• 폴리머
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• 제32권1호
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• pp.13-18
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• 2008

전기 전자재료 중 고분자에 포함된 브롬계 난연제의 분석에 있어 용출이 어려운 4가지 재질 PC(polycar-bonate) PP(polypropylene), PET(poly(ethylene terephthalate)), PBT(poly(butylene terephthalate))에 대하여 추출방법 및 헥산/에세톤, THF, 톨루엔, THF/톨루엔에 대한 용매 특이성과 그 특성을 고찰하였다. 각 고분자에서의 deca-BDE(decabromo diphenyl ether)의 함량을 속슬렛, 초음파. 가속용매, 마이크로파, 초임계 유체 추출법을 사용하여 이들 방법의 효율을 정량분석 하였다. 초음파 추출은 낮은 고분자의 용해도 때문에 낮은 추출효율을 보여 사용한 고분자의 경우에 있어서 추출방법으로는 적합하지 않았으며, 나머지 3가지 방법에서는 톨루엔 사용시 약 80% 이상의 높은 추출효율을 보였다. 초임계 유체 추출은 고분자의 난연제 추출에 시도되지 않았던 방법이었으나, 본 실험에서 PP와 PC의 추출에서는 100%에 가까운 매우 높은 추출효율을 보였다.

• 대한환경공학회지
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• 제32권10호
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• pp.973-978
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• 2010

에너지절감에 대한 인식이 높아짐에 따라 점차 건물이 밀폐화되고 있으며, 이로 인하여 실내공기질에 영향을 미치는 건축자재로부터의 휘발성유기화합물 방출에 대한 관심이 높아지고 있다. 그러므로 실내공기질을 개선하는데 있어 건축자재로부터의 VOCs 방출특성을 파악하는 것이 무엇보다 중요하다. 본 연구에서는 우리나라가 온돌문화인 점을 고려하여 대표적인 건축자재인 온돌마루와 접착제를 대상으로, 방출챔버시험을 통하여 온도 및 시간경과에 따른 헥산, 톨루엔 및 TVOCs 방출특성을 살펴보았다. VOCs의 방출속도는 온도와 비례관계를 나타내었으며, 바닥재에 존재하는 VOCs 발생원이 어느 위치에, 어떠한 형태로 존재하느냐가 시간의 경과에 따른 방출특성에 크게 영향을 미친다는 것을 알 수 있었다. 즉, 건축자재로부터의 헥산, 톨루엔의 방출은 전반적으로 초기에 방출속도가 높고 시간이 지남에 따라 점차 줄어드는 경향을 보이고 있으나, 온돌마루로부터의 톨루엔 방출은 다른 양상을 보이는데 시간이 지남에 따라 방출속도가 오히려 증가하여 6시간 경과 후 최대값을 보인 뒤 점차 감소하는 경향을 나타내었다. 이는 온돌마루에 함유되어 있는 톨루엔 발생원이 자재의 내부에 많이 존재하고 있기 때문에 시간이 경과함에 따라 방출속도가 증가했다가 다시 감소하는 경향을 보인 것으로 추정된다. 바닥재로부터의 VOCs 방출특성 실험결과를 종합하여 살펴보면, 온돌시스템에서 방출되는 고농도의 VOCs에 인체노출을 줄이기 위해서는 이사하기 전에 적어도 72시간 이상의 Bake-out 시간이 필요할 것이라 사료된다.

• Journal of Photoscience
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• 제11권1호
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• pp.11-17
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• 2004

Fluorescence quenching of l,4-bis [2-(2-methylphenyl) ethenyl]-benzene (Bis-MSB) by carbon tetrachloride in five different solvents namely hexane, cyclohexane, toluene, benzene and dioxane has been carried out at room temperature with a view to understand the quenching mechanisms. The Stern-Volmer plot has been found to be non-linear with a positive deviation for all the solvents studied. In order to interpret these results we have invoked the Ground state complex and Sphere of action static quenching models. Using these models various rate parameters have been determined. The magnitudes of these parameters imply that sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation in the Stem-Volmer plots is attributed to the static and dynamic quenching. Further, with the use of Finite Sink approximation model, it was possible to check whether these bimolecular reactions as diffusion limited and to estimate independently distance parameter R' and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R'and D with the values of the encounter distance R and the mutual diffusion coefficient D determined using the Edwardis empirical relation and Stokes-Einstein relation.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.143-144
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• 2002

