• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.87-90
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• 2003

Polyvinyl Alcohol(PVA)와 같이 분자간 결합력이 큰 극성고분자에 극성의 가소제를 도입하여 가역적 가소화기법을 이용하여 비결정영역뿐만 아니라 결정영역까지도 가소화시켜 연신성을 개선시키고자하는 연구가 일부 이루어져 왔다. 특히 요드는 극성고분자의 비결정 영역뿐만 아니라 결정영역까지 침투한다는 사실이 밝혀지면서 PVA의 요드 처리에 대한 연구가 많이 이루어져왔다[1-3]. 그러나 지금까지의 연구에서는 대부분 필름이나 섬유와 같이 성형가공된 상태에서, 즉 결정화가 이루어진 후에 요드화를 시켰기 때문에 그 응용범위나 연구에 있어서 한계를 지니고 있다고 할 수 있다. (중략)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.656-659
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• 2003

Although Hereafter a mass production will claim for patterning nano sized thickness or line in micro-nano industry. existent lithography fabrication has many usable fields, it has complex fabrication steps, expensive values and row work rates. Development of Dip-pen type nano plotter using polymer actuator can construct row cost mass production system because it will change existent lithography fabrication more simple and easy.

• Membrane Journal
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• v.16 no.4
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• pp.294-302
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• 2006

Silver polymer electrolytes are very promising membrane materials for the separation of olefin/paraffn mixtures. Olefin molecules are known to be transported through reversible complex formation with silver ions entrapped iii polymer matrix. However, they have poor long-term stability, which is very important fur the industrial application; the selectivity through the membrane decreases gradually with time mostly due to the reduction of silver ions ($Ag^+$) into silver nanoparticles ($Ag^0$). In this study, the stability of silver polymer electrolyte was investigated for poly(vinyl pyrrolidone) (PVP) and $AgBF_4$ system containing a surfactant, i.e. $C_{18}H_{35}(OCH_2CH_2)_{20}OH$ (Brij98) as a stabilizer. The reduction behavior of silver ions to silver nanoparticles in PVP was also investigated by atomic force microscopy (AFM) and UV-visible spectroscopy. It was found that the growth of silver nanoparticles was slower and selectivity of polymer electrolyte for propylene in propylene/propane was maintained longer time when Brij98 was added as a stabilizer.

• Journal of the Korean Institute of Gas
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• v.25 no.2
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• pp.64-71
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• 2021

Research on polymer matrix composites with excellent molding processability and mechanical properties in the automotive field including hydrogen fuel cell electric vehicles is expanding to Computer-Aided Engineering (CAE) to support the design of materials with specific mechanical properties. CAE automation requires the prediction of the mechanical properties and behavior of materials. Unlike single materials, the mechanical properties prediction of polymer matrix composites is difficult to explain with formulas because the mechanical behavior is complicated to be explained only by the relationship between the matrix and the filler. In this study, the stress-strain curve according to the composition of polymer matrix composites, which was difficult to predict due to its sensitivity to large plastic deformation and composition, was predicted based on machine learning of the test data. The developed model finds a complex correlation between matrix and filler types and compositions, and predicts the total stress-strain curve meaningfully even in the absence of learned test data. It is expected that the material design AI system can be completed in the future based on the developed model that predicts the mechanical properties of polymer matrix composites even for the combination and composition that have not been learned.

• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.181-187
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• 1999

We prepared the side-chain type nonlinear optical NPP(N-(6-nitrophenyl)-(L)-prolinol) polymer films by spin coating method. Ellipsometric spectra were in situ collected by using spectroscopic phase modulated ellipsometer while the NPP polymer films were being corona poled at the temperature above glass transition. We calculated film thickness and the refractive index dispersion by modeling the spectro-ellipsometry data in transparent region. We also calculated the refractive index and the extinction coefficient of the polymer films by numerically inverting the spectro-ellipsometry data in absorbing region, while the previously determined film thickness was used. The independently determined extinction coefficient spectra from the analysis of transmission spectra were compared with those by spectro-ellipsometry and they showed an excellent agreement with each other. From the analysis of the complex refractive index change of the NPP polymer thin films induced by the corona poling, we could determine the vertical complex refractive index and the horizontal complex refractive index separately. Using the volume fraction of the vertical component f⊥, the degree of poling of poled NPP polymer films was quantitatively addressed. It is suggested that the present method can be used to quantitatively address the degree of poling in an absolute manner and to depth profile the poled fraction of thick polymer films. It will be useful to understand the structural change of polymer films and hence the poling mechanism during the poling process.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.585-596
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• 2012

