• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.53-58
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• 2012

In order to improve the surface hardness of transparent plastic films, an organic-inorganic hybrid coating solution was sunthesized by the sol-gel method. Coating solutions that were prepared colloidal silica (CS), poly methyl methacrylate (PMMA), vinyltrimethoxysilane (VTMS), and [3-(methacryloyloxy)]propyltrimethoxy silane (MAPTMS) was varied with synthesizing parameters such as kinds of organic silane and weight ratio of CS to PMMA. Such coating solution was bar coated on the PET film, cured, and investigated on the chemical and physical properties of coating film. The organic-inorganic hybrid coating solutions have better properties at the pencil hardness and adhesion of coating film than those of an organic material such as PMMA.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.554-558
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• 2017

In order to achieve a hydrophobic surface of silica, we reacted silica nanoparticles with hexamethyldisilazane (HMDS) under various reaction conditions. Modification of the surface of silica with organic materials was confirmed by the thermogravity and elemental analysis. The modified silica displayed nearly the same morphology as to the pristine silica. The reaction of 20 g of HMDS with 1 g of silica in decalin at $200^{\circ}C$ for 6 hours was found to be the optimum reaction condition in terms of the dispersity in toluene and the surface roughness of composite films. Oxygen permeation studies of the composite film demonstrated that the modified silica enhanced a gas barrier performance.

• Polymer(Korea)
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• v.30 no.6
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• pp.471-477
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• 2006

Ion exchange metal composite(IPMC) has toughness equivalent to the range of human's muscle, transformation-actuation force by relatively low voltage and the fast response time. Thus, as a new method for preparing thicker IPMC, the solution casting method to make the films of various thicknesses out of liquid nation was attempted in this study. To reduce the surface resistance of electrode, the first plated electrode prepared by Oguro method was replated with Au and Ir using ion beam assisted deposition(IBAD). The microstructures of electrode surfaces before and after IBAD plating were investigated using SEM. The change of water and ion-conductivity in IPMC were measured under applied voltage. The displacement and driving force of IPMCs with various thicknesses were measured to evaluate the driving properties.

• Composites Research
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• v.24 no.6
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• pp.1-6
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• 2011

A new water-soluble and self-doped poly(styrenesulfonic acid-graft-aniline), PSSA-g-PANI, for dispersing carbon nanotubes (CNTs) in water was synthesized and its ability to stabilize aqueous CNT dispersions was examined. It was observed that the PANI in PSSA-g-PANI, which has benzoid and quinoid structure, was strongly adsorbed onto the nanotube surface via a strong ${\pi}-{\pi}$ interaction, and thus only gentle sonication causes exfoliation of CNT ropes to small bundles and the long-term stability of their resulting dispersions was much better than commercial surfactants. Furthermore, when thin films of PSSA-g-PANI/CNT are prepared from aqueous dispersion and their electrical conductivities are measured by the four probe technique, it is observed that their conductivities are in the range of 1.5-2.5 S/cm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.347-347
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• 2008

본 연구에서는 별도의 소결과정 없이 상온에서 치밀한 복합체 후막의 제조가 가능한 Aerosol Deposition Method (ADM)를 이용하여 SOP를 실현시키기 위한 기판 재료로서 알루미나 기반의 알루미나-폴리이미드 복합체를 제조하고 그 특성에 대한 평가를 진행하였다. SEM 관찰결과 기공이 거의 없고 치밀한 구조의 복합체가 상온에서 성공적으로 형성되었음이 확인되었다. XRD 와 FT-IR 분석 결과 알루미나와 폴리이미드 모두가 복합체에 존재함을 확인할 수 있었다. 또한 XRD 분석결과 출발 원료에 폴리이미드 함량이 증가할수록 ADM으로 제조된 복합체 내부의 알루미나의 결정자 크기가 증가하는 결과를 보였다. 복합체의 알루미나 충진율을 확인하기 위한 간접적인 방법으로 복합체 후막을 연마하여 복합체 내부를 노출시킨 후 폴리이미드의 용매인 Methyl Ethyl Ketone으로 폴리이미드를 식각시켜 남아있는 알루미나 영역을 관찰한 SEM 분석결과 알루미나가 60% 이상 복합체의 대부분을 이루고 있다는 사실을 관찰할 수 있었다. 복합체의 미세구조를 확인하기 위하여 TEM 분석결과 기존에 보고된 ADM으로 제조된 알루미나 후막의 결정자 크기인 10~20 nm 보다 큰 100 nm 범위의 결정자 크기를 관찰 할 수 있었다. 유전특성평가 결과 유전율과 tan$\delta$는 1 MHz에서 각각 9.0, 0.0072로서 알루미나만을 원료로 성막시킨 후막의 유전 특성을 크게 떨어뜨리지 않으며 알루미나 후막과 유사한 결과를 보였다. 추후 복합체의 균일성 향상 및 고주파 영역의 유전 특성 향상을 통하여 세라믹의 취성 및 가공성이 개선된 3 차원 적층 기판재료로의 응용이 기대될 것으로 전망된다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.135-138
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• 2004

