• 공업화학
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• 제5권6호
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• pp.981-989
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• 1994

국내에서 상당량 채취되는 자연산 bentonite(Ca계)와 이를 $Na_2CO_3$로 전환시켜 상업적으로 여러 용도에서 사용되는 Na계 bentonite를 신소재 개발을 위한 점토/유기물 복합체에 대한 고찰 측면에서 matrix 수지를 ABS로 하고 이의 충진재로의 특성을 살펴 보았다. 결과, bentonite의 함량이 증가하면 탄성율은 증가하지만 충격강도는 감소하였으며, 경도는 일정하였다. Na계 bentonite가 Ca계에 비하여 탄성율은 낮지만 충격강도에서 상대적 높은 값을 나타내었다. 저장탄성율(E')은 온도가 상승함에 따라 감소하나 tan ${\delta}$는 주파수가 증가할수록 고온으로 shift되었다.

• Journal of the Korean Wood Science and Technology
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• 제34권5호
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• pp.29-41
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• 2006

This study was to investigate the effect of adding additive as tannin, rice husk and charcoal, for reducing the formaldehyde emission level, on the adhesion properties of urea-formaldehyde (UF) resin for particleboard. We controlled the hot-pressing time, temperature and pressure to determine the bonding strength and formaldehyde emission. Blends of various UF resin/additives (tannin, rice husk and charcoal) compositions were prepared. To determine and compare the effect of additives (tannin, rice husk and charcoal) content, 0, 5, 10 and 15%, by weight of UF resin, were used. $NH_4Cl$ as hardener added. To determine the level of formaldehyde emission, we used the desiccator, perforator and 20 L-small chamber method. The formaldehyde emission level decreased with increased additions of additive (except rice husk). Also, increased hot-pressing time decreased formaldehyde emission level. At a charcoal replacement ratio of only 15%, the formaldehyde emission level is under F ✩ ✩ ✩ ✩ grade (emit < $0.3mg/{\ell}$). Curing of the high tannin additive content in this adhesive system indicated that the bonding strength increased. But, in the case of rice husk and charcoal, the bonding strength was much lower due to the inorganic substance. Furthermore, rice husk was poor in bonding strength as well as formaldehyde emission than tannin and charcoal.

• 대한화학회지
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• 제25권3호
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• pp.160-165
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• 1981

2-비닐피리딘계의 세가지 종류의 고분자물질을 합성하여 그들의 구조를 적외선 흡수 스펙트럼으로 확인한 결과, 2-비닐피리딘-디비닐벤젠의 삼중합체임을 알 수 있었다. 또한 2-비닐피리딘-아세트산비닐-디비닐벤젠의 삼중합체는 $98{\circ}C$에서 50분간 반응시킬 때 가장좋은 수율을 나타냈다. 특히 합성된 삼중합체중, 2-비닐피리딘-비닐알코올-디비닐벤젠과, 2-비닐피리딘-인산비닐-디비닐벤젠은 2-비닐피리딘-아세트산비닐-디비닐벤젠보다 큰 이온교환용량을 가지며, 2-비닐피리딘-비닐알코올-디비닐벤젠과 2-비닐피리딘-인산비닐-디비닐벤젠의 이온교환용량은 각각, 3.69 meq/g 및 5.38 meq/g이었다. 마지막으로 Mg(Ⅱ), Co(Ⅱ) 및 Cd(Ⅱ)금속이온에 대한 흡착능을 알아보았다.

• Tribology and Lubricants
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• 제36권5호
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• pp.267-273
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• 2020

This study experimentally investigates hydrophobic surfaces fabricated via additive manufacturing. Additive manufacturing, commonly known as 3D printing, is the process of joining materials to fabricate parts from 3D model data, usually in a layer-upon-layer manner. Digital light processing is used to fabricate hydrophobic surfaces in this study. This method uses photo-curable resins and ultraviolet (UV) sources. Moreover, this technique generally has faster shaping speeds and is advantageous for the fabrication of small components because it enables the fabrication of one layer at a time. Two photo-curable resins with different compositions are used to fabricate micro-patterns of hydrophobic surfaces. The resins are composed of a photo-initiator, monomer, and oligomer. Experiments are conducted to determine suitable process conditions for the fabrication of hydrophobic surfaces depending on the type of resin. The most important factors affecting the process conditions are the UV exposure time and slice thickness. The fabrication capability according to the process conditions is evaluated using the side and top views of the micro-patterns observed using a microscope. The micro-patterns are collapsed and intertwined when the exposure time is short because sufficient light (heat) is not applied to cure the photo-curable resin with a given slice thickness. On the other hand, the micro-patterns are attached to each other when the exposure time is prolonged because the over-curing time can cure the periphery of a given shape. When the slice is thicker, the additional curing area is enlarged in each slice owing to the straightness of UV light, and the slice surface becomes rough.

