• Title/Summary/Keyword: dispersity

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Synthesis of Silica Nanoparticles Having the Controlled Size and their Application for the Preparation of Polymeric Composites (크기가 제어된 실리카 나노입자 합성과 제조된 입자의 고분자계 복합재 응용)

  • Kim, Jong-Woung;Kim, Chang-Keun
    • Polymer(Korea)
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    • v.30 no.1
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    • pp.75-79
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    • 2006
  • Silica nanoparticles for polymeric dental restorative composites were prepared by Stober method, and then the effects of surface treatment of silica particles with Lmethacrylofpropyltrimethofsilane $(\gamma-MPS)$ on the dispersity of the silica particles in the organic matrix was investigated. Particles having various average size were prepared by using controlled amounts of tetraethylorthosilicate(TEOS), water, and catalyst and by changing solvent used for reaction. The site of particles prepared by using methanol as solvent was smaller than that prepared by using ethanol as solvent. In addition, the size of particles was increased by decreasing amounts of water and by increasing amounts of TEOS and catalyst. Hydrophobic silica nanoparticles was prepared by reacting hydrophilic nanoparticles with $\gamma-MPS$ to improve interfacial properties with organic matrix. Amounts of $\gamma-MPS$ per unit mass of the particles was increased by decreasing particle size. even though the amount of $\gamma-MPS$ per specific surface area were nearly the same regardless of the particle size. The dispersity of the silica particles in the organic matrix was improved when the surface treated silica particles were used for preparing the polymeric dental restorative composites.

Tribological Behavior of Lubricating Oil-Based Nanofluids Containing Ag and Carbon Nanoparticles (Ag 및 탄소 나노윤활유의 제조 및 윤활특성 평가)

  • Choi, Cheol;Jung, Mi-Hee;Choi, Young-Min;Oh, Jae-Myung
    • Korean Journal of Materials Research
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    • v.18 no.11
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    • pp.610-616
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    • 2008
  • Oil-based nanofluids were prepared by dispersing Ag, graphite and carbon black nanoparticles in lubricating oil. Agglomerated nanoparticles were dispersed evenly with a high-speed bead mill and/or ultrasonic homogenizer, and the surfaces of the nanoparticles were modified simultaneously with several dispersants. Their tribological behaviors were evaluated with a pin-on-disk, disk-on-disk and four-ball EP and wear tester. It is obvious that the optimal combination of nanoparticles, surfactants and surface modification process is very important for the dispersity of nanofluids, and it eventually affects the tribological properties as a controlling factor. Results indicate that a relatively larger size and higher concentration of nanoparticles lead to better load-carrying capacity. In contrast, the use of a smaller size and lower concentration of particles is recommended for reducing the friction coefficient of lubricating oil. Moreover, nanofluids with mixed nanoparticles of Ag and graphite are more suitable for the improvement of load-carrying capacity and antiwear properties.

Physical Properties of Graphite Nanofiber Filled Nylon6 Composites

  • Park, Eun-Ha;Joo, Hyeok-Jong
    • Carbon letters
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    • v.7 no.2
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    • pp.87-96
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    • 2006
  • This paper describes the physical properties of filled Nylon6 composites resin with nano-sized carbon black particle and graphite nanofibers prepared by melt extrusion method. In improving adhesions between resin and fillers, the surface of the carbon filler materials were chemically modified by thermo-oxidative treatments and followed by treatments of silane coupling agent. Crystallization temperature and rate of crystallization increased with increases in filler concentration which would act as nuclei for crystallization. The silane treatments on the filler materials showed effect of reduction in crystallization temperature, possibly from enhancement in wetting property of the surface of the filler materials. Percolation transition phenomenon at which the volume resistivity was sharply decreased was observed above 9 wt% of carbon black and above 6 wt% of graphite nanofiber. The graphite nanofibers contributed to more effectively in an increase in electrical conductivity than carbon black did, on the other hand, the silane coupling agent negatively affected to the electrical conductivity due to the insulating property of the silane. Positive temperature coefficient (PTC) phenomenon, was observed as usual in other composites, that is, temperature increase results conductivity increase. The dispersity of the fillers were excellently approached by melt extrusion of co-rotational twin screw type and it could be illustrated by X-ray diffraction and SEM.