Conventional piezoelectric lead-zirconate-titanate (PZT) senor has high sensitivity, but it is very brittle. Recently polymer films such as polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride­trifluoroethylene) (P(VDF-TrFE)) copolymer have been used as a sensor. The advantages of polymer sensor are the flexibility and mechanical toughness. Simple process and possible several shapes are also additional advantages. Polymer sensor can be directly embedded in a structure. In this study, nondestructive damage sensitivity of single basalt fiber/epoxy composites was investigated with sensor type and thermal damage using AE and oscilloscope. And AE waveform for epoxy matrix with various damage types was compared to each other. The damage sensitivity of two polymer sensors was rather lower than that of PZT sensor. The damage sensitivity of PVDF sensor did not decrease until thermal damage temperature at $80^{\circ}C$ and they decreased significantly at $110^{\circ}C$ However, the damage sensitivity of P(VDF-TrFE) sensor at $110^{\circ}C$ was almost same in no damage sensor. For both top and side impacts, the difference in arrival time increased with increasing internal and surface damage density of epoxy matrix.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.582-588
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• 2009

Direct electron transfer of hemoglobin (Hb) in the chitosan (CTS) and $TiO_2$ nanoparticles (nano-$TiO_2$) composite films was achieved by using a room temperature ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate ($BMIMPF_6$) modified carbon paste electrode (CILE) as the basal electrode. UV-Vis and FT-IR spectroscopy indicated that Hb in the film retained the native structure. Electrochemical investigation indicated that a pair of well-defined quasi-reversible redox peaks of Hb heme Fe(III)/Fe(II) was obtained with the formal potential located at -0.340 V (νs. SCE) in pH 7.0 phosphate buffer solution (PBS). The electrochemical parameters such as the electron transfer coefficient (α), the electron transfer number (n) and the standard electron transfer rate constant ($k_s$) were got as 0.422, 0.93 and 0.117 $s^{-1}$, respectively. The fabricated CTS/nano-$TiO_2$/Hb/CILE showed good electrocatalytic ability to the reduction of trichloroacetic acid (TCA) and hydrogen peroxide ($H_2O_2$), which exhibited a potential application in fabricating a new kind of third generation biosensor.

• Polymer(Korea)
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• v.31 no.2
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• pp.117-122
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• 2007

In this work, the mechanical and electrical properties, and thermal stability of vapor-grown carbon nanofibers/polyimide (VGCNFs/PI) composite film synthesized by in-situ polymerization were investigated in terms of tensile properties, volume resistivity and thermogravimetric analysis (TGA), respectively. From the results, the addition of VGCNFs with a certain amount into polyimide led to obvious improvement in tensile strength. The volume resistivity of the films was decreased with increasing the VGCNFs content and the electrical percolation threshold appeared between 1 and 3 wt% of VGCNFs content, which was probably caused by the formation of interconnective structures among the VGCNFs in a composite system. The thermal stability of the film was higher than that of pure PI one. This result indicated that the crosslinking of VGCNFs/PI Composites was enhanced by well-distribution of YGCNFs in PI resin, resulting in the increase of the thermal stability of the resulting composites.

• Polymer(Korea)
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• v.33 no.1
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• pp.13-18
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• 2009

To increase mechanical properties of the hydroxyapatite/poly (L-lactide) (HA/PLLA) composite which was a potential bone substitute material, HA was modified by the surface grafting with D-lactide (DLA) and the formation of stereocomplexes between components was introduced. The composite films were prepared by the solvent-nonsolvent technique to minimize the precipitation of HA during drying. The structure and properties of the composites were investigated by thermal gravimetric analysis (TGA), differential scanning calorimeter, and scanning electron microscopy, and mechanical property measurements. TGA results showed that the amount of DLA grafted on the HA surfaces (g-HA) was 6 wt%. The obtained g-HA exhibited better dispersity in an organic solvent than HA. The formation of stereocomplexes in the composites was confirmed by the change in melting temperature. The mechanical properties of g-HA/PLLA composites were increased, compared to the HA/PLLA composites.

• Journal of Sensor Science and Technology
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• v.28 no.2
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• pp.106-112
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• 2019

Flexible impact force sensors composed of piezoelectric PZT/PDMS composite sandwiched between Al/PET films were fabricated and their voltage signal characteristics were evaluated under varying impact forces for electronic mitt applications. The piezoelectric impact force sensor on an ethylene-vinyl acetate (EVA) substrate exhibited an output voltage difference of no greater than 40 mV a periodical impact test in with the impact load was increased by as much as 240 N by a restoration time of 5 s in a five-time experiment, implying good sensing ability. Moreover, the impact force sensor embedded four electronic mitts showed a reliable sensitivity of less than 1 mV/N and good repeatability under 100 N-impact force during a cycle test executed 10,000 times. This indicated that the fabricated flexible piezoelectric impact sensor could be used in electronic mitt applications. However, the relatively low elastic limit of substrate material such as EVA or poly-urethane slightly deteriorated the sensitivity of the impact sensor embedded electronic mitt at over 200 N-impact forces.