• 폴리머
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• 제29권1호
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• pp.59-63
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• 2005

FTIR을 이용하여 폴리(카프로락톤 다이올)과 지방족 이소시아네이트간의 반응속도에 관한 연구를 수행하였다. NCO 피크(2265 $cm^{-1}$)의 흡광도 변화를 통하여 반응속도를 해석하였다. 그 결과, 폴리(카프로락톤 다이올)과 이소시아네이트간의 반응은 전체적으로 단순 2차 반응속도법과 일치함이 확인되었고, 반응온도의 증가에 따라 속도 상수는 증가하였다. 반응속도 상수로부터 구한 활성화에너지는 hexamethylene diisocyanate의 경우 25.4~30.9 kJ/mol, cyclohexylmethane diisocyanate의 경우 16.8~22.1 kJ/mol로 각각 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제25권3호
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• pp.83-95
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• 1997

The degradation mode of lignocellulose by anaerobic ruminal cellulolytic bacterium Ruminococcus albus F-40 was investigated. Birchwood holocellulose and filter paper were incubated as the sole carbohydrate sources with using the Hungate techniques. After 2 or 4 days of incubation, samples were employed for chemical and electron microscopic evaluations. The degradation rate of cellulosic substrates and the adhesion rate of bacteria to the substrates increased proportionally with the decrease of relative crystallinity of cellulose, indicating the preferential breakdown of amorphous cellulose, by this bacterium. X-ray diffraction analyses and polarized light microscopy showed, however, that crystalline cellulose was also degraded by R. albus. FT-IR spectra indicated that not only cellulose but hemicellulose was also degraded by this bacterium. Electron microscopic investigations showed the protuberant structures on the surface of R. albus. These structures were much more significant when bacterial cells were grown in the media containing insoluble substrates, such as cellulose, indicating clearly that bacterial protuberant structures were induced by the substrates. Protuberant structures extended from the bacterial cells adhered tightly to the substrates and numerous vesicles covered the surface of cellulosic substrates affected. Cellulosome-like structures were distributed on the cellulose matrix. Electron microscopic works showed that diverse surface organells of R. albus were involved in the degradation of cellulosic materials. SEM examinations showed the breakdown of cellulose by R. albus was proceeded by severeal routes : short fiber formation, defibrillation and destrafication of cellulose microfibril.

• 한국산업보건학회지
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• 제6권2호
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• pp.202-208
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• 1996

The purposes of this study are the identification and determination of metabolites in the isolated rat liver perfusate of carbon disulfide by two-dimentional thin-layer chromatography and high performance liquid chromatography for understanding the metabolism of carbon disulfide. 2-Thio-thiazolidine-4-carboxylic acid(TTCA) was synthesized by the reaction of carbon disulfide and cysteine, and confirmed by two-dimentional thin-layer chromatography, high performance liquid chromatography, UV spectroscopy, and IR spectroscopy. The absorbance of UV detector for the simultaneous determination of TTCA and thiocarbamide was 254 nm although their maximum spectra were 273 nm and 237 nm, respectively. Two kinds of the developing solvent in the two-dimentional thin-layer chromatography were 2-butanol : 80% HCOOH : $H_2O$ (7 : 2 : 1) as the first developing solvent and 2-propanol : $H_2O$ (4 : 1) as the second developing solvent. After perfusion of carbon disulfide ($8274.23{\mu}mol$), the amount of TTCA and thiocabamide of the perfusate(100 ul) were $12.02-16.4{\mu}mol$ and $5.25-8.15{\mu}g$, respectively. The mean amount of them were $14.08{\mu}mol$ and $6.41{\mu}mol$ respectively, and the former was 2.20 times greater than the latter. For conforming the mechanism of formations of TTCA and thiocarbamide in vivo, we have to clarify whether the reactions between carbon disulfide and ammonia, ammonium salts, amides, cysteine, cystine, or proteins will be formed in vitro.

