• 한국재료학회:학술대회논문집
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• 한국재료학회 1997년도 한국재료학회 추계학술발표회
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• pp.14-14
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• 1997

• 보존과학회지
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• 제28권3호
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• pp.265-276
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• 2012

석조문화재의 보존 복원 작업에 적용할 수 있는 에폭시 수지의 성능을 개선하기 위해 다양한 성분을 조합하여 경화 거동을 제어할 수 있는 접착 시스템을 연구하였다. 사용된 에폭시 수지 주제는 hydrogenated Bisphenol-A (HBA), 경화제로 속경화형 경화제 FH와 저속 경화제 SH를 구성하였으며, 반응성 희석제는 difunctional polyglycidyl epoxide (DPE), 무기 첨가물은 탈크를 사용하였다. 에폭시 수지와 경화제의 혼합 조건에 따라 경화 시 점도, 온도 및 differental scanning calorimetry(DSC)를 이용하여 경화 동력학을 측정하였고, 기계적 특성을 확인하기 위해 무기 첨가물의 함량에 따른 굴곡강도, 인장강도, 압축전단접착강도를 측정하였다. 연구 결과, 다양한 석조문화재의 보존처리 작업에 맞춰 에폭시 수지 구성물의 성분 조합을 통해 경화 특성을 제어하고, 무기 첨가물의 도입을 통해 기계적 특성을 조절하여 성능 개선 및 작업 효율성을 향상 시킨 새로운 접착 시스템을 개발하였다.

• 콘크리트학회논문집
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• 제28권3호
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• pp.317-328
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• 2016

이 연구의 목적은 내부양생을 위한 고흡수성 수지(SAP)의 혼입이 초고성능 콘크리트(UHPC)의 수화특성, 자기수축, 내구성 및 역학적 특성에 미치는 영향을 알아보는 것이다. 이를 위해 입도범위는 유사하지만 화학적 구조가 다른 2 종류의 SAP이 선택되었고, 이러한 SAP이 혼입된 UHPC의 성능이 실험을 통해 평가되었다. 평가결과는 SAP의 종류, 그리고 혼입 여부에 따라 비교되었다. 수화반응성과 수화생성물 확인을 위해 등온열량계 및 XRD를 이용한 실험이 각각 진행되었고, 이 실험을 통해 초기 재령일에서 수화반응성 및 장기 재령일에서의 수화생성물을 확인하였다. UHPC의 수축저감제로서 SAP의 적용 가능성을 확인하기 위해 자기수축 변형율, 압축강도 및 염분침투성을 측정하였다. 또한, SEM 이미지 촬영을 통해 SAP이 UHPC 내부에서 형성한 공극을 실제로 확인하고 분석하였다. 이러한 분석 및 평가결과를 통해, SAP을 이용한 내부양생은 역학적 성능과 내구성 저하 없이 UHPC의 자기수축을 저감시킬 수 있다는 결론을 내렸다. 실험에 사용된 두 종류의 SAP 중에서, UHPC 내부에서 흡수력이 더 우수한 SAP_AM이 SAP_AA 보다 수축저감성능 뿐만 아니라, 장기적인 수화반응성, 압축강도, 염분침투 저항력에서도 성능이 더 우수한 것으로 나타났다.

• Restorative Dentistry and Endodontics
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• 제25권1호
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• pp.85-90
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• 2000

