• Elastomers and Composites
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• 제51권2호
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• pp.113-121
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• 2016

Magneto-rheological elastomer (MRE) is a material which shows reversible and various modulus under magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb broader frequency range of vibration. These characteristic phenomena result from the orientation of magnetic particle (i.e., chain-like formation) in rubber matrix. In this study, silicone rubber was used as a matrix of MREs. Carbonyl iron particle (CIP) was used to give magnetic field reactive modulus of MRE. The surface of the CIP was modified with chemical reactants such as silane coupling agent and poly(glycidyl methacrylate), to improve interfacial adhesion between matrix and CIP. The mechanical properties of MREs were measured without the application of magnetic field. The results showed that the tensile strength was decreased while the hardness was increased with the addition of CIP. Also, surface modification of CIP resulted in the improvement of physical properties of MRE, but the degree of orientation of CIP became decreased. The analysis of MR effect was carried out using electromagnetic equipment with various magnetic flux. As the addition of CIP and magnetic flux increased, increment of MR effect was observed. Even though the surface modification of CIP gave positive effect on the mechanical properties of MRE, MR effect was decreased with the surface modification of CIP due to decrease of CIP orientation. Throughout this study, it was found that the loading amounts of CIP affected the mechanical properties of MRE, and surface property of CIP was an important factor on MR effect of MRE.

• Corrosion Science and Technology
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• 제14권5호
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• pp.213-217
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• 2015

Recently, household electronic industries require environmentally-friendly and highly functional steels in order to enhance the quality of human life. Customers especially require both excellent corrosion and abrasion resistant anti-fingerprint steels for digital TV panels. Thus POSCO has developed new functional electro-galvanized steels, which have double coated layers with organic-inorganic composites on the zinc surface of the steel for usage as the bottom chassis panel of TVs. The inorganic solution for the bottom layer consists of inorganic phosphate, magnesium, and zirconium compounds with a small amount of epoxy binder, and affords both improved adhesion properties by chemical conversion reactions and corrosion resistance due to a self-healing effect. The composite solution for the top layer was prepared by fine dispersion of organic-inorganic ingredients that consist of a urethane modified polyacrylate polymer, hardener, silica sol and a titanium complex inhibitor in aqueous media. Both composite solutions were coated on the steel surface by using a roll coater and then cured through an induction furnace in the electro-galvanizing line. New anti-fingerprint steel was evaluated for quality performance through such procedures as the salt spray test for corrosion resistance, tribological test for abrasion resistance, and conductivity test for surface electric conductance regarding to both types of polymer resin and coating weight of composite solution. New composite coated anti-fingerprint steels afford both better corrosion resistance and abrasion properties compared to conventional anti-fingerprint steel that mainly consists of acrylate polymers. Detailed discussions of both composite solutions and experimental results suggest that urethane modifications of acrylate polymers of composite solutions play a key role in enhanced quality performances.

• 한국응용과학기술학회지
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• 제24권1호
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• pp.10-22
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• 2007

To prepare weather-resistant silicone/acrylic resin coatings for an architectural purpose, tetrapolymers were synthesized by a radical polymerization. 3-Methacryloxypropyltrimethoxysilane (MPTS) as a silicone monomer and n-butyl acrylate, methyl methacrylate, and n-butyl methacrylate as acrylic monomers were used. The compositions of monomers were adjusted to fix the glass transition temperature of acrylic polymer for $20^{\circ}C$. The composition of MPTS in the synthesized polymer were varied from 10 wt% to 30 wt%. On the basis of synthesized resin amber paints were prepared and their physical properties and effects for weatherability were examined. The presence of MPTS in silicone/acrylic resins generally resulted in low molecular weight and broad molecular weight distribution, and also lowered the viscosity of the copolymers. The coated films prepared from these resins showed good and balanced properties in general. Adhesion to the substrate was outstanding in particular. Weatherability tests were carried out in three different types such as outdoor exposure, QUV, and SWO. The test results showed that the silicone/acrylic resins containing 30 wt% of MPTS had weather-resistant properties.

• 한국응용과학기술학회지
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• 제33권4호
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• pp.615-626
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• 2016

약용매에 용해가 가능한 알킬기 변성 에폭시수지를 합성하기 위하여, 1단계에서 당량비 기준 dodecyl phenol (DP)/formaldehyde = 1.25~1.333/1.0로 하여, 합성된 도데실 페놀 노볼락 화합물의 벤젠 고리수가 3.0~5.0가 되도록 합성하였고, 2단계에서는 당량비 기준으로 1단계에서 합성된 도데실 페놀 노볼락 화합물/비스페놀A형 에폭시수지 (YD-128) = 1/2로 합성하였고, 3단계는 지방산을 투입하여 지방산 변성 도데실 페놀 노볼락 에폭시수지를 합성하였다. 합성된 수지의 반응성도, 점성도와 분자량 변화, 약용매 가용성 등을 측정한 결과, 1단계에서 합성된 도데실 페놀 노볼락 화합물의 벤젠고리수가 늘어남에 따라 지방산 변성 도데실 페놀 노볼락 에폭시수지의 점도가 상승하였고, 약용매 가용성이 우수하였다. 도료 제조 후 물성을 측정한 결과, 개환촉매로 triphenylphosphine(TPP)을 사용한 DPFAC-5는 건조속도, 접착성, 도막경도, 내충격성, 내산성 및 저장안정성이 양호하였다.

