• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.544-548
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• 1993

Glass transition temperatures($T_g$) of poly(phenylene sulfide sulfone)[PPSS], which were heat treated at various temperature and time, were studied by DSC. Up to $230^{\circ}C$, $T_g$ of heat treated PPSS were increased with increasing the heat treated time. When the sample was heated at $260^{\circ}C$ for 30 minute and $280^{\circ}C$ for 10 minute, however, $T_g$ of those samples were decreased. These phenomena can be explained by the factors of chain extension reaction, oxidative crosslinking, and thermal crosslinking.

• Korean Journal of Materials Research
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• v.2 no.4
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• pp.257-262
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• 1992

The cure kinetics of a diglycidyl ether of bisphenol A (DGEBA) with 4, 4'-methylene dianiline (MDA) added succinonitrile was studied through the dynamic run method by applying the data to the Kissinger equation which analyses the effect of the heating rate on the temperature at maximum reaction rate using Differential Scanning Calorimetry (DSC) analyzer in the range of 3$0^{\circ}C$-35$0^{\circ}C$. In the DGEBA/MDA system with SN, the activation energy ($E_a$) and the pre-exponential factor (A) were calculated. From these results, the rate constants (k) were obtained according to the different SN contents.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.116-119
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• 2000

본 연구에서는 온도의 상승에 의하여 부피가 팽창하는 열팽창 고무 치공구의 팽창 특성을 이용하여 열경화성 복합재료를 경화하고 압축하는 과정을 실험과 모델링을 통하여 해석하였으며, 열가소성 복합재료의 함침공정을 연구하였다. 열팽창 고무치공구가 사용되는 닫힌계와 열린계에서 예상되는 압력을 이론적으로 유도하였고, 경화가 수반되는 과정에 있어서는 실험을 통하여 열팽창치공구와 프리프레그가 나타내는 압력을 측정하였다. 온도가 상승하고 경화가 수반되는 경우에 등속도 압축실험에 의하여 얻어지는 응력-변형율 곡선은 비선형점탄성 특성을 보여주었는데, 본 연구에서는 Maxwell모델을 KWW(Kohlrausch-Williame-Watts)식으로 변형시킨 모델식을 이용하여 이를 매우 정확하게 표현할 수 있었다. 또한 고무치공구를 이용하여 열가소성 수지의 복합재료 성형공정을 실험하였고, 중성자 레디오그래피 촬영을 통하여 기공의 분포를 관찰하였다.

• Composites Research
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• v.31 no.4
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• pp.171-176
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• 2018

We proposed new and easy fabrication method of micro-nano hierarchical structures for synthetic dry adhesives and conducted feasibility tests of alignment characteristics of nano-materials in the microstructures by capillary effect. Candidates of fabrication conditions were selected based on the degree of cure and viscosity of mixtures of multiwall carbon nanotubes (MWCNTs) and polydimethylsiloxane (PDMS), which were measured with respect to the fabrication conditions. Scanning electron microscopy images of cross sections of MWCNT-PDMS microstructures were analyzed. MWCNT alignment in microstructures was better when fabrication temperature and degree of cure at fabricating start were lower, but areal density of MWCNTs was little affected by fabrication conditions.

• 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%.

• Journal of the Korean Wood Science and Technology
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• v.32 no.5
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• pp.59-65
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• 2004

The present study aims to optimise the process parameters of fish glue and adhesion property through room temperature in terms of curing time and opened assembly time for attaining best adhesion strength to wood (Yellow birch, B. alleghaniensis). The uncured and cured fish glue have been characterised by TGA, DSC, FT-JR. It is observed that with increasing curing time up to 48 H, tensile lap shear strength of adhesive joint of fish glue to wood increases and decreases after 48 H. At 15 min. opened assembly time, lap shear strength increases up to 4833 kgf/cm² and decreases after 15 min.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.22 no.2
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• pp.32-36
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• 1977

Experiments were conducted to know the effects of seed bed temperatures on the sprouting of seeds and seedling growth in the phytotron and field. Sprouting of seeds were most uniform when seed bed was stored under the straw and vinyl mulching for 48 hours after seed bed temperature increased up to 3$0^{\circ}C$ by the sun. In the phytotron, optimum temperature was 32$^{\circ}C$ for sprouting and day/night temperature of 25/30 and 20/15$^{\circ}C$ for greening and hardening of seedlings, respectively. In the field, the best results were obtained under the conditions of sprouting in the seedling chamber heated by electricity and greening the hardening under the double vinyl tunnel in the upland nusery bed.

• Journal of Conservation Science
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• v.33 no.6
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• pp.467-483
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• 2017

In this study, the degradation properties by temperature stress of $Araldite^{(R)}$ rapid-curing epoxy resin used for inorganic cultural heritages, was identified. The tensile and tensile shear strength of durability decreased for 12,624 hours at temperatures of $40{\sim}60^{\circ}C$. In terms of stability of external stress and temperature, the slow-curing epoxy was superior to the rapid-curing epoxy, and cultural heritage conservation plans should therefore consider the strength and stress properties of restoration materials. Color differences increased for 12,624 hours at temperatures of $40{\sim}60^{\circ}C$, and glossiness decreased. Both color and gloss stability were weak, which necessitates the improvement of optical properties. Thermal properties (weight loss, decomposition temperature, and glass transition temperature) of adhesives are linked to mechanical properties. Interfacial properties of the adherend and water vapor transmission rates of adhesives are linked to performance variation. For porous media (ceramics, brick, and stone), isothermal and isohumid environments are important. For outdoor artifacts on display in museums, changes in physical properties by exposure to varying environmental conditions need to be minimized. These results can be used as baseline data in the study of the degradation velocity and lifetime prediction of rapid-curing epoxy resin for the restoration of cultural heritages.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.4
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• pp.433-441
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• 1986

본 연구에서는 인장시험과 인장시 변형율속도 변화와 온도변화를 주는 시험을 통하여 316스테인리스강에 있어서의 비탄성거동을 규명하여 가공경화에 대한 용질강화 효과를 시험하고, Voce형의 발전방정식(evolutionary equation)을 포함하는 Arrhenius 형의 구성식에 용질강화효과를 첨가하여 정확한 비탄성 해석을 기하고자 한다.

• Korean Journal of Materials Research
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• v.6 no.2
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• pp.235-241
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• 1996

등온자비 AuCu에 2.4, 4.3, 6.1at% Zn이 첨가된 합금의 시효경화거동과 상변태를 조사하였다. AuCu l형이 단독으로 존재하는 경우는 경도가 시효초기에 급격히 상승한 후 저하하였고, Zn 첨가량의 증가에 따라 규칙-불규칙 전이온도(Tc)가 약간 하강하였지만, AuCu l형+AuCu ll형의 공존영역의 온도는 훨씬 낮아졌다.