• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.3
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• pp.211-216
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• 2016

In several industrial fields, epoxy resin is widely used as an adhesive for co-curing and manufacturing various structures. Controlling the manufacturing process is required for ensuring robust bonding performance and the stability of the structures. A fiber optic sensor is suitable for the cure monitoring of epoxy resin owing to the thready shape of the sensor. In this paper, a fiber Bragg grating (FBG) sensor was applied for the cure monitoring of epoxy resin. Based on the experimental results, it was demonstrated that the FBG sensor can monitor the status of epoxy resin curing by measuring the strain caused by volume shrinkage and considering the compensation of temperature. In addition, two types of epoxy resin were used for the cure-monitoring; moreover, when compared to each other, it was found that the two types of epoxy had different cure-processes in terms of the change of strain during the curing. Therefore, the study proved that the FBG sensor is very profitable for the cure-monitoring of epoxy resin.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.85-92
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• 2021

The purpose of this study is to investigate the properties of hardener-free epoxy-modified mortars(EMMs) using ground granulated blast furnace slag(GGBFS) and alkali activators. The hardener-free EMMs with a GGBFS content of 20% using 4 types of alkali activators were prepared with various polymer-binder ratios, and tested for strengths, water absorption, carbonation depth, chloride ion and H2SO4 penetration depth. The conclusions obtained from the test results are summarized as follows: The compressive strength of the EMMs with a GGBFS content of 20% attains a maximum at a polymer-binder ratio of 10%. The flexural strength of the hardener-free EMMs using Ca(OH)2 as a alkali activator is improved with increasing polymer-binder ratios. However, the flexural strength of the EMMs using NaCO3, Na2SO4 and Li2CO3 is gradually decreased with increasing polymer-binder ratios. Regardless of the type of alkali activator, the water absorption, chloride ion penetration and carbonation depth are remarkably decreased with increasing polymer-binder ratios due to the epoxy film formed in the EMMs. The H2SO4 penetration depth of the hardener-free EMMs with a GGBFS content of 20% is gradually increased with increasing polymer-binder ratio. In this study, the properties of hardener-free EMMs using Ca(OH)2 as a alkali activator are more excellent than those of other alkali activators.

• Journal of Conservation Science
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• v.32 no.2
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• pp.223-234
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• 2016

Two-component epoxy resin is widely used in the cultural heritage restoration field. However according to mixing ratio of resin and hardener, curing property, mechanical strength and chemical structure differ which have possibility to effect the stability of cultural heritage. Result of questionnaire survey shows hands-on workers in the conservation field tend to mix the epoxy resin with his or her eye measurement when the using amount is small or mix additional hardener to shorten the pot life of epoxy resin. This research aims to analyze the curing property, mechanical strength and chemical structure of rapid curing type epoxy resin and medium curing type one depending on relative ratio of 0.25~4 of hardener to resin. When the amount of hardener was 0.5~2 times more than the resin, exothermic heat and curing speed were both increased. In case of included hardener to resin was lower than official ratio, mechanical strength (tensile shear strength, tensile strength and compressive strength) became higher along with active cross-linking bonding of the epoxy resin. Medium curing type epoxy relatively had lower exothermic heat and slower reaction during curing process. It was observed to be put to definite point of mechanical strength under lower content of hardener than official ratio. While, hardener ratio more than twice the resin slowed down the curing greatly and lowered the adhesion strength also. In conclusion, under the lower mixing rate of hardener than official ratio would show relatively fast reaction with similar mechanical strength. Over the official ratio on the other hand, material property drops rapidly. Accordingly, mixing ratio of epoxy resin is expected to be influential to the stability of cultural heritage.

• Electrical & Electronic Materials
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• v.3 no.2
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• pp.81-89
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• 1990

신소재용 전기 절연재료로 각광받고 있는 에폭시 수지는 경화과정에서 현저한 화학적 반응을 동반하며 경화제와 경화조건에 따라 다양한 물리적, 화학적 성질을 나타내므로 전기적 특성과 경화형태와의 관련성에 대한 연구는 에폭시 수지의 절연특성을 향상시키는 중요한 자료가 된다. 실험결과, 경화는 에폭시의 에폭시환과 경화제의 활성기 사이의 화학반응으로 일어나며 전기 절연특성을 경화할 때 얻어지는 가교에 의하여 영향을 받음을 확인하였고 경화형태는 적외선 파수 915[$cm^{-1}$ /]의 에폭시환이 감소하고 1,453[$cm^{-1}$ ] 파수의 변성메틸이 생성되지 않는 가교를 할 때 우수한 졀연특성이 얻어졌다.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.368-369
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• 2003

