• 펄프종이기술
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• 제40권3호
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• pp.15-22
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• 2008

Properties of pulp fibers can be modified by LbL multilayering technology. We evaluated the effect of stock composition on the polyelectrolyte multilayering performance of pulp fibers in this study. Stock composition was varied with pulp type and fines content. Three types of pulp-Hw-BKP, BCTMP and KOCC-were treated with polyelectrolytes of poly-DADMAC and PSS. Fines content of stock were controlled at 0, 10, 20, 30, and 40%. Zeta potential of pulp fibers and charge demand of filtrate were evaluated. The highest adsorption ratio was obtained for BCTMP because of its shortest fiber length and highest specific surface area. Higher fines content in the stock increased the adsorption ratio of polyelectrolyte onto pulp fiber and it required a higher amount of polyelectrolyte for charge neutralization. For the pulp stock with higher fines content, a higher level of polyelectrolyte and the increased layer number were required to modify and stabilize the electrochemical properties of pulp fibers.

• 펄프종이기술
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• 제46권6호
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• pp.78-86
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• 2014

Since cellulose nanofibrils (CNF) has large specific surface area and high water holding capacity, it is very difficult task to remove water from the CNF suspension. However, dewatering of CNF suspension is a prerequisite of following processes such as mat forming and drying for the application of CNF. In this study, we evaluated the drainage of cellulose fibers suspension under vacuum and pressure conditions depending on the number of grinding passes. Also, the effect of the addition of cationic polyelectrolyte on dewatering ability of CNF suspension was investigated. Regardless of dewatering condition, the total drained water amount as well as the drainage rate were decreased with an increase in the number of grinding passes. Pressure dewatering equipment enables us to prepare wet CNF mat with relatively higher grammage. The cationic polyelectrolytes improved the dewatering ability of CNF suspension by controlling the zeta potential of CNF. The fast drainage was obtained when CNF suspension had around neutral zeta potential.

• 한국염색가공학회지
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• 제21권4호
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• pp.33-38
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• 2009

Poly(vinyl acetate) films containing benzophenone were photocrosslinked by continuous UV irradiation.UV irradiation of PVAc film containing 5% benzophenone induced bulk crosslinking of the polymer indicated by 84.1% of gel fraction after ethyl acetate extraction. The crosslinking was attributed to the recombination of tertiary polymer radicals generated upon UV irradiation, which was enhanced by the hydrogen abstraction of benzophenone. Also the UV irradiation resulted in scission of ester linkage and photooxidation of PVAc surface, which was verified by ATR and zeta potential analysis, implying that the PVAc surface became more polar and hydrophilic. The zeta potential proportionally increased from +4.5mV to -26.8 mV with increasing UV irradiation. Also the surface energy of the PVAc film increased with higher UV irradiation upto 56.5 $mJ/m^2$ by the enhanced Lewis acid/base component with larger contribution of Lewis acid parameter. Accordingly the crosslinked PVAc showed higher thermal stability with increasing UV energy.

• Macromolecular Research
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• 제17권7호
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• pp.483-490
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• 2009

Stable poly(styrene-co-divinylbenzene) [P(St-co-DVB)] micro spheres with narrow size distribution were synthesized in the presence of 2,2'-azobis(2,4-dimethyl valeronitrile) (V-65) and co-initiator in an acetone/water mixture in the precipitation polymerization at $53^{\circ}C$ for 24 h. Potassium peroxodisulfate (KPS), ammonium peroxodisulfate (APS) and sodium peroxodisulfate (NaPS) were used as co-initiators. The optimum ratio of acetone to water for the formation of a narrow distribution of P(St-co-DVB) particles was 49:11 (g/g). The optimum co-initiator compositions for narrow distribution were 9:1 (g/g) for V-65 to KPS, 11:1 for V-65 to APS and 6:1 for V-65 to NaPS. The yield for these compositions was $54{\sim}57%$ and the largest particle size was obtained with the lowest zeta-potential and CV values. From the XPS measurements, the charge density was increased but the zeta potential decreased with increasing sulfur content, implying that the sulfate group provides the electrostatic stabilization on the particle surface. This suggested that the self-crosslinking between styrene and DVB, the electrostatic stabilization of initiators, and the balanced hydrophobic and hydrophilic properties of the solvents are responsible for the formation of stable P(St-co-DVB) spherical particles with narrow size distribution.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.470-470
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• 2011

