• 공업화학
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• 제10권7호
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• pp.1041-1045
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• 1999

세 가지 종류의 방향족 다이안하이드라이드(6FDA, BTDA, PMDA)와 polydimethylsiloxane(SIDA, 평균 분자량 800)을 단독 다이아민으로 하여 축중합반응에 의하여 폴리실록산이미드(PSI) 막을 제조하였다. 이들은 모두 실록산 30~40 wt % 함유하고 있는 고무상의 고분자로서 낮은 밀도, 높은 비자유부피, 그리고 낮은 표면에너지를 가지고 있었다. 제조된 PSI막을 0.05 wt %의 4가지 혼합용매(ethyl acetate, methylene chloride, trichloroethylene, toluene)에 대해 투과증발 특성을 알아본 결과 이들은 유기용매의 소수성 경향이 증가할수록 높은 선택도와 투과도를 보였다.

• 한국막학회:학술대회논문집
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• 한국막학회 1997년도 추계 총회 및 학술발표회
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• pp.39-45
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• 1997

Introduction : Polyimides are one of the most important classes of the high performance polymers due to their excellent electrical, thermal, and high-temperature mechanical properties. But their uses are limited because of their poor solubility. Most polyimide derivatives are processed in the form of polyamic acids, which are subsequently converted into the imide structures.Recently, it has been found that the soluble polyimides with large molecular weight sufficient to application. For enhancing processability, the majority of approaches have involved the following factors. As much as, the separation of the imide ring along the back-bone, that is to say, reducing the density of imide ring in the repeat structure. The introduction of bulky substituents along the back-bone, in order to enhance the free volume of main-chain. The incorporation of flexible or thermally stable linkages in the main-chain, reducing the packing force. The disruption of symmetry or recurrence regularity through copolymerization in order to reduce crystallnity.The objectives of this investigation are the synthesis and characterization of soluble polyimides as membrane materials by the single-step polymerization and the preparation of the asymmetric polyimide membrane by using phase inversion technique. In the present study, three series of polyimide derivatives are synthesized; H series is homopolyimides, A series is prepared from single dianhydride and two diamines, B series is yielded from two dianhydrides and a diamine. The dope solution was directly prepared from the PI solution via one step polymerization from monomers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.190-193
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• 2002

The processing technology of organic thin-film transistors (Ons) performances have improved fur the last decade. Gate insulator layer has generally used inorganic layer, such as silicon oxide which has properties of a low electrical conductivity and a high breakdown field. However, inorganic insulating layers, which are formed at high temperature, may affect other layers termed on a substrate through preceding processes. On the other hand, organic insulating layers, which are formed at low temperature, dose not affect pre-process. Known wet-processing methods for fabricating organic insulating layers include a spin coating, dipping and Langmuir-Blodgett film processes. In this paper, we propose the new dry-processing method of organic gate dielectric film in field-effect transistors. Vapor deposition polymerization (VDP) that is mainly used to the conducting polymers is introduced to form the gate dielectric. This method is appropriate to mass production in various end-user applications, for example, flat panel displays, because it has the advantages of shadow mask patterning and in-situ dry process with flexible low-cost large area displays. Also we fabricated four by four active pixels with all-organic thin-film transistors and phosphorescent organic light emitting devices.

• Fibers and Polymers
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• 제2권2호
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• pp.86-91
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• 2001