• 대한치과보철학회지
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• 제45권5호
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• pp.579-588
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• 2007

Statement of problem: A tenderness of the dentin after tapering of teeth for dental prosthesis is a common phenomenon. In practice, the alternative desensitizer may be used for minor pain after tapering of teeth. Purpose: In this study, the desensitizers were used to investigate the affect decreasing of shear bond strength according to the use of various cement, such as resin, Glass Ionomer, and phosphate cement. Material and method: Three different desensitizers were used on this study Compositions of two dentin desensitizers were HEMA(hydroxyethylmethacrylate) and glutaraldehyde. The other one is oxalic acid. Three dentin desensitizers applied on 12 degrees taper teeth. Then, Ni-Cr crowns were bonded with Resin cement, Zinc Phosphate (ZPC) cement and Glass Ionomer (GIC) cement. 120 human premolar teeth were used for specimens. The specimens were divided into four group as the reference and the empirical each with thirty specimens, then further divided into 12 group according to type of desensitizers and cement types. The shear bond strength were measured by Instron multi task instrument. Results: According to the result, the measured shear bond strength in order from the weakest to the strongest in general was ZPC, Resin, and GIC. And it is found that the application of desensitizers on dentin surface does not affect the shear bond strength. Conclusion: Dentin desensitizers that alleviate or prevent a dentin tenderness, usually contains HEMA and glutaraldehyde compounds. Such desensitizers are widely used in clinical studies. By applying the dentin desensitizer on the exposed dentin surface, the dentin capillary are blocked and periodontal membrane and cementum can not be drawn in pulp cavity. Since HEMA and glutaraldehyde may cause harm to the pulp cavity, an alternative desensitizer was developed.

• 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.

• 접착 및 계면
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• 제15권2호
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• pp.69-76
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• 2014

연구에서는 aminopropyl trimethoxysilane (APTMS)과 aminopropyl triethoxysilane (APTES)를 비스페놀계 에폭시 수지와 각각 반응시켜서 2가지 종류의 epoxy-functionalized alkoxysilane (EAS)을 합성하였다. 합성된 EAS를 다양한 혼합비로 3-glycidyloxypropyl trimethoxysilane (GPTMS)과 tetraethyl orthosilicate (TEOS)와 혼합하고 hydrolysis-polycondensation 반응을 통해서 졸 상태의 실리카/에폭시 나노하이브리드 물질을 제조하였다. 제조된 나노 하이브리드 졸은 투명한 노란색이며 다양한 유기 용매와 상용성을 나타내었다. 경화제(TETA와 acrylic acid)와 나노 하이브리드 졸과 반응을 통해서 경화필름이 얻어졌으며, 나노 하이브리드 경화 필름은 순수 에폭시 수지 경화 필름에 비해서 높은 내열성과 기계적 물성을 나타내었다. TEM과 AFM 측정 결과, 나노 크기의 실리카 입자들이 경화된 하이브리드 필름 내에 생성, 분산되어있는 것을 확인할 수 있었다.

• 대한심미치과학회지
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• 제25권2호
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• pp.98-108
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• 2016

전통적인 Metal-ceramic 보철 제작 방식으로부터 All-ceramic 보철에 이르기까지 최근 신소재 개발에 영향을 주는 가장 큰 요인은 심미적인 욕구일 것이다. 우리가 사용하는 각각의 치과용 수복 재료는 재료 별로 강도, 인성, 기계 가공의 효율성 및 사용에 필요한 다양한 과정을 기반으로 임상에서 다양하게 사용되고 있다. 예를 들어 Glass ceramic과 같은 단일 소재의 경우 약한 물성을 고려하여 주로 싱글 크라운과 같은 간단한 보철에 사용하고 있으며 상대적으로 높은 파괴 인성을 가진 지르코니아 재료의 경우 싱글 크라운은 물론 브릿지의 제작에도 널리 사용하고 있다. 하지만 지르코니아 재료는 제작 과정에서 긴 Sintering 시간을 필요로 하므로 Chair side에서 빠른 보철물 제작에 쉽지 않은 부분이 있으며 주로 Lab. side에서 사용하고 있다. CAD / CAM 시스템을 이용하여 보철물을 제작하는 용도로 개발 된 Hybrid ceramic 소재는 Resin Nano Hybrid Ceramic이라고도 하며, 개선 된 물성을 포함한 나노 세라믹 요소를 기반으로 하고 있다. 이러한 특징들은 심미적이며 기능적인 보철물의 제작이 용이한 과정과 결과를 보이고 있으며 동시에 향상된 내구성을 바탕으로 보철물의 제작 과정에 유리한 조건들을 가지고 있다. 새로운 Nano Hybrid Ceramic 재료는 Composite Resin과 Glass ceramic과 같은 단일 소재들이 가진 장점들을 이용하여 술자들의 요구사항을 바탕으로 오랜 연구를 통해 개발된 치과 수복 아이템이며 Nano ceramic filler가 혼합된 구조로 되어있어 치과 수복용 복합소재로서 널리 사용하고 있다. 또한 Nano Hybrid Ceramic소재는 Composite resin의 가공 과정에서 쉽게 파절되지 않는 개선된 물성과 Glass ceramic이 가진 심미성 동시에 포함하고 있는 것이 특징이다. 따라서 Chair side와 Lab. side에서 CAD/CAM 시스템을 이용하여 보철물을 제작할 때 임상적용이 쉽고 유용한 장점을 가지고 있어 추가적인 연구가 필요하다.