반도체 집적회로의 고집적화 및 고성능화를 위한 기본 소자(MOSFET)의 미세화 및 단위공정의 물리적 한계를 극복하기 위한 다양한 연구가 진행되고 있다. 그 중 다양한 나노입자를 이용한 나노소자 제작 연구가 활발하게 이루어지고 있다. 하지만 이러한 나노입자를 이용한 나노소자의 제작에 있어서 원하는 위치의 나노입자의 배열과 정렬의 어려움을 겪고 있다. 이를 위해서 본 연구에서는 자기조립특성을 가지는 DNA 분자와 CdSe/ZnS 나노입자들의 표면 기능화를 통해서 상호 결합시키는 실험을 하였다. DNA 분자를 형틀로 이용하여 CdSe/ZnS 나노입자를 선택적 배열하고 전자 소자화하기 위해서는 CdSe/ZnS 나노입자의 표면 기능화가 필수적이다. 이를 위하여 무극성인 CdSe/ZnS 나노입자들과 DNA 분자의 phosphate backbone의 음전하와의 경합 특성을 향상시키기 위하여 이들 나노입자의 표면을 양전하로 치환하는 실험을 수행하였다. Core 나노입자인 CdSe 나노입자를 제작한 다음에 CdSe 보다 높은 band gap을 가지고 lattice mismatch가 적은 ZnS 로 shell 층을 형성하는 2-step 방법을 이용하여 합성한 CdSe/ZnS 나노입자를 무극성 용매인 chloroform 용액 0.5 ml에 분산시키고 DMAET 0.3 ml 와 Methanol 0.1 mg/ml를 이용하여 리간드들을 바꿔주고 과잉된 리간드인 DMAET를 제거하기 위해 Methanol로 3차례 세척한 다음 증류수에 용해시키는 실험을 하였다. 나노입자 기능화 과정 이후 기능화 여부를 판단하기 위하여 FT-IR spectroscopy 와 zeta potential 측정을 통하여 나노입자 표면의 변화와 전위를 측정하였다.

• Elastomers and Composites
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• 제44권2호
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• pp.143-149
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• 2009

본 연구에서는 아스팔트가 가지는 단점을 보완하고자 아스팔트를 비이온 계면활성제(Span 80, Span 60, Tween 80, 및 Tween 60), 음이온 계면활성제(SLS), 및 양이온 계면활성제(Imidazole)를 변량 배합하여 반전유화법으로 아스팔트 에멀젼을 제조하였다. 유화아스팔트의 안정성을 규명하고자 입자크기, 점도, 제타전위, 및 내수성을 고찰하였다. 비이온 계면활성제와 음이온 계면활성제를 혼합 사용할 경우 유화아스팔트의 안정성은 우수하였으며 계면활성제의 양이 증가함에 따라 입자크기는 감소하였고, 반면에 점도와 제타전위 및 내수성은 증가하였다.

• 한국분말재료학회지
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• 제25권5호
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• pp.395-401
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• 2018

The improvement of dispersion stability for the primary polishing slurry in a CMP process is achieved to prevent defects produced by agglomeration of the slurry. The dispersion properties are analyzed according to the physical characteristics of each silica sol sample. Further, the difference in the dispersion stability is confirmed as the surfactant content. The dispersibility results measured by Zeta potential suggest that the dispersion properties depend on the content and size of the abrasive in the primary polishing slurry. Moreover, the optimum ratio for high dispersion stability is confirmed as the addition content of the surfactant. Based on the aforementioned results, the long-term stability of each slurry is analyzed. Turbiscan analysis demonstrates that the agglomeration occurs depending on the increasing amount of surfactant. As a result, we demonstrate that the increased particle size and the decreased content of silica improve the dispersion stability and long-term stability.

• Journal of Pharmaceutical Investigation
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• 제41권3호
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• pp.185-190
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• 2011

The purpose of this study was to evaluate the phagocytic uptake of surface modified PLGA microspheres containing ovalbumin (OVA) into dendritic cell. In order to find the most suitable formulation for targeted delivery to antigen presenting cells (APC), OVA was encapsulated by a double emulsion solvent evaporation method with three PLGA microspheres (PLGA 50:50, PLGA 75:25 and PLGA 85:15) and two surface modified microspheres by chitosan and sodium dodecyl sulfate (SDS). Physicochemical properties were evaluated in terms of size, zeta potential, encapsulation efficiency, different scanning calorimeter (DSC), x-ray diffraction, morphology, and OVA release test from microspheres. Phagocytic activity was estimated using dendritic cells and analyzed by fluorescence activated cell sorter (FACS). The result showed that zeta potential of PLGA particles was changed to positive by the chitosan modification. The release profile of chitosan modified PLGA microspheres exhibited sustained release after initial burst. The chitosan modified microspheres had higher phagocytic uptake than the other microspheres. Such physicochemical properties and phagocytic uptake studies lead us to conclude that chitosan modified microspheres is more suitable formulation for the targeted delivery of antigens to APC compared with the other microspheres.

• Journal of Microbiology and Biotechnology
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• 제22권5호
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• pp.614-621
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• 2012

Silver nanoparticles production by the green chemistry approach was investigated using an isolated marine actinomycetes strain. The isolated strain was identified as Streptomyces albidoflavus based on chemotaxonomic and ribotyping properties. The strain revealed production of silver nanoparticles both extracellular and intracellularly. Surface Plasmon Resonance analysis with the function of time revealed that particle synthesis by this strain is reaction time dependent. The produced particles were spherical shaped and monodispersive in nature and showed a single surface plasmon resonance peak at 410 nm. Size distribution histograms indicated production of 10-40-nm-size nanoparticles with a mean size of 14.5 nm. FT-IR spectra of nanopartilces showed N-H, C-H, and C-N stretching vibrations, denoting the presence of amino acid/peptide compounds on the surface of silver nanoparticles produced by S. albidoflavus. Synthesized nanoparticles revealed a mean negative zeta potential and electrophoretic mobility of -8.5 mV and -0.000066 $cm^2/Vs$, respectively. The nanoparticles produced were proteinaceous compounds as capping agents with -8.5 mV zeta potential and revealed antimicrobial activity against both Gram-negative and -positive bacterial strains. Owing to their small size, these particles have greater impact on industrial application spectra.

• 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.