• Elastomers and Composites
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• 제53권2호
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• pp.39-47
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• 2018

Styrene-butadiene rubber (SBR) is widely used in tire treads due to its excellent abrasion resistance, braking performance, and reasonable cost. Depending on the polymerization method, SBR is classified into solution-polymerized SBR (SSBR) and emulsion-polymerized SBR (ESBR). ESBR is less expensive and environmentally friendlier than SSBR because it uses water as a solvent. A higher molecular weight is also easier to obtain in ESBR, which has advantages in mechanical properties and tire performance. In ESBR polymerization, a surfactant is added to create an emulsion system with a hydrophobic monomer in the water phase. However, some amount of surfactant remains in the ESBR during coagulation, making the polymer chains in micelles clump together. As a result, it is well-known that residual surfactant adversely affects the physical properties of silica-filled ESBR compounds. However, researches about the effect of residual surfactant on the physical properties of ESBR are lacking. Therefore, in this study we compared the effects of remaining surfactant in ESBR on the mechanical properties of silica-filled and carbon black-filled compounds. The crosslinking density and filler-rubber interaction are also analyzed by using the Flory-Rehner theory and Kraus equation. In addition, the effects of surfactant on the mechanical properties and crosslinking density are compared with the effects of TDAE oil (a conventional processing aid).

• Archives of Pharmacal Research
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• 제29권2호
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• pp.159-164
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• 2006

The protective properties of Satureja hortensis L. on the rat lymphocytes DNA lesions were tested. Lymphocytes were isolated from blood samples taken from healthy rats. DNA breaks and resistance to $H_{2}O_{2}$-induced damage were measured with the comet assay. Rat lymphocytes were incubated in S. hortensis ethanolic extract (SHE) (0.05, 0.1, 0.5, 1.0, and 2.5 mg/mL), essential oil (SHEO)(0.05, 0.1, 0.5, 1.0, and 2.5 ${mu}L/mL$), $H_{2}O_{2}$ (50, 100, and 200 ${\mu}M$), a combination of $H_{2}O_{2}$ (200 mM) with either SHE (1.0, 2.5 mg/mL) or SHEO (1.0, 2.5 ${\mu}L/mL$) at $4^{\circ}C$ for 30 min, and the extent of DNA migration was measured using a single-cell microgel electrophoresis technique under alkaline conditions. Treatment of rat lymphocytes with SHE or SHEO resulted in significant reduction of $H_{2}O_{2}$-induced DNA damage compared to controls. SHE exhibited a significant (P<0.01) inhibitory effect on oxidative DNA damage at 2.5 mg/mL. SHEO (1.0 and 2.5 ${\mu}L/mL$) also showed significant inhibitory effects (P<0.01) on $H_{2}O_{2}$ induced chromosomal damage. In conclusion both the ethanolic extract and the essential oil of the plant reversed the oxidative damage to rat lymphocytes induced by hydrogen peroxide.

• 생명과학회지
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• 제21권1호
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• pp.134-140
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• 2011

대전일원의 유류오염 지역의 토양으로부터 원유를 단일 탄소원으로 이용하는 총 145균주를 순수분리 하였고, 이중 생물 계면활성제 생성능이 가장 우수한 한 균주를 최종 선별하여 형태 및 생리 생화학적 특성을 조사하고 16S rRNA 염기서열을 분석을 통하여 동정한 결과 Pseudomonas sp.로 확인되어 Pseudomonas sp. Z1이라 명명하였다. 최종 선별된 Pseudomonas sp. Z1은 클로람페니콜과 암피실린 등의 항생제와 리튬, 망간, 바륨 등의 중금속에 대해 강한 내성을 갖고 있었고, 최적 온도와 pH는 각각 $30^{\circ}C$와 pH 6.0-7.0으로 확인되었다. Pseudomonas sp. Z1이 생성하는 생물 계면활성제는 배양 10시간 이후부터 배양액의 표면장력이 급격히 감소해, 배양 21시간 후에 최대 28 dyne/cm까지 감소되었고, 2% 이상의 NaCl을 첨가한 경우 배양액의 생물계면활성제의 활성이 감소하였다.

