• 한국수소및신에너지학회논문집
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• 제18권1호
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• pp.85-94
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• 2007

Rice straw, produced as an agricultural by-product, is usable biomass as fuels if depolymerized to monomer unit, because the chemical structure are similar to high octane materials found in gasoline. In this study, parameters of thermochemical degradation by solvolysis reaction of rice straw such as the effect of reaction temperature, reaction time and type of solvent on conversion yield and degradation products were investigated. It was found that the effectiveness of the solvent on the solvolysis reaction was as follows; acetone>cresol>butanol. When acetone was used as a solvent, the highest rice straw conversion was observed to be 91.5% at $500^{\circ}C$, 40 min. Combustion heating value of liquid products from thermochemical conversion processes was in the range of 7,380 cal/g. The energy yield and mass yield in acetone-solvolysis of rice straw was as high as 69.0% and 38.2 g-oil/100g-raw material after 40 min of reaction at $350^{\circ}C$. Various aliphatic and aromatic compounds were detected in the rice straw solvolysis products. The major components of the solvolysis products, that could be used as fuel, were 4-methyl-2-pentanone, 3,5,5-trimethyl-2-cyclopentan-1-one as ketones.

• 한국전기전자재료학회논문지
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• 제28권1호
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• pp.12-16
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• 2015

$(Na,K)NbO_3$-based piezoelectric ceramics were synthesized by a solid phase sintering method with various milling solvents. The solvents were varied with acetone, ethanol, and pure water to investigate the effect on the microstructure and electrical properties. NKN ceramics showed the maximum values of the relative density (94%), the mechanical quality factor (Qm: 78) and the electro-mechanical coupling factor ($k_p$: 0.25) at the ethanol solvent. It might mean that a solid phase sintering of the NKN piezoelectrics with a suitable solvent could improve the relative density and the piezoelectric properties.

• Macromolecular Research
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• 제15권7호
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• pp.656-661
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• 2007

The effects of a neutral solvent of dioctyl phthalate (DOP) on the phase behavior of symmetric polystyrene-block-poly(n-butyl methacrylate) copolymers (PS-b-PnBMA) were assessed herein. Closed-loop phase behavior with a lower disorder-to-order transition (LDOT) and an upper order-to-disorder transition (UODT) was observed for PS-b-PnBMA/DOP solution when the quantity of DOP was carefully controlled. When the molecular weight of PS-b-PnBMA became larger, the LDOT did not appreciably change at smaller quantities of DOP. With larger quantities of DOP, the reduction in the UODT is greater than the increase in the LDOT. This behavior is discussed in accordance with a molecular theory predicated on a compressible random-phase approximation.

• Elastomers and Composites
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• 제51권2호
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• pp.93-98
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• 2016

The composites of EVA/EPDM including aluminum trioxide (ATH) as a fire retardant were manufactured for the purpose of improving low temperature property and flame resistance in the rubbery materials. The ratio of EVA to EPDM didn't affect the flame resistance of the rubber composites. The addition of ATH resulted in increase of the flame resistance. In the evaluation of the cold resistance, the increasing EPDM content showed enhancement of cold resistance in the composites due to increasing low Tg EPDM. It was found out that tensile strengths of the composites showed a maximum value at 100 phr of ATH by reinforcing effect, but a minimum value at 200 phr of ATH owing to slippage between the flame retardant by the external stress. In the measurement of solvent resistance in tetrahydrofuran, the increasing ATH content yielded enhancement of solvent resistance by reducing swelling of the composite, and increasing EPDM content also resulted from increase of the solvent resistance by reduction of polarizability as well as increase of crosslink in the composites.

• 대한화학회지
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• 제10권3호
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• pp.119-128
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• 1966

The glass electrode was empirically calibrated in methanol-and 2-propanol-water mixed solvents, by means of which the pH-meter reading could be converted to stoichiometric hydrogen ion concentration. The thermodynamic dissociation constants of hydrogen cupferrate in methanol-and 2-propanol-water solution were potentiometrically determined with the changes in composition of organic solvents at 0.01 and 0.05 of the ionic strength and 25$^{\circ}C$. The empirical formula of the constants with mole fraction (n) of the organic solvent are as follow: methanol-water solution $pK_a$= 2.24n + 4.29 at ${\mu}$ = 0.01 n = 0.0476∼0.642 $pK_a$ = 2.35n + 4.38 at ${\mu}$ = 0.05 n= 0.0446~0.642 2-propanol-water solution $pK_a$= 5.50n + 4.48 at ${\mu}$ = 0.05 n = 0.0253~0.259 The relationships between $pK_a$ of acetic acid, propionic acid and HCup and dielectric constant of some mixed solvents were discussed. It would be considered that the factors effecting $pK_a$ value of weak acid in mixed-solvent are not only dielectric constants but acid-base character and solvation effect of the solvent, etc.

• 대한화학회지
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• 제16권6호
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• pp.361-368
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• 1972

5%트리옥틸아민과 5%옥틸알콜이 든 헥산유기용매 1l는 62g의 $WO_3$를 추출할 수 있었는데 반하여 아민만을 사용했을 경우는 37g의 $WO_3$밖에 추출할 수 없었다. 유기용매 추출과정에서 이러한 알콜의 아민-텅스텐 화합물의 용해도의 상승작용 및 아민과 텅스텐산간의 상호작용을 핵자기 공명분광학을 이용하여 연구하였다. 텅스텐은 고분자형의 텅스텐산 이온상태로 유기층으로 추출되어 다중텅스텐산 트리옥틸 암모니움염을 형성함을 알 수 있었으며 이 염은 텅스텐산이온과 알콜간에 수소결합을 형성함으로써 탄화수소 용매에서 더욱 안정화됨을 알 수 있었다.

