• Macromolecular Research
• /
• 제16권6호
• /
• pp.549-554
• /
• 2008

Proton conducting crosslinked membranes were prepared using polymer blends of polystyrene-b-poly(hydroxyethyl acrylate)-b-poly(styrene sulfonic acid) (PS-b-PHEA-b-PSSA) and poly(vinyl alcohol) (PVA). PS-b-PHEA-b-PSSA triblock copolymer at 28:21:51 wt% was synthesized sequentially using atom transfer radical polymerization (ATRP). FT-IR spectroscopy showed that after thermal ($120^{\circ}C$, 2 h) and chemical (sulfosuccinic acid, SA) treatments of the membranes, the middle PHEA block of the triblock copolymer was crosslinked with PVA through an esterification reaction between the -OH group of the membrane and the -COOH group of SA. The ion exchange capacity (IEC) decreased from 1.56 to 0.61 meq/g with increasing amount of PVA. Therefore, the proton conductivity at room temperature decreased from 0.044 to 0.018 S/cm. However, the introduction of PVA resulted in a decrease in water uptake from 87.0 to 44.3%, providing good mechanical properties applicable to the membrane electrode assembly (MEA) of fuel cells. Transmission electron microscopy (TEM) showed that the membrane was microphase-separated with a nanometer range with good connectivity of the $SO_3H$ ionic aggregates. The power density of a single $H_2/O_2$ fuel cell system using the membrane with 50 wt% PVA was $230\;mW/cm^2$ at $70^{\circ}C$ with a relative humidity of 100%. Thermogravimetric analysis (TGA) also showed a decrease in the thermal stability of the membranes with increasing PVA concentration.

• Tribology and Lubricants
• /
• 제32권3호
• /
• pp.95-100
• /
• 2016

As an alternative fuel, biodiesel has excellent lubricating property. Previously, our research group reported that the properties of biodiesels depended on their composed molecular structure. In this study, we investigate lubricity and the mechanism of lubricity improvement of synthesized biodiesel molecules. We synthesize four types of biodiesel components from fatty acid via fisher esterification and soybean biodiesel from soybean oil via transesterification in high yield (92-96%). We analyze the lubricity of the five 5 types of biodiesel using HFRR (high frequency reciprocating rig). We estimate that the mechanism of lubricity is relevant to the molecular structure and structure conversion of biodiesel. The test results indicate that the longer the length of molecules and the higher the content of olefin, the better the lubricity of the biodiesel molecules. However, the wear scar size of the first test samples’ do not show a regular pattern with the wear scar size of the second test samples’. Moreover, we investigated the structure conversion of the biodiesels by using GC-MS for the recovered biodiesel samples from the HFRR test. However, we do not detect structure conversion. Thus, we conclude that the lubricity of biodiesel depends on how effectively solid adsorption and boundary lubrication occurs based on the size of the molecule and the content of olefin in the molecule. In addition, HFRR test condition in not sufficient for Diels-Alder cyclization of biodiesel components.

• Tribology and Lubricants
• /
• 제31권6호
• /
• pp.251-257
• /
• 2015

Heavy oil production is receiving significant attention because of increased demands for thermal power generation systems of the diesel engine and boilers. However, asphaltene, which is a heavy oil components (6-8 wt%), reduces the heat efficiency of the fuels owing to its agglomerated sludge of asphaltene during the burning process. Therefore, for hassle-free operation, we should develop asphaltene dispersants to suppress the formation of the sludge. We prepare variable salt-type polymeric dispersants using poly(isobutenyl succinic anhydride) and poly(amine) through both condensation esterification and acid-base neutralization reactions, which we subsequently evaluate for dispersing performance, using Turbiscan measurement. Total acid number (TAN) and total base number (TBN) of 75Lec-25SynDis.2 composed of lecithin and the prepared polymeric salt having the ratio of 3 : 1 are 18.9 and 33.7 mg KOH/g, respectively, which are comparable to those of the commercial dispersants (15.8 and 26.5 mg KOH/g). We determine the initial turbidity observed for 15 min of the polymeric dispersant was determined with transmittance (%), which can be calculated to separability number (SN). The SN value of 75Lec-25SynDis.2 is close to zero, which is superior to that of commercial dispersants and lecithin (0.015 and 0.017).

