• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.69-74
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• 2000

Applicability of Thermal field flow fractionation (ThFFF) was investigated for the analysis of masticated natural rubber (NR) adhesives produced bya hot melt mastication process. An optimum ThFFF condition for NR analysis was found by using tetrahydrofuran (THF) as a solvent/carrier and a field-programming. Low flowrate (0.3 mL/min) was used to avoid stopping the flow for the sample relaxation. Measured molecular weight distribution was used to monitor degradation of rubber during the mastication process. Rubber samples collected at three different stages of the mastication process and were analyzed by ThFFF. It was found that in an anaerobic process rubber degradation occurs at the resin-mixing (compounding) zone as well as in the initial break-down zone, while in an aerobic process most of degradation occurs at the initial breakdown zone. It was also found that E-beam radiation on NR causes a slight increase in the NR molecular weight due to the formation of a branched structure.

• Bulletin of the Korean Chemical Society
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• v.19 no.8
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• pp.868-874
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• 1998

An equivalent retention has been experimentally observed in thermal field-flow fractionation (ThFFF) for different polymer-solvent systems. It is shown that iso-retention between two sets of polymer-solvent systems can be obtained by adjusting the temperature difference (ΔT) according to the difference in the ratio of ordinary diffusion coefficient to thermal diffusion coefficient. This method uses a compensation of field strength (ΔT) in ThFFF at a fixed condition of cold wall temperature. It is applied for the calculation of molecular weight of polymers based on a calibration run of different standards obtained at an adjusted AT. The polymer standards used in this study are polystyrene (PS), polymethylmethacrylate (PMMA), and polytetrahydrofuran (PTHF). Three carrier solvents, tetrahydrofuran (THF), methylethylketone (MEK) and ethylacetate (ETAc) were employed. Though the accuracy in the calculation of molecular weight is dependent on the difference in the slope of log λ vs. log M which is related to Mark-Houwink constant a, it shows reasonable agreement within about 6% of relative error in molecular weight calculation for the polymer-solvent systems having similar a value.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1165-1168
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• 1998

2-Tetrahydropyranyl methacrylate with a self-crosslinkable moiety was copolymerized with methyl methacrylate and 4-[(2-methacryloxyethyl)methylamino]-4'-nitrostilbene or 4-[(2-methacryloxyethyl)ethylamino]-4'nitroazobenzene to provide second-order nonlinear optical property. Glass transition temperatures (Tg of the copolymers are around 140 ℃. The copolymers were soluble in common organic solvents such as tetrahydrofuran (THF), cyclohexanone, and N,N-dimethylformamide (DMF). Poling was carried out at 140 ℃ for 20 min and identified with UV-Vis spectroscopy. Electro-optic coefficient (r33) of copolymer was 62 pm/V for polymer 2 at 633 nm, and relaxation did not remarkably occur due to the formation of a crosslinked network at 200 ℃ for 15 min.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.437-442
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• 2016

A new route for PBT (Poly butylene terephthalate) production from recycled PET (Poly ethylene terephthalate) has been explored. The route consists of glycolysis of PET (Poly ethylene terephthalate) wastes using 1,4-butandiol into BHBT oligomers and polycondensation of the oligomers into PBT oligomer. This process uses post-consumer or post-industrial recycled PET and converts it into high-end PBT type engineering thermoplastic via a chemical recycling process. Zink acetate was used as a catalyst for both glycolysis and polycondensation. Two types of reactor for the glycolysis, batch and semi-batch reactor, were investigated and their performances were compared. Semi-batch reactor removes ethylene glycol (EG) and THF (tetrahydrofuran) during the reaction. Amounts of EG and THF generated during the glycolysis reaction were measured and used as criteria for the reactor performance. Performance of semi-batch reactor was shown to be better than that of batch reactor. Optimum reaction condition for the semi-batch reactor was BD/PET ratio of 4, and reaction temperature of $220^{\circ}C$, giving high EG yield (max 91%) and low production of THF. In addition, it was confirmed that the molecular weight of PBT oligomer increases in accordance with the progress of the polycondensation reaction.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.78-82
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• 2015

Hollow silica particles were prepared using sodium silicate and organic templates. Polystyrene latex (PSL) particles produced by dispersion polymerization were used as organic templates. PSL particles ranged from $1{\mu}m$ to $3{\mu}m$ in diameter were synthesized by adjusting the amount of 2,2'-azobisisobutyronitrile (AIBN). The PSL/$SiO_2$ core-shell particles were prepared by coating of silica nanoparticles originated from sodium silicate using sol-gel method. The organic templates were removed by the organic solvent, tetrahydrofuran (THF). Morphology of hollow silica particles was investigated with respect to types of the reaction medium and pH during the process. By changing the solvent from ethanol to water, hollow silica particles were successfully formed. Hollow silica particles with the uniform shell thickness were produced at low pH as well. The reflectivity of the as-prepared silica particles was measured in the range of the wavelength of UV and visible light. Hollow silica particles showed much better reflective properties than the commercial light reflector, Insuladd.