For more esthetic treatments the use of composite in molar areas are increasing. But polymerzation shrinkage that cause marginal leakage and cuspal deflection has been the problems of composites. The purpose of this study is to compare the effect of low intensity curing and polishing period on marginal leakage. Cavities were prepared on the buccal or lingual surface of forty five sound extracted human teeth and etching, application of bonding agent and filling of composite was done. Group 1 was light cured at intensity of 600$mW/cm^2$ for 41 seconds and polished. Group 2 was light cured at intensity of 300$mW/cm^2$ for 2 seconds and polished and after polishing it was light cured for 40 seconds at 600$mW/cm^2$. Group 3 was light cured at intensity of 300$mW/cm^2$ for 2 seconds and waited for 5 minutes and after curing at 600$mW/cm^2$ for 40 seconds polishing was done. The specimens were thermocycled at $5^{\circ}C$ and $55^{\circ}C$ for 1000 cycles and immersed in 2% methylene blue solution for 24 hours. Composite-tooth interface was examined under stereobinocular microscope for dye penetration. The results were as follows : 1. Group which were cured at low intensity and polished after curing at high intensity showed less marginal leakage than group which were cured at high intensity for 41 seconds(p<0.05). 2. Marginal leakage between group which were cured at low intensity and polished immediately and group which were cured at high intensity for 41 second were not significantly different. Light curing at low intensity can reduce marginal leakage but polishing immediately after curing at low intensity for short time can affect marginal leakage.

• 치위생과학회지
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• 제21권3호
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• pp.178-184
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• 2021

Background: As the importance of the esthetic function of teeth increases, the use of esthetic restoration materials and whitening treatment are increasing. The purpose of this study was to investigate the color change of esthetic restoration materials upon using staining and whitening toothpaste. Methods: Light curing (LC) packable composite resin, LC flowable resin, LC glass ionomer (GI), and self-curing GI specimens were colored in coffee or curry for three hours a day for seven days. After that, regular toothpaste, whitening toothpaste containing hydrogen peroxide, and whitening toothpaste containing activated charcoal were applied for three minutes three times a day for two weeks. Luminosity (L), chromaticity a (a), and chromaticity b (b) were measured using a spectrophotometer once a week. Results: In the coffee-colored group, the change in L^2*a^2*b² (E²) with time was significant (p=0.004), there was no difference for different toothpaste types (p=0.646), and there was significant difference (p<0.001) for different esthetic restorative materials. The change of E² in the curry-colored group was significant only for different esthetic restorative materials (p<0.001). In the coffee-colored group, the L, a, and b values of the light-curing GI showed greater change than other materials after staining and one week after whitening, turning dark, red, and yellow. In the curry-colored group, L did not differ for different materials and times, and a and b showed the greatest difference in light-curing GI after staining and one and two weeks after whitening. Conclusion: The use of whitening toothpaste for two weeks was not different from the use of general toothpaste in the removal of staining or whitening. Since light-curing GI is the most vulnerable to coloration, it is recommended that coloring by food chromogen should be explained in advance, before using light-curing GI for teeth restoration.

• 한국재료학회지
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• 제29권11호
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• pp.690-696
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• 2019

Geopolymer is an alumina silicate-based ceramic material that has good heat-resistance and fire-resistance; it can be cured at room temperature, and thus its manufacturing process is simple. Geopolymer can be used as a reinforcement or floor finish for high-speed curing applications. In this manuscript, we investigate a high-speed curing geopolymer achieved by adding calcium to augment the curing rate. Metakaolin is used as the main raw material, and aqueous solutions of KOH and $K_2SiO_3$ are used as the activators. As a result of optimizing the high bending strength as a target factor for geopolymers with $SiO_2/Al_2O_3$ ratio of 4.1 ~ 4.8, the optimum ranges of the active agent are found to be $0.1{\leq}K_2O/SiO_2{\leq}0.4$ and $10{\leq}H_2O/K_2O{\leq}32.5$, and the optimum range of the curing accelerator is found to be $$0.82{\leq_-}Ca(OH)_2/Al_2O_3{\leq_-}2.87$$. The maximum flexural strength is found to be 1.35 MPa at $Ca(OH)_2/Al_2O_3=2.82$, $K_2O/SiO_2=0.3$, and $H_2O/K_2O=11.3$. The physical and thermal properties are analyzed to validate the applicability of these materials as industrial insulating parts or repairing finishing materials in construction.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2374-2382
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• 2002