• 대한치과보철학회지
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• 제44권3호
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• pp.284-294
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• 2006

Statement of problem. Proliferation of Candida albicans is primarily within the plaque on the fitting surface of the denture rather than on the inflamed mucosa. Consequently, the treatment of the denture is equally important as treatment of the tissue. Cleansing and disinfection should be efficiently carried-out as the organisms can penetrate into the voids of the acrylic resin and grow in them, from which they can continue to infect and reinfect bearing tissues. Purpose. The purpose of this study was to evaluate the applicability of photocatalytic reaction to eliminate Candida albicans from acrylic resin denture base, and to investigate the anti-fungal effect with various UVA illumination time. Materials and Methods. The specimens were cured by the conventional method following the manufacturer's instruction using thermal polymerized denture base resin (Vertex RS: Dentimex, Netherlands). $TiO_2$ photocatalyst sol(LT), which is able to be coated at normal temperature, was made from the Ti-alkoxide progenitor. The XRD patterns, TEM images and nitrogen absorption ability of the $TiO_2$ photocatalyst sol(LT) were compared with the commercial $TiO_2$ photocatalyst P-25. The experimental specimens were coated with the mixture of the $TiO_2$ photocatalyst sol(LT) and binder material (silane) using dip-coater, and uncoated resin plates were used as the control group. Crystallinity of $TiO_2$ of the specimen was tested by the XRD. Size, shape and chemical compositions were also analyzed using the FE-SEM/ EDS. The angle and methylene blue degradation efsciency were measured for evaluating the photocatalytic activity of the $TiO_2$ film. Finally, the antifungal activity of the specimen was tested. Candida albicans KCTC 7629(1 ml, initial concentration $10^5$ cells/ ml) were applied to the experiment and control group specimens and subsequently two UVA light source with 10W, 353 nm peak emission were illuminated to the specimens from 15cm above. The extracted $2{\mu}l$ of sample was plated on nutrient agar plate ($Bacto^{TM}$ Brain Heart Infusion; BD, USA) with 10 minute intervals for 120 minute, respectively. It was incubated for 24 hours at $37^{\circ}C$ and the colony forming units (CFUs) were then counted. Results. Compared the characteristics of LT photocatalyst with commercial P-25 photocatalyst, LT were shown higher activity than P-25. The LT coated experimental specimen surface had anatase crystal form, less than 20 nm of particle size and wide specific surface area. To evaluate the photocatalytic activity of specimens, methylene blue degradation reaction were used and about 5% of degradation rate were measured after 2 hours. The average contact angle was less than $20^{\circ}$ indicating that the LT photocatalyst had hydrophilicity. In the antifungal activity test for Candida albicans, 0% survival rate were measured within 30 minute after irradiation of UVA light. Conclusion. From the results reported above, it is concluded that the UVA-LT photocatalytic reaction have an antifungal effect on the denture surface Candida albicans, and so that could be applicable to the clinical use as a cleaning method.

• 한국환경보건학회지
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• 제18권2호
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• pp.106-116
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• 1992

In order to examine the influences of diluent, DVB, and ligand content, in the adsorption velocities and capacities of chelating resins to heaw metal ions, the chelating resins containing the PO$_3$H, amide, and PO$_3$H+amide were prepared from AN-STR-DVB copolymer. The adsorption capacities of chelating resins were measured by ICP-AES. The major results of the studies are as follows: The optimized compositions of the chelating resins having the highest adsorptivity for the heavy metal ions were found to be DVB=7 wt%, toluene= 100 vol%. The adsorption rate of the chelating resins to the heaw metal ions was PO$_3$H > PO$_3$H+Amide > Amide in order.