• Applied Chemistry for Engineering
• /
• v.23 no.2
• /
• pp.241-246
• /
• 2012

Cr(VI)-heterocyclic complex (2,2'-bipyridinium dichromate) was synthesized by the reaction between of 2,2'-bipyridine and chromium trioxide in $H_2O$, and characterized by IR and ICP. The oxidation of benzyl alcohol using 2,2'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant, in the order: cyclohexene < chloroform < acetone < N,N-dimethylformamide. In the presence of DMF solvent with acidic catalyst such as $H_2SO_4$ solution, 2,2'-bipyridinium dichromate oxidized the benzyl alcohol and its derivatives (p-$p-OCH_3$, $m-CH_3$, H, $m-OCH_3$, m-Cl, $m-NO_2$). Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant was -0.66 (303 K). The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

• Journal of Radiation Industry
• /
• v.4 no.1
• /
• pp.7-11
• /
• 2010

Clotrimazole [1-{(2-chlorophenyl)-diphenylmethyl}-1H-imidazole, CLT] has been reported to inhibit the proliferation of vascular endothelial and act as an in vitro anti-VEGF drug. It is also shown to inhibit angiogenesis in an animal model. The radioisotope labeled clotrimazole derivative can be utilized to monitor the physiologic processes of cancer. In this study, we synthesized [$^{18}F$]fluoride labeled clotrimazole derivatives as a new tumor imaging agent for PET. The references were prepared by a refluxing with clotrimazole and an excess of fluoroalkyltosylate in acetonitrile for 36 h and clotrimazole reacted with ditosylalkane to give precursors. [$^{18}F$]Fluoride labeled reaction was performed with precursor in Kryptofix[2.2.2]/$K_2CO_3$ for 10 min at $80^{\circ}C$. The radiolabeling mixture was passed through a silica Sep-Pak cartridge to remove $^{18}F^-$. The [$^{18}F$]F-clotrimazole derivatives were synthesized with a 20~25% yield. In the radiofluorination step, we used acetonitrile and DMSO as a solvent and observed a higher yield at the acetonitrile (25%) reaction compared with the DMSO reaction (5%).

• Elastomers and Composites
• /
• v.38 no.1
• /
• pp.72-80
• /
• 2003

Phosphoric ester compound was employed as thermal resistant and flame retardant for chlorinated polyethylene(CPE) rubber material which is used to prepare automotive oil cooler hose. Cure characteristics, physical properties, thermal resistance, and flame retardation of CPE rubber compounds were investigated. CPE rubber which has excellent properties such as cold resistance and chemical corrosion resistance, and is inexpensive in price than existing ethyleneacrylate rubber(EAR) was used to prepare a rubber compound useful for hose. A non-halogen flame retarding agent N,N'-bis- (diphenylphosphoro) diaminohexane(BDPDH), which is condensed phosphoric ester, was synthesized and it was mixed to CPE rubber material with the range of $0{\sim}30 phr$. From the test results, rheological properties, heat resistance, and flame retardance of CPE rubber compounds were found out to be much increased. The optimum content of BDPDH to rubber which gives maximum effect on thermal resistance and flame retardation, within the range of tolerable specification for rubber materials, was determined to be 20 phr.

• Journal of Environmental Science International
• /
• v.28 no.1
• /
• pp.55-64
• /
• 2019

The adsorption properties of $Cs^+$ and $Cu^{2+}$ ions were evaluated by using a polysulfone scoria zeolite (PSf-SZ) composite with synthetic zeolite synthesized from Jeju volcanic rocks (scoria). In order to investigate the adsorption properties, various parameters, such as pH, contact time, reaction rate, concentration, and temperature in aqueous solutions, were evaluated by tests carried out in batch experiments. The adsorption capacities of $Cs^+$ and $Cu^{2+}$ ions increased between pH 2 but achieved equilibrium at pH 4 and above. The adsorption rate increased rapidly up to the initial 24 h, after which it plateaued ; the adsorption rate then sustained at equilibrium from 48 h. The adsorption kinetics of $Cs^+$ and $Cu^{2+}$ ions were described better by the pseudo-second-order kinetic model than the pseudo-first-order kinetic model. The Langmuir model fitted the adsorption isotherm data better than the Freundlich model. The maximum adsorption capacities of $Cs^+$ and $Cu^{2+}$ ions obtained from the Langmuir model were 53.8 mg/g and 84.7 mg/g, respectively. The calculated thermodynamic parameters showed that the adsorption of $Cs^+$ and $Cu^{2+}$ ions on PSf-SZ was feasible, spontaneous and endothermic reaction.

• Korean Chemical Engineering Research
• /
• v.57 no.2
• /
• pp.267-273
• /
• 2019

Hierarchically porous $Fe_2O_3$ nanofibers with meso- and macro- pores are designed and synthesized by electrospinning and subsequent heat-treatment. The macro pores are generated by selectively decomposition of polystyrene as a dispersed phase in the as-spun fibers containing $Fe(acac)_3$/polyacrylonitrile continuous phases during heat-treatment. Additionally, meso-pores formed by evaporation of infiltrated water vapor during electrospinning process interconnected the macro-pores and results in the formation of hierarchically porous $Fe_2O_3$ nanofibers. The initial discharge capacity and Coulombic efficiency of the hierarchically porous $Fe_2O_3$ nanofibers at a current density of $1.0A\;g^{-1}$ are $1190mA\;h\;g^{-1}$ and 79.2%. Additionally, the discharge capacity of the nanofibers is $792mA\;h\;g^{-1}$ after 1,000 cycles. The high structural stability and morphological benefits of the hierarchically porous $Fe_2O_3$ nanofibers resulted in superior lithium ion storage performance.

