• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.933-935
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• 2002

In this paper, new non-chiral molecules with semi-fluorinated alkyl chains were synthesized varying the structure of central bent core unit. Their mesomorphic properties were investigated by DSC and polarized microscopy. The compound with 1,3-dihydroxy phenylene unit could form an enantiomeric smectic phase, but the remaining compounds with bent-core mesogenic unit were not liquid crystalline. In this presentation, their x-ray measurement and electro-optical property will be also described.

• 열처리공학회지
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• 제9권3호
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• pp.187-197
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• 1996

In this study, the properties of coil spring made by Cu-Zn-Al and B added shape memory alloys are investigated. The measurement of recovery displacement and energy with increasing weight, and thermocycling properties have been studied using displacement measuring device. Transformation temperature and phase change by thermocycling have been also investigated by DSC and X-ray diffractometer. Grain size of the alloy is refined from 1.2mm to $400{\mu}m$ by 0.06wt% of B addition. The maximum recovery energy of the coil spring for B added alloy is larger than that of no B added alloy, it is because of grain refinement. And shape memory ability of the coil spring by thermocycling decrease with increasing thermocycling after thermocycle under load. The degradation of shape memory properties of coil spring by thermocycling is improved by B addition.

• 세라미스트
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• 제22권4호
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• pp.393-401
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• 2019

Thermal analysis means the analysis of a change in a property of a sample, which is related to an imposed temperature alteration. Measurements are usually made with increasing temperature, but isothermal measurements or measurements made with decreasing temperatures are also possible. In fact, any measuring technique can be made into a thermal analysis technique by adding thermal control. Simultaneous use of multiple techniques increases the power of thermal analysis, and modern instrumentation has permitted extensive growth of application. The basic theories of thermal analysis are well developed and some of them are explained in this paper.

• 한국식품영양과학회지
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• 제28권1호
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• pp.132-139
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• 1999

Physicochemical properties of the crosslinked potato starches of MDC(Molar Degree of Crosslinking) 0.137~3.333 treated with epichlorohydrin were examined. MDC increased proportionally as epichlorohydrin concentration increased. Water binding capacity increased but blue value decreased with increasing MDC. Gelatinization trends obtained from DSC thermograms and transmittance showed that the gelatinization temperature of the crosslinked potato starch was higher than that of native potato starch, but there was no significant difference among the crosslinked potato starches. Solubility and swelling power decreased with increasing MDC. X ray diffraction patterns and scanning electron micrographs showed that the crosslinking of starch did not affect the crystallinity and the granule shape of starch.

• Fibers and Polymers
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• 제1권2호
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• pp.83-91
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• 2000

Thermotropic liquid crystalline polymer made up of poly(p-hydroxybenzoate) (PHB)-poly(ethylene terephthalate)(PET) 8/2 copolyester, poly(ethylene 2,6-naphthalate) (PEN) and PET were mechanically blended to pursue the liquid crystalline phase of ternary blends. Complex viscosities of blends decreased with increasing temperature and PHB content. DSC thermal analysis indicated that glass transition temperature (Tg) and melting temperature (Tm) of blends increased with increasing PHB content. Both tensile strength and initial modulus increased with raising PHB content and take-up speed of monofilaments. In the WAXS diagram, only PEN crystal reflection at 2Θ=$15.5^{\circ}C$ appeared but PET crystal reflection was not shown in all compositions. The degree of transesterification and randomness of blends increased with blending time but sequential length of both PEN and PET segment decreased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.454-458
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• 1999

절연재료의 성능 개선과 전력계통의 신뢰성을 확보하기 위해 고분자 재료가 많이 사용되고 있다. 고분자 절연재료는 절연저항 및 절연파괴 강도가 우수하며, 유전손실이 낮고 기계적 강도가 우수하며 대량생산 및 제조가 용이하고, 경량이며 유지비용이 절감되는 등의 장점이 있으나 연구의 역사가 짧고 운전 실적이 적어 불분명한 점이 많으며, 내열성 및 내트랙킹성이 비교적 약하며 표면에 오손이 축적되어 열화가 발생, 진행되거나 수분침투에 의한 파괴사고가 발생하는 단점이 있다. 따라서, 고분자 절연재료의 기본적인 화학적 구조 및 인공적 인 오손 환경을 만들어, 오손 환경의 농도 및 시간대별로 오손환경하에서 우수한 특성을 보이는 샘플을 이용하여 LDPE전체에 대한 실험을 진행했다. 또한 측정법으로서는 화학적인 구조 및 함량을 측정하기 위하여 FT-lR, DSC, TGA를 이용했고, 전기적인 측정으로서는 각각의 조건별로 전도도 및 부분방전특성을 평가하였다.