• 마이크로전자및패키징학회지
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• 제4권1호
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• pp.19-30
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• 1997

고분자 Polyimide (PI) film 표면을 반응성 가스 분위기에서 1KeV의 에너지를 가지 는 여러 종류의 이온빔으로 조사하여 표면을 개질하였다. PI표면의 친수성과 표면에너지를 측정하기 위해 접촉각 측정기를 사용하였으며 개질 된 표면의 화학적 변화를 측정하기 위해 X-ray photoelectron spectroscopy (XPS)를 사용하였다. 표면 개질을 위한 이온조사량은 5 $\times$1014 -1$\times$1017 ions/cm2이며 반응가스는 0-8scm까지 변화시켰다. 아르곤 이온빔으로 표면 개질시에는 67。에서 40。까지 감소하였고 표면에너지는 46 dyne/cm에서 64dyne/cm까지 증가하였다. 산소를 6sccm 주입하면서 산소 이온빔으로 표면 개질시 물과의 접촉각은 67。 에서 최대 12。까지 감소하였으며 표면에너지는 46dyne/cm에서 72dyne/cm까지 증가하였고 이때의 이온조사량은 5$\times$1014 -1$\times$1017 ions/cm2 이였다. 여러 종류의 반응성 가스와 이온을 사용하여 개질하여 본 결과 산소분위기에서 산소 이온을 이용하여 개질 하였을 때 접촉각이 8。인 표면을 얻을수 있었다, 산소분위기에서 아르곤 이온빔으로 1$\times$1017 ions/cm2 의 이온 조사량으로 개질 된 Pi 시료를 대기 중에 보관하였을 때에는 110시간 후 65。로 증가하였고 물속에서 보관하였을 때에는 46。로 증가하였다. 그러나 산소 이온빔에 산소분위기에서 개 질 된 시료의 경우 물속에 보관할 경우 접촉강의 증가없이 일정한 값을 나타내었다. 이온조 사로 개질된 시료의 화학적 변화를 확인하기 위하여 XPS 사용하였다. 표면 개질 전의 PI 시료와 산소 분위기에서 1$\times$1017 ions/cm2의 아르곤 이온빔으로 개질한 XPS peak 결과로 보아 Cls의 spectra를 보면 C-C, C-N 그리고 C=O의 결합들은 intensity가 감소하였고 C-O 의 intensity는 증가하였다. Nls peak로 보아 imide N 성분은 이온빔의 조사로 인하여 감소 하였고 C-O의 intensity는 증가하였다. Nls peakk로 보아 imide N성분은 이온빔의조사로 감소하였고 Ols peak로 보아 C-O는 증가하였고 C=O는 약간의 감소가 나타났다. 또한 이온 보조 반응법을 이용하여 처리한 시료의 경우 접착력이 증가하는데 이는 주로 C-O 결합의 산소와 Cu와의 상호작요에 의한 것임을 알수 있었다.

• Journal of Microbiology and Biotechnology
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• 제27권9호
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• pp.1609-1616
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• 2017

The complex roles of cell surface modification in the biofilm formation of Campylobacter jejuni, a major cause of worldwide foodborne diarrheal disease, are poorly understood. In a screen of mutants from random transposon mutagenesis, an insertional mutation in the eptC gene (cj0256) resulted in a significant decrease in C. jejuni NCTC11168 biofilm formation (<20%) on major food contact surfaces, such as polystyrene and borosilicate glass, when compared with wild-type cells (p < 0.05). In C. jejuni strain 81-176, the protein encoded by eptC modified cell surface structures, such as lipid A, the inner core of lipooligosaccharide, and the flagellar rod protein (FlgG), by attaching phosphoethanolamine. To assess the role of eptC in C. jejuni NCTC11168, adherence and motility tests were performed. In adhesion assays with glass surfaces, the eptC mutant exhibited a $0.77log\;CFU/cm^2$ decrease in adherence compared with wild-type cells during the initial 2 h of the assay (p < 0.05). These results support the hypothesis that the modification of cell surface structures by eptC affects the initial adherence in biofilm formation of C. jejuni NCTC11168. In motility tests, the eptC mutant demonstrated reduced motility when compared with wild-type cells, but wild-type cells with the transposon inserted in a gene irrelevant to biofilm formation (cj1111c) also exhibited decreased motility to a similar extent as the eptC mutant. This suggests that although eptC affects motility, it does not significantly affect biofilm formation. This study demonstrates that eptC is essential for initial adherence, and plays a significant role in the biofilm formation of C. jejuni NCTC11168.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.393-393
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• 2010

The biocompatibility of materials used for biomedical applications depends on chemical composition, mechanical stiffness, surface energy, and roughness. The plasma treatment and etching process is a very important technology in the biomedical fields due to possibility of controlling the surface chemistry and properties of materials. In this work, $N_2/H_2$ plasma were treated on single-walled carbon nanotubes (SWCNTs) paper and characterization of treated SWCNTs paper was carried out. Also we investigated neurite outgrowth from SH-SY5Y on treated SWCNTs paper. The results indicated that $N_2/H_2$ plasma-modified SWCNTs paper enhanced neuronal cell adhesion, viability, neurite outgrowth and branching in vitro and exerted a positive role on the health of neural cells.