PVDF(poly vinylidene fluoride) and P(VDF-TrFE)(poly vinylidene fluoride-tetrafluoroethylene) are the typical piezoelectric polymers with unique properties. Even they are inferior to conventional piezoelectric ceramics PZT in electromechanical conversion efficiency and interior loss, though they are superior in receiving sensitivity and frequency bandwidth. Their acoustic impedances are relatively close to water or biological tissue and it is easier to make thin film than other piezoelectric materials. Futhermore, the film is so flexible that it is easy to attach on a complex surface. Those properties are suitable for the ultrasound transducers which are useful for medical and biological application, so that various types of polymer transducers have been developed. In this paper, several important considerations for design and fabrication of piezoelectric polymer transducers were described and their effect on the transducer performance were demonstrated through the KLM model analysis. Then, it was briefly reviewed about the structures of the polymer transducers developed for obtaining images as well as the characteristics of the images in several important medical and biological application fields.

• Polymer(Korea)
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• v.34 no.2
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• pp.144-149
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• 2010

Ag/polystyrene(PS) nanocomposites were prepared by in situ reduction of silver 2-ethylhexylcarbamate (Ag-CB) complex and follwing radical polymerization only by heating at 110 $^{\circ}C$. In contrast to this conventional heating method, the microwave irradiation afforded well-dispersed silver nanoparticles(NPs) in styrene monomer without polymerization. The synthesis of Ag NPs proceeded uniformly throughout the reaction vessel only under microwave irradiation, completing the reaction simultaneously in the whole reaction solution. Successive polymerization of the monomer containing the resultant NPs has successfully produced a hybrid of the silver NPs dispersed in PS matrix. Ag/PS (0.1/100) nanocomposites were prepared successfully by melt-mixing process using Ag/PS(4.0/100) as a master-batch. UV-VIS spectroscopy, TEM, and X-ray diffraction techniques were used to investigate the process of formation of Ag/PS nanocomposites.

• Composites Research
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• v.36 no.5
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• pp.369-376
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• 2023

This study focuses on investigating the influence of epoxy polymer crosslinking density, a crucial aspect in composite material matrices, on the yield surface using molecular dynamics simulations. Our approach involved generating epoxy models with diverse crosslinking densities and subjecting them to both uniaxial and multiaxial deformation simulations, accounting for the elasto-plastic deformation behaviors. Through this, we obtained key mechanical parameters including elastic modulus, yield point, and strain hardening coefficient, all correlated with crosslinking conversion ratios. A particularly noteworthy finding is the rapid expansion of the yield surface in the biaxial compression region with increasing crosslinking ratios, compared to the uniaxial tensile region. This unique behavior led to observable yield surface variations, indicating a significant pressure-dependent relationship of the yield surface considering plastic strain and crosslinking conversion ratio. These results contribute to a deeper understanding of the complex interplay between crosslinking density and plastic mechanical response, especially in the aspect of multiaxial deformation behaviors.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.2
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• pp.1-5
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• 2000

We have investigated dielectric properties of IMI-O LB films for the effect of complex concentration by electrical conductivity, dielectric constant and dielectric relaxation time at different frequencies. In the surface pressure-area$\pi$-A) isotherms for the increase of $FE^{3+}$ concentration, the molecular area was expanded with $FE^{3+}$concentration increase by electrostatic repulsion between the polymer chains and hydrophobic increase of ionic strength. In the I-V characteristics, it is found that the limiting area has effects on the change of conductivity And, the dielectric relaxation time decreased for increase of the $FE^{3+}$concentration.

• Nuclear Engineering and Technology
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• v.27 no.1
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• pp.18-24
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• 1995

Characteristics of poly(vinyl alcohol)-poly(methacrylic acid) system (PVA.-PMAA system) for fixation of radioactive contaminant on sand were studied. Dissociation of carboxyl group in PMAA was found to be suppressed by PVA Permeability of sand layer treated with PVA-PMAA solution is directly proportional to the PMAA concentration when the ［PMAA］ is below 0.082 M and the empirical proportional constant (k) is -8.95$\times$10￣$^4$cm$^{5}$ /mole. The change of permeability can be explained by the formation of an intermacromolecular complex between PVA and PMAA The polymer bridge formed on a sand surface combines sand yams more firmly. The PVA-PMAA system is more effective than the PVA system for the fixation of deposited condensational radionuclides.