• 공업화학
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• 제10권7호
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• pp.990-995
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• 1999

경화된 에폭시수지의 삼차원 망상구조 형성에 관한 정보를 알 수 있는 chemomechanical한 관점에서의 물성 연구는 아직까지 매우 미진하다. 이를 위한 기초적인 작업의 한 일환으로, 선형구조를 가지고 양쪽 말단기에 에폭시기를 가지는 대표적 범용 에폭시수지인 DGEBA(diglycidylether of bisphenol A, YD-128, 국도화학(주))를 양쪽 관능기가 동일하고 주쇄의 사슬길이가 서로 다른 선형아민 경화제인 ethylene diamine(EDA, 주쇄의 탄소원자수: 2개)와 hexamethylene diamine(HMDA, 주쇄의 탄소원자수: 6개)으로 각각 1:1 당량비로 혼합하여 1차 및 2차의 경화조건으로 경화하였고, 이것을 경화제의 주쇄의 탄소원자수에 의한 분자량과 화학구조 차이가 반응특성, 기계적특성, 열적특성에 미치는 영향을 조사하였다. 반응특성을 측정하기 위하여 DSC 열분석, 열안정성을 알아보기 위해 TMA 분석, 에폭사이드기의 전환율 계산을 위해 FT-IR 분석, shrinkage(%)를 구하기 위하여 밀도측정, 유리전 이온도와 선팽창계수 측정을 위해 TMA 분석, 기계적특성 분석을 위하여 인장시험 및 삼점 굴곡시험을 행하였다. 그 결과, 수지 경화물의 특성은 경화제 주쇄의 탄소원자수에 따라 큰 영향을 받는다. 즉, 주쇄의 사슬길이가 짧은 EDA 경화물계는 주쇄 사슬길이가 긴 HMDA 경화물계 보다 열안정성, dpoxide group의 전환율, 밀도, 유리전이온도, 인장탄성율, 굴곡탄성율 및 굴곡강도가 높은 값을 나타냈고, 최대 발열온도, shrinkage(%), 선창팽창계수, 인장강도의 값은 낮은 값을 나타내었다. 이는 주쇄의 탄소원자수 2개를 가지는 EDA가 3차원 망목상 구조 형성과정에서 packing ability가 우수하여 rigid한 특성을 가지기 때문이다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.61-64
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• 2002

Fiber reinforced metal laminate(FRML) consists of alternations layers of metal and fiber reinforced composite. The difference in the coefficients of thermal expansion between metal and composite layer produces remarkable amount of thermal residual stresses between layers. Generally, FRML shows a tensile stress in metal layers, a compressive stress in composite layers after curing. In this study, the thermal residual stresses of several types of FRML are investigated to get the best combination of metal and composite which can reduce the thermal residual stresses. The residual stress level is compared with the strength of each layers to explain the fracture mechanism of FRML.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.79-82
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• 2005

In this study, mechanical properties of carbon fabrics composite under the thermal shock cycling were evaluated. Due to the interactions between fiber and polymer matrix, it is reasonable to conclude that both thermal cycles of thermal shock result in improvement of interlaminar shear strength(ILSS) for the longer conditioning time duration. The rise in ILSS may be attributed to the improved adhesion by cryogenic compressive stress and also by the post-curing strengthening effect. However, the flexural and tensile strength were decreased with increasing conditioning time of thermal cycle.

• Bulletin of the Korean Chemical Society
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• 제21권6호
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• pp.628-634
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• 2000

Crosslink is the most important chemistry in a rubber vulcanizate. Degree and type of crosslinks of the vulcanizate determine its physical properties. Change of crosslink density and deformation of a rubber vulcanizate by thermal aging were studied using natural rubber (NR) vulcanizates with various cure systems (conventional, semi-EV, and EV) and different cure times (under-, optimum-, and overture). All the NR vulcanizates were deformed by the thermal aging at 60-100 $^{\circ}C.$ The higher the aging temperature is, the more degree of the deformation is. The undercured NR vulcanizates after the thermal aging were deformed more than the optimumand overcured ones. The NR vulcanizates with the EV cure system were less deformed than those with the conventional and semi-EV cure systems. The deformation of the NR vulcanizates was found to be due to change of the crosslink density of the vulcanizates. The crosslink densities of all the vulcanizates after the extraction of organic materials were also changed by the thermal ging. The sources to change the crosslink densities of the vulcanizates by the thermal aging were found to be dissociation of the existing sulfur crosslink and the formation of new crosslinks by free sulfur, reaction products of curing agents, and pendent sulfide groups.

