• 폴리머
• /
• 제29권1호
• /
• pp.96-101
• /
• 2005

PTFE 및 PFA 등의 불소수지는 최대 연속 사용 온도가 260$^{\circ}C$에 달하는 고온 내열성 고분자 소재로서, 본 연구에서 수행된 280 $^{\circ}C$, 7주 간의 열노화에 의해서도 충분한 열적 안정성이 유지됨을 관측하였다. 그러나 기계적 강도, 융점 및 열분해 개시 온도 등의 소재적 물성이 유지됨을 의미하는 상기한 열적 안정성은 본 연구에서 수행된 코팅막으로서의 표면접촉각, 미세 모폴로지, 내스크래치성 분석에 의한 방법을 기준하면 충분하지 못하다는 것이 확인 되었다. 공기 치환율이 제어되는 기어식 노화시험기로 진행된 불소수지 코팅막의 280 $^{\circ}C$ 열노화에 대한 분석의 결과는 심각한 표면 모폴로지의 손상과 금속기재에 대한 접착력의 손실을 지적하고 있다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2010년도 하계학술대회 논문집
• /
• pp.81-81
• /
• 2010

This paper presents results of experimental investigations on natural ester regarding the breakdown strength. Aging of insulating material in a pole transformer has been studied by performing accelerated thermal aging test. Sealed aging test vessels containing copper, laminated core, Krapt paper and insulating oil(Natural oil and Mineral oil) were aged at $140^{\circ}C$ for 30days. Compared to the conventional transformer oil, electric property of the natural ester fluid is excellent.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제53권6호
• /
• pp.293-299
• /
• 2004

In this paper, thermal and mechanical properties of electric epoxy with water aging were discussed. We made elastic epoxy specimen adding a ratio of 0〔phr〕20〔phr〕, 35〔phr〕 and 53〔phr〕 with modifier to existing epoxy. We studied mechanical property of elastic resin after absorption in water from 0 to 484 hours. As a result, diffusion factor of elastic epoxy showed 20-21${\times}$10$^{-4}$ $\textrm{mm}^2$/s and general epoxy showed 9.5${\times}$10$^{-4}$ $\textrm{mm}^2$/s. Elastic property increased linearly according to addiction and decreased according to water absorption. Tensile strength was reduced according to addition. It was affected by water absorption of micro-void of elastic epoxy. Hardness inclined to decrease after increasing according to absorbed time. In water-absorption state, it was experimented a change of heat flow by temperature of elastic epoxy and change of thermal expansion coefficient. DSC (Differential Scanning Calorimetry) and TMA (Thermomechanical Analysis) equipments were used to measure Tg. A temperature ringe of DSC was from -0($^{\circ}C$) to 200($^{\circ}C$). One of TMA was from -0($^{\circ}C$) to 350($^{\circ}C$). In addition, we investigated structural analysis of water absorbed specimen using SEM (Scanning Electron Microscope).

• Elastomers and Composites
• /
• 제46권2호
• /
• pp.132-137
• /
• 2011

본 연구는 H-NBR 함량 변화에 따른 H-NBR/NBR 블렌드의 열노화 거동에 대하여 살펴보았다. 이 때 가교제로는 dicumyl peroxide와 황 혼합물을 사용하였으며, 열노화에 따른 H-NBR/NBR 블렌드의 인장강도, 파괴신율, 경도 그리고 내마모성의 변화를 살펴보았다. H-NBR을 첨가함에 따라 인장강도는 증가하였으나 내마모성은 감소하는 현상을 나타내었다. 파괴신율과 경도는 H-NBR의 영향을 받지 않았다. 노화가 진행된 모든 시편은 초기 시편보다 낮은 인장강도, 파괴신율, 경도를 나타내었다. 그러나 H-NBR의 함량이 증가함에 따라 이러한 물성저하 속도가 감소함을 알 수 있었다. 즉 H-NBR 첨가에의해 열노화 특성이 향상됨을 알 수 있었다. 모든 NBR/H-NBR 블렌드는 노화시간이 증가함에 따라 내마모성이 감소하였으며, H-NBR을 첨가한 경우 내마모성의 저하가 상대적으로 낮음을 알 수 있었다.

• 열처리공학회지
• /
• 제12권4호
• /
• pp.303-312
• /
• 1999

An investigation of the CrMoV rotor steel weldment which experienced by cyclic thermal aging heat treatment and as-received condition was performed. This evaluation was carried out to confirm whether this type of weldment is appropriate for the service environment in terms of microstructural examinations, microhardness measurements and tensile tests. The cyclic thermal aging heat treatment, containing continuous heating and cooling thermal cycle was programmed to simulate the real rotor service condition. The heat treatment was performed for 40 cycles(5920hrs). The results indicated that the weldment was composed of 4 different regions such as heat affected zone of the base metal, butter weld(initial weld), full thickness weld(final weld) and the base metal. The double welding process was applied to eliminate the susceptibility of reheat cracking at heat affected zone of base metal. The grain refinement at the HAZ due to the welding process could reduce the possibility of cracking susceptibility, but its tensile properties was appeared to be low due to the weld metal in as-received condition. The benefit effect, grain refinement was extended with carbides coarsening during the cyclic thermal aging heat treatment. However the poor mechanical properties of the weldment was more degraded as undergoing the heat treatment.