A series of alcohols with perfluorinated segments $F(CF_2)_m(CH_2)_n-OH$, with m=8, 10 and n=4, 6, 10, were synthesized. First, the alcohols were reacted with fatty acid to produce several esters $(F(CF_2)_m(CH_2)-OOC-R$ with m=8, 10 and n=2, 4, 8,) containing perfluoro group by condensation reaction, and characterized by FT-IR, GC, and surface tension. The esters were soluble in ethyl ether, toluene, hexane, ethyl acetate, chloroform, and acetone, but insoluble in methyl alcohol, ethyl alcohol and isopropyl alcohol. Preliminary experiments on 1,2-dichloroethane solutions showed a remarkable decrease of surface tension upon addition of the esters. Also, the esters films ranged from 100 to $122^{\circ}$, depending on the structure of fatty acid esters. As the separate experiment, the water-repellency of coated paper and cotton was evaluated. As a result, the water droplet dropped in surface was not permeated for two weeks.

• Journal of Microbiology and Biotechnology
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• 제21권1호
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• pp.20-27
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• 2011

The purification and characterization of a $Mn^{2+}$-dependent alkaline serine protease produced by Bacillus pumilus TMS55 were investigated. The enzyme was purified in three steps: concentrating the crude enzyme using ammonium sulfate precipitation, followed by gel filtration and cation-exchange chromatography. The purified protease had a molecular mass of approximately 35 kDa, was highly active over a broad pH range of 7.0 to 12.0, and remained stable over a pH range of 7.5 to 11.5. The optimum temperature for the enzyme activity was found to be $60^{\circ}C$. PMSF and AEBSF (1 mM) significantly inhibited the protease activity, indicating that the protease is a serine protease. $Mn^{2+}$ ions enhanced the activity and stability of the enzyme. In addition, the purified protease remained stable with oxidants ($H_2O_2$, 2%) and organic solvents (25%), such as benzene, hexane, and toluene. Therefore, these characteristics of the protease and its dehairing ability indicate its potential for a wide range of commercial applications.

• Korean Chemical Engineering Research
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• 제55권5호
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• pp.668-678
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• 2017

Intermolecular interactions were studied for binary mixtures of 2-propanol + cyclohexane, n-hexane, benzene, toluene, o-, m- and p-xylenes by measuring ultrasonic speeds (u) over the entire range of composition at 298.15 K and 308.15 K. From these results the deviation in ultrasonic speed was calculated. These results were fitted to the Redlich-Kister equation to derive the binary coefficients along with standard deviations between the experimental and calculated data. Acoustic parameters such as excess isentropic compressibility ($K_s^E$), intermolecular free length ($L_f$) and available volume ($V_a$) were also derived from ultrasonic speed data and Jacobson's free length theory. The ultrasonic speed data were correlated by Nomoto's relation, Van Dael's mixing relation, impedance dependence relation, and Schaaff's collision factor theory. Van Dael's relation gives the best prediction of u in the binary mixtures containing aliphatic hydrocarbons. The ultrasonic speed data and isentropic compressibility were further analyzed in terms of Jacobson's free length theory.

