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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.
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.
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.
카르복실화 스티렌-부타디엔 라텍스의 중합시간 단축과 안정성 개선을 위한 연구
조을룡 한국고무학회 2002 엘라스토머 및 콤포지트 Vol.37 No.1
카르복실화 스티렌-부타디엔 라텍스의 중합시간은 사용되는 부타디엔 모노머가 공액 이중결합을 가진 화학적 구조로 인하여 라디칼 중합시 홀 전자의 비편재화로 인해 아크릴 에멀젼 의 제조시 보다 중합시간이 매우 길다. 또한 라텍스 자체가 고분자와 분산매의 분리 없이 사용되기 때문에 라텍스의 안정성은 대단히 중요하다. 물성의 저하없이 반응시간을 단축하기 위하여 기존에 사용하던 연쇄이동제인 사염화탄소 대신 tert-dodecylmercaptane 과 α-methylstyrene dimer를 혼합 사용하여 반응시간을 14시간에서 12시간으로 줄일 수 있었다. 반응 성장단계에서 아크릴산의 투입량을 0.3 part로 제한하여 라텍스의 점도 상승을 막고 초기중합단계 직후에 아크릴아미드를 0.1 part 첨가하여 라텍스 입자의 내부영역과 외부영역의 고분자 사슬의 상호간 확산을 막아 단단하면서도 접착력을 유지할 수 있는 라텍스의 합성 결과를 얻었다. Polymerization of carboxylated styrene-butadiene latex takes longer time than that of acrylic emulsion due to delocalization of radical in butadiene unit having conjugated double bond. A latex stability is the most important properties owing to use intact without separating polymer from base latex. For reducing polymerization time without decreasing any properties of latex, carbon tetra-chloride which has been used as the most popular chain transfer agent was replaced to combination of tert-dodecylmercaptane and α-methylstyrene dimer. The replacement yielded reducement of 2 hr in polymerization time. In the increment step, charge amount of acrylic acid was limited to 0.3 part to restrain viscosity enhancement. Just after initial step, addition of 0.1 part acrylamide prevent polymer chain from diffusing between two region followed by giving hardness and final good adhesive force to latex particles.