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.581-587
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• 2005

In order to obtain a highly purified p-dioxanone (PDX) as monomer of biodegradable polymer, suitable solvent must be selected. The selection was based on the solubility of impurities, and partial layer melt crystallization were carried out under the presence of solvent. The solubility of PDX in various solvents such as ethyl acetate, tetrahydrofuran, acetone, alcohols (methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol) were measured over the temperature range of $-10{\sim}15^{\circ}C$. As solubility parameters, the mixing and dissolution enthalpy between the PDX and the solvents was studied based on empirical equations and the regular solution theory. The solubility and the temperature dependency of the solubility with the solvents of acetone, ethylacetate, and tetrahydrofuran of PDX were shown to have relatively high values compared to the alcohol type solvents. Also, in same alcohols, the smaller molecules and higher polarity gave higher solvency. In partial layer melt crystallization, small amount of ethylacetate selectively dissolved impurities and gave highly purified p-dioxanone, over 99.9% purity.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.694-698
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• 2004

A new method for the simultaneous determination of seven transition metal ions in water and food by microcolumn high-performance liquid chromatography has been developed. The lead, cadmium, mercury, nickel, cobalt, silver and tin ions were pre-column derivatized with tetra-(4-aminophenyl)-porphyrin ($T_4$-APP) to form the colored chelates which were then enriched by solid phase extraction with $C_{18}$ cartridge. The enrichment factor of 50 was achieved by eluted the retained chelates from the cartridge with tetrahydrofuran (THF). The chelates were separated on a ZORBAX Stable Bound microcolumn ($2.0{\times}50\;mm,\;1.8\;{\mu}m$)with methanol-tetrahydrofuran (95 : 5, v/v, containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0) as mobile phase at a flow rate of 0.5 mL/min and detected with a photodiode array detector from 350-600 nm. The seven chelates were separated completely within 2.0 min. The detection limits of lead, cadmium, mercury, nickel, cobalt, silver and tin are 4 ng/L, 3 ng/L, 6 ng/L, 5 ng/L, 5 ng/L, 6 ng/L, 4 ng/L respectively in the original samples. This method was applied to the determination of the seven transition metal in water and food samples with good results.

• Journal of the Korean Wood Science and Technology
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• v.43 no.4
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• pp.518-527
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• 2015

In this study, nanocomposite mats consisting of cellulose nanocrystals (CNCs) and poly(lactic acide) (PLA) were electrospun from a suspension mixture consisting of tetrahydrofuran at room temperature. Morphology study showed that fibers of electrospun composite mats were aligned in three dimensional surface along the fiber long-axis. Average diameter of the electrospun fibers decreased with an increase in the CNC loading level. Tensile strength of the electrospun fibers mat decreased with an increase in the CNC loading level because of bead formation in the formed fibers and low interfacial bond strength between PLA and CNC. Meanwhile, thermal stability of the electrospun nanocomposite mats was effectively improved as the amount of CNC increased.

• Analytical Science and Technology
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• v.7 no.1
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• pp.25-31
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• 1994

As for analytes which did not represent the differences of the selectivity on the stationary and mobile phase, secondary chemical equilibrium theory was applied to study pH effects on the separation of alkylphenols. Mobile phase was consisted of an aqueous sodium carbonate-bicarbonate buffer and acetonitrile. The maximum selectivity for adjacent peak pairs was predicted from those values of $k^{\prime}_{HA}/k^{\prime}_{A-}$ and ${\Delta}pK$. The optimum pH determined by this method was 11.18 pH and solvent selectivity were considered at the same time to invoke the full range of selectivity effects possible for separations. Quaternary mixture composed of methanol, acetonitrile, tetrahydrofuran and water was adjusted to optimum pH 11.18. As the statistical simplex technique of an overlapping resolution map (ORM) was used to predict the optimized solvent system. The optimum solvent, which gives complete separation of alkylphenols, was determined as follws MeOH : ACN : THF = 14.4 : 81.8 : 2.8.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.698-698
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• 2009

화력발전이 많은 비중을 차지하는 전력생산 산업은 온실가스($CO_2$)의 최대 배출 원으로 알려져 있으며 증가하는 전력 수요 뿐 만 아니라 다가오는 기후변화협약에 대응하기 위하여 $CO_2$ 회수 및 공정 개선에 관한 연구가 많이 수행되고 있다. 특히 현재 연구되고 있는 전력분야의 대표적인 $CO_2$ 회수기술은 연소 후 포집(Post-combustion capture), 순산소 연소(Oxy-fuel combustion), 연소전 탈탄소화(Pre-combustion) 3가지로 구분된다. 이중 연소전 탈탄소화 기술은 석탄가스화복합발전(IGCC) 기술과 연계하여 $CO_2$를 회수할 수 있는 방법으로 가스화 된 석탄가스에 Water-Gas Shift 반응과, $CO_2$ 분리로 얻어진 탈 탄소 연료를 통해서 전력을 생산한다. 이 기술의 핵심은 생성된 $CO_2/H_2$ 복합가스로부터 $CO_2$를 분리하는 공정으로 차세대 회수 기술로는 Membrance Reactor, SOFC, Oxygen Ion Transfer Membrane(OTM), 그리고 가스 하이드레이트가 있다. 이중 가스 하이드레이트는 $CO_2$의 회수 뿐 만 아니라 처리 기술에도 적용 가능하지만 우리나라에는 이에 관한 기술이 전무한 형편이다. 본 연구에서는 가스 하이드레이트 형성원리를 이용하여 정온 정압 조건에서 $CO_2/H_2$ 하이드레이트를 제조하였으며 특히, 하이드레이트 형성 촉진제인 THF(Tetrahydrofuran)를 첨가하여 THF 농도에 따른 상평형 및 속도론 실험을 수행 하였다. 이러한 연구는 연소전 탄소화 기술에서의 $CO_2$ 회수 분리에 대한 핵심 연구임과 동시에 탄소배출권 규제에 실질적인 기여를 할 수 있을 것으로 사료된다.