
TL;DR: In this article, the Flory-Huggins interaction parameter χ gel was determined for chemically crosslinked poly(vinyl alcohol) hydrogels from swelling pressure and elastic modulus measurements.
TL;DR: The aqueous solutions of poly(ethylene oxide) and poly(polyacrylic acid, poly(vinyl pyrrolidone) blends have been studied by ultrasonic, rheological, and viscometric techniques.
Abstract: 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.
TL;DR: In this paper, the ionization potentials of the transient species CH3CH2O, CH3 CHOH, and CH2CH2OH (generated by the F+ethanol reactions) are measured by photoionization mass spectrometry.
Abstract: The ionization potentials of the transient species CH3CH2O, CH3CHOH, and CH2CH2OH (generated by the F+ethanol reactions) are measured by photoionization mass spectrometry: I.P.(CD3CD2O)=10.29±0.08 eV (tentative), I.P.(CH3CHOH)<6.85 eV, and I.P.(CD2CH2OH) ≤8.35±0.06 eV. The latter results in a cation of uncertain structure. These reactions also generate vinyl alcohol (adiabatic I.P.=9.33±0.01 eV) and acetaldehyde. A redetermined appearance potential of CH3CHOH+ from ethanol enables one to infer the proton affinity of acetaldehyde to be ≥183.8±0.2 kcal/mol and an α (C–H) bond energy in ethanol ≳91.1 kcal/mol (0 K). The appearance potential of m/e=45 ion from bromoethanol is interpreted as formation of a C2H5O+ isomer having the oxirane structure, with ΔHf00 of ∼173.9 kcal/mol, consistent with earlier alternative measurements. A second increase in the m/e=45 ion yield curve from ethanol is interpreted as formation of this same isomer. This interpretation, and an alternative cycle, lead to a β (C–H) bond ener...
TL;DR: In this article, the second stage of the pervaporation process was investigated using the crosslinked polyvinyl alcohol membranes with the low molecular weight of poly(acrylic acid) as the crosslinking agent.
Abstract: The application of the pervaporation process in biotechnology is rapidly growing. A two stage pervaporation process could be applied to the downstream processing of ethanol fermentation. In this paper, the second stage process—a water-selective process—was investigated in detail using the crosslinked poly(vinyl alcohol) membranes with the low molecular weight of poly(acrylic acid) as the crosslinking agent. The ratio of poly(vinyl alcohol) and poly(acrylic acid) in the membrane was 90/10, 85/15, and 80/20 by weight. The prepared membranes were tested to separate the various compositions of the water–ethanol mixtures, specially 50/50 solution at 60°C and 30/70, 20/80, 10/90, and 4.4/95.6 solutions at 60, 70, and 75°C. For water: ethanol = 50 : 50 solution, the separation factor αw/e = 260 at 75°C was obtained by using a PVA/PAA = 80/20 membrane. The permeation rate and the separation factor at the azeotropic point of a water–ethanol mixture showed 30 g/m2/h and 5800 at 75°C, respectively, when a PVA/PAA = 80/20 membranes was used. © 1995 John Wiley & Sons, Inc.
TL;DR: The correlation between hydrogen-bonding self-association and sequence distribution in different polyvinyl acetate-co-vinyl alcohol copolymers of different degrees of hydrolysis and sequence distributions has been studied by infrared and NMR spectroscopy as discussed by the authors.
Abstract: The correlation between hydrogen-bonding self-association and sequence distribution in different poly(vinyl acetate-co-vinyl alcohol) copolymers (ACA) of different degrees of hydrolysis and sequence distributions has been studied by infrared and NMR spectroscopy. For ACA copolymers, quasi-random distributions are obtained by acid alcoholysis, blocker distributions by saponification, and intermediate distributions by acombined method, as shown by 13 C NMR. FTIR spectroscopy has pointed out that hydrogen-bonding distribution in ACA copolymers strongly depends on sequence distribution. For block copolymers, hydroxyl-hydroxyl self-association is preferred
TL;DR: In this article, the authors studied the swelling/shrinking behaviors of chemically cross-linked polyvinyl alcohol (PVA) gel complexed with borate ions as a function of the borate ion concentration, b, and time.