• Bulletin of the Korean Chemical Society
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• 제18권1호
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• pp.38-43
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• 1997

Poly(ethylene 2, 6-naphthalate-co-tetramethylene 2, 6-naphthalate) (PEN/PBN) copolymers were synthesized and studied by 13C NMR spectroscopy, DSC analysis and X-ray diffraction. A minimum in the melting point vs. composition curve was found at approximately 60 mol% tetramethylene 2, 6-naphthalate. The PEN/PBN copolymers were shown to be statistically random throughout the range of 1, 4-butanediol compositions. The melting point depression behavior of annealed PEN/PBN copolymers depended upon the sequence propagation probability, PS, which is suggested by indivisual crystal formation of two pure comonomers; that is, ethylene-naphthalate-ethylene, EE, and tetramethylene-naphthalate-tetramethylene, BB. However, it can be seen from the X-ray curve that the peaks of PEN/PBN copolymers appear from a crystal lattice which is governed only by the rich component between two different aliphatic units in the copolymer composition.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.227-227
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• 2006

It was attempted to synthesize polyimides from PPMDA and 3FPPMDA with mDAPPO/pPDA in order to afford CTE of 17ppm and adhesion property of 80g/mm, besides high Tg (>$300^{\circ}C$), good thermal stability (>$500^{\circ}C$), low water absorption and good solubility. The polyimides were prepared via a conventional two-step process; preparation of poly(amic-acid), followed by solution imidization by refluxing in NMP with o-DCB and the molar ratio of mDAPPO/pPDA was varied. The polyimides were characterized by FT-IR, NMR, DSC and TGA. In addition, intrinsic viscosity, solubility and coefficient of thermal expansion (CTE) were also measured.

• 청정기술
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• 제12권1호
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• pp.19-25
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• 2006

본 연구에서는 폴리에테르 계열의 폴리올과 이소시아네이트 (2,4-toluene diisocyanate) 그리고 하이드록시 아크릴레이트 (hydroxypropyl methacrylae)를 이용하여 광경화가 가능한 우레탄 메타아크릴레이트 계열의 올리고머를 합성하였다. 합성된 우레탄 메타아크릴레이트의 색상, 점도, 굴절율과 같은 기본적인 물성과 광경화후 필름에 대한 인장 강도, 신율, 영율 등을 측정하였다. 광경화 속도는 Photo-DSC를 이용하여 측정하였다. 유사한 폴리올 구조 내에서는 폴리올의 분자량이 증가하면 인장 강도, 영율, 광경화 속도는 감소하고 연신율은 증가하는 결과를 얻었다. 우레탄 메타아크릴레이트 올리고머의 관능기 숫자가 증가하면 인장 강도, 영율, 광경화 속도는 증가하고 반대로 연신율은 감소하는 결과를 얻게 되었다.

• 폴리머
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• 제39권3호
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• pp.426-432
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• 2015

Poly(ether sulfone) (PES)가 첨가된 비스페놀-A 에폭시 복합재가 그 기계적 특성 및 열 안정성을 증진하기 위하여 제조되었다. 인장강도, 굽힘강도 및 충격강도 등의 기계적 강도가 PES 함량에 따라 의미있게 변화하였다. 특히 그 파괴인성 값은 약 24%의 정도 크게 향상되었다. 적분 열분해 진행온도를 통하여 계산된 PES/에폭시 복합재의 열 안정성은 PES 미첨가 에폭시와 비교하여 12%의 향상을 보였다. 또한 DSC 분석 결과 PES 함량이 증가함에 따라 경화온도와 경화열이 점점 감소함을 확인하였다. 이러한 현상은 에폭시 수지와 선형 PES가 가교구조(semi-interpenetrating polymer networks; semi-IPNs)를 형성하고 잘 분산되었기 때문으로 판단된다.