Liquid crystalline (LC) poly(ethylene terephthalate-co-2(3)-chloro-1,4-phenylene terephthalate) [copoly(ET/CPT)] was prepared using poly(ethylene terephthalate) (PET) as a flexible spacer, terephthalic acid (TPA), and chlorohydroquinone diacetate (CHQDA). All reactions involved in the copolymerization were investigated using some model compounds: TAP was used for acidolysis, diphenylethyl terephthalate (DPET) for interchange reaction between PET chains, and 야-o-chlorophenyl terephthalate (DOCT) and di-m-chlorophenyl terephthalate (DMCT) for interchange reaction between PET and rigid rodlike segments. Activation energies obtained for the acidolysis of PET with TPA and for interchange reaction of PET with DPET, DOCT, and DMCT were 19.8 kcal/mol, 26.5 kcal/mole, and 45.9 kcal/mole, respectively. This result supports that the copolymerization proceeds through the acidolysis of PET with TPA first and subsequent polycondensation between carboxyl end group and CHQDA or acetyl end group, which is formed from the reaction of CHQDA and TPA. Also, it was found that ester-interchange reaction can be influenced by the steric hindrance. Copoly(ET/CPT)s obtained has ethylene acetate end groups formed from acetic acid hydroxy ethylene end groups and showed almost the random sequence distribution for all compositions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1219-1225
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• 2003

According to the increase of lifetime and efficiency, the interest in the pLED has dramatically increased recently because pLED can be applied to large-size and flexible displays. The core process in the manufacture of pLED is the printing process of red, green and blue light emitting polymers (LEP), and inkjet printing method is one of the promising technology to print red, green and blue LEP on glass substrates. In this work, we developed a multi-head inkjet patterning system with 3 heads for each color. The developed inkjet patterning system is composed of the precise positioning system, head controller circuit, real-time ink drop evaluation system, maintenance system, and stable ink supply system. Finally, we investigated the stability and reliability of the system by printing red, green and blue LEP on the dummy substrate.

• Steel and Composite Structures
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• 제23권1호
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• pp.87-94
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• 2017

Steel structures often require strengthening due to the increasing life loads, or repair caused by corrosion or fatigue cracking. Carbon Fiber Reinforced Polymers (CFRP) is one of the materials used to strengthen steel structures. Most studies on strengthening steel structures have been carried out on steel beams and steel columns under centric compression load. No independent article, to the author's knowledge, has studied the effect of CFRP strengthening on steel columns under eccentric compression load, and it seems that there is a lack of understanding on behavior of CFRP strengthening on steel columns under eccentric compression load. However, this study explored the use of adhesively bonded CFRP flexible sheets on retrofitting square hollow section (SHS) steel columns under the eccentric compression load, using numerical investigations. Finite Element Method (FEM) was employed for modeling. To determine ultimate load of SHS steel columns, eight specimens with two types of section (Type A and B), strengthened using CFRP sheets, were analyzed under different coverage lengths, the number of layers, and the location of CFRP composites. Two specimens were analyzed without strengthening (control) to determine the increasing rate of the ultimate load in strengthened steel columns. ANSYS was used to analyze the SHS steel columns. The results showed that the CFRP composite had no similar effect on the slender and stocky SHS steel columns. The results also showed that the coverage length, the number of layers, and the location of CFRP composites were effective in increasing the ultimate load of the SHS steel columns.

• Macromolecular Research
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• 제13권1호
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• pp.19-29
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• 2005

Polymer composites based on a thermotropic liquid-crystalline polymer (TLCP) and poly(butylene terephthalate) (PBT) were prepared using a melt blending process. Polymer composites consisting of bulk cheap polyester with a small quantity of expensive TLCP are of interest from a commercial perspective. The interactions between the PBT chains and the flexible poly(ethylene terephthalate) (PET) units in the TLCP phase resulted in an improvement in the compatibility of PBT/TLCP composites. TLCP droplets deformed and fragmented into smaller droplets in the PBT/TLCP composites, which resulted in TLCP fibrillation through the effective deformation of the TLCP droplets. The nucleation activities of the PBT/TLCP composites increased by adding even a small amount of the TLCP component.

