• Journal of Adhesion and Interface
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• 제4권4호
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• pp.1-6
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• 2003

After atmospheric pressure plasma treatment of polypropylene(PP) film surface, we measured the contact angle of the surface by using polar solvent (water) and non-polar solvent (diiodomethane). We also calculated the surface free energy of PP film by using the measured values of contact angles. And then we analyzed contact angle and surface free energy with changing the condition of atmospheric pressure plasma treatment. Upon each condition of atmospheric plasma treatment, contact angle and surface free energy showed an optimum value or leveled off.

• Journal of the Korean Chemical Society
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• 제64권1호
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• pp.30-37
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• 2020

The purpose of this study was to identify the problems faced by students in sub-microscopic representation of acid-base reactions. Herein, we selected 30 students of 12^th grade science classes, who had studied various acid-base models. In order to investigate the sub-microscopic representation ability of the students, we developed nine items related to various contexts, such as one type of solute and solvent, two types of solutes and solvent, cases with water as solvent or with nonaqueous solvents. For all items, we consistently observed lack of concept of chemical change. In context of aqueous and nonaqueous solutions, the frequency of lack of concept of chemical bonding was high if ammonia was the solute or solvent. Moreover, the frequency of lack of concept related to the degree of electrolytic dissociation was high. Therefore, chemistry teachers should understand that students' ability to sub-microscopic representation of acid-base reactions can be enhanced by analyzing the difficulties faced by the students in solving diverse acid-base problems.

• Korean Journal of Food Science and Technology
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• 제15권1호
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• pp.70-76
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• 1983

Separation of fructose from glucose-fructose mixture was studied by utilizing the solubility differences of both sugars in the mixed solvents of water and alcohols with or without the presence of NaCl and $CaCl_2$. Better separation of fructose was obtained in ethanol-water solvent than other solvent-water systems. The addition of NaCl to the ethanol-water solvent system improved the separation factor based on the relative composition of two sugars in the supernatant by twice. The change in feed composition from 50-50 mixture of glucose and fructose resulted in a worse separation factor. It was found in the present studies that the best separation of fructose (fructose 75%, glucose 25%) was achieved when NaCl and ethanol was slowly added to the solution containing 20% water, 40% fructose and 40% glucose to make up the final solution with the parts of ethanol 36 ml, water 4 ml, glucose 8 gm, fructose 8 gm and NaCl 0.25gm.

• Korean Journal of Medicinal Crop Science
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• 제15권3호
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• pp.215-219
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• 2007

This study was conducted to analyze not only for the quality guaranteed of red ginseng but also for the minor ginsenosides. Although several studies have reported to analyze ginseng saponins, those were focused to major saponins, including 6 to 7 ginsenosides. As increase of interest in medicinal effect of ginseng products, anasis of various ginsenosides in both red and white ginseng are strongly demanded. To perform optital condition of 12 ginsenoside analysis, We controlled HPLC conditions, such as the gradient elution of the mobile phase. We found the adequate separation method for 12 ginse-nosides. The optimum condition was as following : H$_2$O/CH$_3$CN ratios were 82/18, 70/30, 55/45 and 50/50, respectively. Sol-vent flow rate was 1.00 ma/min. Column temperature was kept to 35$^{\circ}$C. UV detector was set to 203 nm.

• Resources Recycling
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• 제24권3호
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• pp.3-10
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• 2015

A study has been made on the recovery & separation of cobalt and copper from organic acid leaching solution by solvent extraction. The experimental parameters such as the equilibrium pH, concentration of extractant and phase ratio were observed. Copper was extracted using LIX 84 and Cobalt was extracted using cyanex 272 and versatic acid 10. Experimental results showed that extraction percent of copper was 99% at above eq. pH 2.0 and then more than 90% of cobalt were extracted by cyanex 272 in eq. pH 6.0 and versatic acid 10 in eq. pH 7.5. Stripping of copper and cobalt from the loaded organic phases can be accomplished by sulfuric acid as a stripping reagent and 120 ~ 150 g/L of $H_2SO_4$ was effective for the stripping of copper and cobalt respectively. Finially, the basic optimal process for recovery of copper and cobalt from the bio-leaching solution was proposed.

