• Elastomers and Composites
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• v.50 no.1
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• pp.13-17
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• 2015

A study of the effects of MWCNT as a nucleating agent on the formation reactions of the rigid polyurethane foams (RPUFs) was carried out. Sample PUFs, formulated with grease-type master batch of MWCNT/surfactant, were fabricated by free-rising method. Temperature changes with time during foaming process were measured using a digital thermometer. RPUF foaming process was observed to undergo 2-step processes with temperature inflection around 60 sec after the start of reaction, and then reached slowly the max. temperature. While the max. temperature of neat PUF was measured as ca. $120^{\circ}C$, that of the samples with MWCNT were as higher value as ca. $130^{\circ}C$, and, even the time to reach that temperature was reduced by about 15 sec. Average cell size of PUF samples decreased from 185.1 for the neat PUF to $162.9{\mu}m$ for the sample of 0.01 phr of MWCNT. As the result, it was considered that MWCNT in RPUF foaming process could play a roll both as a nucleating agent and as a catalyst.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.4
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• pp.473-479
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• 1994

보소계면활성제 없이 microemulsion을 형성하는 최적의 계면활성제 구조를 찾기 위한 일련의 연구 중 세번째로 propoxylated nonylphenol sulfates와 ethoxylated 혹은 propoxylated highly-branched tridecyl alcohol sulfates를 연구하였다. 온도, NaCl농도, 보조계면활성제 농도, ethylene oxide몰수(EON), propylene oxide몰수(PON) 등을 변인으로 하여 phase behavior 실험을 한 결과 tridecyl alcohol 친유기를 갖는 계면활성제가 보조계면활성제 없이 microemulsion을 형성하였다. $C_{13}O(EO)_mPO)_nSO_3Na$ 일반식으로부터 m과 n을 변경시킴으로써 계의 다양한 조건을 만족시키는 계면활성제를 디자인할 수 있었다.

• Journal of the Korean Applied Science and Technology
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• v.20 no.1
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• pp.27-32
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• 2003

The core-shell latex particles were prepared by sequential emulsion polymerization of alkyl methacrylate and styrene(ST) by using an water-soluble initiator(APS) after preparing monomer pre-emulsion in the presence of an anionic surfactant(SDBS). In organic/organic core-shell polymerization, the pre-emulsion method, which minimized required quantity of sulfactant, has been used to increase the conversion rate and the stability of core-shell latex particles as well as to reduce the formation of secondary particle that cause problems of soap-free emulsion during shell polymerization. We used several methods to observe the core-shell structure. The core-shell structure was studied by measuring pH change during hydrolysis by NaOH, glass transition temperature($T_g$) by differential scanning calorimeter(DSC), morphology of latex by transmission electron microscope(TEM) and change of particle size and distribution by a particle analyzer.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.455-455
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• 2013

$CeO_2$ nanorings were synthesized by using a surfactant free hydrothermal method. The surface morphology, structural and optical properties of the synthesized $CeO_2$ was investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and ultraviolet-visible (UV) spectroscopy measurements. SEM images showed that the surface morphology of the formed $CeO_2$ appeared as nanorings. The XRD pattern of $CeO_2$ nanorings showed the presence of the polycrystalline $CeO_2$ phase readily indexed to the cubic fluorite structure of the $CeO_2$. The mean crystallite size of the $CeO_2$ was calculated using the Scherrer equation from the XRD line broadening of the (111) planes of the cubic $CeO_2$. The UV-Visible spectroscopy spectrum of the $CeO_2$ nanorings exhibited a strong UV absorption band around 350 nm.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.62-63
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• 2002

To reach 100 Gbit/in$^2$ magnetic recording densities in hard disk drives specular enhancement of giant magnetoresistance (GMR) effect in spin valve (SV) films has become one of the indispensable means for application as read elements in recording heads [1]. More recently specular spin valve (SSV) structure containing nano-oxides layers (NOL) were reported [2], where MR enhancement is caused to extended mean free path of majority spin polarized electrons through specular reflection at metal/insulator interfaces [3] in the SV films. (omitted)

• Journal of Pharmaceutical Investigation
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• v.23 no.1
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• pp.33-39
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• 1993

Polymerized vesicles were prepared from monomeric cholesterol-containing surfactant. These vesicles were used to extract the free cholesterol. To introduce spacer group into [cholesteryloxycarbonylmethyl] [2-(methacryloyloxy)ethyl]dimethylammonium chloride (CHODAMA), [5-[ (cholesteryloxy)carbonyl]pentyl] [2-(methacryloyloxy)ethyl]dimethylammonium bromide (CHODAMA-5) and [10-[(cholesteryloxy)carbonyl]decyl] [2-(methacryloyloxy)ethyl]dimethylammonium bromide (CHODAMA-10) were synthesized, In both case of polymerized vesicle with CHODAMA-5 and CHODAMA-10, the permeability was decreased and the amount of extracted cholesterol was also decreased, compared with the polymerized vesicle of CHODAMA.