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Preparation of Polymer/Drug Nano- and Micro-Particles by Electrospraying

  • Lee, Jong-Hwi;Park, Chul-Ho;Kim, Min-Young;Yoo, Ji-Youn;Kim, Ki-Hyun;Lee, Jong-Chan
    • Proceedings of the Polymer Society of Korea Conference
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    • 2006.10a
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    • pp.217-217
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    • 2006
  • The surface energy control capability of electrohydrodynamic force provides electrospraying with various potential advantages such as simple particle size control, mono-dispersity, high recovery, and mild processing conditions. Herein, the one step nano-encapsulation of protein drugs using electrospraying was developed. The major processing parameters such as the conductivity of spraying liquids, flow rate, the distance between electric potentials, etc were examined to obtain the maximum efficiency. The recovery of particles was found relatively high as could be conjectured based on the principle of electrospraying. When organic solvents were employed, the processing windows of electrospraying were relatively narrow than water systems. Efficient nano-encapsulation of BSA with polymers was conveniently achieved using electrospraying at above 12 kV.

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Sulfonation of Polyamide Containing Carboxylic Acid (Carboxylic acid를 함유한 sulfonated polynmide의 제조)

  • Jeon, Jong-Young;Lee, Gi-Jo
    • Journal of Sericultural and Entomological Science
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    • v.48 no.1
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    • pp.1-5
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    • 2006
  • Polyamide containing carboxylic acid was sulfonated with chlorosulfonic acid in dichloroethane under various conditions. The impact of the sulfonating agent concentration, the reaction temperature, and the reaction time on the ion exchange capacity was investigated. The mechanical and thermal properties, the contact angle, and the change of poly-dispersity were calculated for studying change of their properties. The reactions were effective, when the temperature was below $10^{\circ}C$ and the concentration of chlorosulfonic acid was below 0.05 mol. The value of ion exchange capacity was increased with reaction time. Thermal and mechanical properties were nearly unchanged according to the degree of sulfonation, but the contact angle was increased with increasing the value of ion exchange capacity.

Folate-Targeted Nanostructured Lipid Carriers (NLCs) Enhance (Letrozol) Efficacy in MCF-7 Breast Cancer Cells

  • Sabzichi, Mehdi;Mohammadian, Jamal;Khosroushahi, Ahmad Yari;Bazzaz, Roya;Hamishehkar, Hamed
    • Asian Pacific Journal of Cancer Prevention
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    • v.17 no.12
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    • pp.5185-5188
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    • 2016
  • Objective: Targeted-drug-delivery based lipid nanoparticles has emerged as a new and effective approach in cancer chemotherapy. Here, we investigated the ability of folate-modified nanostructured lipid carriers (NLCs) to enhance letrozol (LTZ) efficacy in MCF-7 breast cancer cells. Methods: New formulations were evaluated regarding to particle size and scanning electron microscope (SEM) features. Anti-proliferative effects of LTZ loaded nanoparticles were examined by MTT assay. To understand molecular mechanisms of apoptosis and cell cycle progression, flow cytometric assays were applied. Results: Optimum size of nanoparticles was obtained in mean average of $98{\pm}7nm$ with a poly dispersity index (PDI) of 0.165. The IC50 value was achieved for LTZ was $2.2{\pm}0.2{\mu}M$. Folate-NLC-LTZ increased the percentage of apoptotic cells from 24.6% to 42.2% compared LTZ alone (p<0.05). Furthermore, LTZ loaded folate targeted NLCs caused marked accumulation of cells in the subG1 phase. Conclusion: Taken together, our results concluded that folate targeted LTZ can be considered as potential delivery system which may overcome limitations of clinical application of LTZ and improve drug efficacy in tumor tissue.

Effects of Intermeshing Rotor for Dispersion of Silica Agglomerates in SBR/BR Compound (Intermeshing Rotor의 구조가 SBR/BR 합성고무 복합소재의 실리카 분산에 미치는 영향의 비교)

  • Kim, Sung-Min;Kim, Kwang-Jea
    • Polymer(Korea)
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    • v.36 no.5
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    • pp.637-642
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    • 2012
  • The effects of mixing geometry (intermeshing vs. tangential rotor) for the dispersion and distribution of silica agglomerates in SBR/BR compound were investigated. Silica dispersion and distribution were found to be better with the intermeshing rotor compared to the tangential rotor. It was concluded that the intermeshing rotor compared to the tangential rotor delivered a higher shear stress due to interlocked rotor geometry to silica agglomerates leading to better dispersity and distribution of silica in the agglomerates.

