• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.116-121
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• 2005

Immobilization technique by PVA encapsulation is an effective alternative for wastewater treatment. However little information is available about the effect of PVA characteristics on physical properties as an encapsulation media. This study aims at investigating the effect of the preparation methods of PVA and filler addition to media on the solubility of PVA. The solubility decreased as the freezing temperature decreased and the vacuum-drying was applied. Addition of the PAC (Powered Activated Carbon) and organoclay decreased the solubility of the PVA gels. Organoclay was more effective for lowering the solubility about 25% than the PAC. Nitrification with the PVA-coating media was less sufficient than with the polyurethane media due to the mass transfer restriction for oxygen and nutrients.

• Clean Technology
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• v.20 no.3
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• pp.251-255
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• 2014

PVA gel beads were made by immobilization of thenoyltrifluoroacetone (HTTA) and trioctylphoshineoxide (TOPO) with poly vinyl alcohol (PVA). The prepared PVA gel beads were used for the removal of $Cu^{2+}$ from aqueous solution. The removal characteristics of $Cu^{2+}$ by PVA gel beads was found to follow the pseudo-second-order kinetic equation. The maximum removal capacity calculated from Langmuir isotherm equation was 9.59 mg/g. The optimal pH was in the range of 3.5~6. Even when the PVA gel beads were reused 5 times, the leakage of extractant and the damage of PVA gel beads was not observed.

• Journal of Wetlands Research
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• v.9 no.1
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• pp.115-121
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• 2007

A novel hydrogen fermentation technique by using polyvinyl alcohol (PVA) gel beads as a biomass carrier was investigated. The hydrogen gas was stably produced throughout the experimental period in a continuous reactor. Even though the hydrogen productivity was suddenly decrease by experimental troubles, the bacteria attached to the PVA gel beads played as an inoculum, it was promptly recovered. The hydrogen yield per glucose was not very high ($1.0-1.2mol-H_2/mol-glucose$), thus the optimization of the experimental conditions such as ORP and HRT should be considered to improve the hydrogen productivity. Bacterial community was stable during experimental period after the PVA gel beads applying, which indicated that applying of biomass carrier was specific to keep not only the biomass but also the bacteria commonly. Clostridium species were phylogenetically detected, which suggested that these bacteria contributed to the hydrogen production in the biofilm attached to the PVA gel beads.

• Polymer(Korea)
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• v.30 no.6
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• pp.563-567
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• 2006

Poly(vinyl alcohol) (PVA) and gelatin (GEL) blend membranes were prepared by solution casting method under a high electric field. SEM observation of the membrane showed that gelatin rich domains were elongated and oriented to the direction of the applied electric field in PVA matrix. This can be attributed to the electrostatic emulsifying effects due to a reduction in interfacial tension. In addition, it was observed through WAXD and swelling measurements that the degree of crystallinity of membranes increased with applied electric field strength. This may be interpreted to be caused by the orientation effect of GEL domains in the blend membrane, and the self-annealing effect due to some heat generated from high electric field during casting.

• Polymer(Korea)
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• v.25 no.5
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• pp.728-735
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• 2001

In this study, hydrogels from mixtures of chitosan/poly(vinyl alcohol) (PVA) and chitosan/poly(N-vinylpyrrolidone) (PVP) were prepared by ${\gamma}$-ray irradiation, and the mechanical properties such as gelation, water absorptivity and gel strength were examined to evaluate the applicability of these for wound dressing. The PVA : chitosan and PVP : chitosan ratio were in the range of 97:3 ~ 90:10, and the solid concentration of PVA/chitosan and PVP/chitosan solution were 15 wt%. Gamma irradiation with doses of 25, 35, 50, 60 and 70 kGy, was exposed to mixtures of PVA/chitosan and PVP/chitosan to evaluate the effect of irradiation dose. Gel content and gel strength increased as chitosan concentrations in PVA/chitosan and PVP/chitosan decreased, and as irradiation dose increased. Swelling degree increased as chitosan concentrations in PVP/chitosan and PVA/chitosan increased, and as irradiation dose decreased.

