• Journal of the Korean Applied Science and Technology
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• v.19 no.2
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• pp.131-136
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• 2002

As model waterborne acrylic coatings, mono-dispersed poly(butyl acrylate-methyl methacrylate) copolymer latexes of random copolymer and core/shell type graft copolymer were prepared by seeded multi-staged emulsion polymerization with particle size of $180{\sim}200$ nm using semi-batch type process. Sodium lauryl sulfate and potassium persulfate were used as an emulsifier and an initiator, respectively. The effect of particle texture including core/shell phase ratio, glass transition temperature and crosslinking density, and film forming temperature on the film formation and final properties of film was investigated using SEM, AFM, and UV in this study. The film formation behavior of model latex was traced simultaneously by the weight loss measurement and by the change of tensile properties and UV transmittance during the entire course of film formation. It was found that the increased glass transition temperature and higher crosslinking degree of latex resulted in the delay of the onset of coalescence of particles by interdiffusion during film forming process. This can be explained qualitatively in terms of diffusion rate of polymer chains. However, the change of weight loss during film formation was insensitive to discern each film forming stages-I, II and III.

• Korean Journal of Medicinal Crop Science
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• v.26 no.5
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• pp.417-429
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• 2018

Background: The objective of this study was to make colloidal dispersions of the active compounds of radix of Angelica gigas Nakai that could be charaterized as nano-composites using hot melt extrusion (HME). Food grade hydrophilic polymer matrices were used to disperse these compound in aqueous media. Methods and Results: Extrudate solid formulations (ESFs) mediated by various HPMCs (hydroxypropyl methylcelluloses) and Na-Alg polymers made from ultrafine powder of the radix of Angelica gigas Nakai were developed through a physical crosslink method (HME) using an ionization agent (treatment with acetic acid) and different food grade polymers [HPMCs, such as HP55, CN40H, AN6 and sodium alignate (Na-Alg)]. X-ray powder diffraction (XRD) analysis confirmed the amorphization of crystal compounds in the HP55-mediated extrudate solid formulation (HP55-ESF). Differential scanning calorimetry (DSC) analysis indicated a lower enthalpy (${\Delta}H=10.62J/g$) of glass transition temperature (Tg) in the HP55-ESF than in the other formulations. Infrared fourier transform spectroscopy (FT-IR) revealed that new functional groups were produced in the HP55-ESF. The content of phenolic compounds, flavonoid (including decursin and decursinol angelate) content, and antioxidant activity increased by 5, 10, and 2 times in the HP55-ESF, respectively. The production of water soluble (61.5%) nano-sized (323 nm) particles was achieved in the HP55-ESF. Conclusions: Nano-composites were developed herein utilizing melt-extruded solid dispersion technology, including food grade polymer enhanced nano dispersion (< 500 nm) of active compounds from the radix of Angelica gigas Nakai with enhanced solubility and bioavailability. These nano-composites of the radix of Angelica gigas Nakai can be developed and marketed as products with high therapeutic performance.

• Journal of the Korean Graphic Arts Communication Society
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• v.14 no.2
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• pp.101-113
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• 1996

In general, printing inks are mainly composed of pigments and vehicles. Its characteristics are affected, to a greater or lesser extent, by the size and distribution of the pigment particles in the dispersion. Color strength, transparency and gloss generally increases with an decrease in particle size of pigments. On the contrary, opacity, lightfastness tend to increases with an increase in particle size of pigments In this work, we have investigated an effect of surface area of pigments on the physical properties of printing of printing ink which made up vehicles for sheet fed and organic pigment Lake Red C(C.I.Pigment Red 53:1) that different surface area and particle size. It was found that gloss, tack and yield value increases with an increase in surface are of pigments, but grindness is reduced.

• Journal of Powder Materials
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• v.18 no.2
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• pp.129-134
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• 2011

Herein, macroporous carbon materials were readily prepared by carbonization of cured body of resorcinol and formaldehyde using poly(methyl methacrylate) colloid microspheres which were employed as the template in the gelation of resorcinol with formaldehyde. The gel in the water was solvent exchanged with methanol and the wet gel was dried. After carbonization of the template-gel composite at $800^{\circ}C$, it was found that pores were left corresponding to the size of the template, yielding carbon materials with a fine porous structure with enlarged surface area and significant porosity. Properties of the carbon foams including the structure, morphology, thermal stability, and porosity were investigated. Finally, it was concluded that the method using polymer colloids as the template provided a facile route to prepare carbon foams.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1021-1024
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• 2003

In this work, we fabricated various 2D metallic and polymeric nanopatterns with the feature resolution of sub-micrometer scale by using the method of microcontact printing ($\mu$ P) based on soft lithography. Silicon masters for the micromolding were made by e-beam lithography. Composite poly(dimethylsiloxane) (PDMS) molds were composed of a thin, hard layer supported by soft PDMS layer. Finally, monodisperse metal or polymer particles could be obtained in the prepared pattern for the application of electronic devices.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.816-822
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• 2011

