• Polymer(Korea)
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• v.26 no.2
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• pp.168-173
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• 2002

Poly (vinyl butyral) (PVB) was synthesized by acetalization of poly (vinyl alcohol) (PVA) PVB was prepared in particulate forms in water, and chemical and physical properties of the products were characterized using various techniques. The prepared PVB had size distribution from 100 to 700 $\mu\textrm{m}$ with mean diameter of about 380 $\mu\textrm{m}$. The chemical structure of PVB was characterized using FT/IR and NMR, and the average degree of acetalization was determined to be 77% from the titration measurement. DSC data showed that the crystalline structure of PVA vanished as acetalization reaction proceeded to produce PVB, and the glass transition temperature emerged at about $70^{\circ}C$. TGA data showed that PVB was much more thermally stable than PVA, and showed no degradation up to $300^{\circ}C$. Solubility test showed that PVB was soluble in alcohols but Insoluble in water, being totally different from PVA.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05b
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• pp.199-202
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• 2004

DMFC 성능을 개선시키기 위한 연구의 큰 영역은 고분자전해질막에 있으며 methanol crossover에 대한 영향을 최소화시킬 수 있는 소재개발이 우선적으로 요구되는 실정이다. 이러한 문제의 해결을 위해 Pivovar와 Cussler [1] 등은 투과증발 막분리공정에서 메탄올 저항체로 잘 알려진 폴리비닐알콜(poly vinyl alcohol, PVA)를 이용한 전해질막 연구를 하였다.(중략)

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1053-1058
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• 1998

Poly(vinyl butyral)s (PVB) with different butyral content were synthesized from poly(vinyl alcohol)(PVA) and n-butylaldehyde with acid catalyst. Bound butyral unit in PVB was determined by elemental analysis. Synthesized PVBs were reacted with p-azidobenzaldehyde to give photosensitive polymer with azidobenzene group(PVB-AZ). Bound photosensitive azidobenzene group in PVB-AZ was determined by UV spectrophotometry. The photosensitivity of PVB-AZ was compared with that of PVB/2,6-bis(p-azidobenzylidene)cyclohexanone(BAC) photosensitizer mixture system by gray scale method. Photosensitivity of PVB-AZ was higher than that of PVB/BAC mixture system. The photosensitivity of PVB-AZ was dependent on the developer used due to the solubility of PVB-AZ in a developer solvent.

• Polymer(Korea)
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• v.35 no.4
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• pp.296-301
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• 2011

This study focuses on the investigation of the impregnation of poly (vinyl alcohol) (PVA) crosslinked with poly(styrene sulfonic acid-co-maleic acid) (PSSA-MA) to porous polyethylene membrane for the fuel cell application. The membranes were characterized by the measurements of the water content, contact angle, FTIR spectra, thermal gravimetric analysis, ion exchange capacity, proton conductivity, methanol permeability and elastic modulus. The existence of hydrophilic moieties in the impregnated membranes was confirmed by contact angle and FTIR measurements. The impregnated PVA/PSSAMA(90:10) membrane exhibited a higher ion exchange capacity (1.2 meq./g dry membrane) than Nafion membrane (0.91 meq./g dry membrane). Through the elastic modulus measurement, the dimensional stability of the resulting membranes was expected to increase higher than the polyethylene membranes. The methanol crossover and water content decreased even if the PSSA-MA content increased due to the reduction of the free volume.

• Membrane Journal
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• v.22 no.4
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• pp.272-279
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• 2012

The neutral polymer, poly (vinyl alcohol) (PVA), was coated onto polyamide (PA) thin film composite reverse osmosis (RO) membranes. And then these membranes were investigated for the model foulants, bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA) whether there are aome improvement. As the operating pressure increased with 2, 4, 8 atm for BSA, HA and SA 100 ppm in feed solution, the fouling phenomena was worse for both none and PSSA coated membranes. The fouling occurred in the sequence of BSA > HA > SA due to the interactions between PVA snd functional groups of foulants, and on the other hand the fouling reduction was observed in the order of HA > BSA > SA. The observation of scanning electron microscopy photographs showed the same trend. As a result, there should be the improvement of fouling phenomena for the PVA coated RO membranes and the case of HA was shown distinct.