• Restorative Dentistry and Endodontics
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• 제21권2호
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• pp.642-651
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• 1996

The purpose of this study was to evaluate the relationship between monomer compositions and the changes in the degree of conversion in the various layers of composites after additional heat curing. Four types of composites and 3 types of inlay ovens were used in this study. Composite was placed in a 4-mm thick teflon mold, and light cured from the top for 60 seconds. Ten samples were prepared for each composite ; 5 of these were additionally heat cured in an inlay oven as the manufacturer recommended. After light curing or light and heat curing, the samples were sectioned into four parts and assigned to groups A, B, C, or D according to their distance from the light source. These sections were then thinned to 50-$70{\mu}m$, and these wafers were analyzed with a Fourier Transform Infrared Spectrometer(FI-IR) to determine the degree of conversion. A standard baseline technique was used to calculate the degree of conversion. $^{13}C$ NMR spectra of bis-GMA, TEGDMA and bis-EMA, were acquired using a Varian Gemini spectrometer operated at 200 MHz. $CDCl_3$ solvent was used for qualitative analysis. The degree of conversion was affected by bis-GMA : TEGDMA ratio but it seemed to be also affected by other factors. When the composites were heat cured, significant increases in the degree of conversion were noted throughout the samples, but the amount of increase differed between materials. Thus, clinical performance of a heat-treated composite inlay may be different depending on materials.

• Journal of Radiation Protection and Research
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• 제3권1호
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• pp.23-28
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• 1978

유기석계(有機錫系) 안정제(安定劑)를 포함하고 있는 polyvinylchloride (PVC)의 내방사성(耐放射性)은 가소제(可塑劑)로서 첨가된 dioctylphthalate(DOP)의 양의 증가와 더부러 증가하며 이와 같은 내방사성(耐放射性)의 평가는 시료의 IR 특성 상에서 안정제의 해이(解離)에 기인(起因)하고 있는 $1,540{\sim}1,640cm^{-1}$에서의 흡수대가 선량과 더부러 변화하는 거동으로 살필 수 있다. 가소화된 PVC에서의 내방사성의 증가는 DOP 분자구조의 일부를 형성하는 benzen 환(環)에서 방사 에너지가 공명흡수 되기 때문이라 사료(思料)되며 이와 같은 견해(見解)는 방사선량에 대한 도전율변화특성(導電率變化特性)의 고찰 결과와도 잘 일치 한다. 실용적면(實用的面)에서 $0{\sim}100Mrad$ 사이의 선량에 대한 충분(充分)한 내방사성(耐放射性)을 얻기 위하여는 30phr 전후의 DOP 첨가량이 필요하다.

• Membrane and Water Treatment
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• 제9권2호
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• pp.95-104
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• 2018

Copper pollution around the world has caused serious public health problems recently. The heavy metal adsorption on traditional membranes from wastewater is limited by material properties. Different adsorptive materials are embedded in the membrane matrix and act as the adsorbent for the heavy metal. The carbonized leaf powder has been proven as an effective adsorbent material in removing aqueous Cu(II) because of its relative high specific surface area and inherent beneficial groups such as amine, carboxyl and phosphate after carbonization process. Factors affecting the adsorption of Cu(II) include: adsorbent dosage, initial Cu(II) concentration, solution pH, temperature and duration. The kinetics data fit well with the pseudo-first order kinetics and the pseudo-second order kinetics model. The thermodynamic behavior reveals the endothermic and spontaneous nature of the adsorption. The adsorption isotherm curve fits Sips model well, and the adsorption capacity was determined at 61.77 mg/g. Based on D-R model, the adsorption was predominated by the form of physical adsorption under lower temperatures, while the increased temperature motivated the form of chemical adsorption such as ion-exchange reaction. According to the analysis towards the mechanism, the chemical adsorption process occurs mainly among amine, carbonate, phosphate and copper ions or other surface adsorption. This hypothesis is confirmed by FT-IR test and XRD spectra as well as the predicted parameters calculated based on D-R model.

• 방사선산업학회지
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• 제6권1호
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• pp.55-59
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• 2012

Polyacrylonitrile (PAN)-based carbon fibers have been widely used due to their unique chemical, electrical, and mechanical properties. Electron beam irradiation has been extensively employed as means of altering properties of polymeric materials. Electron beam irradiation can induce chemical reactions in materials without any catalyst. Electron beam irradiation may be useful in accelerating the thermal compression stabilization of PAN nanofibers. To investigate the irradiation effect on PAN fibers, PAN nanofibers were irradiated by electron beam at 1,000~5,000 kGy. Irradiated and non-irradiated PAN nanofibers were heated at 180 and $220^{\circ}C$ without applying pressure for 15 min. Then 1 metric ton has been applied for 5 min. SEM images have been found that the fiber kept its morphological behavior after the hot pressing up to electron beam irradiated 1,000 kGy. DSC thermograms showed that the peak temperatures of the exothermic reactions were found to decrease with increasing electron beam irradiation doses and temperature. FT-IR spectra have been found to decrease $C{\equiv}N$ stretch band with increasing the electron beam irradiation dose. These results indicate that the modification of PAN via reactions such as cyclization is significantly enhanced by electron beam irradiation and thermal compression technique.

