• 폴리머
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• 제33권3호
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• pp.243-247
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• 2009

셀룰로오스 디아세테이트(CDA)에 가소제로서 트리아세틴(TA)과 에폭시화된 콩기름(ESO)을 첨가하여 고속믹서에서 일차적으로 CDA를 가소화한 후, 여기에 천연 zeolite를 충전제로서 첨가하여 용융압출로 CDA/zeolite 복합체를 제조하였다. DMA 측정을 통하여 가소화한 CDA의 $T_g$는 $106^{\circ}C$이며 여기에 zeolite를 50% 첨가한 복합체의 경우는 $125^{\circ}C$의 $T_g$를 확인하였다. Zeolite의 함량이 10에서 50%까지 증가함에 따라 탄성률은 1.7 GPa에서 3.6 GPa로 2배 이상 증가하였으며, 인장강도는 62 MPa에서 조금 증가하다가 51 MPa로 감소하였고 파단신율도 10%로 증가하다가 3.2%로 감소하였다. 복합체의 SEM 이미지로부터 CDA와 zeolite의 상용성을 확인하였다. Zeolite의 함량이 증가할수록 더 효과적으로 zeolite가 초산기를 흡수하였다.

• 한국식품과학회지
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• 제37권4호
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• pp.567-573
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• 2005

본 연구에서는 키토산/젤라틴 블랜드 필름의 상용성을 평가하기 위하여 solution casting 방법을 이용하여 필름을 제조하였고, 키토산/젤라틴 블랜드 필름의 분자수준에서 블랜드 조성비율에 따른 유리전이온도의 변화를 측정하였다. 또한 블랜드 필름 제조시 가소제로 사용된 glycerol과 고분자내에 존재하는 수분이 키토산, 젤라틴 및 이들의 블랜드 필름에 미치는 영향을 조사하였다. TGA 분석결과, 젤라틴이 키토산 보다 열적 안정성이 우수하였고, 블랜드 내에서 두 구성고분자의 관능기 사이에 상호작용이 일어나기 때문에 블랜드 된 키토산 필름의 열적 안정성은 수분과 가소제가 첨가되지 않은 순수한 키토산 필름 보다 우수하였다. 또한 수분 및 가소제의 첨가유무에 따라서 고분자 주쇄의 분해개시 온도에는 영향을 미치지 않았다. DMA 분석결과, 키토산/젤라틴 블랜드 필름에서 키토산의 함량이 증가할수록 $T_g$는 변화하였다. 전체적인 tan ${\delta}$ 곡선을 관찰할 때 블랜드 조성비율에 따라 $T_g$는 단일 곡선을 나타내었고, 젤라틴의 함량이 증가함에 따라 $T_g$는 증가하였다. 젤라틴의 히드록시기와 키토산의 히드록시기 또는 아미노기 등의 극성기들 사이의 분자내 및 분자간에 존재하는 강한 상호작용에 의해서 키토산과 젤라틴 고분자들 사이에 우수한 상용성이 나타났다. 또한 키토산, 젤라틴 및 블랜드 필름에서 수분과 가소제는 두 구성고분자의 열적특성에 큰 영향을 미쳤지만, 블랜드의 상용성에는 크게 영향을 미치지 않았다. 따라서 키토산/젤라틴 블랜드 필름을 이용하여 의료부문이나 식품포장 등 다양한 분야에 응용을 할 수 있을 것으로 판단된다.

• Journal of Microbiology and Biotechnology
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• 제30권5호
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• pp.662-667
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• 2020

