• 공업화학
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• 제31권1호
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• pp.67-72
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• 2020

Biomaterials are frequently functionalized with Arg-Gly-Asp (RGD) peptides to provide cell adhesion sites. In this study, RGD peptides were enzymatically coupled on to the surface of fibroin microspheres. Papain exhibited a strong preference for dansyl phenylalanine for the peptide formation with fibroin microspheres. Thus, RGD1 peptide was designed to carry cysteine to both sides of the sequence, glycine as a spacer and two residues of phenylalanine at the C-terminal (CRGDCGFF). The enzymatic modification facilitated by an increasing amount of substrate and by the presence of organic solvent, dimethylsulfoxide at 25% (v/v). Microspheres coupled with RGD1, showed a significantly different precipitation property and an increased apparent volume, possibly due to the steric hindrance of RGD peptides on the surface. Transmission electron microscopy also confirmed the presence of cysteine residues in RGD1 coupled on the surface of microspheres stained with gold nanoparticles. RGD1-microspheres significantly facilitated the growth of murine fibroblast 3T3 cells even under non-adhesion culture conditions.

• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1065-1071
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• 2002

The friction and wear behaviors of magnetron sputtered MoS$_2$ films were investigated through the use of a pin and disk type tester. The experiments were performed for two kinds of specimens (ground (Ra 0.5 $\mu\textrm{m}$) and polished (Ra 0.01 $\mu\textrm{m}$) substrates) under the following operating condifions : linear sliding velocities in the range of 22～66 mm/s (3 types), normal loads varying from 9.8～29.4 N(3 types) and atmospheric conditions of air, medium and high vacuum (3types). Silicon nitride pin was used as the lower specimen and magnetron sputtered MoS$_2$ on bearing steel disk was used as the upper specimen. The results showed that low friction property of the MoS$_2$ films could be identified in high vacuum and the specific wear rate in air was much higher than that in medium and high vacuum due to severe oxidation. It was found that the main wear mechanism in air was oxidation whereas in high vacuum accumulation of plastic flow and adhesion, were the main causes of wear.

• 한국분말재료학회지
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• 제11권6호
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• pp.503-509
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• 2004

Dispersion stabilities and photocatalytic activities of rutile $TiO_{2}$ powders with unique nano-structure synthesized by homogeneous precipitation process at low temperature(HPPLT) have been investigated in the acrylic resin containing fluorostyrene in the range of 0~0.16 mole. Isoelectric point of $TiO_{2}$ in the acrylic resin placed in the neutral region whereas that of $TiO_{2}$ in the water placed in the acidic region, indicating that zeta potential and agglomeration of $TiO_{2}$ powder is strongly dependent on the pH and the type of solvent. To prepare an adhesion, an acrylic resin containing fluorostyrene was synthesized by a radical polymerization. The adhesion of coating layer was increased with increasing fluorostyrene's contents without changing the dispersion stabilities and degrading photocatalytic properties.

• 공업화학
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• 제16권3호
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• pp.361-365
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• 2005

$O_2$, $H_2O$, acrylic acid, diaminocyclohexane 등의 저온 플라즈마를 이용하여 시멘트 보강용 탄소 섬유 표면을 친수성으로 개질한 다음, 이에 대한 효과를 살펴보았다. 물과의 접촉각이 $75{\sim}80^{\circ}$ 정도로 소수성이던 표면이 친수성으로 변하여 접촉각이 $10^{\circ}$ 이하로까지 낮아졌으며, 이에 따라 흡습성 및 수용액에서 분산성이 크게 향상되었다. 또한, 섬유표면의 제타 포텐셜이 변하여 시멘트와 정전기적 인력이 향상됨으로써 시멘트의 결착도 향상과 함께 시멘트와의 결합이 57~124%까지 향상되었다.

• 접착 및 계면
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• 제7권4호
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• pp.39-44
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• 2006

A new kind of silicone-epoxy composite is reported in this research. The silicone-epoxy resin was synthesized by the hydrosilylation of tetramethycyclotetrasiloxane and 4-vinyl-1-cyclohexene 1,2-epoxy with a high reaction yield. It was found that the obtained silicone-epoxy resin shows a high reactive activity to the aluminum complex-silanol catalyst. The resin could be cured under the catalysis of $(Al(acac)_3/Ph_2Si(OH)_2$ at a concentration below 0.1 wt% to give a hard cured resin showing excellent optical clarity, UV resistance and thermal stability. It was also found that the Si-H groups facilitated the curing reaction and the silicone-epoxy resin bearing Si-H group could be cured effectively even if $Ph_2Si(OH)_2h$ was absent. Moreover, the UV resistance and thermal stability were improved significantly by the introduction of Si-H groups. This is possibly due to the reductive property of Si-H groups which can annihilate radical and peroxide effectively. This kind of silicone-containing epoxy composite might have very promising applications as optical resin, optical adhesive and encapsulation materials for electronic devices.