• International Journal of Oral Biology
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• 제46권3호
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• pp.105-110
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• 2021

The physicochemical properties of crystalline titanium dioxide nanoparticles (TiO₂ NPs) were investigated by comparing amorphous (amTiO₂), anatase (aTiO₂), metaphase of anatase-rutile (arTiO₂), and rutile (rTiO₂) NPs, which were prepared at various calcination temperatures (100℃, 400℃, 600℃, and 900℃). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed that the phase-transformed TiO₂ had the characteristic features of crystallinity and average size. The surface chemical properties of the crystalline phases were different in the spectral analysis. As anatase transformed to the rutile phase, the band of the hydroxyl group at 3,600-3,100 cm^-1 decreased gradually, as assessed using Fourier transform infrared spectroscopy (FT-IR). For ultraviolet-visible (UV-Vis) spectra, the maximum absorbance of anatase TiO₂ NPs at 309 nm was blue-shifted to 290 nm at the rutile phase with reduced absorbance. Under the electric field of capillary electrophoresis (CE), TiO₂ NPs in anatase migrated and detected as a broaden peak, whereas the rutile NPs did not. In addition, anatase showed the highest photocatalytic activity in an UV-irradiated dye degradation assay in the following order: aTiO₂ > arTiO₂ > rTiO₂. Overall, the phases of TiO₂ NPs showed characteristic physicochemical properties regarding size, surface chemical properties, UV absorbance, CE migration, and photocatalytic activity.

• 산업식품공학
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• 제13권1호
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• pp.24-31
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• 2009

The structural and physicochemical properties of dried aloe vera gel by DIS (dewatering impregnation soaking) process under optimum conditions were investigated. FT-IR spectra for dried samples of DIS aloes showed the typical patterns of standard aloe polysaccharide, and surface structures by SEM (scanning electron microscopy) were similar to a gel-like structure. In case of physicochemical properties of dried aloe samples by DIS process, solubilities and swelling powers of control (not osmotic treated aloe), DIS (S) and DIS (G), samples treated by osmotic solution of 60% sucrose/0.25% NaCl and 50% glucose/0.5% NaCl, were 48.3-57.3% and 8.3-11.7%, respectively, showing no significant differences among samples, but swelling power of DIS (PEG), sample treated by using 50% polyethylene glycol as an osmotic agent was about 5 times higher that of control. Also, water holding capacities of control, DIS (S) and DIS (G) were similar to each other, but that of DIS (PEG) was about 5 times higher that of control. Oil holding capacities of control and DIS aloes maintained the 50.9-86.4% levels of water holding capacities showing no significant differences among samples. Rehydration ratio of DIS (PEG) aloes were significantly dependent on the temperature of rehydrated solvent (water), and rehydration ratio of not-fileted aloe was about two folds higher than that of fileted aloe.

• 한국전기전자재료학회논문지
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• 제32권1호
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• pp.86-92
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• 2019

Although perylene bisimide derivatives have advantages such as excellent thermal stability and high luminance efficiency, they have poor solubility characteristics in organic solvents. In this research, in order to improve the solubility characteristics, we prepared perylene bisimide derivatives (1C) and (2C) with swallow-tail substituted imide, which is known to lead to excellent solubility. The structures and properties of swallow-tail perylene bisimide (1C) and (2C) were analyzed by $^1H-NMR$, FT-IR, UV/Vis spectroscopy, and thermogravimetric analysis (TGA). The maximum absorption wavelengths of (1C) and (2C) in the UV/Vis spectrum were 558 nm and 556 nm, respectively, and the maximum emission wavelengths were 602 nm and 600 nm, respectively. In the TGA, (1C) demonstrated good thermal stability with less than 5 wt% weight loss up to $242^{\circ}C$. In the solubility test, (1C) and (2C) exhibited solubilities of more than 5 wt% in chloroform, ethyl acetate, and dimethylformamide, but not in methanol. When the compounds (1C) and (2C) were mixed with PMMA (polymethyl methacrylate), thin films showed peaks at 679 nm and 677 nm, respectively, in the photoluminescence spectra. (1C) was found to be a possible candidate as red organic phosphor for hybrid LEDs.