Preparation of high molecular weight poly(vinyl alcohol) with high yield using low‐temperature solution polymerization of vinyl acetate

Lyoo, Won Seok; Han, Sung Soo; Choi, Jin Hyun; Ghim, Han Do; Yoo, Sung-Won; Lee, Jinwon; Hong, Sung Il; Ha, Wan Shik

doi:10.1002/app.1183

Cited by 23 publications

(7 citation statements)

References 19 publications

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“…It is notable that the dimension ratio between the core and shell of the PVA/PVAc microspheres is approximately five. [24] The cross section of the silane-PVA/PVAc film is estimated based on three facts. The first is the chemical composition of a PVA/PVAc microsphere; it has a well-defined hydrophilic/hydrophobic structure, which provides the shell/ core geometry.…”

Section: Zeta Potential Measurement and Simulationmentioning

confidence: 99%

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Formation Mechanism of a Silane‐PVA/PVAc Complex Film on a Glass Fiber Surface

Repovský

Jáné

Pálszegi³

et al. 2013

ChemPhysChem

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Mechanical properties of glass fiber reinforced composite materials are affected by fiber sizing. A complex film formation, based on a silane film and PVA/PVAc (polyvinyl alcohol/polyvinyl acetate) microspheres on a glass fiber surface is determined at 1) the nanoscale by using atomic force microscopy (AFM), and 2) the macroscale by using the zeta potential. Silane groups strongly bind through the Si-O-Si bond to the glass surface, which provides the attachment mechanism as a coupling agent. The silane groups form islands, a homogeneous film, as well as empty sites. The average roughness of the silanized surface is 6.5 nm, whereas it is only 0.6 nm for the non-silanized surface. The silane film vertically penetrates in a honeycomb fashion from the glass surface through the deposited PVA/PVAc microspheres to form a hexagonal close pack structure. The silane film not only penetrates, but also deforms the PVA/PVAc microspheres from the spherical shape in a dispersion to a ellipsoidal shape on the surface with average dimensions of 300/600 nm. The surface area value Sa represents an area of PVA/PVAc microspheres that are not affected by the silane penetration. The areas are found to be 0.2, 0.08, and 0.03 μm(2) if the ellipsoid sizes are 320/570, 300/610, and 270/620 nm for silane concentrations of 0, 3.8, and 7.2 μg mL(-1), respectively. The silane film also moves PVA/PVAc microspheres in the process of complex film formation, from the low silane concentration areas to the complex film area providing enough silane groups to stabilize the structure. The values for the residual silane honeycomb structure heights (Ha ) are 6.5, 7, and 12 nm for silane concentrations of 3.8, 7.2, and 14.3 μg mL(-1), respectively. The pH-dependent zeta-potential results suggest a specific role of the silane groups with effects on the glass fiber surface and also on the PVA/PVAc microspheres. The non-silanized glass fiber surface and the silane film have similar zeta potentials ranging from -64 to -12 mV at pH's of 10.5 and 3, respectively. The zeta potentials for the PVA/PVAc microspheres on the glass fiber surface and within the silane film significantly decrease and range from -25 to -5 mV. The shapes of the pH-dependent zeta potentials are different in the cases of silane groups over a pH range from 7 to 4. A triple-layer model is used to fit the non-silanized glass surface and the silane film. The value of the surface-site density for Γ(Xglass) and Γ(Xsilane), in which X denotes the Al-O-Si group, differs by a factor of 10(-4), which suggests an effective coupling of the silane film. A soft-layer model is used to fit the silane-PVA/PVAc complex film, which is approximated as four layers. Such a simplification and compensation of the microsphere shape gives an approximation of the relevant widths of the layers as the follows: 1) the layer of the silane groups makes up 10% of the total length (27 nm), 2) the layer of the first PVA shell contributes 30% to the total length (81 nm), 3) the layer of the PVAc core contributes 30% to the to...

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Section: Zeta Potential Measurement and Simulationmentioning

confidence: 99%

“…The dimensionless flow velocity of electrolyte is defined with V(X) = v(x)/(DpH 2 /hL 0 ) (Dp is the pressure difference between the beginning and the end of the channel, L 0 is the length of the channel, and h is the viscosity of the electrolyte) depending on position x to the Brinkman Equations (24) and (25):…”

Section: Zeta Potential Measurement and Simulationmentioning

confidence: 99%

Formation Mechanism of a Silane‐PVA/PVAc Complex Film on a Glass Fiber Surface

Repovský

Jáné

Pálszegi³

et al. 2013

ChemPhysChem

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“…[4] DMSO is actually used in industrial aspects due to its low transfer constant, resulting into reduction polymer chain growth and degree of polymerisation. [5] Recently, PAN is used as a filtration medium for water treatment due to its good solvent resistance. Yoon et al prepared a new type of high flux ultrafiltration based on an electrospun PAN nanofibrous scaffolds and an polyethylene terephthalate (PET) nonwoven microfibrous substrate with a hydrophilic and water resistant properties.…”

