• The Korean Journal of Pesticide Science
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• v.12 no.2
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• pp.127-133
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• 2008

The foliar uptake of dimethomorph into cucumber was assessed by spray application of aqueous dimethomorph solution containing fatty alcohol ethoxylate (FAE) or fatty acid alkyl ester as activator adjuvants. Afterward, the possible mechanism of action of FAE on foliar penetration of active ingredient was suggested by speculating on the effect of lipophile and hydrophile of FAEs. The amount of absorbed dimethomorph induced by polyoxyethylene mono-9-octadecenyl ether (6 moles ethylene oxide, $C_{18=9}E_6$) was linearly related to the concentrations of surfactant as well as dimethomorph in spray solution, suggesting that it is simply a diffusion phenomenon of the solute molecule through a cuticular membrane from leaf surface. Octadecanol attached to FAE was most effective lipophile on the leaf penetration of dimethomorph. And, the more ethylene oxide had the polyoxyethylene chain of FAE up to 20 moles, the higher the uptake rate was. Therefore, the role of lipophile of FAE on dimethomorph penetration to cucumber leaf, probably, is to modify the physico-chemical properties of cuticular membrane to be permeable to dimethomorph, and the polyoxyethylene chain having less than 20 moles ethylene oxide, which is moderately permeable to cuticular membrane by its molar volume, is to let the physically-modified cuticular membrane to be maintained for a longtime.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.352-355
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• 2003

비자성이며 비전도성의 물리적 성질을 갖는 자연산 퀄쯔(quartz)와 용암석 스코리아를 대상으로 마그네타이징 처리를 하여 분석하였다. 마그네타이징 처리를 위하여 강력한 기계화학적 분쇄 반응을 시켰으며, 분쇄 반응시 알코올계의 솔벤트를 반응 용매로 사용하였다. 퀄쯔와 스코리아의 마그네타이징 처리에서 비교적 비중이 큰 퀄쯔의 경우와 비중이 작은 스코리아의 경우에도 분쇄된 분말이 물에 뜨는 것을 확인할 수 있으며, 친유성으로 기름에 대한 흡착 성질이 우수함을 확인하였다. 자연산 퀄쯔와 함께 스코리아를 바탕물질로 하여 기계-화학적 반응 기술로 고 분산성 흡착반응에 의한 고분자 물잘 생성을 유도하여 나노복합체를 제조하였다. 반응의 처리조건과 적용과정에 따라서 기계-화학적 반응을 통하여 얻어진 물질은 자기적 성질과 유전체 및 전기적 성질을 동시에 나타낸다. 부착성 융합 복합물질의 특징을 고려하여 시그니토마그네틱스(Segneto-magnetics)로 분류되는 합성분말은 특히 유류성분에 대하여 높은 흡착성을 가지며, 강한 자기적 성질을 띄는 10-50 nm 두께의 하나 또는 그 이상의 이질적 융합 화합물 층이 석영이나 수정체의 표면에 합성되어 특유의 자기, 전기적 성질을 나타낸다.

• Polymer(Korea)
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• v.29 no.5
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• pp.451-456
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• 2005

In the field of designing of nano-fillers of polyimide nanocomposites, the two strategic points are the heat-resistance and compatibility with polyimide, a matrix polymer. In this study, we designed oligo(amic acid) having alkyl side chains and terminal amine groups to satisfy previous requirements and studied the modification of surface of layered silicates. Oligo(amic acid)s were prepared by the reaction of diamine monomers and PMDA and their molecular weight was controlled in about 2000g/mol. After that, acidification and ion exchange reaction led to the high-temperature organophilic layered silicate (OLS). XRD pauerns of OLS showed the more increased gallery spacing by $4{\AA}$ than that of the pristine layered silicate and the initial decomposition temperatures of OLS were in above $280^{\circ}C$. The polyimide nanocomposite films based on heat resistant OLS showed that the OLSs were well dispersed through the matrix and their CTEs showed a decrease of $26\%$ compared with pristine polyimide films.

