• Korean Journal of Materials Research
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• v.6 no.5
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• pp.494-503
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• 1996

에폭시/산무수물계의 등온 경화거동을 새로이 제작된 Torsion Pendulum(TP)으로 다양한 온도에서 조사하였으며 경화반응을 촉진시키기 위하여 두 종류의 경화촉진제를 사용하였다. 새로이 제작된 TP는 개인용 컴퓨터를 이용하여 모든 기계\ulcorner인 작동과 date 수집 및 분석이 자동으로 처리될 수 있도록 하였다. 이 기기로부터 얻어진 결과인 경화 동안의 상대전단강성율(RSR, relative shear rigidity)과 log decrement(LD)의 변화로부터 제작된 TP가 잘 작동한다는 것을 알 수 있었다. 두 종류의 촉진제가 전체적인 경화과정에 미치는 촉진효과는 비슷하였으나 각 촉진제로부터 얻어진 LD 곡선을 보면 서로 다른 모양을 나타내었다. 이것은 경화촉진제가 반응 촉진효과 이외에도 경화거동에 영향을 미친다는 것을 의미하며, 따라서 이러한 경화거동의 차이는 경화물의 성질에 영향을 줄 수 있다.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.78-78
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• 2010

모바일 정보통신기기를 중심으로 패키지의 초소형화, 고집적화를 위해 플립칩 공법의 적용이 증가되고 있고 있으며 접속피치의 미세화에 따라 솔더 및 언더필을 사용하는 C4 공법보다 ACA(Anisotropic Conductive Adhesive), NCA (Non-conductive Adhesive) 등의 접착제를 이용하는 칩본딩 공법에 대한 요구가 증가하고 있다. 특히, NCA 공법의 경우 산업 현장의 대량생산에 대응하기 위해서는 접착제의 속경화 특성이 요구되어 진다. 일반적으로 접착제의 경화거동은 DSC(Differential Scanning Calorimeter)를 사용해 확인하지만, 수초 이내에 경화되는 접착제의 경우는 적용되기 어렵다. 본 연구에서는 이러한 전자패키지용 접착제의 속경화 거동을 효과적으로 평가할 수 있는 방법을 조사 하였다. 실험에서 사용된 접착제는 에폭시계 레진 기반에 이미다졸계 경화제를 사용한 기본적인 포뮬레이션을 사용하였고, 경화시간은 160^{\circ}C에서 1분 이내에 경화되는 특성을 가지고 있다. 경화 거동을 확인하기 위해서 isothermal DSC와 DEA(Dielectric Analysis)의 두가지 방법을 사용해 비교하였다. 두 실험 방법 모두 $160^{\circ}C$를 유지하며 경화 거동을 확인하였고, DoC(Degree of Cure)의 측정오차를 비교 분석하였다. DEA는 이온 모빌리티 변화에 따른 유전손실율을 측정하는 방법으로 80~90% 이후의 경화도는 측정되지 않았지만, 수초 이내에 경화되는 속경화 특성을 평가하기에 적합한 것으로 확인되었다.

• Composites Research
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• v.33 no.5
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• pp.302-308
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• 2020

We measured the thermal conductivity of composite materials manufactured by the autoclave and vacuum bag only processes and predicted the cure behavior of the external and internal of composite parts with a cure kinetics model. The temperature difference between the external and internal depends on the processes because of the change of thermal conductivity. In the autoclave process, the temperature and cure behavior of the internal were similar to those of the external because of the high thermal conductivity. However, the temperature of the internal of the vacuum bag only process was different from that of the external. The difference can influence the part quality and evacuation of air. Compression tests were performed to find the mechanical property using 0° unidirectional specimens. The composite of the vacuum bag only process was found to have a lower compressive strength than that of the autoclave process.

• Polymer(Korea)
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• v.37 no.2
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• pp.240-248
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• 2013

The curing behaviors of diglycidyl ether of bisphenol A (DGEBA) with mercaptan hardener were studied by the comparison with amine-adduct type hardener. Curing behaviors were evaluated by DSC at dynamic and isothermal conditions. In the DSC, the dynamic experiments were based on the method of Kissinger's equation, and the isothermal experiments were fitted to the Kamal's kinetic model. Activation energy of epoxy/amine-adduct type hardener was ca. 40 kcal/mol. As the functional group of mercaptan hardener, -SH increased, on epoxy/mercaptan hardeners, the activation energies decreased from 28 to 19 kcal/mol. Epoxy/amine-adduct type hardener was initiated at $90^{\circ}C$ or higher. However, epoxy/mercaptan hardeners reduced the initiation temperatures below $80^{\circ}C$ and shortened the durations of curing reaction within 10 min. We found out that the reaction kinetics of epoxy with mercaptan hardener followed the autocatalytic reaction models, and the maximum reaction rates were shown at the conversions of 20~40%.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.5
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• pp.47-56
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• 2003

In this paper, the cyclic soil behavior model. which can accommodate the cyclic hardening, was developed by modifying the original parallel IWAN model. In order to consider the irrecoverable plastic strain of soil. the cyclic threshold strain, above which the backbone curve deviates from the original curve, was defined and the accumulated strain was determined by summation of the strains above the cyclic threshold in the stress-strain curve with applying Masing rule on unloading and reloading curves. The isotropic hardening elements are attached to the original parallel IWAN model and the slip stresses in the isotropic hardening elements are shown to increase according to the hardening functions. The hardening functions have a single parameter to account for the cyclic hardening and are defined by the symmetric limit cyclic loading test in forms of accumulated shear strain. The model development procedures are included in this paper and the verifications of developed model are discussed in the companion paper.

