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RISS 인기검색어
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- 저자 : ( Ur-ryong Cho ) (검색결과 73 건)
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조을룡 한국기술교육대학교 2006 論文集 Vol.13 No.1
The water-born polyurethane/acrylic emulsion with core-shell morpology was used to develop water-born base coat for automotive coating. Compared to solvent based base coat, water-born base coat showed good water resistance and rust resistance, excellent appearance, and good workability at spray coating. The increase of polyurethane content in hybridized emulsion yielded improvement of adhesion, chip resistance, and film flexibility. The hardness of film with mole ratio of isocyanate group to hydroxy group increased with increasing isocyanate group. In the rheological measurement, unlike solvent based coating, water-born coating resulted in rapid rise of viscosity with increasing shear rate. The range of 3 to 6 of thixotropy index(TI) with use of thickener showed good storage stability and appearance, excellent orientation of color components.
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조을룡 한국기술교육대학교 2004 論文集 Vol.10 No.2
Acryl monomers such as acrylic acid(AA), methylmethacrylate(MMA), and ethyl acrylate(EA) were polymerized to use as water reducing agent for cement mortar. Acrylic acid was employed to show good final physical properties with polyoxyethylene aklyphenyl ether(Poly-E) and 2-acrylamido-2-methyl-1-propanesulfonic acid(AMPS). All the polymerizations were carried out in water-based solution to obtain environmentally freindly system. The viscosities of the synthesized solutions for the research have less than 800 cps. Especially, copolymer of AA, MMA, AMPS, and Poly-E resulted in high water retention, low bleeding, good dimensional stability, excellent resistance to freeze-thawing, and high compression strength due to hydrogen bonding of amide group of AMPS and ethylene oxide group of Poly-E.
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조을룡 한국기술교육대학교 2006 論文集 Vol.12 No.1
Tint pastes for water-based coatings were formulated and the properties were investigated as water-based coatings is being important due to environmental problems of solvent-based coatings. In the rheological behavior, viscosity of intermediate varies with respect to increased addition of wetting dispersant. The largest viscosity restitution occured at 8% of wetting dispersant when shear stress was removed, and anionic wetting dispersant yielded excellent restitution of viscosity at removal of shear stress. In terms of rheological behavior with pH, we could get the most stable dispersion at pH 8.5. Rheological behavior regarding to amount of dispersing resin showed the most stable pigmented dispersion at 6wt% of it. Particle size of pigment also affected jetness by variation of workability owing to differences of surface area.
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Miscibility and Properties of cis-Polybutadiene/Ethyl-Branched Polyethylene Blends (II)
Cho, Ur-Ryong The Polymer Society of Korea 2000 Korea polymer journal Vol.8 No.2
Cis-Polybutadiene (cis-PBD) and the three polyethylenes (PE's) having different branch content were mixed to investigate crystallinity, thermodynamic interaction parameter(c), and diluents effect. Crys-tallinty of PE's decreased with increasing content of amorphous cis-PBD because of a decrease in both the degree of annealing and kinetics of diffusion of the crystallizable polymer content. The thermodynamic interaction parameter(c) for the three blend systems approximately equals to zero near the melting point. These systems were determined to be miscible on a molecular scale near or above the crystalline melting point of the crystalline PE's. From the measurement of T$\sub$m/ vs. T$\sub$c/ behavior, all the three blends showed a straight line for a plot of T$\sub$m/ vs. T$\sub$c/. This result means that the melting behavior of PE is mainly due to a diluent effect of cis-PBD component.
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Miscibility and Properties of Ethyl-Branched Polyethylene/Ethylene-Propylene Rubber Blends(Ⅱ)
Cho, Ur Ryong 한국고무학회 2002 엘라스토머 및 콤포지트 Vol.37 No.2
2몰% 에틸가지를 포함하는 에틸 가지화 폴리에틸렌[PE(2)]과 에틸렌-프로필렌 몰비가 50:50 으로 같지만 입체규칙성이 다른 랜덤-에틸렌-프로필렌 고무(r-EPR), 교호-에틸렌-프로필렌고무(alt-EPR) 및 이소탁틱-교호-에틸렌-프로필렌 고무(iso-alt-EPR)를 에틸렌-프로필렌 고무의 입체규칙성의 차이에 대한 혼화성과 물성의 차이를 조사하기 위하여 혼합하였다. 혼합된 블렌드의 결정화도는 고무상 EPR 성분의 증가에 따라 감소되었으며, EPR의 입체규칙성이 작을수록, 혼합조성의 증가할수록 감소하였다. 열역학적 interaction parameter( x) 값은 3가지 블렌드 모두 거의 영에 가까운 값을 나타내어 본 블렌드계는 PE(2)의 녹는점 가까이 또는 그 이상에서 상호간 섞일 것으로 판단되었다. 녹는점(Tm)과 결정화온도(Tc)의 측정에서부터 세가지 블렌드는 혼합조성과 입체규칙성에 관계없이 직선관계를 보여주어 이 블렌드계의 PE(2)의 용융거동은 주로 희석효과(diluent effect)에 기인함을 알 수 있었다. Small angle light scattering(SALS) 방법에 의한 PE(2)의 spherulite의 크기는 세가지 블렌드계가 EPR의 혼합비 증가에 따라 증가하였으며, 같은 혼합비에서는 r-EPR>alt-EPR>iso-alt-EPR> 순서로 증가하였다. Ethyl-branched polyethylene [PE(2)] containing 2mole% ethyl branch and three ethylene-propylene rubbers (EPR's) having the same ethylene(E)-propylene(P) molar ratio(E/P=50/50) with different stereoregularity, that is, random EPR (r-EPR), alternating-EPR (alt-EPR) and isotactic-alternating-EPR (iso-alt-EPR) were mixed for the investigation of their properties depending on the stereoregularity. Crystallinity of the prepared blends decreased with increasing content of amorphous EPR because of a decrease in both the degree of annealing and kinetics of diffusion of the crystallizable polymer content. With blend composition, crystallinity was reduced with the stereoregularity in EPR. The thermodynamic interaction parameter( x) for the three blend systems approximately equals to zero near the melting point. These systems were determined to be miscible on a molecular scale near or above the crystalline melting point of the crystalline PE(2). From the measurement of Tm vs. Tc, the behavior of PE(2) is mainly due to a diluent effect of EPR component. The spherulite size measured by small angle light scattering (SALS) technique depended upon blend composition, and stereoregularity of EPR. The size of spherulite was enlarged with the content of rubbery EPR and the decrease of stereoregularity in EPR.
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에틸 가지화된 폴리에틸렌과 에틸렌 - 프로필렌 고무 블렌드의 혼화성과 물성 (1)
조을룡(Ur Ryong Cho) 한국고무학회 2001 엘라스토머 및 콤포지트 Vol.36 No.3
N/A Ethyl-branched polyethylene[PE(2)] containing 2mole% ethyl branch and three ethylene-propylene rubbers(EPR`s) having the same ethylene(E)-propylene(P) molar ratio(E/P=50/50) with different stereoregularity, that is, random EPR(r-EPR), alternating-EPR(alt-EPR) and isotactic-alternating-EPR(iso-alt-EPR) were mixed for the investigation of their properties depending on the stereoregularity. The three blends were immiscible at room temperature, and showed the simple additivity effect in density behavior. The melting point depression with blend composition increased in order of PE(2)/r-EPR$gt;PE(2)/alt-EPR$gt;PE(2)/iso-alt-EPR. In the tensile test, this blend systems have the lowest value of the breaking strength at PE(2) fraction of 0.5. This phenomenon results from the greastest separated phase morphology at this blend composition.
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