선진 복합재료의 매트릭스 수지로서 자장 많이 사용되고 있는 에폭시는 수지 및 경화제의 종류에 따라 여러 가지 물성을 나타낼 수 있다. 에폭시 수지는 기계적 물성 및 내화학성이 우수하고 경화시 수축변형이 적은 장점이 있으나 높은 가친밀도 때문에 순간적인 충격에 취약하다는 단점을 지니고 있다. 따라서 이러한 에폭시 수지의 취성 (brittleness)을 개선하기 위해 충격강도를 증가시킬 수 있는 강인화제를 혼합하여 경화시키는 방법이 사용되고 있다[1]. (중략)

• Polymer(Korea)
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• v.38 no.2
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• pp.171-179
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• 2014

Low temperature cure prepregs are being developed for use in the preparation of large-structured fiber-reinforced polymer (FRP) composites with good performance. Cure behavior and chemorheology of low temperature cure epoxy resin system, based on epoxy resin, curing agent, and accelerators, were investigated to provide a matrix resin suitable for the prepreg preparation. Characteristics of cure reaction were studied in both dynamic and isothermal conditions by means of differential scanning calorimetry and rheometry. The low temperature cure epoxy resin system suggested in this study as a matrix resin was curable at $80^{\circ}C$ for 3 h, and showed the gel times of 120 and 20 min at 80 and $90^{\circ}C$, respectively. Thermal and mechanical properties of the cured sample were almost the same as high temperature cure counterparts.

• Polymer(Korea)
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• v.26 no.1
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• pp.80-87
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• 2002

A comparative study using electron-beam(EB) and thermal curing techniques was carried out to determine the effect of cure behavior and thermal stability of epoxy resins. In this work, benzylquinoxalinium hexafluoroantimonate(BQH) was used as a latent cationic catalyst for an epoxy resin. According to the thermogravimetric analysis(TGA), the decomposed activation energy based on Coats-Redfern method was higher in the case of thermal curing technique. This could be interpreted in terms of slow thermal diffusion rate resulted from high crosslink density of the thermally cured epoxy resin. However, the increase of hydroxyl group in the epoxy resin cured by EB technique was observed in near-infrared spectroscopy(NIRS) measurements, resulting in improving the stable short aromatic chain structure, integral procedural decomposition temperature, and finally ductile properties for high impact strengths.

• Journal of Conservation Science
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• v.28 no.2
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• pp.131-139
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• 2012

The exothermic cure kinetics of epoxy resin was controlled by hardener containing fast and slow curing agents. The epoxy risen comprises hydrogenated bisphenol A-based epoxide (HBA), fast curing agent (FH) and slow curing agent poly(propyleneglycol)bis(2-aminopropylether) (SH). Talc was used as an inorganic additive. In the process of curing, cure kinetics along with temperature was monitored by differential scanning calorimeter (DSC) and thermocouple to show that the temperature increase was well controlled by adjusting the hardener mixture. Additionally, bending and tensile strengths of the epoxy/talc composites were also measured to be lower and higher with the amount of the talc inorganic additive, respectively. It is thus concluded that the increase in the temperature during exothermic curing reaction and mechanical properties of epoxy resins are tuned by optimizing hardener mixture for successful stone conservation.

• Composites Research
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• v.32 no.6
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• pp.349-354
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• 2019

The Aluminum conductor composite core consists of fast-curing thermosetting epoxy used as reinforcements and carbon fiber and glass fiber used as matrix. In this study, we have investigated fast curing epoxy cured products used for composite core(Aluminum Conductor Composite Core, ACCC). Tetrafunctional epoxy(PA 806) was used as a multifunctional epoxy, along with two kinds of curing agents, MNAn(5-Methyl-5-norbornene-2,3-dicarboxylic anhydride) and HHPA(Hexahydrophthalic Anhydride), to make an epoxy cured product and their properties were evaluated. Optimum conditions are confirmed by varying the content of curing accelerator in the selected epoxy and curing agent.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.451-454
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• 2002

최근 우주 항공 및 자동차 산업 등에서 기존의 금속재료를 대체하기 위하여 고강도 경량 구조 재료인 선진 복합재료 (advanced composite materials)의 개발에 관심이 모아지고 있다[1]. 선진 복합재료의 매트릭스 수지로서 가장 많이 사용되고 있는 에폭시는 수지 및 경화제의 종류에 따라 여러 가지 물성을 나타낼 수 있다. 에폭시 수지는 기계적 물성 및 내화학성이 우수하고 경화시 수축변형이 적은 장점이 있으나 높은 가교밀도 때문에 순간적인 충격에 취약하다는 단점을 지니고 있다. (중략)