Abstract: Swelling/shrinking behaviors of chemically cross-linked poly(vinyl alcohol) (PVA) gel complexed with borate ions were studied as a function of the borate ion concentration, b, and time. The equilibrium swelling ratio, Q/Q 0 , was compared with the intrinsic viscosity ratio, [η]/[η] 0 , of the corresponding PVA solutions in the presence of borate ions, where Q 0 and [η] 0 are the equilibrium swelling volume of the gel and the intrinsic viscosity of the solution without borate ions, respectively. The b dependence of [η]/[η] 0 was almost the same as that of [η]/[η] 0
Patent•
09 Aug 1994TL;DR: In this paper, a mixture of a cross-linked, vinyl alcohol/acrylic acid salt copolymer and a carrier solution containing a carbon dioxide carrier is used for the separation of carbon dioxide.
Abstract: A membrane for the separation of carbon dioxide is disclosed which includes a hydrogel film of a cross-linked, vinyl alcohol/acrylic acid salt copolymer impregnated with an aqueous carrier solution containing a carbon dioxide carrier dissolved therein. A composition containing a solvent, an alkali metal carbonate or bicarbonates, and a polydentate ligand capable of forming a complex with an alkali metal ion is suitably used as the carrier solution. This composition may also be used for the preparation of a liquid film of a carbon dioxide separation membrane.
TL;DR: There is no difference in the biodegradability based on the molecular weight of PVA being larger than the octamer, and the isotactic moiety was preferentially biodegraded.
Abstract: The biodegradability of poly(vinyl alcohol) (PVA) was analyzed with respect to its molecular weight and stereoregularity using the isolated PVA-assimilating microbial strain,Alcaligenes faecalis KK314. The biodegradability of PVA was influenced by its stereoregularity, and the isotactic moiety was preferentially biodegraded. However, there is no difference in the biodegradability based on the molecular weight of PVA being larger than the octamer.
TL;DR: In this article, the Raman spectra of 88% hydrolyzed polyvinyl alcohol (PVOH) were examined from the partially crystalline solid, from PVOH dissolved in both H2O and D2O, and from films precipitated from these solutions.
Abstract: We have measured the Raman spectra of ethylene-vinyl alcohol copolymer (EVOH) and poly(vinyl alcohol) (PVOH). Spectra of 88% hydrolyzed PVOH were examined from the partially crystalline solid, from PVOH dissolved in both H2O and D2O, and from films precipitated from these solutions. The spectrum in H2O differs from that of the starting material by disappearance of sharp bands having Raman shift values of 1146 and 1093 cm−1, strengthening of a band near 915 cm−1, decrease in frequency of bands at 480, 1356, and 1441 cm−1, and increase in frequency of bands at 369, 413, 1023, 1371, and 2910 cm−1. The spectrum of the film shows partial reversal of these trends. With D2O as the solvent, the band shifts are slightly different from those listed above and new bands appear. These changes are indicative of loss of crystallinity, change in stereochemistry, and partial deuteration of hydroxyl during dissolution of this PVOH sample at room temperature. © 1994 John Wiley & Sons, Inc.
TL;DR: In this paper, a new alcohol dehydration membrane, polyvinyl alcohol-chitosan blended composite membrane (PVA-CS), has been prepared, which has high selectivity and promising permeability, especially in separating ethanol near the azeotropic region.
TL;DR: In this paper, the interacting blends of poly(acrylic acid) with poly(vinyl pyrrolidone) or poly (vinyl alcohol) in aqueous solutions have been studied by ultrasonic, rheological and viscometric techniques.
TL;DR: In this article, the free radical copolymerization of O-D vinyl alcohol and maleic anhydride was investigated and the polymerization was determined to be first order in both anhydrous and vinyl alcohol.
Abstract: Vinyl alcohol was generated through the hydrolysis of ketene methyl vinyl acetal I. In general, we have observed that room temperature addition of 0.9 mol equiv of I to a 1% (v/v) D[sub 2]O solution in acetone-d[sub 6], made such that the concentration of the overall solution is 10[sup [minus]4]M in DCl, yields 90% O-D vinyl alcohol which tautomerizes to acetaldehyde only very slowly at ambient temperature (k[sub t] [approx] 10[sup [minus]6] M/s, vide infra). The remaining 10% of I is converted into vinyl acetate, a side product in the hydrolysis, as well as to a small amount of acetaldehyde from tautomerization. Spectroscopic data for the vinyl alcohol were identical to previously reported data. Our observations suggest that the key to generating persistent vinyl alcohol solutions is to drive the system toward an anhydrous state through use of nearly stoichiometric amounts of water in the rapid hydrolysis step. By taking advantage of stabilizing electron donor-acceptor interactions, the free radical copolymerization of O-D vinyl alcohol and maleic anhydride proved successful. The polymerization was determined to be first order in both maleic anhydride and vinyl alcohol. Since the rate of polymerization is far greater than that of tautomerization under the conditions (ca.more » 30 times faster at [minus]10[degree]C), there is no significant increase in acetaldehyde concentration during polymerization. 20 refs., 1 fig.« less
TL;DR: Close correspondence between the network consistency and the degree of crystallinity developed in the matrix suggested that the hyaluronic acid could provide heterogeneous crystallization nuclei for poly (vinyl alcohol) thus increasing the crystallization degree, and consequently, the storage modulus.
