• Polymer(Korea)
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• v.25 no.1
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• pp.33-40
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• 2001

Fluorinated polyurethane elastomers were synthesized by two step polyaddition of a perfluorinated polyether diol(trade name of Fomblin $ZDOL^{\circledR}$) and diisocyanates such as 4,4'-diphenyl methane diisocyanate(MDI) and toluene 2,4-diisocyanate(TDI). In order to control the Fomblin moiety of the soft segment in the synthesized elastomers to 10~50%, polyether type polyols such as polypropylene glycol(PPG) and polytetramethylene glycol(PTMG) were mixed during the polymerization reaction. Ethylene diamine or 1,4-butane diol was used as chain extenders. The structure and average molecular weight of the produced polyurethanes were confirmed by using FT-IR, $^1H-NMR$, DSC, and GPC. The surface properties were analyzed by using X-ray photoelectron spectroscopy(XPS) and contact angle meter. From the results of the surface analysis it was concluded that the fluorine groups were localized on the surface rather than the inside of the polyurethane films.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.843-849
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• 2007

Monitoring of NOM characteristics is important for improving removal efficiency of natural organic matter (NOM) in water treatment processes. In this study, several NOM characteristics, which include specific UV absorbance (SUVA), total carbonate content, molecular weight distribution, and fluorescence properties, were measured using samples collected from a pilot-scale water treatment plant consisting of coagulation/flocculation (C/F), filtration, ozonation and granular activated carbon (GAC) processes. The highest removal of NOM was observed in C/F and filtration processes as demonstrated by the reduction of dissolved organic carbon (DOC) by 25% and 21%, respectively. Despite nearly no change in DOC, however, the lowest SUVA value and the highest total carbohydrate content were observed in the sample from ozonation process. This indicates that non-degradable aromatic compounds become depleted and biodegradable organic compounds are enriched during the process. Comparison of synchronous fluorescence spectra of the samples showed that ozoation process increased protein-like fluorescence while it decreased fulvic-like and terrestrial humic-like fluorescence. Consistently, a slight peak of protein-like fluorescence was observed in the sample from ozonation process. The greatest change in molecular weight distributions of the samples was observed in C/F process. Comparison of size exclusion chromatogram of the samples revealed that NOM fractions with the molecular weight greater than 2000 Da were reduced by over 90% after C/F process. SUVA values and total carbohydrate content of the samples were well correlated with a ratio of protein-like fluorescence and terrestrial humic-like fluorescence intensities with the correlation coefficients of 0.99 and 0.91, respectively. This suggests that synchronous fluorescence properties of NOM could be used as useful tolls for monitoring changes of some NOM characteristics during water treatment processes.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.12-15
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• 2006

The purpose of this study was to investigate the effect of reaction conditions, solvents, and surfactants on the average size and size distribution of silica particles in preparing silica fine powders by sodium silicate. Silica fine particles were synthesized by varying kinds of solvents and surfactants using the emulsion method. Span 20, Span 40, Span 60, and Span 80 were used as nonionic surfactants, Dispersing solvents were n-Hexane, n-Heptane, iso-Octane, and n-Decane of the alkane group. In these experiments, it was known that the optimum dispersion stirring time to form the emulsion of the constant size was around 6 min. The mean sizes of silica particles, at a variety of the dispersion stirring speeds, decreased as the dispersion stirring speed increased. Also, in the case of the solvents, the size of the formed silica particles decreased when the molecular weight of the solvent increased. Lastly, in the case of the surfactants, the mean size of silica particles increased as the hydrophobic lipophilic balance (HLB) value of the surfactant decreased.

• Polymer(Korea)
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• v.30 no.5
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• pp.437-444
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• 2006

Reactive hydroxypropyl methylcellulose phthalate (reactive HPMCP) was synthesized by using a stepwise urethane reaction with isophorone diisocyanate (IPDI) and 2-hydroxyethyl moth acrylate (HEMA). Molecular weight, acid number, and critical micelle concentration (CMC) of the synthesized reactive HPMCP and pristine HPMCP were measured and used as a polymeric surfactant in the emulsion polymerizations of styrene. In the preparation of HPMCP-hybrid poly styrene nanoparticles, 6, 9, 12, 18, and 24 wt% of HPMCPs were introduced, and the maximum rate of polymerization ($R_{p,max}$), the average number of radicals per particle (n), particle size distribution were investigated. In addition, core - shell morphology of the nanoparticles were observed by using TEM and their thermal stabilities were measured by using TGA. Reactive HPMCP showed higher $R_{p,max}$, smaller particle size, larger values of n and gel contents as compared with pristine HPMCP, due to the vinyl groups from HEMA, which can be reacted with styrene oligomers, in the reactive HPMCP.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.655-655
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• 2013