Aluminum alloy/aramid fiber reinforced plastic(Al/AFRP) laminates consists of high strength metal(A15052) and laminated aramid fiber with structural adhesive bond. The mixture ratio effect of epoxy resin curing agent accelerator on the tensile strength and T-peel strength characteristic in Al AFRP laminates were investigated in this study. The epoxy. diglycidylether of bisphenol A(DCEBA), It'as cured by methylene dianiline(MDA) with or without an accelerator(K-54). Eight different kinds of resin mixture ratios were selected for the test , five kinds of Al/AFRP laminates were named as Al/AFRP(1) and three others of Al/AFRP laminates were named as Al/AFRP(2). The comparison of tensile strength and T-peel strength with variation of resin mixture ratio were studied. Respectively. Al/AFRP(1) and Al/AFRP(2) indicated approximately 6.0 times and 7.0 times more improved maximum tensile strength in comparison with those of monolithic A15052. Al/AFRP(2) indicated approximately 1.5 times more impoved maximum T-peel strengths in comparison with those of Al/AFRP(1). As results. Al/AFRP(2) turned out to have more effective characteristics on the tensile strength and T-peel strength than those of Al/AFRP(1).

• 한국정밀공학회지
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• 제16권8호
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• pp.149-154
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• 1999

FRMLs(Fiber Reinforced Metal Laminates) is a new type of hybrid materials. FRMLs consists of high strength metal and fiber which are laminated using a structural adhesive bond(epoxy resin). The effect of resin mixture ratios on the fatigue crack propagation behavior and mechanical property of Aramid fiber reinforced aluminum composites was investigated. The epoxy, diglycidylether of bisphenol A(DGEBA) was cured with methylene dianiline(MDA) with or without accelerator(K-54). Eight kinds of resin mixture ratio were tested for the experiment ; five kinds of FRMLs(1))epoxy & curing agent) and three kinds of FRMLs(2)(epoxy & curing agent & accelerator). FRMLs(2) have a more effective characteristics on the fatigue crack propagation behavior and mechanical property than FRMLs(1)

• Restorative Dentistry and Endodontics
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• 제17권2호
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• pp.421-430
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• 1992

The purpose of this study was to evaluate the bond strength between the composite resin and light - cured glass ionomer cement base / liners treated by the several methods. The light - cured glass ionomer cement(Vitrebond / Cavalite) were injected into cavites prepared in acrylic plates. One hundred and twenty specimens were uniformly prepared and devided into 3 groups. For the first group, primer was not applied to glass ionomer cement. For the second group, no application of primer was undertaken and light - curing procedure to uncured glass ionomer cement surface which was covered by bonding agent was undertaken. After bonding composite resin to light - cured glass ionomer surface, the specimens, were stored in $37^{\circ}C$, 100% humidity for 1 hour. The following results were obtained : 1. The omission of application of a primer did not produce a significantly poorer bond strength. 2. Light - curing technique to uncured glass ionomer cement which was covered by bonding agent did not produce a significantly poorer bonding strength. 3. The bond strength of Cavalite to composite resin was significantly higher than that of Vitrebond. 4. There was no significant difference between two different types of composite materials(Silux-Plus / Herculite XR) when it was applied to bond to glass ionomer cement.

• Composites Research
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• 제34권3호
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• pp.180-185
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• 2021

기존 아민계 경화제를 사용해 액정 에폭시를 경화할 경우, 랜덤 한 3차원 네트워크 구조의 생성으로 인해 phonon의 산란이 많이 발생하기 때문에 열전도도가 낮게 나타났다. 이러한 문제를 mesogen그룹을 적층된 구조로 형성하는 양이온 개시제를 이용하여 해결하기 위해 본 연구에서는 아민계 경화제와 양이온 개시제를 사용한 에폭시의 TGA분석(Thermogravimetric Analysis)을 통해 등온 열분해 활성화에너지를 조사하여 열적안정성을 비교하였다. 양이온 개시제를 이용한 에폭시의 경우 활성화가 에너지가 높았으며 기존 실험과 비교했을 때, 열적안정성은 열전도도와 비슷한 양상을 보인다.