• 한국전기전자재료학회논문지
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• 제30권11호
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• pp.693-698
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• 2017

In this study, the thermal degradation properties of polyethylene terephthalate film has been examined by the capacitance, Tan ${\delta}$, thermography, FTIR, and SEM results at temperatures of $90{\sim}170^{\circ}C$ and frequencies of 0.3~3,000 kHz. It was found that the capacitance decreased with increasing thermal imaging temperature, probably caused by weakening of chemical bond with increasing temperature. Tan ${\delta}$ decreased upon increasing temperature from $90^{\circ}C$ to $170^{\circ}C$, probably due to the molecular motion of COOH radical or OH radical. The FT-IR measurement reveals that no structural change of the material occurs upon thermal radiation. The SEM measurement shows that the material is stabilized by thermal decomposition with increasing temperature; however, excessive thermal degradation obstructs the stabilization of the material.

• 한국식품영양학회지
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• 제11권6호
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• pp.635-639
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• 1998

The thermal degradation pattern of $\alpha$-, ${\gamma}$-and $\delta$-tocopherols in glycerol was investigated during heating at 100~25$0^{\circ}C$ for 5-60 min in the absence of oxyge. The tocopherols and thermally decomposed products were separated by HPLC with a reversed phase $\mu$-Bondapak C18-column. The degradation pattern of $\alpha$-tocopherol during the heating in the absence of oxygen was different from those of ${\gamma}$-and $\delta$-tocopherols. But the degradation patterns of ${\gamma}$-and $\delta$-tocopherols were similar to each other. The residual content of $\alpha$-tocopherol during the heating in the absence of oxygen decreased to the range 12~65% and those of ${\gamma}$-and $\delta$-tocopherols decreased to the range 4~96%. The thermal degradation of tocopherols in the absence of oxygen was less than that in the presence of oxygen.

• 대한화학회지
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• 제11권2호
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• pp.70-76
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• 1967

Structural changes attending polyacrylonitrile(PAN) upon heating and treating with nucleophilic reagents have been studied for some time and a few authors have studied on the thermal degradation, particularly on the characterization of degradation products in PAN. It is the purpose of this paper to report the kinetic study on the thermal degradation above $250^{\circ}C$ and make some suggestions as to the degradation process and mechanism in PAN. The degradation process in PAN is considered that three reactions are combined in two steps. Random chain scission accompanying the naphthylidine-type ring formation is the first step and the degradation of naphthylidine-type ring occurred as the next step. The reactions in the first step are competitive so that the maximum weight loss on pyrolysis of PAN, under such a condition that the degradation of naphthylidine-type ring is negligible, is depended on the relative reaction rate of these two competitive reactions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.975-976
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• 2007

Thermal and mechanical stresses, caused by repetitive start and stop and load fluctuation during long time operation, on winding stator bars are one of the main causes for electrical degradation of insulating materials. To understand the degradation process, we manufactured bar specimens with the same processes that make generator winding stator bars and the specimens were subjected to various degrees of thermal cycling. Measurements of the insulation properties, such as dissipation factor, tip-up and partial discharge, for un-aged specimens and for specimens aged by thermal cycling at 50, 100, 250, 500 and 1000 thermal cycles were performed. Finally all specimens were tested to obtain electrical breakdown voltages. In this paper we present the data and electrical degradation analysis results obtained during this program.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.321-324
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• 2009

Upgrading of pyrolysis wax oil has been conducted in a continuous fixed bed reactor at $450^{\circ}C$, 1hour, LHSV 3.5/h. The catalytic degradation using HZSM-5 catalyst are compared with the thermal degradation and also was studied with a function of experimental variables. The raw pyrolysis wax oil shows relatively high boiling point distribution ranging from around $300^{\circ}C$ to $550^{\circ}C$, which has considerably higher boiling point distribution than that of commercial diesel. The product characteristic from thermal degradation shows a similar trend with that of raw pyrolysis wax oil. This means the thermal degradation of pyrolysis wax oil at high degradation temperature is not sufficiently occurred. On the other hand, the catalytic degradation using HZSM-5 catalyst relative to the thermal degradation shows the high conversion of pyrolysis wax oil to light hydrocarbons. This liquid product shows high gasoline range fraction as around 90% fraction and considerably high aromatic fraction in liquid product. Also, in the catalytic degradation the experimental variable such as catalyst amount and reaction temperature was studied.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.115-118
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• 2000

In case of developing new motor, many examinations was tested to decide a motor efficiency and reliability. To give reliability judgment, traction motor winding insulation was tested by electrical method after appling electrical, heat, mechanical, environmental stress. In this study, stator form-wound winding of traction motor in urban transit E.M.U was tested by accelerative thermal degradation test. Stator form-wound winding was tested on the accelerative degradation composed of heat, vibration, moisture, overvoltage and researched insulation resistance, dielectric loss, partial discharge for insulation degradation properties, evaluated withstand voltage. Degradation temperature was $230[^\circ{C}]$, $250[^\circ{C}]$, $270[^\circ{C}]$, for stator form-wound winding respectively. On the test results of accelerative thermal degradation, insulation properties were relied all temperature until 10 times and expected life was evaluated by the rule of reducing $10[^\circ{C}]$ life into halves. Expected life was 31.8 years. It is guaranteed insulation reliability because of exceeding 25 years life times as considering.