그래핀은 높은 전자 이동도, 열전도도, 기계적 강도, 유연성 등의 고유한 특성으로 다양한 분야에 응용하기 위한 연구가 수행되고 있으며, 특히 전자 소자에의 적용에 관한 연구가 활발히 이루어지고 있다. 전자 소자에 적용하기 위해서는 성장 및 물성에 관한 규명, 응용 소자에 따른 특성 평가가 필요하다. 이러한 소자 특성은 그래핀 물성에 의한 영향이 기본적이지만 에칭, 전사 등의 공정 중 발생하는 오염, 표면 특성, 잔여물 등에 의한 물성 변화 또한 분석 및 제어에 관한 연구가 필요하다. 열화학증착법(thermal chemical vapor deposition)을 이용한 그래핀 합성은 구리 기판을 사용하며, 합성된 그래핀의 에칭, 박리 및 전사 공정이 있다. 이러한 공정 중 발생하는 오염 입자가 그래핀 표면에 흡착되거나, 제거되지 않은 PMMA 잔여물이 그래핀의 특성에 영향을 미치게 된다. 따라서 본 연구에서는 $CO_2$ 클러스터의 표면 충돌을 이용하여 이러한 오염 물질 및 잔여물을 제거하고 그래핀 표면을 평탄화하는 것에 관한 연구를 수행하였다. 가스 클러스터란 작동기체의 분자가 수십에서 수백 개 뭉쳐 있는 형태를 뜻하며 이렇게 형성된 클러스터는 수 nm 크기를 형성하게 된다. 그리고 짧은 시간의 응축에 의해 수십 nm 크기 까지 성장 하게 된다. 클러스터를 이용한 표면 처리는 충돌에 의한 제거에 기반 한다. 따라서 생성 및 가속되는 클러스터로부터 대상으로 전달되는 운동량의 정도가 세정 특성에 영향을 미치며 이는 생성되는 클러스터의 크기에 종속적이다. 생성 클러스터의 크기 분포는 분사거리, 유량, 분사 각도, 노즐 냉각 온도 등의 변수에 관한 함수이다. 본 연구에서는 이러한 변수들을 제어하여 클러스터를 이용한 그래핀 표면 처리 실험을 수행하였다. 평가는 클러스터 표면 처리 전과 후의 특성 비교에 기반 하였으며, 광학 현미경을 이용한 표면 형상 측정, 라만분광 분석, AFM을 이용한 표면 조도 측정, 그래핀 면저항 측정 결과를 비교하였다. 평가 결과를 통하여 표면 처리를 하지 않은 그래핀에 비하여 면저항과 표면 조도가 낮아지는 것을 확인 할 수 있었다. 또한 클러스터 세정은 300 mm 웨이퍼 크기 이상의 대면적을 짧은 시간에 건식으로 세정할 수 있다는 장점이 있어 향후 최적화를 통해 그래핀 양산 시 특성 향상을 위한 후처리 방법으로 사용될 수 있음을 확인하였다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.4
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• pp.187-192
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• 2007

To prepare oligouronic acids from high-molecular-weight alginates prepared from sea tangle (Laminaria japonica), the alginates were hydrolyzed at various temperatures for 1 hr at pH 5.0. The effects of hydrolysis temperature $(H_{Temp})$ on the average molecular weight (AMW) and distribution ratio of MW (DR) in the hydrolyzed alginates were investigated. As $(H_{Temp})$ increased, the AMW of the alginates decreased exponentially; in addition the DR of the alginates with MW>500 kDa decreased exponentially, while the DR of those with MW=50-100 and MW<50 kDa increased exponentially. For the alginates with MW=300-500 and MW=100-300 kDa the DR increased exponentially until $H_{Temp}$ reached $80^{\circ}C$, and then decreased exponentially at above $80^{\circ}C$. AS $H_{Temp}$ increased, the MW cutoff size and AMW Of the alginates fraction With the highest DR both decreased. For $H_{Temp}<60^{\circ}C$, the MW cutoff size with the highest DR was MW>500 kDa; the DR was 39-67% and the AMW 1,000-1,300 kDa. For $H_{Temp}$ $80^{\circ}C$, the MW cutoff size with the highest DR was MW=300-500 kDa and the DR was about 33% and the AMW about 400 kDa. For $H_{Temp}\;100-121^{\circ}C$, the MW cutoff size with the highest DRs was MW=50-100 kDa, with a DR of 39-44% and an AMW of 70-80 kDa.