• Polymer(Korea)
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• v.25 no.2
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• pp.263-269
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• 2001

MAPTAC-MMT was prepared by exchanging the mineral cation (sodium montmorillonite) with 3-(methacryloyl amino) propyltrimethyl ammonium chloride, thus rendering the mineral organophilic and forming polymerizable moieties directly bonded to the surface of montmorillonite (MMT). Thermoresponsive nanocomposites (PNIPAM-MMT) were synthesized by polymerization of N-isopropyl acrylamide in an aqueous suspension of MAPTAC-MMT at room temperature. Thermoresponsive nanocomposites exhibited a low critical solution temperature (LCST) similar to unmodified poly(N-isopropyl acrylamide) (PNIPAM). The LCST of thermoresponsive nanocomposites decreased in proportion to the amount of MAPTAC-MMT. TGA results showed that the thermal stability of thermoresponsive nanocomposites was improved compared to PNIPAM itself the thermoresponsive polymer.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.218-218
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• 2003

21세기 정보기반사회에서는 정보처리량의 증가로 인한 대용량 정보 교환을 위하여 신호처리의 고속화/광대역화가 요구되어진다. 완전 광통신망의 구축에 의한 대용량의 광통신을 위해서는 고속이며, 집적화가 가능한 저가의 광전자 소자 개발이 필요하다. 광전자 소자 중 전기-광학 변조 효과를 이용한 광소자의 구현을 위한 소재로서 극성 배향된 비선형 광학 유기고분자 소재는 가공성이 뛰어나 원하는 형태의 광도파로로 제조할 수 있다는 장점에 많은 연구가 진행되고 있다. 그러나 아직 전기광학계수의 향상과 더불어 유기고분자가 가지고 있는 열 및 광화학적 안정성이 낮은 기본적인 문제점과 폴링(poling)에 의해 배향된 극성이 시간에 따라 완화되는 문제의 해결이 요구되고 있다. 이러한 문제점 해결을 위한 기초 연구로 유기물을 졸-겔 매트릭스에 나노 사이즈로 분산하는 방법으로 유기물의 내화학적 안정성을 향상하고자 시도하였다. 잘 알려져 있는 바와 같이 유/무기 하이브리드 졸-겔 재료는 광 투광성이 우수하고 저온에서의 재료 합성과 저가 공정이 가능하여 광기능성 유기물의 호스트(host) 재료로 많이 연구되고 있다. 본 연구에서는 MTMS(methyltrimethoxysilane)과 TEOS (tetra-ethoxyorthosilicate)를 0-100 mol%로 혼합하고 가수분해하는 방법으로 친수성/친유성 특성을 제어하여, 분산되는 유기물의 사이즈를 조정하였다. 각 실험 조건에 따른 유기물 분산체의 크기를 SEM 및 TEM으로 관찰하였으며, 나노 사이즈로 분산된 유/무기 졸-겔 코팅막의 광학적 특성을 프리즘 커플러를 이용하여 조사하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.46-46
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• 2008

스텔스 기능을 가진 군사용 항공기는 레이다 망의 추적을 피하기 위해 일반 냉각수 대신에 절연유를 냉각매체로 사용한다. 그러나 절연유는 물에 비하여 열전달특성이 매우 낮기 때문에 항공기 전기전자 기기/부품 발열부를 효과적으로 냉각시키지 못하는 한계성을 가지고 있다. 따라서 본 연구에서는 나노유체(Nanofluid) 개념을 이용하여 절연유에 알루미나 및 질화알루미늄 나노분말을 미랑 분산시킨 나노절연유를 제조하고 이것의 열전달특성을 순수 절연유의 그것과 비교 평가함으로써, 냉각특성이 크게 개선된 새로운 냉매로서의 적용 가능성을 확인하고자 하였다. 다만 나노절연유를 제조함에 있어서 가장 큰 장애물은 오일에 대한 분산성 확보에 있기 때문에, 비드밀 및 초음파를 이용한 나노분말 응집체의 습식분산 및 분산제를 이용한 친유성 표면개질을 동시에 수행함으로써 장시간 안정된 분산성을 확보하도록 노력하였다. 나노유체의 열전도도 및 대류열전달계수는 비정상열선법을 이용하여 측정하였으며, 유체 속의 분말 분산 상태는 원심력을 이용한 분산안정성 평가장치 및 cryo FE-SEM을 이용하여 확인하였다. 또한 분말 형상이 대류열전달에 미치는 영향을 조사하기 위하여 알루미나 나노분말은 구상과 침상의 분말을 모두 사용하였고, 질화알루미늄 외에 다이아몬드 나노절연유도 함께 제조, 평가함으로써 냉각 및 절연특성, 그리고 물리화학적 안정성이 우수하고 실적용 가능성이 가장 높은 재료를 도출하고자 하였다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.36 no.1
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• pp.1-16
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• 2010

