• 한국응용과학기술학회지
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• 제17권4호
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• pp.257-261
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• 2000

Monodisperse polymer particles have many industrial applications such as surface coatings for metal panels, chromatographic media, spacers for liquid crystal display panel, and fillers for cosmetics, etc.. Micron-size monodispersed poly(methyl methacrylate) particles were prepared by dispersion polymerization in methanol medium in the presence of poly(vinyl pyrrolidone) and 2,2'-azobis(isobutyronitrile) as steric stabilizer and initiator, respectively. Effects of polymerization parameters, such as monomer and initiator concentration, stabilizer type and concentration, solvent composition on average particle size and size distribution were studied.

• 대한기계학회논문집B
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• 제24권7호
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• pp.1020-1027
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• 2000

A simple model for describing the non-spherical particle growth phenomena has been developed. In this model, we solve simultaneously particle volume and surface area conservation sectional equations that consider particles' non-sphericity. From the correlation between two conserved properties of sections, we can predict the evolution of the aggregates' morphology. This model was compared with a simple monodisperse-assumed model and more rigorous two-dimensional sectional model. For comparison, formation and growth of silica particles have been simulated in a constant temperature reactor environment. This new model showed good agreement with the detailed two-dimensional sectional model in total number concentration and primary particle size. The present model successfully predicted particle size distribution and morphology without costing very heavy computation load and memory needed for the analysis of two dimensional aerosol dynamics.

• 공업화학
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• 제9권5호
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• pp.634-638
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• 1998

응집이 없는 단분산의 $PMSQ/TiO_2$ 복합 미립자를 얻기 위하여 300 nm 크기의 $TiO_2$ seed가 분산되어 있는 메탄올 수용액과 MTMS (Methyltrimethoxysilane)를 메탄올에 녹인 용액을 혼합하여 $TiO_2$ seed 표면에서 MTMS가 가수분해 및 축합 반응이 일어나도록 유도하여 복합 미분말을 제조하였다. 촉매로 암모니아를 사용하였고, 반응온도는 실온이었으며, 모든 반응은 질소분위기에서 행하였다. 교반속도, 반응온도, $[H_2O]/[MTMS]$, $[MTMS]/[TiO_2]$ 등을 변화하여 입자의 크기 및 형태에 영향을 주는 인자들을 조사한 결과, [MTMS]=0.2 M, $[NH_4OH]=0.6M$, $[H_2O]/[MTMS]=100$, $[MTMS]/[TiO_2]=10-50$이고 실온에서 서서히 교반한 경우 단분산된 약 $1-2{\mu}m$의 크기를 갖는 복합입자를 얻을 수 있었다. 얻어진 입자에 대한 소수성을 물에 대한 접촉각 측정을 통해 조사한 결과 거의 180도에 가까운 접촉각을 보임으로써 복합입자의 소수성이 매우 뛰어남을 확인할 수 있었다. 자외선 차폐효과도 UV 투과도 측정을 통해 조사되었다.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1891-1896
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• 2010

Submicron-sized polymeric colloidal particles can self assemble into 3-dimensional (3D) opal structure which is a useful template for photonic crystal. Narrowly dispersed polymer microspheres can be synthesized by emulsion polymerization in water using water-soluble radical initiator. In this report, we demonstrate a facile and reproducible emulsion polymerization method to prepare various polymeric microspheres within 200 - 400 nm size ranges which can be utilized as colloidal photonic crystal template. By controlling the amount of monomer and surfactant, monodisperse polymer colloids of polystyrene (PS) and acrylates with various sizes were successfully prepared without complicated synthetic procedures. Such polymer colloids self-assembled into 3D opal structure exhibiting bright colors by reflection of visible light. The colloidal particles and the resulting opal structures were rigorously characterized, and the wavelength of the structural color from the colloidal crystal was confirmed to have quantitative relationship with the size of constituting colloidal particles as predicted by Bragg equation. The tunability of the structural color was achieved not only by varying the particle size but also by infiltration of the colloidal crystal with liquids having different refractive indices.