• 한국전기전자재료학회논문지
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• 제35권1호
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• pp.50-57
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• 2022

Reliability of CMOS has been severed under aggressive device scaling. Conventional technologies such as lightly doped drain (LDD) and forming gas annealing (FGA) have been applied for better device reliability, but further advances are modest. Alternatively, electro-thermal annealing (ETA) which utilizes Joule heat produced by electrodes in a MOSFET, has been newly introduced for gate dielectric curing. However, concerns about mechanical stability during the electro-thermal annealing, have not been discussed, yet. In this context, this paper demonstrates the mechanical stability of nanosheet FET during the electro-thermal annealing. The effect of mechanical stresses during the electro-thermal annealing was investigated with respect to device design parameters.

• Advances in concrete construction
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• 제2권1호
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• pp.29-37
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• 2014

Increasing emphasis on energy conservation and environmental protection has led to the investigation of the alternatives to customary building materials. Some of the significant goals behind understaking such investigations are to reduce the greenhouse gasemissions and minimize the energy required formaterial production.The usage of concrete around the world is second only to water. Ordinary Portland Cement (OPC) is conventionally used as the primary binder to produce concrete. The cement production is a significant industrial activity in terms of its volume and contribution to greenhouse gas emission. Globally, the production of cement contributes at least 5 to 7 % of $CO_2$. Another major problem of the environment is to dispose off the fly ash, a hazardous waste material, which is produced by thermal power plant by combustion of coal in power generation processes. The geopolymer concrete aims at utilizing the maximum amount of fly ash and reduce $CO_2$ emission in atmosphere by avoiding use of cement to making concrete. This paper reports an experimental work conducted to investigate the effect of curing conditions on the compressive strength of geopolymer concrete prepared by using fly ash as base material and combination of sodium hydroxide and sodium silicate as alkaline activator.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1613-1619
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• 2011

A hybrid thermosetting maleimido epoxy compound 4-(N-maleimidophenyl) glycidylether (N-MPGE) containing Co(II), Ni(II) and Cu(II) ions was prepared by curing N-MPGE and tetradentate Schiff base Co(II), Ni(II) and Cu(II) complexes. The curing polymerization reaction of N-MPGE with metal complexes as curing agents was studied. The cured samples were studied for thermal stability, chemical (acid/alkali/solvent) and water absorption resistance and homogeneity of the cured systems. The tetradentate Schiff base, 3-[(Z)-2-piperazin-1-yl-ethylimino]-1,3-dihydro indol-2-one was synthesized by the condensation of Isatin (Indole-2, 3-dione) with 1-(2-aminoethyl)piperazine (AEP). Its complexes with Co(II), Ni(II) and Cu(II) have been synthesized and characterized by microanalysis, conductivity, Uv-Visible, FT-IR, TGA and magnetic susceptibility measurements. The spectral data revealed that the ligand acts as a neutral tetradentate Schiff base and coordinating through the azomethine nitrogen, two piperazine nitrogen atoms and carbonyl oxygen.

• 폴리머
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• 제25권3호
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• pp.327-333
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• 2001

아세틸렌기가 치환된 fluorene 유도체 2-ethynylfluorene과 2,7-diethynylfluorene을 합성하였고 이를 진공 증착하여 박막을 제조하였다. 심중결합이 치환된 fluorene 유도체들은 자외선 및 열에 의해 경화가 가능하였다. DSC 측정 결과 2-ethynylfluorene은 $231^{\circ}C$에서 그리고 2,7-diethynylfluorene은 198$198^{\circ}C$에서 경화가 일어나는 것이 관측되었다. 경화된 poly(2-ethynylfluorene) 및 poly(2,7-diethynylfluorene)의 분해는 380 및 385$^{\circ}C$에서 일어나기 시작하였으며 T$T_g$는 관측되지 않았다. 경화된 박막의 광발광 특성은 단량체와 매우 유사하나, 발광 효율은 3에서 10배 정도 감소하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.31-36
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• 2008

This study aims to examine the effects of thickness of the concrete members and curing temperature on the properties of low heat concrete through heat of hydration analysis. Type of the members that was analyzed in the experiment is ternary mixture of ordinary portland cement, blast-furnace slag incorporating ratio(20%) and fly ash incorporating ratio(30%), which formed a mat foundation. Thicknesses of the concrete members were 1, 2 and 3(m) and three levels of curing temperatures were 10, 20 and 30(℃). They were applied to analyze the effects on the temperature and thermal cracking index. As a result, for temperature history, temperature difference between the central area and the surface tended to decrease as the thickness of the concrete members get thinner. For the temperature cracking index, on the other hand, the risk of cracking tended to decrease as the curing temperature gets higher and as the thickness gets thinner.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.71-73
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• 2002

The Induction heating is used in various industry and ever-increasing number of applications. The heating roll, which is a kind of induction heating, widely used in curing of coatings and fiber industry. In this papaer, we analized thermal characteristic of induction heating roll by three dimensional eddy-current analysis. Using this analytic results, We could predict the thermal distribution of induction heating roll.