• Composites Research
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• 제37권1호
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• pp.1-6
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• 2024

합성한 Diglycidyl ether of 4,4'-dihydroxy-α-methylstilbene (DGE-DHMS)에 1-Methyl Imidazole을 2:1의 비율로 첨가하여 새로운 액정 에폭시 올리고머인 DDA를 합성하여 열안정성을 평가하였다. TGA분석을 통해 얻어진 결과로 볼 때 액정상과 isotropic상에서 열안정성의 차이는 관찰되지 않았고, Flynn-Wall-Ozawa method와 Kissinger method를 이용하여 계산한 열분해 활성화 에너지값의 비교 결과 열분해가 진행되는 동안 일정한 메커니즘이 작용함을 확인할 수 있었다.

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권2호
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• pp.48-54
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• 2003

To evaluate the radiation degradation of ethylene propylene rubber (EPR), radiation effects on EPR were investigated by using dielectric analysis and thermal-gravimetric analysis. Permittivity, loss factor, tan$\delta$, and thermal decomposition temperature were observed for ${\gamma}$-ray irradiated EPR. As the radiation dose was increased, the peak temperature of the loss factor and tans of EPR were increased and loss factor and tan$\delta$ at peak temperature were decreased. Activation energies were calculated using loss factor and thermal decomposition for ${\gamma}$-ray irradiated EPR as well. The trends of both calculated activation energies showed the same tendencies as radiation dose was increased.

• 한국안전학회지
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• 제17권2호
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• pp.39-44
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• 2002

This study was investigated the thermal decomposition characteristics of azo type sponge blowing agent azodicarbonamide(ADCA) using differential scanning calorimeter(DSC). The experimental results showed that the exothermic onset $temperatures(T_{o})$ for ADCA were about $201{\sim}206^{\circ}C$ and evolution heats(Q) were about $144{\sim}150cal/g$. The exothermic onset $temperatures(T_{o})$, exothermic maximum $temperature(T_{m})$ and exothermic final $temperature(T_{f})$ were decreased by decreasing particle size of ADCA and evolution heats(Q) were increased with it. $T_{o}$ and Q for $6.1{\sim}7.2{\mu}m$ ADCA were increased by increasing heating rate at constant sample weight and activation energy was about 37.29kcal/mol. A positive gas pressure was employed in the elucidation of the decomposition behavior of ADCA because it sublimes during linear heating at atmospheric pressure. $T_{o}$ and Q of ADCA tended to increase with a pressure in air or nitrogen. In the case of azo dye, experimental results showed that $T_{o}$ were about $280{\sim}420^{\circ}C$ and Q were about $2{\sim}30cal/g$.

• 공업화학
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• 제23권3호
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• pp.352-357
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• 2012

1,3,5-trinitro-1,3,5-triazacylohexane (RDX)와 octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)의 입자크기에 대한 열적 특성을 알아보기 위해서 DSC (Differential Scanning Calorimetry)와 TGA (Thermo-Gravimetric Analysis)를 사용하였다. 활성화 에너지와 빈도인자는 Kissinger 방법과 Vyazovkin 방법으로 계산하였다. DSC를 이용할 경우 RDX의 경우에는 고에너지 분자화약의 높은 분해열에 의하여 입자크기에 따른 활성화에너지의 경향성이 없었으나, TGA를 이용할 경우 입자크기가 클수록 활성화에너지가 커짐을 알 수 있었다. 그러나 HMX의 경우에는 DSC와 TGA의 방법 모두 입자 크기에 따라 활성화 에너지가 커지는 경향성을 보였다. 또한, Vyazovkin 방법을 이용하여 RDX와 HMX의 분해정도에 따른 활성화 에너지의 변화로 분해반응의 메커니즘을 이해할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2483-2488
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• 2012

The X-ray line broadening technique was used to calculate the grain size of MgO at 1023, 1123, 1223 K respectively either in $CO_2$ or during the thermal decomposition of magnesites in air as well as in vacuum. By referring to the conventional grain growth equation, $D^n=kt$, the activation energy and pre-exponential factor for the process in air are gained as 125.8 kJ/mol and $1.56{\times}10^8\;nm^4/s$, respectively. Ranman spectroscopy was employed to study the surface structure of MgO obtained during calcination of magnesite, by which the mechanism of grain growth was analyzed and discussed. It is suggested that a kind of highly reactive MgO is produced during the thermal decomposition of magnesites, which is exactly the reason why the activation energy of the grain growth during the thermal decomposition of magnesite is lower than that of bulk diffusion or surface diffusion.