• 방사선산업학회지
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• 제5권4호
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• pp.371-376
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• 2011

The surface property of the materials used in tissue engineering application has been essential to regulate cellular behaviors by directing their adhesion on the materials. To modulate surface property of the synthetic biodegradable materials, a variety of surface modification techniques have used to introduced surface functional groups or bioactive molecules, recently polydopamine coating method have been introduce as a facile modification method which can be coated on various materials such as polymers, metals, and ceramics regardless of their surface property. However, there are no reports about the degree of polydopamine coating on the materials with different hydrophilicity. In the present study, we prepared acrylic acid grafted nanofibrous meshes using electron-beam irradiation, and then coated meshes with polydopamine. Polydopamine successfully coated on the all meshes, both properties of acrylic acid and polydopamine were detected on the meshes. In addition, the degree of polydopamine deposition on the materials has been altered according to surface hydrophilicity, which was approximately 8-times greater than those on the non-modified materials. In conclusion, dual effect from the acrylic acid grafting and polydopamine may give a chance as a alternative tool in tissue engineering application.

• Journal of Korean Neurosurgical Society
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• 제64권6호
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• pp.853-863
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• 2021

Objective : Biodegradable poly-L-lactic acid (PLLA) with a highly biocompatible surface via tantalum (Ta) ion implantation can be an innovative solution for the problems associated with current biodegradable stents. The purpose of this study is to develop a Taimplanted PLLA stent for clinical use and to investigate its biological performance capabilities. Methods : A series of in vitro and in vivo tests were used to assess the biological performance of bare and Ta-implanted PLLA stents. The re-endothelialization ability and thrombogenicity were examined through in vitro endothelial cell and platelet adhesion tests. An in vivo swine model was used to evaluate the effects of Ta ion implantation on subacute restenosis and thrombosis. Angiographic and histologic evaluations were conducted at one, two and three months post-treatment. Results : The Ta-implanted PLLA stent was successfully fabricated, exhibiting a smooth surface morphology and modified layer integration. After Ta ion implantation, the surface properties were more favorable for rapid endothelialization and for less platelet attachment compared to the bare PLLA stent. In an in vivo animal test, follow-up angiography showed no evidence of in-stent stenosis in either group. In a microscopic histologic examination, luminal thrombus formation was significantly suppressed in the Ta-implanted PLLA stent group according to the 2-month follow-up assessment (21.2% vs. 63.9%, p=0.005). Cells positive for CD 68, a marker for the monocyte lineage, were less frequently identified around the Ta-implanted PLLA stent in the 1-month follow-up assessments. Conclusion : The use of a Ta-implanted PLLA stent appears to promote re-endothelialization and anti-thrombogenicity.

• Nano
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• 제13권12호
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• pp.1850137.1-1850137.9
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• 2018

A series of silica surface-capped with hexamethyldisilazane (denoted as $H-SiO_2$) were prepared by liquid-phase in-situ surface-modification method. The as-obtained $H-SiO_2$ was incorporated into acrylic amino (AA) baking paint to obtain AA/$H-SiO_2$ composite extinction paints and/or coatings. $N_2$ adsorption-desorption tests were conducted to determine the specific surface area as well as pore size and pore volume of $H-SiO_2$. Moreover, the effects of $H-SiO_2$ matting agents on the physical properties of AA paint as well as the gloss and transmittance of AA-based composite extinction coatings were investigated. Results show that $H-SiO_2$ matting agents possess a large specific surface area and pore volume than previously reported silica obtained by liquid-phase method. Besides, they have better dispersibility in AA baking paint than the unmodified silica. Particularly, $H-SiO_2$ with a silica particle size of $6.7{\mu}m$ and the dosage of 4% (mass fraction) provides an extinction rate of 95.2% and a transmittance of 79.3% for the AA-based composite extinction coating, showing advantages over OK520, a conventional silica matting agent. Along with the increase in the silica particle size, $H-SiO_2$ matting agents cause a certain degree of increase in the viscosity of AA paint as well as a noticeable decrease in the gloss of the AA-based composite extinction coating, but they have insignificant effects on the hardness and adhesion to substrate of the AA-based composite coatings. This means that $H-SiO_2$ matting agents could be well applicable to preparing low-viscosity and low-gloss AA-based matte coatings.