• KSBB Journal
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• 제32권2호
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• pp.146-152
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• 2017

Vulvovaginal candidiasis (VVC) is one of the urogenital infections occurring in women worldwide. Candida albicans is generally observed among various types of microorganisms causing VVC. Antibiotic therapy is typical, and the use of Lactobacilli probiotics is to be recognized as a promising alternative. The aim of this study was to select vaginal lactobacilli with probiotic properties against C. albicans. In a previous study, we isolated 38 lactobacilli from vagina of Korean women and 20 isolates were shown to inhibit C. albicans. We further selected 10 isolates which were able to inhibit C. albicans less than $10^5CFU/mL$. Among these selected strains, Lactobacillus salivarius MG242 (identified by 16s rRNA sequencing) was finally selected based on its strong anti-candidal activity, acid/bile salt resistance and adhesion property. Indirect adhesion activity of MG242 measured by auto-aggregation assay showed more than 60% auto-aggregation after 5 h standing. Taken these results together, the selected strain MG242 may have potential for application in vagina health related products.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.157-160
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• 2005

The surface energies and acid-base interaction between the untreated and treated Jute or Hemp fibers and different matrix compositions of polypropylene-maleic anhydride polypropylene copolymers (PP-MAPP) were investigated using dynamic contact angle measurement. The contribution of the acid-base property into the interfacial adhesion of the natural fibers/matrix systems were characterized by calculating the work adhesion coming from the acid-base interaction. On the other hand, microfailure mechanism of both single Jute and Hemp fiber bundles were investigated using the combination of single fiber tensile test and acoustic emission. Distinctly different micro failure modes of the different natural fiber/polypropylene systems wet ε observed using optical microscope and determined indirectly by AE and their FFT analysis.

• 접착 및 계면
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• 제9권2호
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• pp.1-7
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• 2008

생분해성이 있는 polycaprolactone을 사용하여 용액 상태에서 건조시키는 방법으로 마이크로 캡슐을 제조하였다. 심물질로는 화장품 분야에서 중요한 성분으로 쓰이는 retinol을 선택하였으며 안정제로는 poly(vinyl alcohol)을 사용하였다. 제조 조건에 따른 마이크로캡슐의 형태 변화와 물성 변화를 scanning electron microscope와 differential scanning calorimeter를 이용하여 측정하였으며 심물질의 방출 속도에 미치는 영향들을 UV를 이용하여 측정하였다. 사용한 벽재 물질 용액의 농도, 교반속도, 안정제의 농도 등을 변화 시켜 가면서 마이크로캡슐을 제조하여 보았으며, 최적 조건에서 지름이 5~6 um인 구형 모양의 균일한 크기를 갖는 마이크로캡슐들이 형성되었음을 확인하였다.

• 소성∙가공
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• 제26권6호
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• pp.365-371
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• 2017

During sling wear of a ferrous metal, a surface layer is formed. Its microstructure, constituting phases, and mechanical property are different from those of the original wearing material. Since wear occurs at the layer, it is important to characterize the layer and understand how wear rate changes with different layers. Various layers are formed depending on external wear conditions such as load, sliding speed, counterpart material, and environmental conditions. In this research, sliding wear tests of pure iron were carried out against two different counterparts (AISI 52100 bearing steel and $Al_2O_3$) in the air and in an inert Ar gas atmosphere. Pure iron was employed to exclude other effects from secondary phases in steel on the wear. Wear tests were performed at room temperature. Worn surfaces, wear debris, and cross-sections were analyzed after the test. It was found that these two different counterparts and environments produced diverse layers, resulting in significant changes in wear rate. Against the bearing steel, pure iron showed higher wear rate in an Ar atmosphere due to severe adhesion than that in the air. On the contrary, the iron showed much higher wear rate in the air against $Al_2O_3$. Different layers and wear rates were analyzed and discussed by oxidation, severe plastic deformation, and adhesion at wearing surfaces.

• 한국염색가공학회지
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• 제26권3호
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• pp.201-208
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• 2014

The high value-added functionality for synthetic fiber can be considered through a plasma enhanced treatment. In this study, PET(Polyethyleneterephthalate) was treated with a glow plasma and corona treatment. Surface characteristics of treated fabric were investigated using electron scanning microscopy(SEM), contact angle, X-ray photoelectron spectroscopy(XPS), tensile and adhesion strength. It was found that the contact angle showed $85.5^{\circ}$ for untreated fabric, $0^{\circ}$ for plasma and corona treatment at the condition of 200W for 7min. By XPS analysis, atomic ratio of O 1s/C 1s was increased from 0.27 to 0.43 by glow plasma and 0.27 to 0.41 by corona treatment at 200W for 7min, respectively. Glow plasma and corona treatment did not significantly change the tensile strength of PET fabric. Adhesion strength showed a substantial enhancement for the surface treated with the glow plasma, while corona treatment was adversely affected.