• 한국환경과학회지
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• 제23권9호
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• pp.1593-1600
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• 2014

Adsorption and desorption characteristics of the representative 10 kinds components consisting of gasoline vapor on activated carbon were investigated at the temperature range of $-30^{\circ}C{\sim}25^{\circ}C$. The breakthrough curves of each vapors obtained by the Thomas model were well described the breakthrough experimental results of this study. The breakthrough times of each vapors were correlated with the molecular weight, density, and vapor pressure. The breakthrough times had greater correlation with boiling point than molecular weight and density. The slope of the breakthrough curve was a proportional relationship with the rate constant (k) of Thomas model expression. The higher the slope of the breakthrough curve, the rate constant was larger. The biggest slope vapor had the smallest adsorption capacity ($q_e$). Adsorption and desorption characteristics of mixed vapor similar to the gasoline vapor were studied at room temperature ($25^{\circ}C$). The mixed vapor consisting of 9 components; group A (pentane, hexene, hexane), group B (benzene, toluene), group C (octane, ethylbenzene, xylene, nonane) was examined. Group A was not nearly adsorbed because of substitution by group C, and the desorption capacity of group A was smaller than group C. The adsorbed substances were confirmed to be Group C.

• Asian Journal of Atmospheric Environment
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• 제4권2호
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• pp.63-71
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• 2010

The removal characteristics for aromatic and aliphatic VOCs by electron beam (EB) were discussed in terms of several removal variables such as initial VOC concentration, absorbed dose, background gas, moisture content, reactor material and inlet temperature. It was reviewed that only reactor material was an independent variable among the potential control factors concerned. It was also suggested that main mechanism by EB should be radical reaction for the VOC removal rather than that by primary electrons. It was discussed that the removal efficiency of benzene was lower than that of hexane due to a closed benzene ring. In the case of aromatic VOCs, it was observed that the decomposition of the VOCs with more functional groups attached on the benzene ring was much easier than those with less ones. As for aliphatic VOCs, it was also implied that the longer carbon chain was, the higher the removal efficiency became. An EB-catalyst hybrid system was discussed as an alternative way to remove VOCs more effectively than EB-only system due to much less by-products. This hybrid included supporting materials such as cordierite, Y-zeolite, and $\gamma$-alumina.

• 통합자연과학논문집
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• 제3권3호
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• pp.168-173
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• 2010

Novel porous silicon chip exhibiting dual optical properties, both Frbry-Perot fringe (optical reflectivity) and photoluminescence had been developed and used as chemical sensors. Porous silicon samples were prepared by an electrochemical etch of p-type sillicon wafer (boron-doped, <100> orientation, resistivity 1 - 10 ${\Omega}$). The ething solution was prepared by adding an equal volume of pure ethanol to an aqueous solution of HF (48% by weight). The porous silicon was illuminated with a 300 W tungsten lamp for the duration of etch. Ething was carried out as a two-electrode Kithley 2420 preocedure at an anodic current. The surface of porous silicon was characterized by FT-IR instrument. The porosity of samples was about 80%. Three different types of porous silicon, fresh porous silicon (Si-H termianated), oxidized porous silicon (Si-OH terminated), and surface-derivatized porous silicon (Si-R terminated), were prepared by the thermal oxidation and hydrosilylation. Then the samples were exposed to the wapor of various organics vapors. such as chloroform, hexane, methanol, benzene, isopropanol, and toluene. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organic wapors.

• Preventive Nutrition and Food Science
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• 제14권3호
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• pp.246-251
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• 2009

The partitioning behavior of five printing ink solvents was studied in cookie ingredients and cookies to examine migration behavior, and to determine if one could predict Kp of a cookie from summing the Kp of each ingredient multiplied by its weight factor in the cookie formula. Solvents were ethyl acetate, hexane, isopropanol, methyl ethyl ketone, and toluene. Gas chromatography was used to measure Kp values on each raw and baked ($260^{\circ}C$ for 10 min) cookie ingredients, and lab-made cookies. The baking process-decreases in water content in each sample generally affected Kp of polar solvents, but did not affect that of the non-polar solvents. Structural changes in cookie ingredients during the baking process also caused some change of migration behavior. While the prediction of Kp of lab-made cookies using the Kp of raw ingredients showed significant differences between calculated and experimentally found values, predictions with baked ingredients showed much smaller differences. This suggests that loss of water and changes of crystallinity in cookies and cookie ingredients due to the baking process are important and affect the Kp.