• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1539-1542
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• 2007

We have synthesized novel organic passivation materials to protect organic thin film transistors (OTFTs) from $H_2O$ and $O_2$ using polyvinyl alcohol (PVA)/layered silicate (SWN) nano composite system. Up to 3 wt% of layered silicate to PVA, very homogeneous nanocomposite solution was prepared.

• Macromolecular Research
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• 제13권2호
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• pp.156-161
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• 2005

The thermal transitions of a nylon 6/layered silicate nanocomposite were studied by differential scanning calorimetry and in-situ synchrotron X-ray diffraction. The drawn film of the nylon 6/layered silicate nanocomposite typically showed three endotherms in the DSC thermogram; a very broad endotherm at $\sim120^{\circ}C(T_{1})$, a double-melting endotherm at $\sim215^{\circ}C(T_{2})$, and a high temperature endotherm at $\sim240^{\circ}C(T_{3})$. The drawn film of the nylon 6/ layered silicate nanocomposite was comprised of a mixture of the $\alpha and \gamma$ forms, with $the \alpha form$ being generated by drawing the pressed film having $the \gamma form$. The melting and crystallization of the crystals were observed at the above thermal transitions during the heating experiment performed at the Pohang X-ray synchrotron radiation source (4C2). The newly generated form was meta-stable and melted $at {\sim}T_{1}$. The double-melting $at {\sim}T_{2}$ was due to the exothermic crystallization of $the \alpha form$ during the main endothermic melting of $the \gamma form$. $The \alpha form$ crystallized $at {\sim}T_{2}$ and melted $at {\sim}T_{3}$.

• 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.

• 멤브레인
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• 제15권4호
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• pp.255-271
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• 2005

고분자/층상실리케이트 나노복합체(polymer/layeres silicate nanocomposite, PLSNs) 필름은 보통 내부층을 나트륨과 같은 양이온을 이용한 이온교환을 통해 유기화된 clay로 만든 재료의 새로운 형태이다. 이것은 중합법, 용액법, 그리고 용융법과 같은 다양한 방법으로 제조할 수 있으며, 열경화성, 열가소성이나 탄성고분자와 같은 넓은 범위의 고분자를 기질로 사용할 수 있다. PLSNs 필름은 고분자 사슬이 일정한 간격으로 쌓여있는 실리케이트에 삽입하여 간격을 넓히는 삽입형과 각각의 실리케이트 층이 고분자 기질에 불균일하게 분산되어 형성하는 박리형 두 가지 형태의 구조를 얻을 수 있다. 이러한 새로운 분야의 재료는 보통 5 wt$\%$ 이하의 소량의 clay 함유만으로도 향상된 기계적, 열적 특성을 얻을 수 있다. 그리고 clay의 함유량이 증가할수록 기체 투과경로인 tortuosity가 증가하여 기체 투과도가 감소한다.

• Macromolecular Research
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• 제8권2호
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• pp.95-101
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• 2000

Clay/poly(styrene-co-acrylonitrile) copolymer (SAN) hybrids have been prepared by simple meltmixing of two components, SAN and organophilic clays with a twin screw extruder. Effects of intercalant on the dispersibility of silicate layers in clay-dispersed nanocomposite were studied by using five different organophilic clays modified with the intercalants of different chemical structures and different fractions of intercalant. The dispersibility of 10-$\AA$-thick silicate layers of clay in the hybrid was investigated by using an X-ray diffractometer and a transmission electron microscope. It was found that if the fraction of intercalant in the organophilic clay becomes too high, SAN is difficult to intercalate into the inter-gallery of silicate layers in the hybrid prepared at 180$\^{C}$, and thus the hybrid shows poor dispersibility of silicate layers. The flexural modulus of the hybrid increases as the dispersibility of silicate layers in the hybrid increases.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.18-18
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• 2003