The preparation and properties of emulsions stabilized by the adsorption of solid particles at the oil-water interface are reviewed. Comparison is made with the behaviour of surfactant-stabilized emulsions. Many of the properties of Pickering emulsions are attributed to the large free energy of adsorption for particles. The main differences is due to the irreversible adsorption of particles to the interface. Phase inversion from w/o (water-in-oil) to o/w (oil-in-water) can be brought by increasing the volume fraction of water. Hydrophilic particles tend to form o/w emulsion whereas hydrophobic particles form w/o emulsion. The contact angle at the oil-water interface is main parameter to decide the emulsion type. The aspects of stability of Pickering emulsions are in contrast to general emulsions in some points. The possibility using Pickering emulsions for cosmetics is also proposed.

• Polymer(Korea)
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• v.29 no.2
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• pp.177-182
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• 2005

Montmorillonite (MMT) modified with siloxane diamine was reacted with a reactant obtained from 4,4'-diphenyl methane diisocyanate (MDI) and polyester type polyol, $Nippollan4010(\bar{M}_n2000)$. Finally, polyurethane (PU)/MMT composites were prepared by using 1,4-butane diol as a chain extender in $25\;wt\%$ solution of N,N-dimethyl acetamide (DMAc). It was expected that these nanocomposites had superior exfoliation property to that of MMT dispersed polyurethanes produced by simple mixing due to insertion of siloxane main chain to the silicate interlayer of MMT. Extent of reaction and formation of final products were analysed by using FT-IR spectroscopy. Dispersion into the PU and intercalation of MMT were identified by applying X-ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile data were acquired by universal test machine (UTM). Thermal stability and variation of surface energy were characterized by thermal gravimetric analysis (TGA) method and measurement of contact angle on the synthesized composites, respectively. As the results the organo-MMT modified with siloxane diamine in the PU composites has an intercalated structure relatively well-expanded rather than a completely exfoliated structure. The tensile strengths and the moduli for the PU/organo-MMT composites were drastically enhanced in comparison to those of $PU/Na^+-MMT$ composites.

• Polymer(Korea)
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• v.30 no.1
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• pp.56-63
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• 2006

We have synthesized two types of diamine monomers containing various chain length to prepare polyimides with layered structure. By using these diamines, homo-polyimides and co-polyimides having hydrophobic and hydrophilic segment of flexible side chain were synthesized. The segregated layered structures were formed by repulsive force with main chain as the side chains reach a critical length because the rigid main chains are packed into layered structure with the flexible side chains occupying the space between layers. As a result, the gallery space of each homo-polyimide was increased at spacing of $32.7\~48{\AA}\;or\;7\~10.5{\AA}$ as the increased hydrophobic or hydrophilic side chain length through X-ray diffraction. The gallery space of co-polyimides was also showed similar phenomenon by repulsive force of side chains with different properties. We have also confirmed that gallery space and molar volume were significantly depended on length of flexible side chain via molecular modeling.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.528-535
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• 2016

Two types of oleophilic acrylic prepolymers were prepared by the solution copolymerization of either ethyl acrylate (EA) or lauryl acrylate (LA) with hydroxy ethyl acrylate (HEA). For the formation of oil-absorbent materials, a mixed solution of the prepolymer and hexamethylene diisocyanate (HDI) as a cross-linker in toluene was applied to polypropylene knit velvet fabric through the conventional pad-dry-cure procedure. The gel fraction of the crosslinked resin, EA-HEA-HDI, increased with increasing feed ratio of HEA to total acrylate or HDI concentration. The oil absorbancy and retention ratio of the prepared materials were compared according to the add-on ratio of resin to fabric, and were assessed with n-decane, toluene, soybean oil, lubricant and bunker C oil as test oils. The optimal oil absorbancy of the materials were observed at around 6% of the add-on ratio for all these oils except for soybean oil. On the other hand, the oil retention ratio increased as the add-on ratio increased. Futhermore, heavier and more viscous oil generally showed higher oil retention ratios. In addition, the oil absorbancy of the materials treated with LA-HEA-HDI resin was higher than that treated with EA-HEA-HDI resin, which showed that the acrylic resins are more absorptive with increasing length of their side alkyl chain.