Section: Introductionmentioning

confidence: 99%

Effect of POSS content on the electrical, thermal, mechanical, and wetting properties of electrospun polyacrylonitrile (PAN)/POSS nanofibrous mats

Khil

Beom

et al. 2015

Journal of Experimental Nanoscience

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Although polyacrylonitrile (PAN) has excellent properties as a precursor of carbon fibre, octa-amic polyhedral oligomeric silsesquioxane (POSS) nanoparticles which are hybrid organicÀinorganic materials can be incorporated into PAN to tune up the properties such as the mechanical strength, thermal conductivity, and electronic conductivity for a broad range of potential applications. In this work, PAN with POSS of 1, 3, and 5 wt % based on acrylonitrile weight was prepared by solution polymerisation. The synthesised product was dissolved in dimethyl sulphoxide, followed by electrospinning. After electrospinning, the nanofibrous mats were stabilised at 250 C for 1 h. The diameter of resulting PAN/POSS nanofibrous mats were less than 1 mm, as confirmed by SEM analysis. The effect of POSS on PAN/POSS nanofibrous mats was studied by SEM, universal testing machine, contact angle measurement, Fourier transform infrared spectroscopy, wide angle X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The usefulness of the PAN/POSS nanofibre composites was realised from the improved electrical, thermal, mechanical, and wetting properties compared to pure PAN.

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“…In the second stage, PVA/PVAc microspheres are prepared by the partial saponification of PVAc beads . The dimension ratio between the core and shell of PVA/PVAc microspheres is approximately five …”

Section: Introductionmentioning

confidence: 99%

“…[11] The dimension ratio between the core and shell of PVA/PVAc microspheres is approximately five. [12] The thermal degradation of PVA has been reported. [13][14][15][16] Generally for degradation below 300°C, the major product of thermal degradation has been observed to be water, produced by the elimination of hydroxyl side-groups form conjugated polyenes and non-conjugated polyenes.…”

Section: Introductionmentioning

confidence: 99%

Thermal curing and water re-exposure of silane-PVA/PVAc complex film on glass fiber surface

Repovský

Michalka

Velič

2014

Surf. Interface Anal.

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Because glass fiber reinforced composites are in industrial demand, chemistry and topography of the glass fiber sizing are of interest. Silane–PVA/PVAc (polyvinyl alcohol/polyvinyl acetate) complex film on the glass fiber surface is studied during thermal curing and water re‐exposure by using atomic force microscopy. The complex film consists of silane with the honeycomb structure film and PVA/PVAc with the hexagonal close pack structure of ellipsoidal shaped microspheres (270 × 620 nm). The thermal curing at 100 °C is leading to the evaporation of water contained in the microspheres. Because of water evaporation, the average roughness value of 1‐min thermal curing decreases from initial 7.3 to only 2.7 nm. Such a collapse of microsphere is followed by an intermixing between silane film and PVA/PVAc microspheres leading to a change of silane honeycomb structure along with silane tips. The average value of the silane honeycomb structure wall width decreases from 144 nm to 54 nm, for curing times of 15 and 30 min, respectively. A re‐exposure to an aqueous environment after 100 °C curing leads to almost completely restored microspheres regarding shape and size. The average complex film thickness increases from 180 nm for thermal curing for 30 min to 225 nm for water re‐exposed film. Interestingly, the pits in the microsphere structure are observed presumably because of the tips from intermixing. The thermal curing at 200 °C enhances the intermixing, and after 15 min, an intramixing is suggested to occur between PVAc core and PVA shell of the microsphere. The water re‐exposure after 15 min of 200 °C curing leads to a re‐containing of water but without restored microsphere structure; Because of the intramixing, leaving the silane–PVA/PVAc film is not complex anymore. Copyright © 2014 John Wiley & Sons, Ltd.

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Preparation of high molecular weight poly(vinyl alcohol) with high yield using low‐temperature solution polymerization of vinyl acetate

Cited by 23 publications

References 19 publications

Formation Mechanism of a Silane‐PVA/PVAc Complex Film on a Glass Fiber Surface

Formation Mechanism of a Silane‐PVA/PVAc Complex Film on a Glass Fiber Surface

Effect of POSS content on the electrical, thermal, mechanical, and wetting properties of electrospun polyacrylonitrile (PAN)/POSS nanofibrous mats

Thermal curing and water re-exposure of silane-PVA/PVAc complex film on glass fiber surface

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