• 한국가스학회지
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• 제26권5호
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• pp.41-48
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• 2022

2-Chloro-N-(Cyano-2-thienyl methyl) acetamide(CCTA)는 농약을 합성하는데 사용하는 중간체로써 상온 및 상압에서는 안정하지만 열축적 시 분해될 수 있다. 본 연구에서는 열중량분석기(TGA) 실험을 통해 온도에 따른 질량 변화 측정으로 분해거동을 확인하고, 시차주사열량계(DSC)를 이용하여 열분해특성을 평가하였다. CCTA는 약 91℃에서 발열 분해반응이 급격하게 발생하였으며, Kissinger method, Kissinger-Akahira- Sunose(KAS) method, Flynn-Wall-Ozawa(FWO) method를 이용한 활성화 에너지 계산 결과, 각각 162 kJ/mol, 140 kJ/mol, 139 kJ/mol 으로 나타났다. 활성화에너지를 이용하여 계산된 24시간 이내 최대발열속도에 도달하는 온도인 T_D24는 52~55 ℃로 평가되었다.

• 한국안전학회지
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• 제21권6호
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• pp.38-45
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• 2006

Polymeric floorings mainly consisted of PVC are easily decomposed by many kinds of hot environmental factors, then generate hazardous asphyxiate gases and/or toxic gases etc. Therefore the mechanism of decomposition and quantitative toxic indices of products are very important for preventing safety and health disasters, especially in case of confined area. So we have investigated decomposition kinetics, numbers of process involved, toxicity indices of product and so on, using DSC, TGA, FT-IR and Pyrolyzer-GC/MS. The thermal decomposition process of polymeric floorings can be mainly divided by dehydrochlorinated reaction and polyene decomposition step, and activation energies of those are approximately $53.93{\sim}62.42kcal/mol$. Especially lethal concentration($LC_{50}$), fractional effective dose (FED) are calculated by measuring the amount of decomposition product. The values on $LC_{50}$ of sample G are ranged $2,003{\sim}2,019(mg/m^{3})$ in case of sample K and H are $1,877,\;1,998(g/m^{3})$ respectively. Even if the results are estimated by calculation method without animal test and/or clinical demonstration, these values could be very useful data for occupational health, hygiene and safety control.

• 에너지공학
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• 제21권4호
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• pp.373-377
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• 2012

Among the fossil fuels, the brown coal is a great deal of resources. However, it is hardly used due to the high moisture content and low calorific value. It has both the week points such as spontaneous combustion and high volatile content and the strong points such as the low-sulfur and low ash content. If we overcome these week points, the using amount of brown coal would be increased. Also, it is well known that biomass is one of the important primary renewable energy sources because of carbon neutral energy. Furthermore, the utilization of biomass has been more and more concerned with the depletion of fossil fuel sources as well as the global warming issues. Combustion and thermal decomposition of biomass is one of the more promising techniques among all alternatives proposed for the production of energy from biomass. In this study, combustion of brown coals and mushroom waste was done. Mass change of samples and emission of hydrocarbon components were measured. As the results, we obtained combustion rate constant. Also activation energy was calculated in char combustion step. Hydrocarbon components were more generated in low oxygen concentration than high. Emission amount of hydrocarbon components in mushroom waste was significantly increased comparing to brown coal.

• Macromolecular Research
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• 제12권5호
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• pp.490-492
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• 2004

We report a new method using a heating medium for the thermal decomposition of epoxy resin (EP) at temperatures ranging from 50 to 200$^{\circ}C$. EP decomposition also occurred below 50$^{\circ}C$ during a 6-day period to generate bisphenol A (BPA) at concentrations as high as 5 ppm. When polyethylene glycol was used as a heating medium, we determined the kinetics of the EP decomposition at low temperature. We determined the apparent activation energy of the overall decomposition to be 40.8 kJ/mol and the frequency factor to be 2.3${\times}$10$^3$ by monitoring the rate of BPA formation. Thus, EP is clearly unstable upon the application of heat.

• Composites Research
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• 제35권2호
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• pp.53-60
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• 2022

본 연구에서 액정성 에폭시인 Diglycidyl ether of terephthalylidene-bis-(4-amino-3-methylphenol) (DGETAM)을 사용해 경화제로는 아민계 경화제인 4,4'-diaminodiphenylethane (DDE)와 양이온 개시제인 N-benzylpyrazinium hexafluoroantimonate (BPH)를 사용하여 필름의 형태로 샘플을 제작하였다. 합성의 확인을 위하여 ¹H-NMR과 FT-IR을 사용하였고, DSC와 POM을 이용하여 DGETAM의 액정성을 확인하고, LFA를 사용하여 샘플의 열전도도를 측정하였다. 활성화 에너지는 TGA를 사용하여 등온 열분해를 진행해 측정한 데이터를 토대로 Arrhenius 식을 사용하여 구하였다. 에폭시 필름의 열전도도를 측정한 결과 DDE를 사용하였을 때, 더 높은 열전도도를 나타내었고, 5% 분해시 BPH를 사용한 필름과 유사한 활성화 에너지를 나타내는 것으로 보아, 열전도도가 열적 안정성에 영향을 미치는 것을 확인할 수 있었다.