• 폴리머
• /
• 제35권6호
• /
• pp.526-530
• /
• 2011

바이오매스에서 유래된 2,5-dihydroxymethylfuran(DHMF)을 $KMnO_4$ 산화반응으로 furan-2,5-dicarboxylic acid(FDCA)를 합성하였다. 합성한 FDCA와 다이올류를 에스테르화 반응과 축중합 반응을 진행시켜 폴리에스터를 중합하였다. 폴리에스터는 NMR을 통해 조성을 분석하였고 DSC와 TGA를 통해 열적특성을 분석하였다. 합성된 폴리에스터의 고유점도는 0.78~1.2 dL/g으로 상용화된 poly(ethylene terephthalate)(PET)와 비슷하였다. 다이올의 길이가 증가할수록 Young's modulus와 strength는 낮아지고 elongation-to-break는 높아지는 경향을 확인하였다. 합성한 poly(ethylene furandicarboxylate)(PEF)의 Young's modulus는 3551 MPa, strength는 103 MPa로 상용화된 PET와 비슷하였다.

• 한국응용과학기술학회지
• /
• 제35권4호
• /
• pp.1048-1056
• /
• 2018

비식용 원료인 Palm Acid Oil, 동물성 폐유지 등은 상대적으로 자유 지방산 함량이 높기 때문에 일반적인 염기 촉매를 이용한 전이에스테르화 반응에 적합하지 않다. 효소 촉매를 이용하면 염기 촉매에서 해결할 수 없는 몇 가지 문제를 해결할 수 있으며, 에너지 소비가 작고, 바이오디젤 부산물인 글리세롤 회수가 쉬우며, 자유 지방산 함량이 높은 트리글리세라이드에 대한 전이에스테르화 반응이 가능하다. 본 연구에서는 고정화 효소 촉매를 이용하여 1 ton/day 용량의 반응기에서 비식용 폐유지를 바이오디젤로 합성하였으며, 반응 공정의 변수를 최적화하였다.

• 한국미생물·생명공학회지
• /
• 제48권4호
• /
• pp.491-505
• /
• 2020

A newly isolated strain, Proteus vulgaris OR34, from olive mill waste was found to secrete an alkaline extracellular lipase at 11 U·ml-1 when cultivated on an optimized liquid medium. This lipase was purified 94.64-fold with a total yield of 9.11% and its maximal specific activity was shown to be 3232.58 and 1777.92 U·mg-1 when evaluated using the pH-stat technique at 55℃ and pH 9 and Tributyrin TC4 or olive oil as the substrate. The molecular mass of the pure OR34 lipase was estimated to be around 31 kDa, as revealed by SDS-PAGE and its substrate specificity was investigated using a variety of triglycerides. This assay revealed that OR34 lipase preferred short and medium chain fatty acids. In addition, this lipase was stable in the presence of high concentrations of bile salt (NaDC) and calcium ions appear not to be necessary for its activity. This lipase was inhibited by THL (Orlistat) which confirmed its identity as a serine enzyme. In addition, the immobilization of OR34 lipase by adsorption onto calcium carbonate increased its stability at higher temperatures and within a larger pH range. The immobilized lipase exhibited a high tolerance to organic solvents and retained 60% of its activity after 10 months of storage at 4℃. Finally, the OR34 lipase was applied in biodiesel synthesis via oleic acid mediated esterification of methanol when using hexane as solvent. The best conversion yield (67%) was obtained at 12 h and 40℃ using the immobilized enzyme and this enzyme could be reused for six cycles with the same efficiency.

• 공업화학
• /
• 제22권2호
• /
• pp.230-234
• /
• 2011

반도체산업은 고집적화된 회로를 요구하면서 미세 패턴을 형성하기 위해 계속해서 발전해가고 있다. 이에 반도체 산업에서 미세 패턴을 형성하기 위하여 하드마스크를 도입하여 사용되고 있다. 일반적으로 하드마스크는 화학증기증착법(CVD) 공정을 이용하여 다층구조로 제작된다. 이에 본 연구에서는 스핀공정이 가능하고 단층의 하드마스크용 조성물을 제조하기 위하여 유-무기 하이브리드 중합체를 이용하여 그 특성에 대하여 연구하였다. Silanol로 처리된 siloxane 화합물과 acetonide 그룹을 가지는 propionic acid를 에스터화 반응을 통하여 얻은 유-무기 하이브리드 중합체에 가교제 및 첨가제들의 첨가로 광학적, 열적, 그리고 표면 특성이 조절된 하드마스크 막을 제조하였다. 또한 하드마스크 막과 감광층의 식각비를 비교하여 유-무기 소재의 하이브리드 중합체에 대해 미세패턴을 형성시킬 수 있는 하드마스크 막으로써의 유용성을 확인하였다.