• Korean Journal of Microbiology
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• v.24 no.1
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• pp.38-45
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• 1986

Effect of sodium deoxycholate and sodium dodecyl sulfate on Rhizopus oryzae were investigated. Morphological change was obtained by supplement of these surfactants into culture media during the sumerged culture. In accordance with morphological changes, composition of phospholipid was changed. In case of surfactant-free culture, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine were measured more than 95% of total phospholipid. But cardiolipin and phosphatidylinositol were conspicuously increased by treatment of both sufactants. Presence of phospolipase A, C, and D were detected from mycelium. Phospholipase A and D were activated by supplement of sodium deoxycholate and C was activated by sodium dodecyl sulfate. These results were interpreted in respect of polymorphism of phospholipid and membrane stability against solubilization effect of surfactants.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1054-1059
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• 1998

Fluorescence and dynamic light scattering measurements were applied to the study of formation and structure of aggregated colloidal particles in modified poly(ethylene-co-methylacrylate) ionomers in aqueous solution. Both 8-anillino-l-naphthalene-sulfonic acid (ANS) and pyrene were used as fluorescence probe to obtain the information on the structure of particle surface and inside, respectively. Three different ionomers used in this study started to aggregate at very dilute concentration, 3-8 x 10-6 g/mL. In this study, we demonstrate that the polyethylene ionomers can form stable nanoparticles. The hydrophobic core made of the polyethylene backbone chains is stabilized by the ionic groups on the particle surface. Such a formed stable nanoparticles have a relatively narrow size distribution with an average radius in the range of 27-48 nm, depending on the kind of ionic groups. Once the stable particles are formed, the particle size distributions were nearly constant. This study shows another way to prepare surfactant-free polyethylene nanoparticles.

• Journal of Pharmaceutical Investigation
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• v.41 no.1
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• pp.19-24
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• 2011

In order to enhance the clinical efficacy of 5-aminolevulinic acid-induced photodynamic therapy (ALA-PDT), liposomal formulations using bulk hydrogenated phospholipids from soybean were introduced. Three types of lipids, S75-3, S100-3, and SL80-3 were used for formulating ALA. The pH of all the liposomal ALA is 4.5~5.5 and the size is 50~200 nm. All the liposomal formulations gave better ex vivo ALA skin penetration using nude mice skin in Franz cell than free ALA did. Among them, SL80-3 including 22% of lyso-phosphocholine achieved excellent ALA penetration when compared with those of S75-3 and S100-3 which have only 1~2% of lyso-phospholipids. S100-3 showed a little better results than S75-3 did. Addition of humectants (glycerine, propylene glycol, butylene glycol, betaine) in liposomal ALA formulated with SL80-3 produced little enhancing effect in ALA penetration. On the other hand, addition of surfactants (Tween 20, 60, Brij 72, 76, 78) in same liposomal system produced significant increase in ALA penetration. Among them, transferosomal system of lyso-phospholipid, SL80-3 and the surfactant, Brij76 showed the highest ALA penetration. Furthermore, this system also established the highest in vivo PpIX biosynthesis in hairy mice skin of C57BL/6. These results concluded that the transferosome of SL80-3 and Brij76 produced the best results in both ALA penetration and PpIX biosynthesis, and proved good correlation between them.

• Journal of the Korean Applied Science and Technology
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• v.31 no.2
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• pp.238-243
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• 2014

The mechanical properties of NATM resin were measured by SEM, FT-IR spectra, tensile properties, mole ％ of [NCO/OH], and particle size analyzer on stainless steel. Growing concerns in the environment-friendly NATM resin, we have synthesized the solvent-free NATM resin to be coating on metals such as stainless. The properties of the synthesized NATM resin to be contained polyols, MDI, silicone surfactant, fillers and crosslink agents(diethyltoluene diamine, anhydrosorbitol), that they have highly stronger in intensity and longer durability than general NATM resin to be contained polyols, IPDI, silicone surfactant, fillers in general packing materials and coatings. The rigid segments of polyurethane in mechanical properties of coatings were due to cross linkage and the increase mole % of [NCO/OH]. In conclusion, the NATM microstructure with cross linkage can be good material for coating of anticorrosion of metal substrates such as stainless steel.