• Textile Coloration and Finishing
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• v.21 no.4
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• pp.39-45
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• 2009

PVA films were crosslinked with dimethylol dihydroxy ethylene urea (DMDHEU) and three polycarboxylic acids of butanetetracarboxylic acid (BTCA), citric acid and malic acid Different factors influencing the crosslinking treatment with BTCA were investigated including BTCA and sodium hypophosphite (SHP) concentration, curing temperature and time. The cured films was extracted with boiling water and gel fraction was calculated based on weight change of the PVA films. The gel fraction of PVA films increased with increasing curing temperature and time. And the resistance to water and thermal stability of the crosslinked PVA films improved with the BTCA crosslinking treatment. While crosslinking with citric acid gave the highest gel fraction among the crosslinkers, crosslinking with malic acid showed the highest absorbancy in 0.9% saline solution, which was attributed to lower crosslink density and high number-average molecular weight between crosslinks. The superabsorbent PVA films could be prepared by adjusting the crosslinking condition of PVA with polycarboxilic acids.

• Applied Microscopy
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• v.31 no.2
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• pp.117-128
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• 2001

DMF is not a good solvent for PVA. There is no solvent-PVA interaction such as H-bonding. DMF/PVA makes a UCST system. DMF/PVA makes a gel through crystallization-induced gelation. X-ray, thermal analysis, and other experimental proofs are presented. The gelation rate was faster at low temperature. Small addition of PEG increased the rate of gelation, but urea decreased the rate. SEM showed the phase demixing process very clearly. In the early stage of gelation, only phase demixing was occurring at a low rate. Hence, no holes appear in the early stage photographs. As demixing proceeded further, the holes began to appear and the sizes became bigger. DMF phase remains many holes after vaporization and PVA phase constitute the matrix phase.

• Applied Biological Chemistry
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• v.39 no.5
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• pp.349-354
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• 1996

The Polyvinyl alcohol(PVA) oxidase involved in PVA degradation by microorganism has been purified to homogeneity from culture broth of Xanthomonas campestris J2Y grown in a minimal medium containing PVA as a sole carbon source. The enzyme was purified by DEAE-cellulose chromatograpy and Sephadex G-150 gel filtration. The purified PVA oxidase was electrophoretically homogeneous both in the absence and presence of SDS. The molecular weight of the enzyme was estimated to be about 55,000 daltons by SDS-polyacrylamide gel electrophoresis and Sephadex G-150 gel filtration. The native enzyme existed as a monomer. The optimal pH and temperature was shown to be pH 7 and $37^{\circ}C$ respectively. The activity of enzyme was stable below $55^{\circ}C$ and between pH range of $5{\sim}11$. The enzyme activity was significantly inhibited by metal compounds such as $Ag^{2+},\;Hg^{2+}$. While, metal ions such as $Mn^{2+},\;and\;Cu^{2+}$ stimulated the reaction. Km value of the enzyme for PVA was $7.04{\times}10^{-2}mmol/{\ell}$.

• Polymer(Korea)
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• v.32 no.6
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• pp.587-592
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• 2008

High molecular weight poly(vinyl alcohol) (PVA) hydrogel to be expected as a candidate material for the wound-dressing was successfully prepared by electron beam (EB) irradiation. To produce PVA hydrogels with various gel fractions, degrees of swelling in water, gel strengths, and elongations, two different number-average degrees of polymerization [($P_n$)s] of PVA were adapted such as 1700 and 4000, and the PVA solution concentration and irradiation dose of EB were controlled to range of 5 $\sim$ 20% and 30 $\sim$ 100 kGy, respectively. The gel fraction and strength of PV A hydrogel were increased with increasing molecular weight of PVA, solution concentration, and irradiation dose of EB. On the contrary, the degree of swelling and elongation of PVA hydrogel were decreased. The thermal property and crystallinity related to degree of crosslinking of PVA hydrogel were examined by the analyses of differential scanning calorimetry and X-ray diffraction.

• Polymer(Korea)
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• v.37 no.4
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• pp.486-493
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• 2013

The structure, morphology, and physical properties of syndiotatic poly(vinyl alcohol) (s-PVA) gel spun fibers were investigated to prepare polymeric embolization coils. S-PVA was prepared by saponification of the poly(vinyl acetate)/poly(vinyl pivalate)(PVAc/PVPi) copolymer. The viscosity of s-PVA solutions showed shear thinning behavior and the solution formed a homogeneous phase. Based on shear viscosity change with concentration, the optimum dope concentration was selected as 13 wt%, after which s-PVA fibers were spun and the solvent was removed. The fibers were then drawn with a maximum draw ratio of 15. A polymeric embolization coil was made of the s-PVA gel-spun fibers. The fibers were wound densely onto rigid rod and then annealed at different annealing temperatures. The polymeric embolization coil annealed at $200^{\circ}C$ was similar to metallic coils and its shape was maintained well after extension. Overall, gel-spun PVA fibers performed well for the preparation of primary and secondary coils to replace metallic coils.