• 한국기계가공학회지
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• 제20권5호
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• pp.121-127
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• 2021

Reverse offset printing is considering as an emerging technology for printed electronics owing to its environmentally friendliness and cost-effectiveness. In reverse offset printing, selecting the materials for cliché and blanket is critical because of its minimum resolution, registration errors, aspect ratio of reliefs, pattern area, and reusability. Various materials such as silicon, quartz, glass, electroplated nickel plates, and imprinted polymers on rigid substrates can be used for the reverse offset printing of cliché. However, when new structures are designed for specific applications, new clichés need to re-fabricated each time employing multiple time-consuming and costly processes. Therefore, by modifying the blanket materials containing the printing ink, several new structures can be easily created using the same cliché. In this study, we investigated various elastomeric materials and evaluated their applicability for designing a highly stretchable blanket with controlled elastic deformation to implement tunable reverse offset printing.

• 폴리머
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• 제33권3호
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• pp.207-212
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• 2009

감광성 폴리이미드의 전구체 폴리이미드는 2, 2, 2-트리플루오르에탄 디안하이드라이드의 유도체와 3,3'-디히드록시-4,4'-디아미노비페닐로부터 제조하였다. 감광성 폴리이미드(PI-SP6와 PI-SP12)는 전구체 폴리이미드와 감광성 2-스티릴피리딘알킬렌(헥실렌과 도데실렌)유도체로부터 제조하였다. 합성한 광반응성 폴리이미드는 여러 가지 유기 용매에 잘 녹았다. 감광성 폴리이미드의 초기 열분해온도는 $350^{\circ}C$였다. PI-SP6와 PI-SP12의 유리전이온도는 $130^{\circ}C$와 $85^{\circ}C$였다. 이는 헥실렌기를 가지는 PI-SP6 보다 도데실렌기를 가지는 PI-SP12가 유연하다는 것을 의미한다. 이들 감광성 고분자의 필름은 $250^{\circ}C$에서도 90%의 투과율을 유지하였다. 이 결과는 이들 감광성 폴리이미드가 투명성 및 내열성이 우수한 고분자라는 것을 의미한다. PI-SP6와 PI-SP12는 $1.5\;J/cm^2$ 광량에서 이색비가 각각 0.01과 0.03이었다. 이 결과는 광배향에 유연한 알킬렌 스페이서를 가지는 감광성 폴리이미드가 보다 효과적이라는 것을 뜻한다.

• Composites Research
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• 제34권6호
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• pp.357-372
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• 2021

에너지 수확장치는 석유자원의 고갈로 인한 자원난을 해결할 수 있는 대안으로 유망하다고 알려져 있다. 기계적 움직임을 전기 에너지로 전환할 수 있는 압전 소자들의 한계(환경오염 및 낮은 기계적 특성)를 극복하기 위하여, 고분자 기지재 기반 복합재료 압전 에너지 수확장치에 대한 많은 연구들이 수행되었다. 본 논문에서는 사용된 재료 및 공정에 기초하여, 보고된 압전 복합재료의 출력 성능 및 관련된 응용 분야를 검토하였다. 압전 필러는 티탄산 지르콘산 연 및 티탄산바륨 기반의 세라믹 필러뿐만 아니라, 친환경, 생체적합성 및 유연성 측면에서 유리한 산화아연을 검토하였다. 기지재는 폴리비닐리덴플로오라이드 및 공중합체로 구성된 압전 고분자 및 에폭시 및 폴리디메틸실록산 기반의 유연한 고분자로 분류하여 복합재료의 압전 시너지 및 높은 외력 적용에 의한 압전 출력 향상을 논의하였다. 또한, 금속 혹은 탄소 소재 기반 2차 필러의 적용에 의한 복합재료의 전도성 혹은 기계적 특성의 향상이 압전 수확장치의 출력 성능에 미치는 영향을 복합재료의 구조 측면에서 검토하였다. 향상된 성능으로 소형 전자기기, 스마트 센서, 의학 분야 등에 응용 가능한 복합재료 기반 압전 수확장치는 미래의 일상에서 접할 수 있는 무선 전자 장치의 전원으로써 잠재적인 통찰을 제공할 수 있다.