• 공업화학
• /
• 제22권1호
• /
• pp.72-76
• /
• 2011

본 연구에서는 폐커피가루를 이용하여 커피유를 추출한 후 커피유를 이용한 바이오디젤의 제조특성을 고찰하였다. 커피유의 바이오디젤 제조의 변수로는 메탄올/커피유 반응몰비(6~18), 반응온도($45{\sim}60^{\circ}C$) 등을 선정하여 커피유의 바이오디젤 제조 시 최적조건을 결정하고자 하였다. 제조된 바이오디젤의 성능은 바이오디젤 수율, methyl ester 함량, 점도, 발열량 등을 측정하여 평가하였다. 평가결과 바이오디젤 수율 및 methyl ester 함량을 고려한 최적 반응온도는 $55^{\circ}C$이었으며, 메탄올/커피유 몰비가 12일 경우 가장 우수한 바이오디젤을 제조할 수 있었다. 커피유를 이용하여 제조된 바이오디젤의 발열량을 측정한 결과 39.0~39.4 MJ/kg으로 바이오디젤 기준인 39.3~39.8 MJ/kg을 만족하였다.

• Nutrition Research and Practice
• /
• 제15권4호
• /
• pp.431-443
• /
• 2021

BACKGROUND/OBJECTIVES: Nobiletin (NOB), a citrus flavonoid, is reported to have beneficial effects on cardiovascular and metabolic health. However, there is limited research investigating the effect of long-term supplementation with low-dose NOB on high-cholesterol diet (HCD)-induced hypercholesterolemia and non-obese nonalcoholic fatty liver disease (NAFLD). Therefore, we investigated the influence of NOB on hypercholesterolemia and NAFLD in HCD-fed mice. SUBJECTS/METHODS: C57BL/6J mice were fed a normal diet (ND) or HCD (35 kcal% fat, 1.25% cholesterol, 0.5% cholic acid) with or without NOB (0.02%) for 20 weeks. RESULTS: HCD feeding markedly reduced the final body weight compared to ND feeding, with no apparent energy intake differences. NOB supplementation suppressed HCD-induced weight loss without altering energy intake. Moreover, NOB significantly decreased the total cholesterol (TC) levels and the low-density lipoprotein (LDL)/very-LDL-cholesterol to TC ratio, and increased the high-density lipoprotein-cholesterol/TC ratio in plasma, compared to those for HCD feeding alone. The plasma levels of inflammatory and atherosclerosis markers (C-reactive protein, oxidized LDL, interleukin [IL]-1β, IL-6, and plasminogen activator inhibitor-1) were significantly lower, whereas those of anti-atherogenic adiponectin and paraoxonase were higher in the NOB-supplemented group than in the HCD control group. Furthermore, NOB significantly decreased liver weight, hepatic cholesterol and triglyceride contents, and lipid droplet accumulation by inhibiting messenger RNA expression of hepatic genes and activity levels of cholesterol synthesis-, esterification-, and fatty acid synthesis-associated enzymes, concomitantly enhancing fatty acid oxidation-related gene expression and enzyme activities. Dietary NOB supplementation may protect against hypercholesterolemia and NAFLD via regulation of hepatic lipid metabolism in HCD-fed mice; these effects are associated with the amelioration of inflammation and reductions in the levels of atherosclerosis-associated cardiovascular markers. CONCLUSIONS: The present study suggests that NOB may serve as a potential therapeutic agent for the treatment of HCD-induced hypercholesterolemia and NAFLD.

• Composites Research
• /
• 제35권6호
• /
• pp.412-418
• /
• 2022

메타크릴산과의 에스터화 반응을 통해 브롬화 에폭시 수지와 일반 에폭시 수지의 혼합물로부터 난연성 비닐에스터 핫멜트 필름을 제조하였고 이를 이용하여 탄소섬유와 비닐에스터 복합 프리프레그를 제조하였다. 저점도 비스페놀-A와 고점도 브롬화 비스페놀-A 에폭시 전구체를 혼합하여 필름 생산에 적합한 VE 수지의 점도를 최적화하였다. 경화된 VE 수지의 브롬 함량 증가는 비 브롬화 VE에 비해 제한 산소 지수(LOI)(39%), 25℃에서의 저장 탄성률(2.4 GPa) 및 잔류 탄화물(16.1%) 값을 더 증가시켰다. 합성한 VE 프리프레그의 수동 레이업과 후속 경화로 인장 및 굴곡 강도가 우수한 CF 강화 복합재를 성공적으로 제작하였다. 본 연구 결과는 스티렌이 없는 친환경적인 VE 복합 재료 공정의 향후 산업화에 대한 높은 가능성을 보여준다.