• Polymer(Korea)
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• v.37 no.1
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• pp.74-79
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• 2013

Polyvinylidene fluoride (PVDF) and its copolymer with hexafluoropropylene (HFP) were successfully prepared from free radical solution polymerizations using diisopropyl peroxidicarbonate (DIPPDC) in the presence of 1,1,2-trichlorotrifluoroethane (R-113). The reactivity ratios of VDF and HFP were estimated as$r_{VDF}=2.06{\pm}0.03$ and $r_{HFP}{\approx}0$. This result indicates that HFP cannot undergo self propagation. The weight-average molecular weight and molecular weight distribution of copolymers were found to decrease with increasing HFP content. The melting temperature of copolymers linearly decreased with the increase of HFP content because of the introduction of HFP. Moreover, no melting peak was observed for the copolymers with high HFP content. The glass transition temperature of copolymers gradually increased with the increase of HFP content due to the restricted flexibility of the polymer chains.

• Korean Journal of Food Science and Technology
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• v.31 no.6
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• pp.1488-1494
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• 1999

Effect of ${\gamma}-irradiation$ on the SDS-PAGE pattern, secondary structure content, the solubility of commercial soy protein isolate (SPI) and whey protein concentrate (WPC) was investigated. The change in the subunit molecular weight of SPI and WPC irradiated in aqueous solution or dried state was studied using SDS-PAGE. The SDS-PAGE pattern of SPI irradiated in aqueous solution revealed the fragmentation and aggregation of the subunit protein. For WPC irradiated in aqueous solution. fragmentation of the subunit protein up to 10 kGy was observed. In contrast, ${\gamma}-irradiation$ of SPI and WPC in dried state did not cause any significant changes in the SDS-PAGE pattern. The change In the secondary structure of irradiated SPI and WPC solution was studied using circular dichroism. The aperiodic structure content of SPI and WPC solution increased at higher irradiation doses, which suggests that ${\gamma}-irradiation$ caused the disruption of the ordered structure of SPI and WPC solution. Gamma-irradiation also caused the change in solubility of SPI and WPC in dried state.

• Journal of Adhesion and Interface
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• v.1 no.1
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• pp.15-22
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• 2000

To prepare acrylic type pressure-sensitive adhesive, quarter polymers were synthesized from butylacrylate (BA), 2-ethylhexylacrylate (2-EHA), methyl methacrylate (MMA), 2-hydroxyethylmethacrylate (2-HEMA). The quarter polymer was identified by FT-IR. Molecular weight was measured by Gel Pearmeation Chromatograhy. Also, viscosity, solid content and peel strength were investigated. The peel strength was $160g_f/25mm$ when the volume ratio of feed monomer to solvent was 1.3:1 and the ratio was relevant to commercial usage. The pot life of adhesive was 30 s at the 50 m/min of heat treatment rate, and it indicated that the minimum drying time was 30 s. Not only weathering resistance keep up peel strength $160{\sim}180g_f/25mm$ after 1000 h, but also no residual remains.

• Journal of the Korea Organic Resources Recycling Association
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• v.29 no.4
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• pp.107-114
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• 2021

This study applied with pre-treatment combined with thermal hydrolysis and seperation for disintegration of sludge. As results of particle size distribution D10, D50 and D90 of thermal hydrolyzed and centrifuged sludge was 8.6, 59.2 and 425.1 ㎛, which are lower than those of thermal hydrolyzed. The molecular weight distribution results showed that the thermal hydrolyzed sludge showed the highest proportion in the 10-100kDa range. But, Sludge, treated with combined pre-treatment, showed the highest proportion <1kDa range. Results of DOC and UVA₂₅₄ found that the organic matters of hydrolyzed sludge composed high molecular weight component above 10kDa. While, the organic matters of sludge, treated by combined pre-treatment, composed relarively low molecular weight below 1kDa. The specific methane yield of hydrolyzed and centrifuged sludge was higher 1.7 times than that of only hydrolyzed sludge.