• 폴리머
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• 제26권3호
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• pp.375-380
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• 2002

합성한 polyamic acid의 말단기인 anhydride기와 반응시키기 위하여 나트륨 몬모릴로나이트에 diamine (p-phenylenediamine, m-phenylenediamine, and n-hexamethylenediamine)을 삽입시켰다. 그리고 4,4'-oxydianilline : 1,2,4,5-benzene tetracarboxylic dianhydride의 몰비를 1.50 : 1.53으로 하여 말단기가 anhydride된 polyamic acid를 합성하였다. 이렇게 치환된 몬모릴로나이트를 말단기가 anhydride된 polyamic acid와 N-methyl-2-pyrrolidone용액에서 반응시켰다 (polyamic acid/clay nanocomposite) 이것을 열이미드화하여 polyimide/clay 나노복합재료를 제조하였다. XRD와 TEM으로 관찰한 결과 실리케이트 층이 단일층으로 폴리이미드 매트릭스에 잘 분산되어 있는 박리형 폴리이미드 나노복합재료가 제조되었음을 알 수 있었다. 이들의 기계적 특성을 관찰한 결과 박리형 폴리이미드 나노복합재료의 경우가 순수한 폴리이미드와 삽입형 폴리이미드 나노복합재료의 경우보다 우수함을 알 수 있었다.

• 한국포장학회지
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• 제19권2호
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• pp.95-102
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• 2013

고밀도 폴리에틸렌(High density polyethylene, HDPE)을 수분에 민감한 전기전자제품, 의약품 등을 위한 하이배리어 패키징 소재로써 적용하기 위해서 높은 가로세로비(High aspect ratio)를 가진 Exfoliated graphite (이하 EFG)를 필러로 도입하였다. 또한, 효과적인 분산성과 혼화성을 위해서 상용화제를 첨가하여 HDPE/EFG 나노복합필름을 제조하였다. HDPE/EFG 나노복합필름의 EFG 함량에 따른 화학적 특성, 모폴로지(Morphology), 열적 특성 및 수분차단 특성을 조사하였다. HDPE와 EFG 사이에 화학적 결합이나 상호작용이 약하지만, EFG를 첨가함에 따라 수증기 투과도는 127에서 78 (70 ${\mu}m{\cdot}g/m^2$, $day{\cdot}atm$)까지 감소되었다. 특히, HDPE/EFG 나노복합필름은 EFG의 함량이 0.5%일 때 가장 효과적이며, 그 이상의 함량에서는 물성이 향상되지 않았다. 따라서, 물성의 극대화를 위해서는 EFG의 분산성 향상 및 HDPE와 EFG의 화학적 결합 등의 혼화성 개선에 관한 추가적인 연구가 필요하다.

• 한국응용과학기술학회지
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• 제20권3호
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• pp.243-250
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• 2003

Poly(methyl methacrylate)/clay nanocomposite particles with particle size of 275${\sim}$292 nm range were successfully prepared using emulsion polymerization. The content of montmorillonite based on the methyl methacrylate monomer was chosen as 30 wt.%. 2,2-azobis(isobuthylamidine hydrochloride) and n-dodecyltrimethylammonium chloride were used as an initiator and a surfactant in cationic emulsion system. Potassium persulfate and sodium lauryl sulfate were used as an initiator and a surfactant in anionic emulsion system. The evidence of intercalated /exfoliated structure of montmorillonite in the nanocomposite prepared in our experiment was confirmed by wide angle x-ray diffraction patterns of $d_{001}$ plane. Thermal behavior of nanocomposite was traced using DSC and TGA. It was found that the nanocomposite particle prepared by cationic emulsion system showed intercalated structured. We also found that the nanocomposite particle obtained from anionic emulsion system resulted in the fully exfoliated structure.

• Fibers and Polymers
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• 제4권3호
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• pp.97-101
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• 2003

Polymer/silicate nanocomposites were prepared via two-step manufacturing process: a master batch preparation and then mixing with matrix polymer. A hybrid of PMMA and Na-MMT with exfoliated structure was first prepared by emulsion polymerization of MMA in the presence of Na-MMT. For the case that SAN24, miscible with PMMA, is used as matrix, we could prepare a nanocomposite with exfoliated structure. However, SAN31 nanocomposite shows the aggregation and/or reordering of the silicate layers due to the immiscibility between SAN31 and PMMA.

• Macromolecular Research
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• 제15권2호
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• pp.178-184
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• 2007

A poly(ethylene terephthalate) (PET)/organosilicate nanocomposite, with enhanced mechanical properties, has been prepared using the melt intercalation method. For this purpose, a new organic modifier has been synthesized for the preparation of organosilicate, which is thermally stable and compatible with PET. The use of the new organosilicate yielded almost exfoliated PET nanocomposite; whereas, the PET nanocomposites prepared by use of commercial organoclays (Cloisite 15A and 30B) show only an intercalated morphology. Particularly, the use of the new organosilicate showed an enhanced tensile modulus, and without sacrifice of the tensile strength and elongation on breaking, while the use of commercial organoclays only exhibit a trade-off between those mechanical properties.