Epidermal growth factor receptor (EGFR) mutations are not only genetic markers for diagnosis but also biomarkers of clinical-response against tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC). Among the EGFR mutations, the in-frame deletion mutation in EGFR exon 19 kinase domain (EGFR exon 19-del) is the most frequent mutation, accounting for about 45% of EGFR mutations in NSCLCs. Development of sensitive method for detecting the EGFR mutation is highly required to make a better screening for drug-response in the treatment of NSCLC patients. Here, we developed a fluorometric tandem gene amplification assay for sensitive detection of low-abundance EGFR exon 19-del mutant genomic DNA. The method consists of pre-amplification with PCR, thermal cycling of ligation by Taq ligase, and subsequent rolling circle amplification (RCA). PCR-amplified DNA from genomic DNA samples was used as splint DNA to conjugate both ends of linear padlock DNA, generating circular padlock DNA template for RCA. Long stretches of ssDNA harboring multiple copies of G-quadruplex structure was generated in RCA and detected by thioflavin T (ThT) fluorescence, which is specifically intercalated into the G-quadruplex, emitting strong fluorescence. Sensitivity of tandem gene amplification assay for detection of the EGFR exon 19-del from gDNA was as low as 3.6 pg, and mutant gDNA present in the pooled normal plasma was readily detected as low as 1% fraction. Hence, fluorometric detection of low-abundance EGFR exon 19 deletion mutation using tandem gene amplification may be applicable to clinical diagnosis of NSCLC patients with appropriate TKI treatment.

• 한국재료학회지
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• 제32권9호
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• pp.379-383
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• 2022

In this study, Barium Germanium glasses were prepared with a composition of xBaO-(72-x)GeO₂-8La₂O₃-20ZnO where x = 16.0, 18.0, 20.0, 22.0 and 24.0 mol% respectively. Their physical and optical properties, such as refractiveness index, glass transition temperature (T_g), softening temperature (T_s), transmittance and Knoop hardness were studied. The results showed that refractive index, T_g, T_s and coefficient of thermal expansion (CTE) increased with increasing BaO concentration. The refractive index of all the prepared samples was observed between 1.7811 to 1.7881. The Abbe number was calculated by formula using n_d (589.3 nm), n_f (656.3 nm) and n_c (486.1 nm) and observed to be between 38 to 40. The Abbe number of the prepared sample was similar to that of BaO and GeO₂. The transmittance of the prepared glasses was observed to be between 80 ~ 82 % throughout the range from 200 nm to 800 nm. Knoop hardness divided into seven steps were measured 5 class (≥ 450 ~ < 550) of all prepared samples.

• 한국결정성장학회지
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• 제12권6호
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• pp.272-282
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• 2002

Mercurous bromide ($Hg_{2}0Br_{2}$) crystals hold promise for many acousto-optic and opto-electronic applications. This material is prepared in closed ampoules by the physical vapor transport (PVT) growth method. Due to the temperature gradient between the source and the growing crystal region, the buoyancy-driven convection may occur. The effects of thermal convection on the crystal growth rate was investigated in this study in a horizontal configuration for conditions ranging from typical laboratory conditions to conditions achievable only in a low gravity environment. The results showed that the growth rate increases linearly with Grashof number, and for 0.2 $\leq$ Ar (transport length-to-height, L/H)$\leq$1.0 sharply for Ar=5 and $\Delta$T=30 K. We have also shown that the magnitude of convection decreases with the Ar. For gravity levels of less than $10^{-2}$g the non-uniformity of interfacial distribution is negligible.

• Macromolecular Research
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• 제12권5호
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• pp.478-483
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• 2004

Two different diene monomers [dicyclopentadiene (DCPD) and 5-ethylidene-2-norbornene (ENB)] as self-healing agents for polymeric composites were microencapsuled by in situ polymerization of urea and formaldehyde. We obtained plots of the storage modulus (G') and tan $\delta$ as a function of cure time by using dynamic mechanical analysis to investigate the cure behavior of the unreacted self-healing agent mixture in the presence of a catalyst. Glass transition temperatures (T$\_$g/) and exothermic reactions of samples cured for 5 and 120 min in the presence of different amounts of the catalyst were analyzed by differential scanning calorimetry. Of the two dienes, ENB may have advantages as a self-healing agent because, when cured under same conditions as DCPD, it reacts much faster in the presence of a much lower amount of catalyst, has no melting point, and produces a resin that has a higher value of T$\_$g/. Microcapsules containing the healing agent were successfully formed from both of the diene monomers and were characterized by thermogravimetric analysis. Optical microscopy and a particle size analyzer were employed to observe the morphology and size distribution, respectively, of the microcapsules. The microcapsules exhibited similar thermal properties as well as particle shapes and sizes.

