• Macromolecular Research
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• 제17권10호
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• pp.797-806
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• 2009

The mechanical and thermal behaviors of polyamide-6/clay nanocomposites were studied using the continuum-based, micromechanical models such as Mori-Tanaka, Halpin-Tsai and shear lag. Mechanic-based model prediction provides a better understanding regarding the dependence of the nanocomposites' reinforcement efficiency on conventional filler structural parameters such as filler aspect ratio ($\alpha$), filler orientation (S), filler weight fraction (${\Psi}_f$), and filler/matrix stiffness ratio ($E_f/E_m$). For an intercalated and exfoliated nanocomposite, an effective, filler-based, micromechanical model that includes effective filler structural parameters, the number of platelets per stack (n) and the silicate inter-layer spacing ($d_{001}$), is proposed to describe the mesoscopic intercalated filler and the nanoscopic exfoliated filler. The proposed model nicely captures the experimental modulus behaviors for both intercalated and exfoliated nanocomposites. In addition, the model prediction of the heat distortion temperature is examined for nanocomposites with different filler aspect ratio. The predicted heat distortion temperature appears to be reasonable compared to the heat distortion temperature obtained by experimental tests. Based on both the experimental results and model prediction, the reinforcement efficiency and heat resistance of the polyamide-6/clay nanocomposites definitely depend on both conventional (${\alpha},\;S,\;{\Psi}_f,\;E_f/E_m$) and effective (n, $d_{001}$) filler structural parameters.

• Advances in nano research
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• 제2권2호
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• pp.121-133
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• 2014

Polymer nanocomposites are advanced nanomaterials which exhibit dramatic improvements in various mechanical, thermal and barrier properties as compared with the neat polymer. Polystyrene/ alumina nanocomposites were prepared by an ultrasound-assisted solution casting method at filler loadings ranging from 0.2 to 2% and also at different ultrasonic frequencies, viz. 58 kHz, 192/58 kHz, 430 kHz, 470 kHz and 1 MHz. The composites were subjected to mechanical property tests (tensile and impact tests) and cavitation erosion tests to study the enhancement in functional properties. Filler dispersion in the polymer matrix was observed by SEM analysis. The effect of frequency on filler dispersion in the matrix was studied by SEM analysis and functional property enhancement of the composite material. The composites prepared at dual (high/ low) frequency (192/58 kHz) were found to show better property enhancement at low filler loadings as compared with neat polymer and also with composites prepared without ultrasound, thus reinforcing the finding that ultrasound-assisted synthesis is a promising method for the synthesis of nanocomposites.

• 전기학회논문지
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• 제57권9호
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• pp.1572-1578
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• 2008

The effect of the organoclay_10A nanoparticles on the DSC and Structural and Dielectrics Properties(1Hz-1MHz) for epoxy/Organoclay_10A Nanocomposites has been studied. Dielectric properties of epoxy-Organoclay nanocomposites were investigated at 1, 3, 5, 7, 9 filler concentration by weight. Epoxy nanocomposites samples were prepared with good dispersion of layered silicate using power ultrasonic method in the particles. As structural analysis, the interlayer spacing have decreased with filled nanoparticles contents increase using power ultrasonic dispersion. The maximum increase interlayered spacing was observed to decease for above 5wt% clay loading. The other hand, as decrease with concentration filler of the layered silicate were increased dispersion degree of nanoparticles in the matrix. The interesting dielectric properties for epoxy based nanocomposites systems are attributed to the large volume fraction of interfacesin the bulk of the material and the ensuring interactions between the charged nanoparticle surface and the epoxy chains.

• Macromolecular Research
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• 제12권1호
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• pp.85-93
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• 2004

We have prepared poly(ethylene terephthalate) (PET) nanocomposites filled with two different types of fumed silicas, hydrophilic (FS) and hydrophobic (MFS) silicas of 7-nm diameter, by in situ polymerization. We then investigated the morphological changes, rheological properties, crystallization behavior, and mechanical properties of the PET nanocomposites. Transmission electron microscopy (TEM) images indicate that the dispersibility of the fumed silica was improved effectively by in situ polymerization; in particular, MFS had better dispersibility than FS on the non-polar PET polymer. The crystallization behavior of the nanocomposites revealed a peculiar tendency: all the fillers acted as retarding agents for the crystallization of the PET nanocomposites. The incorporation of fumed silicas increased the intrinsic viscosities (IV) of the PET matrix, and the strong particleparticle interactions of the filler led to an increased melt viscosity. Additionally, the mechanical properties, toughness, and modules of the nano-composites all increased, even at low filler content.

• Composites Research
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• 제31권5호
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• pp.282-287
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• 2018

본 연구는 광물화된 탄소나노튜브를 고분자 기지재료의 강화재로 사용할 때, 계면 결합력이 기존 탄소나노튜브 강화재에 비해 어떤 차이를 보이는지 분자동역학 시뮬레이션을 통해 탐구한다. 최근 탄소나노튜브에 질소를 도핑한 후 표면을 광물화 하는 실험 연구가 보고되고 있다. 하지만 복합재료의 강화제로 첨가되었을 때 보일 수 있는 물성 증가 현상에 대한 연구는 아직 부족하다. 광물질로는 실리카($SiO_2$)를 사용했고 고분자 기지재료로는 열 가소성 수지인 poly(methyl metacrylate) (PMMA)를 사용했다. 계면 결합력과 계면 전단 응력을 계산하기 위해 강화재를 기지재료로부터 빼내는 pull-out 시뮬레이션이 진행되었다. 계산 결과, 실리카 광물화된 탄소나노튜브가 고분자 기지재료와 향상된 계면 상호작용을 가지는 것으로 조사되었다. 본 연구진은 향후 광물화된 탄소나노튜브 강화재가 첨가된 나노 복합재료의 열 기계적 물성을 분석하여 다양한 분야에서의 활용 가능성을 제시할 계획이다.