• 대한기계학회논문집B
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• 제28권3호
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• pp.349-358
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• 2004

A low pressure impactor is an impaction device to separate airborne particles into aerodynamic size classes at low pressure condition. We designed a two-stage low-pressure impactor to classify submicron sized environmental aerosols. Performance evaluation was carried out for stages 1 and 2 by using an electrical method. Monodisperse liquid dioctyl sebacate (DOS) particles were generated using evaporation-condensation process followed by electrostatic classification using a DMA (differential mobility analyzer). The test particles were in the range of 0.08∼0.8$\mu\textrm{m}$. For the evaluation of the impactor we used two electrometers; one was connected to the impaction plate of the impactor and the other was to the Faraday cage used as a backup filter. The effect of polydispersity of test aerosols on the performance was investigated. The results showed that the experimental 50-% cutoff diameters at each impactor's operation pressure were 0.53 and 0.187$\mu\textrm{m}$ for stages 1 and stage 2, respectively. The effects of operation pressure on the cutoff diameter and the steepness of collection efficiency curves were also investigated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1417-1422
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• 2003

An electrical cascade impactor is a multistage impaction device to separate airborne particles into aerodynamic size classes using electrical method. We designed a real-time three-stage electrical low-pressure impactor, which is proper to nanometer sized environmental aerosols. Performance evaluation was carried out for stage 1 and 2. The monodisperse liquid dioctyl sebacate (DOS) particles were generated using condensation-evaporation followed by electrostatic classification using DMA (differential mobility analizer) for particles with diameters in the range of $0.04{\sim}0.8{\mu}m$. The evaluation of the electrical impactor is based on the use of two electrometers, one connected to the impaction plate of the impactor, and the other to the faraday cage as backup filter. The results showed that the experimental 50% cutoff diameters in the operation pressure were 0.53 and $0.12{\mu}m$ for stage 1 and stage 2. The effect of operation pressure on the cutoff diameter and the steepness of collection effcieicy curves is investigated.

• 공업화학
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• 제19권6호
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• pp.609-616
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• 2008

본 연구는 크기가 다른 두 종류의 입자를 가진 비(非)콜로이드성 현탁액의 평균 침강 속도를 예측하는 수치적 방법을 제공한다. 이 방법은 무수히 많은 입자들이 유체에 불규칙적으로 분포된 현탁액 시스템의 유체 속도, 온도 등의 물리량을 앙상블 평균의 개념을 사용해서 표현하는 유효 매체 이론에 기초한다. 본 연구에서는 Acrivos와 Chang[1]이 단일(單一) 입도 현탁액에 대해 제안한 모델을 이중(二重) 입도 현탁액에 응용한다. 구체적으로 방사 분포 함수(radial distribution function)에 대한 계산과 stream function을 이용하여 침강 속도를 계산하고 그 결과를 Davis와 Birdsell[2]과 Cheung 등[3]의 실험 결과와 비교하였다. 그 결과 본 연구의 모델에 의한 예측이 실험 결과와 일치하는 것으로 나타났다.

• Macromolecular Research
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• 제12권5호
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• pp.512-518
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• 2004

We have synthesized a novel macromonomer of vinyl-terminated bifunctional polyurethane having a molecular weight of 37,000 g/mol and successfully applied it to the dispersion polymerization of methylmethacrylate(MMA). We verified the presence of the vinyl terminal group and the macromonomer grafted onto the poly(ethylene glycol)(PEG) block in the PMMA particles by using $^1$H and $\^$13/C NMR spectroscopies. Monodisperse PMMA microspheres that have good uniformity of 1.01 were prepared at 20 wt% macromonomer content; we investigated the characteristics of the PMMA particles in terms of their molecular weight, molecular weight distribution, size of the particles, thermal properties, and glass transition temperature. We have found that the synthesized polyurethane macromonomer is an effective stabilizer.

• 접착 및 계면
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• 제15권3호
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• pp.93-99
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• 2014

본 Styrene (ST)과 sodium 1-allyloxy-2-hydroxypropane sulfonate (COPS-I)의 무유화 공중합을 다양한 중합조건(ST, COPS-I, KPS, DVB의 농도 및 중합온도)하에서 실시하여, 165~550 nm 입자경 범위의 단분산 라텍스를 제조하였다. 일반적으로 COPS-I와 KPS의 농도, 중합온도, DVB의 농도 등의 변화는 고분자 입자수(입자경), 중합속도, 분자량, 제타전위 등에 밀접한 영향을 미침을 발견하였다. 입자수의 증가는 중합속도와 제타전위를 증가시켰으나 분자량은 감소하였다.

• 대한기계학회논문집
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• 제16권3호
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• pp.547-554
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• 1992

본 연구에서는 Climet사의 백색광원 OPC인 CI226와 PMS사의 laser 광원 OPC인 LAS-X 및 HS-LAS의 응답특성을 측정하여 제작사가 제시한 응답특성과 비교하여 그 정 확성을 논하였으며 아울러 고유량(high flow rate) Clean Room용 OPC인 Climet CI- 7300, Met One 200, Hiac/Royco5120 등 3가지 장치에 관한 오계수의 원인을 박히고자 하였다.