• 대한기계학회논문집A
• /
• 제24권7호
• /
• pp.1771-1778
• /
• 2000

The purpose of this study is to investigate the thermal embrittlement and the mechanical properties of 2.25Cr-1Mo steel aged at high temperature for the extended periods. Original, aged artificiall y and used material were tested to obtain the tensile strength, hardness and impact absorbed energy. Tensile strength, hardness and impact absorbed energy decreased with the increasing aging time. The carbide morphology with the thermal embrittlement was found to contribute to the mechanical property change by X-Ray diffraction method.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 추계학술대회 논문집 전기설비전문위원
• /
• pp.77-79
• /
• 2004

It is caused that insulation paper, which had got a lot of thermal stress by over-load after installation, should have been deteriorated in electrical and mechanical characteristics. Beside, insulation material is decreased the insulating property and accelerated aging of them in case of dielectric loss when transformers are manufactured with some moisture or transformers would have been them because of moisture-permeation. Therefore, in this study we experienced the influence of moisture content in case of the thermal aged insulation paper. we have measured tan 6 and breakdown voltage in the ratio of paper' moisture content before the aging and then taken the same tests again after insulation paper thermally accelerating-aged. There is a purpose to gain data for a life-design and to establish aging mechanism in order to continuously study life expectancy of the insulation paper

• 한국염색가공학회지
• /
• 제29권3호
• /
• pp.155-161
• /
• 2017

In CPB(Cold-Pad-Batch) dyeing, the rubber of the padder roll is influenced by the heat, chemical and mechanical influences and thus aging of the padder roll rubber occurs. This study presents an accelerated thermal aging test of the CPB padder roll rubber with strong alkali conditions. Using Arrhenius formula of the various property values for the various aging temperatures($80^{\circ}C$, $90^{\circ}C$, $100^{\circ}C$) of the padder roll, the accelerated life predictions could be calculated. The threshold value of the property was set at different values. The hardness was set at the point where 5% degradation occurs based on the actual use conditions, and the tensile strength was set at the point where 50% degradation occurs based on the general life prediction standards. From the results of the different physical properties at differing temperatures, the Arrhenius plot could be obtained. Through the usage of the Arrhenius Equation, significant duration expectation could be predicted, and the chemical aging behavior of the CPB padder roll could be found at the arbitrary and actual temperatures.

• Composites Research
• /
• 제22권3호
• /
• pp.35-43
• /
• 2009

본 연구에서는 카본블랙이 충전된 ethylene-propylene dine monomer(EPDM) 고무에 대한 가교밀도 측정법을 확립하고 EPDM 고무호스에 대해 열가속 및 산소스트레스를 가하여 가교밀도 변화를 측정하였다. 노화 초반에는 산화황가교의 형성으로 고무의 가교밀도측정값이 약간 저하하였다가 노화시간이 지남에 따라 일부 미반응 황 분자들의 가황반응으로 추가적인 가교 결합을 형성하면서 가교밀도측정값은 점차 증가하였다. 이들 가교밀도 변화거동은 인장강도의 거동과 유사하였다. $180^{\circ}C$의 고온노화에서는 노화시간이 길어짐에 따라 노화에 따른 가교밀도의 증가폭은 그다지 크지 않았으나, 인장강도와 신장률은 크게 저하하였다. 즉, 온도가 높을 수록 EPDM 고무의 가교밀도의 변동보다는 EPDM 분자사슬에서의 산화물(carbonyl groups) 형성과, 가교점의 산화황 생성으로 기계적 물성의 열화가 일어난 것이다.

• Journal of Electrical Engineering and Technology
• /
• 제13권2호
• /
• pp.918-927
• /
• 2018

Based on the actual operating environment of transformer, the aging tests of nitrile butadiene rubber (NBR) were conducted systematically under four conditions: in air, in transform oil, under compression in air and under compression in transform oil to studythe effect of high temperature, transform oil and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber and predict the lifetime. The effects of liquid media and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber were studied by using characterization methods such as IR spectrosc-opy, thermogravimetric measurements, Differential Scanning Calorimetry (DSC) measurements and mechanical property measurements. The changes in physical properties during the aging process were analyzed and compared. Different aging conditions yielded materials with different properties. Aging at $70^{\circ}C$ under compression stress in oil, the change in elongation at break was lower than that aging in oil, but larger than that aging under compression in air. The compression set or elongation at break as evaluation indexes, 50% as critical value, the lifetime of NBR at $25^{\circ}C$ was predicted and compared. When aging under compression in oil, the prediction lifetime was lower than in air and under compression in air, and in oil. It was clear that when predicting the service lifetime of NBR in oil sealing application, compression and media liquid should be involved simultaneously. Under compression in oil, compression set as the evaluation index, the prediction lifetime of NBR was shorter than that of elongation at break as the evaluation index. For the life prediction of NBR, we should take into account of the performance trends of NBR under actual operating conditions to select the appropriate evaluation index.