• Membrane and Water Treatment
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• 제9권2호
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• pp.105-113
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• 2018

Maillard reaction products like melanoidins present in industrial fermentation wastewaters are complex compounds with various functional properties. In this work, novel ultrafiltration (UF) mixed matrix membrane (MMM) composed of polysulfone (PSF) and nanocomposites was prepared through a phase inversion process for the recovery of melanoidins. Nanocomposites were prepared with acid functionalized multiwalled carbon nanotubes (MWCNTs) as the reinforcing filler for chitosan-thermoplastic starch blend. Higher nanocomposites content in the PSF matrix reduced the membrane permeability and melanoidins retention indicating tighter membrane with surface defects. The membrane surface defects could be sealed with dilute polyvinyl alcohol (PVA) solution. The best performing membrane (1% nanocomposites in 18% PSF membrane sealed with 0.25% PVA coating) resulted in uniform melanoidins retention of 98% and permeability of 3.6 L/m2 h bar over a period of 8h. This demonstrates a low fouling PSF membrane for high melanoidins recovery.

• Macromolecular Research
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• 제10권4호
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• pp.221-229
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• 2002

PET nanocomposites filled with fumed silicas were prepared via direct melt compounding method at various mixing conditions such as filler type and filler content. Some fumed silicas were pre-treated to improve the wettability and dispersibility, and principal characterizations were performed to investigate the effects of nano fumed silicas on polymer matrix. Hydrophobic fumed silica (M-FS), which has the similar contact angles of water with neat PET, acted as the best reinforcement for the thermal stability and mechanical properties of PET nanocomposite, and FE-SEM images also showed that M-FS was uniformly dispersed into matrix and had good wettability. But, some filler (O-FS) had low dispersibility and caused the deterioration of mechanical properties. Besides, the results of DSC revealed the nucleation effect of all fillers in polymer matrix, and PET nanocomposite filled with hydroptilic fumed silica (FS) showed markedly the characteristic dynamic rheological properties such as shear thinning behavior at very low frequencies and the decrease of viscosity.

• 동력기계공학회지
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• 제18권6호
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• pp.174-179
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• 2014

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the specific wear rate under the various applied load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and followed by scanning electron microscope observations. The presence of silica filler in epoxy composites was demonstrated significant influence on the friction and wear behavior of epoxy nanocomposites. With the incorporation of silica filler into the epoxy matrix, reduction of the coefficient of friction and specific wear rate were identified. Wear mechanism was discussed by analyzing the worn surface by scanning electron microscope as well.

• Macromolecular Research
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• 제17권10호
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• pp.776-784
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• 2009

N,N-dimethyldodecylamine (tertiary amine)-modified MMT (DDA-MMT) was prepared as an organically modified layered silicate (OLS), after which styrene-butadiene rubber (SBR) nanocomposites reinforced with the OLS were manufactured via the latex method. The layer distance of the OLS and the morphology of the nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By increasing the amount of N,N-dimethyldodecylamine (DDA) up to 2.5 g, the maximum values of torque, tensile strength and wear resistance of the SBR nanocomposites were increased due to the increased dispersion of the silicate layers in the rubber matrix and the increased crosslinking of the SBR nanocomposites by DDA itself. When SBR nanocomposites were manufactured by using the ternary filler system (carbon black/silica/OLS) to improve their dynamic properties as a tire tread compound, the tan $\delta$(at $0^{\circ}C$ and $60^{\circ}C$) property of the compounds was improved by using metal stearates instead of stearic acid. The mechanical properties and wear resistance were increased by direct substitution of calcium stearate for stearic acid because the filler-rubber interaction was increased by the strong ionic effect between the calcium cation and silicates with anionic surface. However, as the amount of calcium stearate was further increased above 0.5 phr, the mechanical properties and wear resistance were degraded due to the lubrication effect of the excessive amount of calcium stearate. Consequently, the SBR/organoclay nanocomposites that used carbon black, silica, and organoclay as their ternary filler system showed excellent dynamic properties, mechanical properties and wear resistance as a tire tread compound for passenger cars when 0.5 phr of calcium stearate was substituted for the conventionally used stearic acid.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.215-216
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• 2007

Semiconducting layers are thin rubber film between electrical cable wire and insulating polymer layers having a volume resistivity of ${\sim}10^2{\Omega}cm$. A new semiconducting material was suggested in this study based on the carbon nanotube(CNT)-reinforced polymer nanocomposites. CNT-reinforced polymer nanocomposites were prepared by solution mixing with various polymer type and dual filler system. The mechanical, thermal and electrical properties were investigated as a function of polymer type and dual filler system based on CNT and carbon black. The volume resistivity of composites was strongly related with the crystallinity of polymer matrix. With decreased crystallinity, the volume resistivity decreased linearly until a critical point, and it remained constant with further decreasing the crystallinity. Dual filler system also affected the volume resistivity. The CNT-reinforced nanocomposite showed the lowest volume resistivity. When a small amount of carbon black(CB) was replaced the CNT, the crystallinity increased considerably leading to a higher volume resistivity.