• 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.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.11-15
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• 2003

In order to suppress a repulsive interfacial energy between hydrophilic clay and hydrophobic polymer matrix in preparing a polymer/clay nanocomposite, a third component of amphiphilic nature such as poly($\varepsilon$-caprolactone) (PCL) was introduced into the model system of styrene-acrylonitrile copolymers (SAN)/Na-montmorillonite. Once $\varepsilon$-caprolactone was polymerized in the presence of Na-rnontmorillonite, the successful ring-opening polymerization of $\varepsilon$-caprolactone and the well-developed exfoliated structure of PCL/Na-montmorillonite mixture were confirmed, Thereafter, SAN was melt-mixed with PCL/Na-montmorillonite nanocomposite, which resulted in that SAN matrix and PCL fraction were completely miscible to form homogeneous mixture with retention of the exfoliated state of Na-montmorillonite, exhibiting that PCL effectively stabilizes the repulsive polymer/clay interface and contributes the improvement of mechanical properties of the nanocomposites.

• Carbon letters
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• 제11권4호
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• pp.279-284
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• 2010

Graphene is one of the most promising materials for many applications. It can be used in a variety of applications not only as a reinforcement material for polymer to obtain a combination of desirable mechanical, electrical, thermal, and barrier properties in the resulting nanocomposite but also as a component in energy storage, fuel cells, solar cells, sensors, and batteries. Recent research at Michigan State University has shown that it is possible to exfoliate natural graphite into graphite nanoplatelets composed entirely of stacks of graphene. The size of the platelets can be controlled from less than 10 nm in thickness and diameters of any size from sub-micron to 15 microns or greater. In this study we have investigated the influence of melt compounding processing on the physical properties of a polyamide 6 (PA6) nanocomposite reinforced with exfoliated graphite nanoplatelets (xGnP). The morphology, electrical conductivity, and mechanical properties of xGnP-PA6 nanocomposite were characterized with electrical microscopy, X-ray diffraction, AC impedance, and mechanical properties. It was found that counter rotation (CNR) twins crew processed xGnP/PA6 nanocomposite had similar mechanical properties with co-rotation (CoR) twin screw processed or with CoR conducted with a screw design modified for nanoparticles (MCoR). Microscopy showed that the CNR processed nanocomposite had better xGnP dispersion than the (CoR) twin screw processed and modified screw (MCoR) processed ones. It was also found that the CNR processed nanocomposite at a given xGnP content showed the lowest graphite X-ray diffraction peak at $26.5^{\circ}$ indicating better xGnP dispersion in the nanocomposite. In addition, it was also found that the electrical conductivity of the CNR processed 12 wt.% xGnP-PA6 nanocomposite is more than ten times higher than the CoR and MCoR processed ones. These results indicate that better dispersion of an xGnP-PA6 nanocomposite is attainable in CNR twins crew processing than conventional CoR processing.

• 공업화학
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• 제24권6호
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• pp.621-627
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• 2013

친환경 소재인 폴리프로필렌카보네이트(PPC)를 포장소재로서 응용하기 위하여 가로세로비가 큰 박리흑연 EFG(exfoliated graphite)를 이용하여 함량을 달리한 6종류의 PPC/EFG 나노복합필름을 제조하였다. 제조한 나노복합필름의 수분흡수 거동을 gravimetric method를 이용하여 측정하였으며, 나노복합필름의 수분에 대한 화학적 친화성(chemical affinity)과 모폴로지(morphology) 변화를 이용하여 해석하였다. 필름 내로의 수분확산 거동은 박막의 불균일성에도 불구하고 Fickian diffusion model에 잘 부합하였으며, EFG의 함량이 증가할수록 수분 확산계수와 수분 흡수량은 $12.5{\times}10^{-10}cm^2sec^{-1}$에서 $7.2{\times}10^{-10}cm^2sec^{-1}$, 8.9 wt%에서 4.2 wt%로 각각 감소하였다. 이는 수분에 대한 PPC의 차단특성이 EFG의 도입에 따라 향상되는 것을 의미한다. 높은 가로세로비를 가진 EFG를 PPC에 도입함으로써 PPC/EFG 나노복합필름의 수분에 대한 우수한 차단성 특성 발현은 패키징분야를 포함한 차단성이 요구되는 분야로의 친환경 PPC 응용성이 클 것으로 기대된다. 한편, EFG의 도입효과를 극대화하기 위한 추가적인 EFG의 분산성 향상연구가 필요하다.

• Macromolecular Research
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• 제11권6호
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• pp.410-417
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• 2003

Poly(methyl methacrylate-co-acrylonitrile) [P(MMA-co-AN)]/Na-MMT nanocomposites were synthesized through emulsion polymerization with pristine Na-MMT. The nanocomposites were exfoliated up to 20 wt% content of pristine Na-MMT relative to the amount of MMA and AN, and exhibited enhanced storage moduli, E', relative to the neat copolymer. The exfoliated morphology of the nanocomposite was confirmed by XRD and TEM. 2-Acryla-mido-2-methyl-1-propane sulfonic acid (AMPS) widened the galleries between the clay layers before polymerization and facilitated the comonomers, penetration into the clay to create the exfoliated nanocomposites. The onset of the thermal decomposition of the nanocomposites shifted to a higher temperature as the clay content increased. By calculating areas of tan$\delta$ of the nanocomposites, we observed that the nanocomposites show more solid-like behavior as the clay content increases. The dynamic storage modulus and complex viscosity increased with clay content. The complex viscosity showed shear-thinning behavior as the clay content increased. The Young's moduli of the nano-composites are higher than that of the neat copolymer and they increase steadily as the silicate content increases, as a result of the exfoliated structure at high clay content.