• Polymer(Korea)
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• v.28 no.2
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• pp.135-142
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• 2004

Poly(vinyl acetate) (PVAc) prepared by emulsion polymerization has broad applications for additives such as paint binder, adhesive for wood and paper due to its low glass transition temperature which help to plasticize substrate resins. Since emulsion polymerization has a disadvantage that surfactant and ionic initiator degrade properties of the product polymer, poly(vinyl acetate-co-butyl acrylate) (VVc-BA) was synthesized using potassium persulfate as catalyst and poly(vinyl alcohol) (PVA) as protective colloid to prevent the degradation. The copolymer latex product was internally plasticized and has enhanced colloid stability, adhesion, tensile strength and elongation. During VAc-BA emulsion polymerization, no coagulation and complete conversion occur with the reactant mixture of 0.7wt% potassium persulfate, 15wt% poly(vinyl alcohol) (PVA-217), and the balanced monomer that the weight ratio of vinyl acetate to butyl acrylate is 19. As the concentrations of PVA increase, the copolymerization becomes faster and polymer particles are more stable, resulting in enhanced mechanical stability of the VAc-BA copolymer. However, the size of the polymer particles decreases with increasing PVA contents. Properties of the VAc-BA copolymer, such as minimum film formation temperature, glass transition temperature, surface morphology, molecular weight and molecular weight distribution, tensile strength and elongation, were characterized using differential scanning calorimeter, transmission electron microscope and other instruments.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.217-221
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• 2012

Blending films having enhanced water-resistance and barrier properties were prepared using the mixtures of poly(vinyl alcohol) (PVA) aqueous solution and poly(ethylene-co-acrylic acid) (EAA) dispersed in water. Thermal-mechanical properties, contact angles, water-vapor transmission rates (WVTR) and oxygen transmission rates $(O_2TR)$ were measured with the content of EAA of blending films, and their water-resistance was evaluated. The tensile strength of the films was found to be $9.16{\sim}11.75\;kg/mm^2$ which showed no significant difference compared with that of PVA, and the hardness increased with the content of EAA. The glass transition temperature and melting temperature of the blending films were slightly improved. The film prepared with PVA/EAA (= 90/10), of which the swelling and solubility were measured to be 109 and 0%, respectively, showed improved water-resistance. The WVTR and $O_2TR$ for the PET film (thickness $50\;{\mu}m$) coated with PVA/EAA (= 90/10) film (thickness $2.5\;{\mu}m$) were measured to be $9.1\;g/m^2/day$ and $2.0\;cc/m^2/day$, respectively.

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.252-255
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• 1998

PVA(Poly Vinyl Alcohol)는 폴리에틸렌과 함께 최고 수준의 결정 탄성율(250~300 GPa)을 보유하고 있고, 이론적으로 높은 기계적 특성을 지녔기 때문에 초연신에 의한 고강도 고탄성율 섬유를 얻을 가능성이 매우 크다. 그러나 분자에 많이 존재하는 -OH기에 의한 강력한 분자내 및 분자간 수소결합 때문에 융점이 228~25$0^{\circ}C$ 정도로 높은 편이라는 장점이 있는 반면, 연신이나 열처리동안 분자 사슬의 alRMfj짐이나 재배열이 입체장애로 방해를 받아서 충분히 배향시키는데 상당한 어려움이 있다. (중략)

• Journal of Adhesion and Interface
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• v.13 no.2
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• pp.64-72
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• 2012

Vinyl acetate/alkyl acrylate copolymers were prepared by water-born emulsion copolymerization according to the compositional change of vinyl acetate and various alkyl acrylates such as methyl acrylate (MA), ethyl acrylate (EA), and n-butyl acrylate (BA). Ammonium persulfate (APS) was used as an initiator and poly(vinyl alcohol) (PVA) was used as a protective colloid. The significant result was described as follows. The activation energy determined by an isothermal analysis in the temperature region between $100{\sim}200^{\circ}C$ of the copolymer had the order of PVAc/PMA > PVAc/PEA > PVAc/PBA. The peel strengths before and after the plasma treatment were the order of PVAc/PMA > PVAc/PEA > PVAc/PBA.

• 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.