• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.25-28
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• 2002

비공역형 단량체인 비닐아세테이트(VAc)는 공역형 비닐계 단량체와 달리 라디칼의 활성이 너무 커서 중합 도중 빈번한 연쇄이동반응과 정지반응에 의해 분지구조의 고분자가 얻어지며 고분자량의 폴리비닐아세테이트를 얻기가 어려운 것으로 알려져 있다. 폴리비닐알코올(PVA)은 비닐알코을 단량체의 호변이성질화 때문에 단량체의 직적중합에 의해서는 얻을 수 없고 일반적으로 비닐아세테이트(VAc)를 라디칼 중합하여 얻어진 폴리비닐아세테이트(PVAc)를 비누화하여 합성한다. (중략)

• Proceedings of the Korean Fiber Society Conference
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• 1995.10a
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• pp.20-20
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• 1995

• Proceedings of the Membrane Society of Korea Conference
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• 1992.04a
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• pp.7-8
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• 1992

역삼투막에 이용되고 있는 고분자물질은 셀루로오스 아세테이트(CA)를 비롯하여 방향족 폴리아마이드가 주로 이용되고 있으며, 최근에는 폴리설펀막의 지지층 위에 계면중합법을 응용한 복합막이 주류를 이루고 있다. 여기서는 가장 많이 이용되고 있는 셀루로오스아세테이트를 이용한 역삼투 투과 특성에 관하여 연구하였다.

• Clean Technology
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• v.16 no.2
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• pp.73-79
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• 2010

Vinyl acetate(VAc) was dispersion-polymerized using supercritical carbon dioxide that has many environmental advantages. To get poly(vinyl acetate) (PVAc) of larger molecular weights from conventional emulsion polymerization, VAc was polymerized at temperatures between 333.15 and 343.15 K and pressures between 20 and 40 MPa with initiator (0.5 ~ 5% of monomer) and silicone-based stabilizer (1 ~ 10% of monomer) for 2 ~ 50 hr. The resulting PVAc was analyzed to see the variations in the yield and the molecular weight. The final product of this research, PVA (poly(vinyl alcohol)), was prepared from PVAc by saponification. The effect of saponification conditions on the yield and the molecular weight of polymer were also studied.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.191-194
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• 2002

완전히 가수분해 된 폴리비닐알콜(PVA)는 쉽게 결정화되기 때문에 일부 가수분해된 PVA보다 에멜전 안정화와 계면활성이 약하다$^{1)}$ . 이러한 성질을 개선하려면 폴리비닐알콜분자에 hydrophobic한 알킬기를 도입하는 것이 주요한 방법이다. 폴리비닐알콜 분자에 긴 알킬기를 도입하는 방법에는 chain transfer 반응을 통하여 폴리비닐아세테이트(PVAc)분자의 말단에 긴 알킬기를 도입한 후 가수분해하는 방법$^{1)}$ ; 비닐아세테이트 (VAc)가 긴 알킬리를 가진 비닐 단량체와 copolymerization 한 후 가수분해하는 방법 $^{2),3)}$ ; 합성된 PVA가 긴 알킬리를 긴 알킬리를 가진 acyl chloride와 직접 반응하여 얻는 방법$^{4)}$ 등이 있다. (중략)

• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.701-706
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• 2015

In this study, experimental and computer simulation results are compared and analyzed. Three-dimensional (3D) fabricated matrices from an MJM 3D printer were joined with poly-acetate thermoplastic polymers using a diode laser. A power range of 5-7 W was used to irradiate the boundary of two polymers. The heated polymers flowed into the matrices of the 3D fabricated structure, and reliable mechanical joining was achieved. Computer simulation showed the temperature distribution in the polymers, and flow direction was estimated based on the flux and temperature information. It was found that the more than the minimum energy threshold was required to effectively join the polymers and that two scans at low-speed were more effective than four scans at high speed.

• Korean Journal of Food Science and Technology
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• v.49 no.3
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• pp.331-337
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• 2017

To evaluate the antioxidant activity of hexane, ethyl acetate, and butanol fractions obtained from Agastache rugosa extract, we measured the total polyphenol levels, DPPH radical scavenging activity, and reducing power. The ethyl acetate fraction of A. rugosa (AREA) displayed high phenolic levels, potent DPPH radical scavenging effect, and powerful reducing power. In addition, we examined the ability of AREA to inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 microglia. AREA suppressed NO production and inducible nitric oxide synthase (iNOS) expression and downregulated interleukin-6 (IL-6) mRNA level in LPS-stimulated BV-2 microglia. Furthermore, we detected rosmarinic acid in AREA by HPLC, which suggested that rosmarinic acid could be one of the bioactive materials responsible for the antioxidant and anti-inflammatory activities of AREA. These results suggested that AREA may be a good source of functional foods with antioxidant and anti-inflammatory activities.

• Food Science and Preservation
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• v.13 no.4
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• pp.501-505
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• 2006

This study was carried out to investigate the antioxidative activity and cytotoxicity on human KB cell of extract from Rhododendron mucronulatum flower, and also to determine the contents of total polyphenol and flavonoid. The methanol extract of Rhododendron mucronulatum flower was fractionated with various solvents such as hexane, chloroform, ethyl acetate, butanol and water. The DPPH radical scavenging activities of ethyl acetate fraction had stronger activity than other fractions. So, antioxidative substances of ethyl acetate fraction were crude purified by silica gel column chromatography. The DPPH radical scavenging activities of crude purified fraction 2 and 3 were more than 90% at 40 ppm. In the presence of $100{\mu}g/mL$, growth inhibition on human KB cell by WST-1 assay showed 81.2% in chloroform fraction and 74.6% in hexane fraction. The contents of total polyphenol and flavonoid of ethyl acetate traction were 32.70% and 20.30%, respectively, The antioxidative activity showed correlation with total polyphenol and flavonoid contents.

• Korean Journal of Food Science and Technology
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• v.50 no.2
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• pp.209-215
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• 2018

To evaluate the radical scavenging activity of phenolic-rich fractions of Gardenia jasminoides, we first measured the levels of total polyphenols in hexane, ethyl acetate, and butanol fractions from the extract of G. jasminoides. The ethyl acetate fraction of G. jasminoides extract (GJ-EA) showed high level of phenolics, potent reducing power, and 2,2-diphenyl-1-picrylhydrazyl/2,2'-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid radical scavenging effect. In addition, GJ-EA inhibited the overproduction of nitric oxide in lipopolysaccharide-activated BV-2 microglia. Furthermore, we found that GJ-EA suppressed $H_2O_2$-induced PANC-1 pancreatic cancer cell proliferation in a concentration-dependent manner and also reduced their migratory ability. These results suggest that GJ-EA may be a good source for functional foods with antioxidant and chemo-preventive activities.