• Journal of the Korean Applied Science and Technology
• /
• v.35 no.4
• /
• pp.1243-1249
• /
• 2018

Ceramides are commonly studied and developed in the cosmetics industry as ingredients that help a moisturized skin and strengthen a skin barrier. In this study, we determined how much great effects the moisturing cream containing a ceramide, obtained from evening primrose oil instead of using a common synthetic ceramide, made on the changes in moisturizing and transdermal water loss of skin. The result showed that the cream with a ceramide showed much better results than the cream without a ceramide at the skin moisture resistance and transdermal water loss of skin.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.29 no.1
• /
• pp.1-12
• /
• 2019

Objective: Significant concerns have been raised over chemical exposure and potential health risks such as increased cancer mortality among laboratory workers. The aim of this study was to investigate the overall exposure and unit task exposure levels of researchers in organic synthesis laboratories at universities. Methods: Seventy-seven personal Time-weighted average(TWA) samples and 139 task-based samples from four organic synthesis laboratories at two universities were collected over three days. The concentrations of acetone, chloroform, dichloromethane(DCM), diethyl ether, ethyl acetate, n-hexane, tetrahydrofuran(THF), benzene, toluene, and xylene were determined using the GC-FID. Results: The most frequently used chemicals in the laboratories were acetone, DCM, n-hexane, methanol, and THF. Carcinogens such as benzene, chloroform, and DCM were used in one or more laboratories. The TWA full-shift exposures of researchers to acetone was the highest(ND-59.3 ppm). Benzene was observed above the occupational exposure limit in 18-40% of the samples. The levels of exposure to organic solvents were statistically different by task(p<0.05), while washing task was the highest. Washing was not perceived as a part of the real lab tasks. Rather it was considered as simple dish-washing or experimental preparation and performed in an open sink where exposure to organic solvents was unavoidable. TWAs and task-based concentrations were compared by substance, which suggests that TWA-based assessment could not reflect short-term and high concentration exposures. Conclusions: Laboratory workers may be exposed to various organic solvents at levels of concern. TWA-based measurement alone cannot guarantee holistic exposure assessment among lab workers as their exposures are very dependent on their tasks. Further investigation and characterization for specific tasks and overall chronic exposures will help protect lab workers from unnecessary exposure to chemicals while they perform research.

• Applied Chemistry for Engineering
• /
• v.31 no.6
• /
• pp.630-634
• /
• 2020

We developed a processing recipe to synthesize flexible polyurethane foam with a pore size of 335 ± 107 ㎛. The gelling reaction time was varied from 0 to 30 minutes and the physical properties of the foam were evaluated. The gelling reaction where the polypropylene glycol and tolylene 2,4-diisocyanate (TDI) were reacted to form urethane prepolymer, proceeded until a chemical blowing agent, deionized water, was introduced. Fourier transform infrared (FT-IR) spectra showed that the composition of the foam did not change but the foam height reached a peak value when the gelling reaction time was 10 minutes. We found that increasing the gelling time lessened the coalescence and helped the formation of cells. Lastly, the repeatability of polyurethane foam was confirmed by one-way analysis of variance (ANOVA) by synthesizing ten identical polyurethane foams under the same experimental conditions, including the gelling reaction time. Overall, the new time parameter in-between the gelling and blowing reactions will give extra stability in manufacturing identical polyurethane foams and can be applied to various polyurethane foam processes.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.2
• /
• pp.644-650
• /
• 2021

This study characterized the reforming of methane with carbon dioxide, which is a major cause of global warming. The methane decomposition reaction with carbon dioxide was carried out using transition metal catalysts. The reactivity of tin was lower than that of a transition metal, such as nickel and iron. Most of the decomposition reaction occurred in the solid state. The melting point of tin is 505.03 K. Tin reacts in a liquid phase at the reaction temperature and has the advantage of separating carbon produced by the decomposition of methane from the liquid tin catalyst. Therefore, deactivation due to the deposition of carbon in the liquid tin can be prevented. Methane decomposition with carbon dioxide produced carbon monoxide and hydrogen. Ni was used to promote the catalyst performance and enhance the activity of the catalyst and lifetime. In this study, catalysts were synthesized using the excess wet impregnation method. The effect of the reaction temperature, space velocity was measured to calculate the activity of catalysts, such as the activation energy and regeneration of catalysts. The carbon-deposited tin catalyst regeneration temperature was 1023 K. The reactivity was improved using a nickel co-catalyst and a water supply.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.12
• /
• pp.63-70
• /
• 2011

Expanded Polystyrene (EPS) is a type of geosynthetic material manufactured with various strengths, unit weights, and dimensions. Due to recent advances in research on EPS, the use of EPS has increased dramatically. This super light weight material has a unit weight of approximately $0.16{\sim}0.47kN/m^3$, equivalent to 6.3~15.7 of that of most natural soils with conditions of fill materials. In spite of this advantage, it is noted that no standard method of resilient modulus test on EPS geofoam was reported and no literature on resilient modulus test methods for EPS geofoam exist. The main object of this study was to investigate feasibility of the resilient modulus of EPS when it was applied for flexible pavement. The investigation of the feasibility was completed based on the results from triaxial tests.