• Environmental Engineering Research
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• 제24권2호
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• pp.263-270
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• 2019

Palm oil mill effluent (POME) is the largest pollutant discharged into the rivers of Malaysia. Thus UF membrane study was conducted to investigate the effect of pressure and stirring speed on performance of POME treatment and fouling of membrane. Two types of membrane polyethersulfone (PES) and regenerated cellulose (RC) with molecular weight cut-off (MWCO) 5 and 10 kDa were used in this study. Results showed that, as pressure increased, fouling increased however permeate quality improved, the best pressure was 1.0 bar, where the fouling was not too high and produce good permeate quality. As stirring speed increased, fouling reduced and permeate quality improved, however, when stirring speed increased from 600 rpm to 800 rpm, there was no significant improvement on the permeate quality. Therefore, the best condition was at 1.0 bar and 600 rpm. PES membrane with MWCO 5 kDa showed the best permeate quality, even fouling slightly higher than RC membrane. The permeate quality obtained were analyzed in term of dissolved solid, turbidity, suspended solid, biological oxygen demand ($BOD_5$) and chemical oxygen demand (COD) were 538 mg/L, 1.02 NTU, < 25 mg/L, 27.7 mg/L and 62.8 mg/L, respectively with dominant type of fouling is cake resistance. Thus, it can be concluded water reuse standard was successfully achieved in terms of $BOD_5$ and suspended solid.

• 공업화학
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• 제22권2호
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• pp.149-154
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• 2011

연료전지 스택 작동환경에서의 열노화 특성을 살펴보기 위하여 다양한 고무 compound의 내열 및 압축 영구 줄음률의 평가를 실시하고, 스택의 장시간 운전을 통해 접합할 수 있는 대상액인 $H_2SO_4$, $H_2O$, LLC (Ethylene glycol : $H_2O=50:50$)에 대하여 장시간 평가를 실시하였다. NBR과 EPDM은 시간이 경과할수록 침적액의 변색하는 것을 알 수 있었으며, VMQ는 $H_2SO_4$ 분위기에서 시간에 따라 고무가 노화되는 것을 TGA, SEM, EDS 분석을 통하여 확인하였다.

• 대한본초학회지
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• 제39권3호
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• pp.49-56
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• 2024

Objective : Obesity, which has recently been rapidly increasing in the obese population, is caused by an imbalance in energy intake and consumption. The reason why we need to manage obesity well is that the prevalence of complications such as diabetes, atherosclerosis, insulin resistance, and cardiovascular disease increases. In this study, the effect of FO (Fragaria orientalis) water extract on fat metabolism in 3T3-L1 cells was observed to develop a new anti-obesity material based on Mongolian medical books. Methods : The effect of FO extract on adipogenesis in 3T3-L1 cells was observed using DPPH scavenging, pancreatic lipase inhibitory activity, MTT analysis and Oil-red-O staining method. And the expression of proteins related to lipid metabolism was analyzed by Western blot. Results : The FO group significantly increased the DPPH radical scavenging activity at 5 mg/ml compared to the positive control BHA at 0.1 mg/ml. In oil red O staining at a safe concentration without cytotoxicity, lipid accumulation was significantly inhibited by less than 80% compared to the control group at all concentrations. Moreover, treatment of FO significantly increased the expression of proteins related to lipid metabolism, such as p-AMPK and p-ACC, in 3T3-L1 cells, and the expression of CPT-1 tended to increase in a dose-dependent manner. However, the expression of PPAR-γ was significantly decreased in a dose-dependent manner. Conclusion : These results suggest that FO water extract has a potential anti-obesity effect and are expected to be utilized in the development of materials for obesity prevention and treatment.

• 한국해양공학회지
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• 제30권4호
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• pp.334-340
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• 2016

The combustion chamber of a diesel engine is often exposed to a more serious wear and corrosion environment than other parts of the engine because its temperature increases as a result of using heavy oil of low quality. Therefore, repair and built-up welding methods must be performed on worn or corroded parts of the piston crown, exhaust valve, etc. from an economical point of view. In this study, Inconel 718 filler metal was used in repair welding on the groove of a forged steel specimen for a piston crown, along with built-up welding on the surface of another forged steel specimen. Then, the corrosion characteristics of the weld metal zone for the repair welding and the deposited metal zone for the built-up welding were investigated using electrochemical methods in a 35% H₂SO₄ solution. The deposited metal zone indicated better corrosion resistance than the weld metal zone, showing a nobler corrosion potential, higher impedance, and smaller corrosion current density. It is considered that metal elements with good corrosion resistance were generally included in the filler metal, and these elements were also greatly involved in the deposited meta by built-up welding, whereas the weld metal consisted of metal elements mixed with both the filler metal and base metal elements because of the molten pool produced by the repair welding. Finally, it is considered that the hardness of the weld metal was increased by the repair welding, whereas the built-up welding improved the corrosion resistance of the deposited metal.