• Journal of the Korean Chemical Society
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• 제30권2호
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• pp.188-194
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• 1986

The rate constants for the solvolysis reactions of p-chlorobenzyl chloride in ethanol-water mixtures were determinded at 30${\circ}\;and\;40{\circ}$C up to 1,600bar. Rates of reaction were increased with increasing temperature and pressure, and decreased with increasing solvent composition of ethanol mole fraction. The plots of ln k against pressure are fitted to a second-order function in P, and values of ${\Delta}V^{\neq}\;and\;${\Delta}{\beta}^{\neq}$ are obtained. The values of ${\Delta}V^{\neq}\;and\;${\Delta}{\beta}^{\neq}$ extremum behavior at about 0.20 mole fraction of ethanol. This behavior is discussed in terms of solvent structure variation. From the relation between the plots of ln k versus the solvent parameter, q ≡ (D-1)/(2D+1), or the logarithmic molar water concentration, In $C_w$, it could be estimated that the reaction proceeds through $S_N1(2)$ mechanism.

• Journal of Conservation Science
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• 제28권2호
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• pp.95-99
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• 2012

The compressive strength of PEG along processing concentration and solvent is willing to be measured and proper processing condition for exhibition and storage is also willing to be measured by comparing with dimensional stability. In the advanced research of setting PEG-preprocessing concentration & solvent for freeze drying of waterlogged archaeological wood of high water content, vacuum freeze drying showed the highest dimension stability after 40% PEG-preprocessing of aqueous solution. In this study, the compressive strength increased in proportion of processing concentration and water showed the relatively-higher compressive strength than t-butanol regarding solvent. Especially, it showed that there is no big strength difference between PEG 40% and PEG 50% in aqueous solution by 6.6%(16kgf/$cm^2$). According to the above results, it was recognized that it is most effective to implement freeze drying after 40% PEG-preprocessing when want to dimensional stability and compressive strength simultaneously.

• Applied Chemistry for Engineering
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• 제4권2호
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• pp.403-408
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• 1993

Hydroxypropyl chitin(HPCH) was prepared from chitin by reacting it with propylene oxide. The formation of liquid crystalline character of HPCH was investigated using halogenated organic solvents. Solid state $^{13}C$ NMR spectra for chitin and HPCH confirmed the incorporation of hydroxypropyl moiety. The degree of substitution of HPCH was around 0.8 as detected by elemental analysis. WAXD patterns of chitin and HPCH showed that an incorporation of hydroxypropyl unit in chitin contributed to reducing the crystallinity and enhancing the solubility in organic solvents. Polarized light microscopic pictures of concentrated HPCH solution showed that HPCH formed cholesteric liquid crystalline character at about 25w/v% solution in dichloroacetic acid and 1, 2-dichloroethane. Inherent viscosity of HPCH solution in a mixed solvent showed a transient decrease.

• Membrane Journal
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• 제26권3호
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• pp.212-219
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• 2016

The alumina hollow fiber membranes were prepared by spinning and sintering a polymer solution containing suspended alumina powders. For determine pore structure of hollow fiber membranes formed by different solvent-nonsolvent interaction rate, dimethylsulfoxide (DMSO), dimethylacetamide (DMAc), triethylphosphite (TEP) were prepared in dope solution by solvent, polyethersulfone (PESf) and polyvinylpyrrolidone (PVP) were used as a polymer binder and additive. The pore structure of hollow fiber membranes was characterized using scanning electron microscope (SEM). The alumina hollow fiber membranes prepared by DMSO, DMAc were had the asymmetric structure mixed sponge-like and finger-like morphology, while TEP solvent were had single sponge-like structure. The prepared hollow fiber membranes were analyzed gas permeation and mechanical strength experiment also. The hollow fiber membrane having single sponge-like structure was had high gas permeation performance. On the contrary to this, more finger-like morphology was less gas permeation performance.

• Membrane Journal
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• 제2권1호
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• pp.67-73
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• 1992

The effects of after-treatment condition on the permeability of polysulfone hollow fiber membranes were investigated. It was well known that the permeability of and the rejection of hollow fiber membranes prepared by dry-wet spinning technique was highly affected by spinning conditions such as composition of spinning solution, inner and outer coagulant and spinning height. But these are also governed by after-treatment condition such as drying, hot water treatment and glycerine treatment. Since it was difficult to remove DMAc and NMP in membranes by washing with in cold water and even traces of such solvent affected the reproducibility of the membrane characteristics, the hot water-treatment should be required.