• KIEAE Journal
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• 제15권6호
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• pp.11-18
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• 2015

Purpose: The current study analyzed trends in thermal insulation performance with aging, and condensation characteristics caused by the former. Method: Thermal insulation and condensation prevention performance of an architecture were assessed using Temperature Difference Ration Inside, or TDRi. Subjects of this quantitative analysis in thermal insulation performance change due to aging included recently constructed apartments and aged apartments older than 40 years. Time series comparison and analysis were conducted to observed changes in the thermal insulation performance and condensation characteristics. Result: Analysis showed that wall insulation performance degraded with aging regardless of fortified insulating material usage or insulating material type, which caused increased danger of condensation. In addition, when fortified insulating material was installed on the connection between the walls, insulation performance degradation was lower compared to cases in which fortified materials were not used. In all cases from 1 to 10, the rate of thermal insulation performance degradation increased after 20 years of aging.

• Journal of the Korean Wood Science and Technology
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• 제42권6호
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• pp.682-690
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• 2014

본 연구에서는 WPC의 열안정성을 향상시키기 위해 폴리프로펠렌 매트릭스에 목분과 폴리인산염(ammonium polyphosphate, APP)의 삼종혼합 후, 목분과 난연제 첨가에 따른 목재플라스틱 복합재(wood plastic composites, WPC)의 열분해 거동이 조사되었다. 모든 배합비의 WPC 열분해 거동은 질소의 환경에서 분당 $10^{\circ}C$ 상승속도로 제어하여 열중량분석기(Thermogravimetric analyzer)를 통해 분석하였다. 목분의 열분해온도가 PP의 열분해온도 보다 낮기 때문에 목분에 의해 생성된 char막은 PP로의 열전달 속도를 낮추며, 2차 열분해온도 증가 및 열분해속도를 늦춘다. APP를 첨가한 WPC의 경우 1차 열분해온도 감소 및 2차 열분해온도의 증가를 보여준다. 목분의 함량이 높은 WPC의 경우, APP 첨가 시 1차 열분해온도 감소 및 2차 열분해속도가 증가하였고, 고온에서 잔여물의 양은 APP 함량이 증가할수록 크게 증가하였다. APP가 첨가된 WPC 경우, 목분의 함량이 10 wt%에서 50 wt%로 증가 시 고온에서 잔여물 양이 증가하였는데, 이는 APP 및 목질섬유의 char화가 동시에 발생되기 때문으로 보이며 결과적으로 목분 함량이 증가할수록 APP의 효과가 높게 나타나 열안정 효과를 관찰할 수 있었다.

• 한국태양에너지학회 논문집
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• 제35권4호
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• pp.9-15
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• 2015

Black cobalt solar selective coatings were prepared by using an electroplating method. The changes in the optical properties of the black cobalt selective coating due to thermal degradation were analyzed by using the Auger electron spectroscopy (AES) and spectrophotometer. The black cobalt selective coating was prepared on a copper substrate by using a synthesized electrolyte with $CoCl_2$ and KSCN at a current density of ${\sim}0.5A/dm^2$ for 45s ~ 60s. Its optical properties were a solar absorptance (${\alpha}$) of the order of 0.80 ~ 0.84 and a thermal emittance (${\epsilon}$) of 0.01. From the AES depth profile analysis of heated sample, thermal degradation of the black cobalt selective coating heated for 33 hours at temperature of $350^{\circ}C$ occurred primarily due to interdiffusion at interface of cobalt and copper substrate. This results were predictable that the ${\alpha}$ decreases due to the thermal oxidation and diffusion.

• 대한기계학회논문집A
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• 제30권12호
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• pp.1526-1533
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• 2006

The aim of this research was to confirm the existence of the thermal creep degradation by hydrides of Zr-2.5Nb pressure tube materials. Small punch creep tests were performed to obtain the relationship between a creep displacement and a loading period at $300^{\circ}C$. A creep stress and a creep strain rate were also converted from the previous results. The creep material constants and the creep stress exponents at the different hydride contents were compared. Finally the hydrides of the axial and circumferential section were observed using OM, SEM and TEM. The following conclusions were made: 1) The degradation of the thermal creep by hydrides was existed and it strongly depended on the hydride contents. 2) As the hydride contents were increased, the creep stress exponents (m) were also increased. 3) Even though the hydride was not precipitated in 50 ppm materials at $300^{\circ}C$, the degradation of thermal creep was found. Therefore, it was believed that this phenomenon strongly related to the hydride precipitation at room temperature.