• 수산해양기술연구
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• 제37권1호
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• pp.65-70
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• 2001

바다모래에 의해 뒷채움된 지하연료저장탱크용 연강재의 부식전류밀도, 개로전위, 전식거동 및 연간부식률에 관하여 연구한 결과 다음과 같은 결론을 얻었다. 1) 습바다모래 중에서 비저항이 감소할수록 개로전위는 비전위화되고, 부식전류밀도는 높게 배류된다. 2) 습바다모래의 비저항이 감소할수록 인가전위 부가에 의한 부식전류밀도는 자연전위에서의 부식전류밀도보다 급격히 증가한다. 3) 습바다모래 중에서 비저항이 감소할수록 연간부식률은 선형적으로 증가함으로 지하연료저장탱크에 바다모래로 뒷채움하는 경우 습기가 유입하면 지하연료저장탱크의 부식성은 민감할 것으로 판단된다.

• 한국미생물·생명공학회지
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• 제35권1호
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• pp.58-65
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• 2007

중금속으로 오염된 토양을 정화하기 위한 rhizoremediation 기법에서 식물이 중금속을 흡수하고 이동시키는 효율을 증가시키기 위하여 토양 미생물 특히, 근권세균의 역할이 중요하다. 이를 위하여 본 연구에서는 정유공장 주변의 유류 및 중금속으로 장기간 오염된 토양에서 서식하는 4가지 식물의 근권토양으로부터 Methylobacterium sp. SY-NiR1 균주를 분리하였다. 분리한 Methylobacterium sp. SY-NiR1는 분홍색 콜로니 형성, 막대모양 및 $\alpha-proteobacteria$에 속하는 특성으로 보아 pink-pigmented facultative methylotroph인 것으로 사료된다. 이 균주는 식물성호르몬인 indole acetic acid(IAA) 생산능을 가지고 있으며, 카드뮴, 크롬, 구리, 납, 니켈 그리고 아연 등과 같은 다양한 중금속에 대하여 내성을 가지고 있었으며, $EC_{50}$을 기준으로 한 SY-NiR1의 중금속에 대한 내성은 Zn > Ni > Cu > Pb > Cd > Cr 순이다. 따라서 본 연구에서 분리한 Methylobacterium sp. SY-NiR1 균주는 중금속으로 오염된 토양에서 식물의 발아, 생장 및 발달을 도와 식물의 중금속 흡수를 증가시켜 rhizorememdiation 효율을 증가시킬 수 있을 것으로 기대된다.

• Elastomers and Composites
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• 제47권1호
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• pp.75-81
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• 2012

주단량체로 에틸 아크릴레이트, 부틸 아크릴레이트, 메톡시에틸 아크릴레이트, 가교 단량체로 글리시딜 메타아크릴레이트를 유화중합하여 아크릴고무를 제조한 후, 가교제로써 2,2-bis[4-(4-aminophenoxy)phenyl]propane를 첨가하여 고무컴파운드를 제조하였다. 주단량체의 조성에서 에틸 아크릴레이트의 함량이 증가하면 내열성이 증가하는 경향을 보였는데 이는 아크릴고무의 유리전이온도가 감소되었기 때문이다. 또한 에틸 아크릴레이트의 에스테르 그룹 농도가 3개의 주단량체 중 가장 높기 때문에 에틸 아크릴레이트 함량이 증가할수록 내유성이 향상되었다. 2,2-Bis[4-(4-aminophenoxy)phenyl]propane의 함유량에 따른 영향은 2 phr 첨가까지 인장강도와 신장율은 증가하지만, 그 이상의 첨가에서는 가교밀도의 증가에 따른 점성과 탄성이 감소하여 그 값들이 감소하였다.