Natural clays are composed of oxide layers whose thickness is about 1nm and cations existing between the layers. A number of these layers makes primary particles with a height of about 8∼10nm and these primary particles make aggregates with a size of about 0.1∼10$\mu\textrm{m}$. When layered silicate was made to be organophilic, by exchanging the interlayer cations with organic cationic molecules, the matrix polymer can penetrate between the layers to give a nanocomposite, where 1nm-scal clay layers exist separately in a continuous polymer matrix. These nanostructured hybrid organic-inorganic composites have attracted the great interest of researchers over the last 10 years. They exhibit improved performance properties compared with conventional composites, because their unique phase morphology by layer intercalation or exfoliation maximizes interfacial contact between the organic and inorganic phases and enhances interfacial properties. Since the advent of nylon-6/montmorillonite nanocomposite developed by Toyota Motor Co., the studies on layered silicate-polymer nanocomposites have been successfully extended to other polymer systems. They greatly improved the thermal, mechanical, barrier, and even the flame-retardant properties of the polymers.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 봄 학술발표회 논문집
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• pp.195-197
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• 2003

Polymer layered silicate nanocomposite has become an important area of polymer research becaues of its predominant properties in mechanical and thermal properties. Polymer layered silicate nanocomposites show outstanding improvements in tensile strength and modulus, heat distortion temperature, gas and liquid permeability, solvent resistance, and so on. But These improved properties are realized only when silicate particles are well dispersed in polymer matrix. (omitted)

• Macromolecular Research
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• 제14권3호
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• pp.318-323
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• 2006

We investigated the rheological behaviors and orientation of three different types of layered silicate composite systems under external flow: microcomposite, intercalated and exfoliated nanocomposites. Rheological measurements under shear and uniaxial extensional flows, two-dimensional, small-angle X-ray scattering and transmission electron microscopy were conducted to investigate the properties, as well as nano- and micro-structural changes, of polymer/layered silicate nanocomposites. The preferred orientation of the silicate layers to the flow direction was observed under uniaxial extensional flow for both intercalated and exfoliated systems, while the strain hardening behavior was observed only in the exfoliated systems. The degree of compatibility between the polymer matrix and clay determined the microstructure of polymer/clay composites, strain hardening behavior and spatial orientation of the clays under extensional flow.

• Fibers and Polymers
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• 제3권3호
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• pp.103-108
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• 2002

The viscosity effect of matrix polymer on melt exfoliation behavior of an organoclay in poly($\varepsilon$-caprolactone) (PCL) was investigated. The viscosity of matrix polymer was controlled by changing the molecular weight of poly($\varepsilon$-eaprolactone), the processing temperature, and the rotor speed of a mini-molder. Applied shear stress facilitates the diffusion of polymer chains into the gallery of silicate layers by breaking silicate agglomerates down into smaller primary particles. When the viscosity of PCL is lower, silicate agglomerates are not perfectly broken into smaller primary particles. At higher viscosity, all of silicate agglomerates are broken down into primary particles, and finally into smaller nano-scale building blocks. It was also found that the degree of exfoliation of silicate layers is dependent upon not only the viscosity of matrix but thermodynamic variables.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.137-140
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• 2005

Exfoliated nanocomposites of polypropylene/layered silicate were prepared by a melt compounding process using maleic anhydride modified polypropylene (PP-g-MAH) and organoclay. It was found that polypropylene/layered silicate nanocomposites exhibited remarkable reinforcement compared with the pure polypropylene or conventional composite filled with agglomerated organoclay. The polypropylene /layered silicate nanocomposites showed stronger and earlier shear thinning behaviors and outstanding strain hardening behavior than pure polypropylene or other conventional composites in shear and uniaxial elongational flows, respectively. We simulated rheological modeling for the pure polymer matrix and polypropylene/layered silicate nanocomposite in shear and elongational flows using K-BKZ integral constitutive equation. The two types of K-BKZequations have been examined to describe experimental results of shear and uniaxial elongational viscosities of pure polypropylene and polypropylene/layered silicate nanocomposite.