Pervaporation is known to be a low energy consumption process since it needs only an electric power to maintain the permeate side in vacuum. Also, the pervaporation is an environmentally clean technology because it does not use the third material such as an entrainer for either an azeotropic distillation or an extractive distillation. In this study, Silicalite-1 particles are hydrothermally synthesized and polydimethylsiloxane(PDMS)-zeolite composite membranes are prepared with a mixture of synthesized Silicalite-1 particles and PDMS-polymer. They are used to separate n-butanol from its aqueous solution. Pervaporation characteristics such as a permeation flux and a separation factor are investigated as a function of the feed concentration and the weight % of Silicalite-1 particles in the membrane. A 1,000 $cm^3$ aqueous solution containing butanol of low mole fraction such as order of 0.001 was used as a feed to the membrane cell while the pressure of the permeation side was kept about 0.2~0.3 torr. When the butanol concentration in the feed solution was 0.015 mole fraction, the flux of n-butanol significantly increased from 14.5 g/ $m^2$/hr to 186.3 g/$m^2$/hr as the Silicalite-1 content increased from 0 wt% to 10 wt%, indicating that the Silicalite-1 molecular sieve improved the membrane permselectivity from 4.8 to 11.8 due to its unique crystalline microporous structure and its strong hydrophobicity. Consequently, the concentration of n-butanol in the permeate substantially increased from 0.07 to 0.15 mole fraction. This composite membrane could be potentially appliable for separation of n-butanol from insitu fermentation broth where n-butanol is produced at a fairly low concentration of 0.015 mole fraction.

• Membrane Journal
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• v.20 no.2
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• pp.159-168
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• 2010

In this study, high porous PVdF flat sheet membranes were prepared to obtain reinforced membrane support for polymer electrolyte membrane fuel cell. Nano-size laponite was randomly dispersed in the membranes to improve mechanical property which lowered by the high porosity. The morphology and porosity of prepared PVdF/Laponite composite membranes were examined using the SEM analysis and the weight method and all membranes showed over 60% porosity. The membrane thermal stability depending on the laponite contents in the composite membranes was evaluated by membrane heat shrinkage at $105^{\circ}C$ and $135^{\circ}C$. MD and TD heat shrinkage of the PVdF composite membrane containing 5 wt% laponite was 2~3% and 2~3.5% at $135^{\circ}C$, respectively. The mechanical strength was enhanced after incorporating laponite particles and 30% increase in the modulus compared to pure PVdF membrane was obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1465-1471
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• 2013

The electrical and mechanical properties of room temperature vulcanized (RTV) silicone rubber composites are investigated as functions of multi-walled carbon nanotube (CNT), carbon black (CB), and thinner content. The thinner is used to improve the CNT and CB dispersion in the matrix. The electrical and mechanical properties of the composite with CNT are improved when compared to the composite with CB at the same content. As the thinner content is 80 phr, the electric resistance of the composite decreases significantly with the CNT content and shows contact point saturation of CNT at 2.5 phr. As the thinner content increases, the dispersion of conductive particles improves; however, the critical CB content increases because of the reduction in the CB weight ratio. It is believed that an electrode that needs good flexibility and excellent electrical properties can be manufactured when the amount of CNT and CB are increased with the thinner content.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.29-34
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• 2014

Particulate reinforced composite is composed of hard particles and polymer matrix. This material has been widely applied for engineering industry such as automobile, construction and aerospace. For the safe application, it is important to assess crack resistance behavior. Especially in aerospace industry, crack could cause significant problem when the material is used for solid rocket fuel. Therefore, it is inevitable to estimate the characteristics of the crack propagation. In this study, crack propagation tests were conducted using particulate reinforced composite under crosshead rate 2.54 mm/min in the range of temperature $-60^{\circ}C$ to $60^{\circ}C$. The strain contour of surface for specimen was generated using digital image correlation method.

• Composites Research
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• v.30 no.1
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• pp.41-45
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• 2017

Magnetite nanoparticles were synthesized by adding an ammonium hydroxide to a mixed solution of iron (II) and (III) chlorides. A silicon surfactant of ${\alpha},{\omega}$-(3-aminopropyl)polydimethylsiloxane was adsorbed on the particles as dispersant and a polydimethylsiloxane polymer was used to prepare ferrofluids of silicone oil base. Fluorinated surfactants of anionic ammoniated perfluoroalkyl sulfonamide and nonionic fluoroaliphatic polymeric esters were applied to the particles and a perfluoropolyether was used to prepare ferrofluids of fluorine oil base. The experimental conditions were used for preparing the ferrofluids with concentrations of 200, 300 and 400 mg/mL, and density, magnetization and viscosity of the products were characterized. The density values increased in proportion to the concentration, indicating 1.11-1.27 g/mL for silicone-oil-based fluids and 1.95-2.10 g/mL for fluorine-oil-based fluids in the range of 200-400 mg/mL. The saturation magnetization of the silicone-oil-based and fluorine-oil-based fluids indicated 14.7, 24.4, and 30.7 mT and 15.8, 23.3, and 33.7 mT for 200, 300, and 400 mg/mL, respectively, depending on the content of magnetic particles in the fluid. The viscosity of the silicone-oil-based ferrofluids was highly stable compared to that of the fluorine-oil-based with increasing temperatures. The ferrofluids are usually applied to seals and speakers with the silicone base and to seals with the fluorine base.