Abstract: Hydrogels are three-dimensional polymeric networks very similar to biological tissues and potentially useful as soft tissue substitutes and drug delivery systems. Many synthetic polymers can be used to make hydrogels: poly (vinyl alcohol) is widely employed to make hydrogels for biomedical applications. Improvements in the biocompatibility characteristics of synthetic materials could be achieved by the addition of biological macromolecules. The resulting materials named “bioartificial polymeric materials” could possess the good mechanical properties of the synthetic component and adequate biocompatibility due to the biological component. We have used poly (vinyl alcohol) to make hydrogels containing various amounts of hyaluronic acid. These bioartificial materials were studied to investigate the effect of the presence of the hyaluronic acid on the structural properties of the hydrogels. Thermal, mechanical, morphological and X-ray analyses were performed. A close correspondence between the network consistency and the degree of crystallinity developed in the matrix suggested that the hyaluronic acid, when its content is about 20%, could provide heterogeneous crystallization nuclei for poly (vinyl alcohol) thus increasing the crystallization degree, and consequently, the storage modulus.
TL;DR: In this article, the small angle neutron scattering spectra were decomposed into a static and a dynamic component, the former being assumed to follow an Ornstein-Zernike form and the latter a stretched exponential.
Abstract: Neutron and light scattering observations are reported for chemically cross-linked poly(vinyl alcohol) hydrogels differing in cross-link density and for the corresponding semidilute polymer solution. The small angle neutron scattering spectra could be decomposed into a static and a dynamic component, the former being assumed to follow an Ornstein-Zernike form and the latter a stretched exponential. Macroscopic sweelling pressure and shear modulus measurements were also performed on the same gels to provide an estimate of the scattering from dynamic concentration fluctuation in the zero wave vector limit
TL;DR: In this article, the effects of solvent and electrolyte on the electrochromic behavior and degradation of polyaniline in nonaqueous aprotic media, as well as its electrochemical redox and degradation mechanisms, were investigated with chemically prepared polyanile-poly (vinyl alcohol) composite films and polyanin homogeneous films.
Abstract: Effects of solvent and electrolyte on the electrochromic behavior and degradation of polyaniline in nonaqueous aprotic media, as well as its electrochemical redox and degradation mechanisms, were investigated with chemically prepared polyaniline-poly (vinyl alcohol) composite films and polyaniline homogeneous films. Visible and FT-IR absorption spectra of the polyaniline films, oxidized electrochemically at various polarization potentials, showed that the mechanisms in aprotic media involved two successive oxidation processes. In contrast to aqueous systems, the higher oxidation process involved further anion insertion without deprotonation, and the degradation was due to partial formation of the electrochemically inactive quinonediimine structure at excessive polarization potentials
TL;DR: In this article, a mixture of benzene and cyclohexane was used for pervaporation processes and the coordination of the feed with cobalt in the membrane played a major role in the separation of the mixture.
Abstract: 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.
TL;DR: In this article, the authors investigated the complexation of polyvinyl alcohol (PVA) with congo red (CR) ions in aqueous solutions as functions of PVA (C PVA ) and CR concentrations (C CR ) and temperature.
Abstract: The complexation of poly(vinyl alcohol) (PVA) with congo red (CR) ions in aqueous solutions was investigated as functions of PVA (C PVA ) and CR concentrations (C CR ) and temperature. The PVA-CR complexation resulted in a gelation around pH 7 when both C PVA and C CR were high enough. However, in the case of intermediate PVA concentrations in monomer unit, i.e., 0.6 mol/L, a sol-gel-sol-gel-type transition was observed with increasing CR concentration. The origin of this re-entrant-type phase transition was studied by estimation of the enthalpy of cross-link formation. The gelation was classified into two steps (a) weak cross-link and (b) strong cross-link formations