• Multiscale and Multiphysics Mechanics
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• v.1 no.1
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• pp.65-76
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• 2016

In this study, an influence of local variation of nanoparticulate volume fraction on the homogenized elastic properties is investigated. It is well known that interface effect is dependent on the radius and volume fraction of reinforced nanofillers. However, there is no study on the multiscale modeling and analysis of polymer nanocomposites including polydispersed nanoparticles with consideration of interphase zone, which is dependent on the volume fraction of corresponding nanoparticles. As results of numerical examples, it is confirmed that an influence of local variation of nanoparticulate volume fraction should be considered for non-dilute system such as cluster of nanoparticles. Therefore representative volume element analysis is conducted by considering local variation of nanoparticle volume fraction in order to analyze the practical size of cell including hundreds of nanoparticles. It is expected that this study could be extended to the multiparticulate nanocomposite systems including polydispersed nanoparticles.

• Macromolecular Research
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• v.11 no.6
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• pp.418-424
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• 2003

Exfoliated poly(methyl methacrylate-co-styrene) [P(MMA-co-ST)]/silicate nanocomposites were synthesized through a multistep emulsion polymerization. The methyl methacrylate monomers were polymerized first and then the styrene monomers were polymerized. The nanocomposites had core-shell structures consisting of PMMA (core) and PS (shell); these structures were confirmed by $^1$H NMR spectroscopy and TEM, respectively. P(MMA-co-ST) copolymers showed two molecular weight profiles and two glass transition temperatures (T$_{g}$) in GPC and DMA measurements. At 30 $^{\circ}C$, the nanocomposites exhibited 83 and 91 % increases in their storage moduli relative to the neat copolymer because the silicate layers were dispersed uniformly in the polymer matrix.x.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.303-303
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• 2006

In-situ ring opening polymerization of ${\varepsilon}-caprolactum$ was carried out in the presence of aminoethylaminopropylisobutyl POSS and stoichiometric amount of adipic acid. The covalent bond formation of POSS on the polyamide was confirmed by the appearance of FT-IR peak at $1123\;cm^{-1}$ that corresponds to the Si-O stretching of POSS structures. Gradual decrease in melting endotherm peak was observed on loading POSS in PA6/POSS nanocomposites. Sharp increase in intrinsic viscosity was observed upto 2.5 wt % loading POSS in the polyamide 6 nanocomposites. These nanocomposites were further characterized using nuclear magnetic resonance, melt viscosity and X-ray diffraction.

• Carbon letters
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• v.10 no.4
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• pp.320-324
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• 2009

We investigated the effect of diameter and content of carbon nanotubes (CNTs) on the physical properties of styrenebutadiene rubber (SBR)/CNTs nanocomposites. CNTs-reinforced SBR nanocomposites were prepared by the melt mixing process. CNTs with different diameters were synthesized by the chemical vapor deposition method (CVD). In this work, the mechanical property and other physical properties of SBR/CNTS nanocomposites were discussed as a function of the content and diameter of CNTs.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3411-3420
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• 2014

Deficiencies in wear and frost resistance as well as mechanical strength constitute the main causes of equipment failure under the harsh climatic conditions of the Earth's polar regions. To improve the properties of the materials used in this equipment, nanoparticle composites have been prepared from clays such as kaolinite, hectorite, and montmorillonite in combination with polytetrafluoroethylene (PTFE) or ultrahigh molecular weight polyethylene (UHMWPE). A number of techniques have been proposed to disperse silicate particles in PTFE or UHMWPE polymer matrices, and several successful processes have even been widely applied. Polymer nanocomposites that exhibit enhanced mechanical and thermal properties are promising materials for replacing metals and glass in the equipment intended for Arctic use. In this article, we will review PTFE- and UHMWPE-based layered silicate nanocomposites.