• Journal of the Korean Wood Science and Technology
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• v.18 no.1
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• pp.10-14
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• 1990

한국산 옻액의 경화거동을 알아보기 위하여 F.T.-I.R. 분석을 수행하였다. Acetone 추출한 urushiol의 F.T.-I.R. peak는 $3,422cm^{-1}$, $2,928cm^{-1}$, $1,622cm^{-1}$, $1,475cm^{-1}$, $1,281cm^{-1}$, $984cm^{-1}$, $947cm^{-1}$, $735cm^{-1}$이었다. 또한, 옻액의 정시경화거동에서 $1,651cm^{-1}$ peak는 urushiol-quinone이 laccase의 촉매작용에 의하여 산화중합한 후 982와 $947cm^{-1}$의 conjugated diene와 결합해서 dimer 형성을 알 수 있었다.

• Composites Research
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• v.33 no.2
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• pp.44-49
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• 2020

The cure kinetics of carbon fiber-reinforced prepreg for Vacuum Bag Only(VBO) process was studied by differential scanning calorimetry (DSC). The total heat of reaction (ΔH_total = 537.1 J/g) was defined by the dynamic scanning test using prepregs and isothermal scanning tests were performed at 130℃~180℃. The test results of isothermal scanning were observed that the heat of reaction was increased as the temperature elevated. The Kratz model was applied to analyze the cure kinetics of resin based on the test results. To verify the simulation model, the degree of cure from panels using different cure cycles were compared with the measurement. The simulation model showed that the error against the experimental value was less than 3.4%.

• Polymer(Korea)
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• v.24 no.5
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• pp.599-609
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• 2000

In order to improve the mechanical properties of unsaturated polyester (UPE) resins, the UPE resins with different glycol molar ratios were prepared. The effects of molar ratios of the UPE resins on the curing behaviors and mechanical properties were investigated. The microgel reaction mechanism was employed to characterize the system. It was found that the final conversion increased with increasing NPG molar ratios, and the conversion at the peak of differential scanning calorimetry (DSC) thermogram appeared to decrease with increasing NPG molar ratios. The flexural strength, tensile modulus, water resistance, and infiltration increased with increasing NPG content, but the tensile strength, tensile elongation, and flexural modulus decreased. Among the UPE resins prepared from the glycols with the molar ratios (PG/NPG) of 0.5/0.5, 0.25/0.75, those of laminated composites plates showed better mechanical properties.

• Korean Journal of Materials Research
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• v.7 no.12
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• pp.1089-1096
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• 1997

본 연구에서는 에폭시/산무수물계에 화학양론비(r=산무수물/에폭시)를 0.5, 0.7,0.9,1.1로 변화시켜 서로 다른 두종류의 경화촉진제 1-cyanoethy1-2-ethy1-4-methy1 imidazole(2E4MZ-CN)과 N,N-dimethy1 benzy1 amine(BDMZ)을 첨가한 시료에 대한 경화거동과 경화 후 물성을 관찰하였다. 이 시료의 등온 경화거동은 동역학 측정기(dynamic mechanical analyzer, DMA)와 시차주사 열량분석기(differential scanning calorimeter, DSC)를 이용하여 조사하였다. DMA로부터 구해진 결과를 보면 경화시 상대저장강성을 (relative storage rigidity, RSR)과 상대손실강성율(relative loss rigidity, RSR)과 상대손실강성율(relative loss rigidity, RLR)의 변화가 r값과 경화촉진제의 종류에 영향을 받았다. 그리고 DSC결과는 r값이 감소함에 따라 경화가 촉진되는 것으로 나타났다. 경화물의 성질을 조사하기 위하여 사용된 DMA로부터 얻어진 유리전이온도(glass transition temperature, T$_{g}$)와 가교결합간의 평균분자량(average molecular weigh between crosslinks, M$_{c}$은 사용한 두 경화촉진제에 대하여 r값의 영향이 다르게 나타났다. BDMA의 경우는 T$_{g}$가 1:1화학양론비인 r=0.9에서 최고치를 보였으나, 2E4MZ-CN은 r이 감소함에 따라 계속 증가하는 양상을 보였다. 이와 같은 경향은 2E4MZ-CN을 경화촉진제로 사용하였을 때 에폭시가 과량으로 될수록 잔류 에폭시기들간의 에케르반응이 추가적으로 일어나 M$_{c}$가 감소하기 때문이다.

• Geotechnical Engineering
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• v.10 no.1
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• pp.103-118
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• 1994

A series of drained triaxial testis was performed on a Band by use of cubical triaxial apparatus, in which three principal stresses could be applied independently. The stress -strain behavior on the same stress path with cubical triaxial test was analyzed with application of the isotropic single hardening constitutive model presented by Lade. The behavior predicted by the constitutive model presented good coincidence with experimental results during poi mary loading. However, the predicted Mo윤ding and reloading behavior wan much different from results of cubical triaxial testy. That is, the softening part of the prediction might result in a rough approximation, since the plastic work parameters of single hardening model were based on the hardening portion of the data.