• Elastomers and Composites
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• 제47권2호
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• pp.168-173
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• 2012

폴리아미드산을 안정제로 사용한 스티렌의 분산중합에 의해 core-shell 구조를 갖는 폴리스티렌-폴리이미드 core-shell 마이크로스피어를 얻었다. Iron pentacarbonyl을 마이크로스피어에 함침시킨 후 열분해하여 산화철 나노 입자를 갖는 자성 폴리스티렌-폴리이미드 마이크로스피어를 제조하였다. 자성 폴리스티렌-폴리이미드 마이크로스피어의 크기와 구조, 열적 특성 및 자성 특성을 조사하였는데, 자성 폴리스티렌-폴리이미드 마이크로스피어는 크기가 약 500 nm 정도로 균일하였으며 40%의 산화철 나노 입자를 가졌다. 산화철은 X선 회절시험에 의해 $Fe_3O_4$임이 확인되었다.

• Bulletin of the Korean Chemical Society
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• 제25권11호
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• pp.1648-1652
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• 2004

A set of unprecedented syndiospecific dimethyl- and diethylamino-functionalized polystyrenes was prepared by catalytically polymerizing the corresponding monomers using (pentamethylcyclopentadienyl)titanatrane/MMAO catalytic system. Dialkylamino-functionalized styrene monomers were synthesized by Wittig reaction from the corresponding aldehyde in high yield. The resulting polymers are soluble in polar organic solvents such as THF and show good thermal stability. The chemical transformation of the syndiospecific poly(4-diethylaminostyrene) also gave new polar polymers, namely syndiotactic poly(4-diethylaminostyrene hydrochloride), which is unattainable by traditional synthetic methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 G
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• pp.3316-3318
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• 1999

PMMA(poly-methyl methacrylate) microlens array is fabricated using transparent acrylic resin. PMMA is commonly used material for plastic lens due to its excellent visibility larger than 90% and other optical characteristics so much close to those of glass. Orthodontic resin (DENTSPLY International Inc.), commonly used in dentistry, is an transparent acrylic resin kit including MMA liquid and polymerization powder. Their mixture results in PMMA through polymerization. Using the resin PMMA layer is formed on the substrate through spin-coating. Designed pattern of lens structure is transferred to PMMA layer by RIE (Reactive Ion Etching) with oxygen plasma. Final lens shape is formed by thermal treatment that causes PMMA to reflow, The thickness of PMMA spun on the substrate is $17{\mu}m$ that is also final sag of microlens, Designed diameters of the microlenses are $200{\mu}m$, $300{\mu}m$,and $500{\mu}m$, respectively.

• 통합자연과학논문집
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• 제12권2호
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• pp.29-34
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• 2019

In dental resin cement studies, viscosity is also an important factor in the adhesion of tooth defects and implants. This study used BisGMA and HPMA as the main ingredients, triethylene glycol dimethacrylate (TEGDMA) as a diluent, and benzoyl peroxide (BPO) as a photoinitiator. The physical properties of graphene oxide used as an additive for functionality were evaluated, and its use as a dental resin cement material was investigated.The rupture strength has the tendency to increase along with the increase of the ratio of graphene oxide that was added, which seemed to reflect the effect of the high strength property of graphene oxide. The flexural strength also has the tendency to increase when about 0.5% of graphene oxide was added the same as the increase of rupture strength.When graphene oxide was added, according to viscosity use, the utilization as high-quality dental resin cements will increase.

• Advances in Computational Design
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• 제4권3호
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• pp.239-250
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• 2019

The insertion of femoral implants is the most important phase for surgeons, given the characteristics of the cement during its mixing phase, generating residual stresses of thermal origin that increase the different stresses induced in the bone cement. The aim of our study is to determine the different stresses that affect the cement and more particularly at the cement-implant interface for different temperatures, and to make a comparison with the cement at ambient temperature. It was concluded that, there are a large concentration of stresses in the proximal part of the cement. For normal stresses, the bone cement is affected by stresses of tension and compression due to the effect of polymerization and the contraction of the cement.