• Transactions on Electrical and Electronic Materials
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• v.14 no.2
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• pp.53-58
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• 2013

Graphene-based polymer nanocomposites are very promising candidates for new high-performance materials that offer improved mechanical, barrier, thermal and electrical properties. Herein, an approach is presented to improve the mechanical, thermal and electrical properties of unsaturated polyester resin (UPR) by using graphene nano sheets (GNS). The extent of dispersion of GNS into the polymer matrix was also observed by using the scanning electron microscopy (SEM) which indicated homogeneous dispersion of GNS through the UPR matrix and strong interfacial adhesion between the GNS and UPR matrix were achieved in the UPR composite, which enhanced the mechanical properties. The tensile strength of the nanocomposites improved at a tune of 52% at a GNS concentration of 0.05%. Again the flexural strength also increased around 92% at a GNS concentration of 0.05%. Similarly the thermal properties and the electrical properties for the nanocomposites were also improved as evidenced from the differential scanning caloriemetry (DSC) and dielectric strength measurement.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.4
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• pp.315-321
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• 2012

In this study, a sequential multiscale homogenization method to characterize the effective thermal conductivity of nano particulate polymer nanocomposites is proposed through a molecular dynamics(MD) simulations and a finite element-based homogenization method. The thermal conductivity of the nanocomposites embedding different-sized nanoparticles at a fixed volume fraction of 5.8% are obtained from MD simulations. Due to the Kapitza thermal resistance, the thermal conductivity of the nanocomposites decreases as the size of the embedded nanoparticle decreases. In order to describe the nanoparticle size effect using the homogenization method with accuracy, the Kapitza interface in which the temperature discontinuity condition appears and the effective interphase zone formed by highly densified matrix polymer are modeled as independent phases that constitutes the nanocomposites microstructure, thus, the overall nanocomposites domain is modeled as a four-phase structure consists of the nanoparticle, Kapitza interface, effective interphase, and polymer matrix. The thermal conductivity of the effective interphase is inversely predicted from the thermal conductivity of the nanocomposites through the multiscale homogenization method, then, exponentially fitted to a function of the particle radius. Using the multiscale homogenization method, the thermal conductivities of the nanocomposites at various particle radii and volume fractions are obtained, and parametric studies are conducted to examine the effect of the effective interphase on the overall thermal conductivity of the nanocomposites.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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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.

• Polymer(Korea)
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• v.36 no.3
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• pp.364-371
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• 2012

Polystyrene/single-walled carbon nanotube (PS/SWCNT) nanocomposites were prepared by latex technology and the effect of surfactant (SDS) on nanotube dispersion, rheological and electrical properties was investigated. The nanocomposites were prepared through freeze-drying after mixing PS particles and aqueous SWCNT/SDS suspension. As the SDS content increased, the storage modulus and complex viscosity of the nanocomposites were increased due to enhanced dispersion of nanotubes, but if the content excessively increased, the modulus and viscosity began to decrease due to low molecular weight of SDS. The electrical conductivity sharply increased with the addition of SDS, and then did not show significant changes. This result is speculated to be the competition between the increased dispersion of nanotubes and the deterioration of electrical conductivity by SDS adsorption. An optimal ratio of SDS to SWCNT for improving electrical conductivity and end-use properties was 2. With this ratio, the electrical percolation threshold of SWCNT was less than 1 wt%.

• Carbon letters
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• v.11 no.4
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• pp.325-331
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• 2010

This study investigates the effect of filler content (wt%), presence of interphase and agglomerates on the effective Young's modulus of polypropylene (PP) based nanocomposites reinforced with exfoliated graphite nanoplatelets ($xGnP^{TM}$) and carbon nanotubes (CNTs). The Young's modulus of the composites is determined using tensile testing based on ASTM D638. The reinforcement/polymer interphase is characterized in terms of width and mechanical properties using atomic force microscopy which is also used to investigate the presence and size of agglomerates. It is found that the interphase has an average width of ~30 nm and modulus in the range of 5 to 12 GPa. The Halpin-Tsai micromechanical model is modified to account for the effect of interphase and filler agglomerates and the model predictions for the effective modulus of the composites are compared to the experimental data. The presented results highlight the need of considering various experimentally observed filler characteristics such as agglomerate size and aspect ratio and presence and properties of interphase in the micromechanical models in order to develop better design tools to fabricate multifunctional polymer nanocomposites with engineered properties.