• 폴리머
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• 제26권1호
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• pp.1-8
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• 2002

열 안정성과 우수한 기계적 성질을 갖는 poly(arylene ether sulfone) (PAES)을 음이온교환수지의 지지체로 이용하였다. $1^{\circ}$-Aminated poly(arylene ether sulfone) ($1^{\circ}$-APAES)은 PAES을 리튬화한후 환원 반응시켜 제조하였고, $3^{\circ}$-APAES의 아민기를 알킬화 반응시켜 제조하였다. PAES와 APAES들의 구조는 FT-IR과 H$^1$-NMR으로 확인하였고, 열적 특성은 DSC와 TG 분석을 통하여 조사하였다. PAES에 아민기가 도입됨에 따라 $T_g$는 증가하였고, 초기 열분해 온도는 감소하였다. $1^{\circ}$-APAES과 $3^{\circ}$-APAES의 이온교환용량은 각각 1.19와 1.45 meq/g 이었다.

• Transactions on Electrical and Electronic Materials
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• 제12권4호
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• pp.160-163
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• 2011

Polymer nanocomposite has been attracting more attention as a new insulation material because homogeneous dispersion of nano-sized inorganic fillers can improve various properties significantly. In this paper, various kinds of epoxy-based nanocomposites were made, and the AC breakdown strengths of Nano filler and micro-$SiO_2$ filler mixtures of epoxy-based composites were analyzed using sphere-to-sphere electrodes. Moreover, nano- and microfiller combinations were investigated as an approach to practical application of nanocomposite insulation materials. Its composition ratio was 100 (resin):82 (hardener):1.5 (accelerator). AC breakdown tests were performed at room temperature ($25^{\circ}C$), $80^{\circ}C$, and $100^{\circ}C$ in the vicinity of $T_g$ ($90^{\circ}C$). Thermal conductivity was measured using TC-30.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.479-482
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• 1999

Cured epoxy resins are extensively used for the electrical insulation in high-voltage equipments. The bisphenol A-based epoxy resins lured with azine show, especially, good thermal properties and mechanical resistances. For the technical and economic reasons, varing amount of inorganic fillers are added to endow the required special properties. In the large generators and motors of power plants, epoxy insulation is disclosed to the harsh conditions like the superheated steam and abrupt temperature variation. Hygrothermal aging at elevated temperatures tends to induce degradation in epoxy resins. To predict the effect of this degradation in DGEBA/MDA/SN/zeolite system, we proceeded the forced moisture absorption experiment using the autoclave. The thermal properties of the untreated and treated specimens were analyzed by DSC and TGA under the nitrogen flowing condition. The moisture absorption results showed a weight increase during hygrothermal aging at 1207. At the initial aging period, the system leaded to more or less postcuring but more prolonged environmental aging leaded the discoloration of specimen and lowering the T$_{g}$./.

• 한국염색가공학회지
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• 제3권1호
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• pp.8-16
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• 1991

In order to investigate the fine structure of PET films, PET films were stretchd at various draw ratios (2, 3, 4, 5) below $T_g$ ($72^{\circ}C$) and then annealed at various temperatures (125, 150, 175, $200^{\circ}C$) under free-annealed (FA) and taut-annealed (TA) conditions. Such changes as thermal shrinkage, crystallinity, crystallite size, dynamic viscoelasticity and thermal behaviour were measured in relation to the draw ratio and annealing condition.The following results were obtained. 1. Thermal shirinkage increased with increasing annealing temperature and draw ratio, but decreased in case of draw ratio 4 (draw ratio 3 at $200^{\circ}C$) and above it. 2. The degree of crystallinity of FA samples were higher than those of TA samples. 3. Tan 5 of TA samples were less than those of FA samples, and storage moduli (E') and loss moduli (E") of FA samples were less than those of TA samples; moreover, maximum tan '||'&'||' temperature of FA samples were shifted toward higher temperature than those of TA samples. 4. The melting endotherm ($T_m$) and heat of fusion $(\DeltaH)$ of the PET film increased with the draw ratio and annealing temperature; in addition, premelting endotherm ($T_m$) and heat of fusion $(\DeltaH)$ of the local crystallization in the FA samples were larger than those of TA samples. 5. The X-ray diffraction pattern displayed sharp peaks gradually with the draw ratio and annealing temperature. 6. Crystallite sizes of FA samples were larger than those of TA samples.