• Bulletin of the Korean Chemical Society
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• 제19권3호
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• pp.328-332
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• 1998

Anionic ring-opening polymerization of 3,4-[(dimethylsilyl)isopropyl]benzo-1,1-dimethyl-1-silacyclopentene in the presence of n-butyllithium and HMPA in THF at - 78 ℃ afforded poly[3,4-(dimethylsilylisopropyl)benzo-1,1-dimethyl-1-silapentene]. The characteristic Si-H stretching frequency in the IR is observed at 2100 cm-1. The polycarbosilane has been modified by chloroplatinic acid catalyzed addition of styrene to the polycarbosilane SiH units. Molecular weights and thermal properties of the polymers were compared. The sol-gel polymerization of 3,4-[(dimethoxysilyl)isopropyl]benzo-1,1-dimethoxy-1-silacyclopentene in the presence of aqueous HCl or NaOH in THF resulted in a cross-linked polysiloxane. The xerogel has a low surface area of 13-14 m2/g and is stable up to about 400 ℃ with only 5% weight loss under a nitrogen atmosphere.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.99-100
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• 2006

Orthogonally protected block copolymers of based on p-hydroxystyrene were prepared with high control via nitroxy mediated radical polymerization using an alkoxyamine as an unimolecular initiator. Thin films of partially protected block copolymer were prepared by spin or dip coating. A well defined nanostructure could be observed as a result of phase separation e.g. cylinders in a matrix oriented perpendicular or parallel to the substrate. The nanostructure of the polymeric films can be defined by the block copolymer composition and it determines surface properties and allows further, selective functionalization, e.g. via click chemistry. The thin films can be designed in a way to allow a patterning based on a thermal or photochemical stimulus.

• 분석과학
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• 제21권1호
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• pp.25-33
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• 2008

Organic disulfide compounds are having higher theoretical capacity than the conventional cathode material and are considered as the important storage material. Here, we are reporting the preparation of poly (2,2'-dithiodianiline) PDDA/multiwall carbon nanotubes, (MWCNTs) composites under different experimental conditions. Amine functionalized and unfunctionalized MWCNTs were independently used for the preparation of composites. Composites were prepared in the presence of cetyl trimethyl bromide (CTAB), a cationic surfactant, and also in the absence of CTAB. A physical mixture of PDTDA and MWCNTs was formed with unfunctionalized MWCNTs. Grafting of PDDA onto MWCNTs was performed by chemical oxidative polymerization of 2, 2'-dithiodianiline in the presence of amine functionalized MWCNTs. The composites of MWCNTs and PDTDA were characterized for structure, morphology and thermal properties through Fourier transform infrared spectroscopy, Fourier transform Raman spectroscopy, scanning electron microscopy and UV-visible spectroscopy. The composite materials prepared by this method are expected to find applications as electrode materials for lithium batteries.

• 청정기술
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• 제16권4호
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• pp.245-253
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• 2010

대구경 강관 표면 보호를 위해 사용되는 필라멘트 와인딩 공정에 불포화 폴리에스터 (unsaturated polyester: UP)를 이용한 자외선 (ultraviolet) 경화 방법을 적용하고자, UP를 이용한 최적의 UV 경화 조건을 찾아보았다. 기존의 유기계 과산화물을 개시제로 사용한 열경화 방법에서는 개시제의 불안정성, 휘발성 유기물 발생, 열에 약한 대상물질의 변형 등 문제점이 발생하므로 이에 대한 개선책으로 UV 경화방법을 시도하였다. UV 경화에 사용되는 다양한 개시제 중에서 비교적 침투력이 높아서 두꺼운 고분자 층 형성이 가능한 개시제 2 종(Irgacure 819 및 Darocure 1173)을 선정하여 이들의 조합비율에 따라 경화된 UP 고분자에 대한 열역학적, 기계적 물성을 비교 분석하여 우수한 경화조건 (개시제 함량 1.5 phr, 혼합 비율 1:1.2, UV 램프로는 갈륨램프)을 찾아내었다. 또한 UP 광경화수지의 경도, 충격강도, 굴곡강도 향상을 위해 유리섬유를 수지 내에 적층하여 복합재료를 제조하고 이들의 특성을 비교한 결과 충격강도가 매우 향상되었다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.840-845
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• 2017

In this paper, in order to investigate the lifetime of oil-paper insulation, specimens were artificially aged with thermal and electrical multiple stresses. Accelerated ageing factors and equivalent operating years for each aging temperatures were derived from results of tensile strengths for the aged paper specimens. Also, the evaluation for the multi-stress aged specimens were carried out through the measurement of impulse breakdown voltage at high temperature of $85^{\circ}C$. The lifetimes of the oil-paper insulations were calculated with the value of 66.7 for 1.0 mm thickness specimens and 69.7 for 1.25 mm thickness specimens throughout the analysis of impulse BD voltages using equivalent operating years, which means that dielectric strengths would not be severely decreased until the mechanical lifetime limit. Therefore, for the lifetime evaluation of the oil-paper insulation, thermal aging would be considered as a dominant factor whereas electrical degradation would be less effective.