• 산업기술연구
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• 제27권B호
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• pp.161-167
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• 2007

The objetives of this study are to set up optimum extraction temperature, time and organic solvent for propolis extraction, to investigate chemical properties, and to develop health foods from propolis preparation. In this study, ethanol and ultrasonic extracts method performed to optimum extraction temperature was at 60, $20^{\circ}C$, optimum extraction time was at 12, 4 hours and optimum extraction amount of solvent was at 20, 15 times of propolis weight. When various ethanol solutions were used, whereas flavonoid content was highest in 70, 80% aqueous ethanol, respectively. So the ultrasonic extracts method used gave better results than the ethanol extracts method in this work. Extraction of propolis with etanol and ultrasonic extracts method was performed by using the water and various concentrations of aqueous ethanol as solvent. Sensitivity of propolis samples to Staphylococcus aureus was investigated and the results were shown. Samples of water extract did not inhibit microbial growth, where as 50% aqueous ethanol extract the largest inhibitory zone for Staphylococcus aureus, then decreased inhibition with increasing ethanol concentrations.

• Macromolecular Research
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• 제8권2호
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• pp.80-88
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• 2000

Biodegradable microspheres were prepared with poly(L-lactide-co-glycolide) (PLGA, 75 : 25 by mole ratio) by an oil/oil solvent evaporation method for the sustained release of anti-AIDS virus agent, AZT The microspheres of relatively narrow size distribution (7.6$\pm$ 3.8 ㎛) were obtained by controlling the fabrication conditions. The shape of microspheres prepared was smooth and spherical. The efficiency of AZT loading into the PLGA microsphere was over 93% compared to that below 15% for microspheres by a conventional water/oil/water method. The effects of Preparation conditions on the morphology and in vitro AZT release pattern were investigated. in vitro release studies showed that different release pattern and release rates could be achieved by simply modifying factors in the fabrication conditions such as the type and amount of surfactant, initial amount of loaded drug, the temperature of solvent evaporation, and so on. PLCA microspheres prepared by 5% of initial drug loading, 1.0% (w/w) of surfactant concentration, and 25$\^{C}$ of solvent evaporation temperature were free from initial burst effect and a near-zero order sustained release was observed. Possible mechanisms of the near-zero order sustained release for our system have been proposed.

• Bulletin of the Korean Chemical Society
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• 제14권4호
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• pp.510-514
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• 1993

The retention behavior of proteins was investigated by using reversed-phase chromatography (RPC), comparing to the retention behavior of small molecules in RPC. The evaluation was carried out on a SynChropak RP-P($C_{18}$) column with 0.1% aq. TFA-organic solvent modifier such as acetonitrile, isopropanol, and ethanol. The Z value (the number of solvent molecules required to displace the solute from the surface) was a general index for the characterization of protein retention as a function of organic concentration over a range of temperature between 5 and 70$^{\circ}C$. Van't Hoff plots provided the basis for evaluating the enthalpic and entropic changes associated with the interaction between protein and the stationary phase. Z values did not change significantly at the range of temperature showing the consistent ${\Delta}H^{\circ}$ and ${\Delta}S^{\circ}$ values. From these investigation, it was concluded that the retention behavior of proteins in RPC was able to be predicted by the retention parameters applied to small molecules. Furthermore, myoglobin and hemoglobin in RPC as stated above showed a similar retention behavior regardless of their molecular weights.

• 한국식품영양과학회지
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• 제33권9호
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• pp.1432-1438
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• 2004

In vitro SOS chromotest 실험계에서 콩된장 메탄올 추출물의 경우 100 ${\mu}$g/assay 첨가시 97%의 돌연변이 억제효과를 70% 콩된장 메탄올 추출물은 87%의 억제효과를 가졌고, 청국장, 미소, 원재료인 콩과 콩/밀가루 메탄올 추출물보다 높은 저해 효과를 보였다. 된장의 메탄올 추출물을 더욱 분획하여 얻어진 분획물들, 즉 헥산, 메탄올, 디클로로메탄, 에틸아세테이트, 부탄올, 물 분획물을 100 ${\mu}$g/assay 첨가했을 때 MNNG에 대한 돌연변이 억제효과는 각각 73%, 73%, 91%, 95%, 82%, 73%로 전반적으로 매우 높은 저해효과를 나타내었으며, 특히 디클로로메탄과 에틸아세테이트 분획물의 항돌연변이 효과가 가장 높았음을 관찰할 수가 있었다. 초파리의 wing hairs spots 시스템의 small mwh spots의 경우, $AFB_1$ 단독 처리군을 체세포 돌연변이 유발 100%로 기준해서 된장 메탄올 추출물 2.5%, 5% 첨가농도의 경우, 각각 22%, 30%의 낮은 항돌연변이 효과를 나타내었다. 분획물들 중 가장 활성이 높았던 된장의 에틸아세테이트 분획물 5%, 10% 첨가농도의 경우, 각각 97%의 높은 항돌연변이 효과를 가짐으로 낮은 농도에서부터 강하게 체세포 돌연변이를 억제함을 알 수 있었고, large mwh spots의 경우는 된장의 에틸 아세테이트 분획물 5%의 낮은 농도에서 체세포 염색체 재조환이나 mwh+ 좌위에 유전자 돌연변이를 현저하게 억제하는 것으로 나타났다. 이상의 결과로부터 된장 메탄올 추출물은 다른 콩 관련 발효식품과 콩의 메탄올 추출물에 비해 in vitro SOS chromotest에서 높은 돌연변이 유발 억제 작용을 나타냈고 분획물들 중 에틸아세테이트 분획물은 in vitro와 in vivo 돌연변이 유발실험에서 가장 높은 저해효과를 나타내어 된장의 항돌연변이 활성을 가지고 있는 분획물로 추정되어진다.