• Tribology and Lubricants
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• 제31권6호
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• pp.258-263
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• 2015

Biodiesel is an environmentally-friendly fuel with low smoke emission because it contains about 10% oxygen. Biodiesel fuel prepared by transesterification of vegetable oil or animal fats is susceptible to auto-oxidation. The rate of auto-oxidation depends on the number of methylene double bonds contained within the fatty acid methyl or ethyl ester groups. Biodiesel may be easily oxidized under several conditions, i.e., upon exposure to sunlight, temperature, oxygen environment. Maintenance of the fuel quality of biodiesel requires the development of technologies to increase the resistance of biodiesel to oxidation. Treatment with antioxidants is a promising approach for extending the shelf-life or storage time of biodiesel. The chemical properties of various amine-based antioxidants were evaluated after synthesis of the antioxidants by condensation of phenylenediamine with alkylamines at room temperature. In general, the oxidative stability can be assessed based on various experimental parameters. Such parameters may include temperature, pressure, and the flow rate of air through the samples. The Rancimat method (EN14112) was selected because it is a rapid technique that requires very little sample and provides good precision for oxidative degradation analysis. Specifically, the EN 14112 technique provides enhanced efficiency for oxidative stability evaluation when a larger ester head group is utilized. Therefore, this technique was employed for evaluation of the oxidation stability of biodiesel by the Rancimat method (EN14112).

• 한국축산식품학회지
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• 제23권1호
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• pp.86-95
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• 2003

비타민 E에 의한 육색소의 산화 안정성 향상 기작을 정리하였다. 지용성 산화제인 $\alpha$-토코페롤이 수용성 단백질인 옥시마이오글로빈을 보호하는 원리가 밝혀지고 있다. 최근의 연구들에서 $\alpha$-토코페롤이 세포막 지방산화의 2차 산화물들의 방출을 지연시켜 옥시마이오글로빈 산화를 억제시키고 식육의 바람직한 육색을 유지시킨다는 증거가 제시되고 있다. 지방산화물의 한 그룹인 $\alpha$,$\beta$-분포화 알데하이드들은 단백질과 서로 결합하는 역할을 하여 옥시마이오글로빈의 산화를 증진시키는 것으로 밝혀졌다. 만약 $\alpha$-토코페롤이 이런 활동적인 알데하이드들의 발생을 지연시킨다면 이런 지방산화물들이 옥시마이오글로빈의 산화에 미치는 영향도 억제될 것이다. 또한$\alpha$-토코페롤은 메트마이오글로빈의 환원에 작용하여 쇠고기의 육색 안정성 유지에 일정부분 역할을 담당하는 것으로 사료된다.

• 한국재료학회지
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• 제15권7호
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• pp.439-443
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• 2005

The oxidation behavior and the thermal stability of nanocrystalline Al-25Ti-8Mn intermetallic compound were investigated. $Al_3Ti$ intermetallic compound, which has a potential for high temperature structural material, was fabricated by mechanical alloying(MA) with $8at.\%$ Mn to enhance the thermal stability and ductility. And Al-25Ti-8Mn intermetallic compound was sintered by spark plasma sintering(SPS) at $700^{\circ}C$. After sintering process, cubic $Ll_2$ structure was maintained without phase transformation and the grain size was about 50nm. To investigate the oxidation behavior of the specimens, thermal gravimetric analysis(TGA) was performed at 700, 800, 900, and $1000^{\circ}C$ for 24 h in $O_2$. As the temperature increased from $700^{\circ}C\;to\;900^{\circ}C$ the weight gain of specimens increased. However at $1000^{\circ}C$, unlike the oxidation behavior of $700^{\circ}C\;to\;900^{\circ}C$, the weight gain of specimen decreased drastically and the transition from linear rate region to parabolic rate region occurred rapidly due to the dense $\alpha-Al_2O_3$.

• KSTLE International Journal
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• 제2권2호
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• pp.120-126
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• 2001

Performance requirements for automatic transmission fluids have been changed reflecting the design changes of automatic transmissions. The major purpose of these design changes is concentrated upon improvements of both fuel economy and drivability. In order to formulate such high performance ATFs as satisfy those requirements, it is necessary to use high quality base oils like VHVI base oils and PAOs. In this study, the effect of base oils characteristics on ATF performance is investigated, mainly regarding differences in frictional characteristics with deterioration. Frictional characteristics are determined using the SAE No. 2 machine and ATFs are deteriorated under various controlled conditions. Moreover low-temperature fluidity, oxidation stability, and seal compatibility are also compared for four different ATFs. From the investigation, it was found that the use of Group III and IV base oils in ATFs gives several benefits with respect to low temperature viscosity, oxidation stability and SAE No.2 friction characteristics.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.579-584
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• 2007

대두유로부터 생산된 바이오디젤과 바이오디젤 혼합 연료유를 대상으로 지방산메틸에스터 함량과 화학적 분석을 통해 산화 특성과 오일의 수명 예측 연구를 수행하였다. 바이오디젤, 경유, BD5, BD20은 산화가 진행될수록 산가(Acid number), 동점도(Kinematic Viscosity) 및 밀도(Density)는 증가하였다. 산가 측정결과의 활용에 의해 임의의 온도조건에서 정확한 사용수명을 예측하기 위하여 화학속도론에 의거하여 각각의 연료에 대한 사용수명식을 도출하였다. 도출된 사용수명식으로부터 바이오디젤이 가장 빠르게 산화가 진행되었고 바이오디젤 혼합량이 증가할수록 사용수명이 단축되는 것을 확인할 수 있었다.