Influence of Amorphous Polymer Nanoparticles on the Crystallization Behavior of Poly(vinyl alcohol) Nanocomposites

  • Lee, Kyung-Jin;Lee, Ji-Hye;Hong, Jin-Yong;Jang, Jyong-Sik
    • Macromolecular Research
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    • v.17 no.7
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    • pp.476-482
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    • 2009
  • The crystallization behavior of poly(vinyl alcohol) (PVA) in the presence and absence of polypyrrole nanoparticles (PPy NPs) was investigated in terms of the heterogeneous nucleation effect of PPy NPs using FTIR, X-ray diffraction, differential scanning calorimeter and polarized optical microscope analysis. PPy NPs were prepared by dispersion polymerization method stabilized by PVA in aqueous solution. A polymer nanocomposite with uniform dispersity could be readily obtained due to the enhanced compatibility between the filler and matrix. Compared with the PPy NP-absent PVA, the PPy NP/PVA nanocomposite exhibited an enhanced degree of crystallinity. The degree of crystallinity increased up to 17% at the PPy NP concentration of 1 wt%, compared to the pristine PVA. The PPy NP acted as an effective nucleating agent during the crystallization process, thereby enhancing the degree and rate of crystallization. The kinetics study of the crystallization also revealed the decreased value of the Avrami coefficient in the case of the PPy NP/PVA nanocomposite.

Effects of Preparation Conditions on Thermal and Electrical Properties of Oil-based Nanofluids for Transformer Application (변압기 냉각용 오일 기지 나노유체의 제조조건이 열 및 전기적 특성에 미치는 영향)

  • Choi, Cheol;Yoo, Hyun-Sung;Oh, Jae-Myung
    • Korean Journal of Materials Research
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    • v.17 no.9
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    • pp.493-499
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    • 2007
  • Oil-based nanofluids were prepared by dispersing nonconducting fibrous $Al_2O_3$ and spherical AlN nanoparticles in transformer oil. In this study, the effects of wet grinding and surface modification of particles on thermal and electrical properties of nanofluids were investigated. Grinding experiments were conducted with high-speed bead mill and ultrasonic homogenizer and nanoparticles were surface modified by oleic acid and polyoxyethylene alkyl acid ester(PAAE) in n-hexane or transformer oil, at the same time. It is obvious that the combination of nanoparticle, dispersant and dispersion solvent is very important for the dispersity of nanofluids. For nanofluids containing 1.0vol.% AlN particles in transformer oil, the enhancement of thermal conductivity was 11.6% compared with pure transformer oil. However, the electric-insulating property of AlN nanofluids was very low due to used dispersant itself. Therefore, the effect of the dispersant on thermal/electrical/physical properties of the transformer oil should be considered before selecting a proper dispersant.

Effect of PVP on the Dispersity of Pt Nanoparticles and Catalytic Activity in Synthesis of Pt/C Catalysts for Fuel Cell (연료전지용 Pt/C 촉매 합성에 있어서 PVP가 Pt 나노입자의 분산 및 촉매 활성에 미치는 영향)

  • Leem, Young-Min;Park, Nam-Hee;Yu, Yeon-Tae
    • Korean Journal of Materials Research
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    • v.18 no.8
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    • pp.401-405
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    • 2008
  • Pt-loaded carbon black for the catalyst of a PEM fuel cell was synthesized with different molar ratios of polyvinylpyrrolidone and $H_2PtCl_6$ solution to improve the dispersion of Pt nanoparticles on carbon black and decrease the size of Pt nanoparticles. From transmission electron microscopy results, Pt nanoparticles of a size of approximately 2 nm were highly dispersed when the polyvinylpyrrolidone concentration was 10mM. The electrochemical activity of the synthesized Pt/C catalysts was investigated by cyclic voltammetry, showing that the as-synthesized Pt-loaded carbon black catalyst had the best activity at a polyvinylpyrrolidone concentration of 10 mM.