• 한국식품조리과학회지
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• 제5권2호
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• pp.27-34
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• 1989

In the present study, the oxidative stability of Korean evening primrose oil (EPO) stored in various conditions, i.e., dark, cool, fluorescent light and daylight irradiation were investigated. Furthermore difference between the compositional content of gamma-linolenic acid (GLA) of EPO and that of alpha-linolenic acid of soybean oil (SOY) undergoing various modes of oxidation was observed. The results of the present study were as follows: More rapid autoxidative reations of EPO than that of SOY in vairous conditions increased in order of daylight, fluorescent light, cool and dark. Espectially, autoxidative rates of EPO increased rapidly on exposure to daylight and fluorescent light. This probably was due to chlorophyll functioned as a photosensitizer resulting in rapid oxidation of the EPO during irrdadiation of light. However, there was no difference between compositional content of GLA in EPO and alpha-linolenic acid in SOY undergoing various modes of oxidation. Therefore, theripid oxidative rate of EPO could be due to the catalytic effect of the chlorophyll on the photoxidation and the free radical reaction of PUFA.

• Preventive Nutrition and Food Science
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• 제9권1호
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• pp.1-6
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• 2004

Fresh ground beef was mixed with ascorbic acid, basil essential oil, majoram essential oil, or each essential oil combined with ascorbic acid and stored at 1 $\pm$ 1$^{\circ}C$ for 7 days. Color, lipid oxidation (TBARS formation), aerobic bacterial counts and pH were determined. Basil and majoram essential oils were effective in inhibiting color deterioration, lipid oxidation and bacterial growth. The combined addition of basil and ascorbic acid showed the highest protection against color fading, followed by majoram + ascorbic acid, and ascorbic acid alone. Basil and majoram essential oils were most effective in delaying TBARS formation (p < ().01). Ascorbic acid did not exert an antioxidative effect and even exhibited a pro-oxidant effect. The pH values of all samples increased slightly, but no significant differences were observed, either among treatments or throughout the storage time (p > 0.05).

• 신재생에너지
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• 제3권2호
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• pp.17-23
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• 2007

대두유로부터 생산된 바이오디젤과 바이오디젤 혼합 연료유를 대상으로 지방산메틸에스터 함량과 화학적 분석을 통해 산화 특성과 오일의 수명 예측 연구를 수행하였다. 바이오디젤, 경유, BD5, BD20은 산화가 진행될수록 산가(Acid number), 동점도(Kinematic Viscosity) 및 밀도(Density)는 증가하였다. 산가 측정결과의 활용에 의해 임의의 온도조건에서 정확한 사용수명을 예측하기 위하여 화학속도론에 의거하여 각각의 연료에 대한 사용수명식을 도출하였다. 도출된 사용수명식으로부터 바이오디젤이 가장 빠르게 산화가 진행되었고 바이오디젤 혼합량이 증가할수록 사용수명이 단축되는 것을 확인할 수 있었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.191-197
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• 2001

Performance requirements for automatic transmission fluids have been changing to reflect the design changes of automatic transmission. The major purpose for these design changes is to improve fuel economy and drivability. The use of special base oils like API Group III and IV base oils has increased in order to formulate high performance ATF. In this study. the effect of base oils characteristics on ATF performance is investigated, mainly regarding differences in frictional characteristics with deterioration. Moreover, low-temperature fluidity. oxidation stability. and seal compatibility are also compared for four different ATFs. From the investigation, it was found that the use of Group III and IV base oils in ATF has several benefits in low temperature viscosity. oxidation stability and SAE No.2 friction characteristics.

• Bulletin of the Korean Chemical Society
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• 제17권8호
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• pp.715-719
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• 1996

Thin films of polyaniline (PANI) salts were in situ deposited on a Pt plate during either chemical polymerization or electrochemical polymerization. The oxidation states of the salt films were controlled by the applied DC potential. AC impedance of the Pt/PANI electrode were measured in monomer-free 1 N HCl solution in order to investigate the electrodic properties of the films at the following applied DC potentials: 0, 0.45 and 0.75 V vs. SCE. Very small differences in film conductivity according to its oxidation state were observed by analysis of the impedance spectra, the reasons of which are complicated by enriched water content in the film and possible decrease in the film thickness during the measurements. The electrochemical activity of the film/solution interface varied with its oxidation state. Stability of the film in 1 N HCl solution was also evaluated by impedance and cyclic voltammetry measurements.