• 방사선산업학회지
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• 제4권1호
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• pp.19-23
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• 2010

Vinyl ester (VE) resins, introduced in the late 1960s, have made large strides in reinforced plastics applications as adhesive and matrix materials on their appropriate mechanical performance characteristics in the glassy state. Generally, VE resins are a group of dimethacrylate resins based on bisphenol A type epoxy resin. They exhibit easy handling properties as well as good resistance to most chemical agents due to their mechanical and thermal properties. In this study, the effects of curing methods of vinyl ester resins on gel contents, flexural strength and dynamic mechanical properties were investigated. Thermal curing (room temperature, $80^{\circ}C$) and electron beam curing were used to crosslink a VE resin/styrene complex (65/35 wt%) with methyl ethyl ketone peroxide (MEKPO) as a catalyst and an 8 wt% cobalt naphthenate in styrene solution as a accelerator. For the samples, gel contents as well as flexural strength and dynamic mechanical properties were characterized and compared by soxhlet apparatus, universal testing machine (UTM) and dynamic mechanical analysis (DMA). As a result, the electron-cured VE resin was confirmed as a better condition than those for gel contents, flexural strength and dynamic mechanical properties, respectively.

• Tribology and Lubricants
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• 제21권6호
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• pp.268-271
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• 2005

In this study, the wear characteristics of five different dental composite resins cured by conventional halogen light and LED light sources were investigated. Five different dental composite resins of Surefil, Z100, Dyract AP, Fuji II LC and Compoglass were worn against a zirconia ceramic ball using a pin-on-disk type wear tester with 15N contact force in a reciprocal sliding motion of sliding distance of 10mm/cycle at 1Hz under the room temperature dry condition. The wear variations of dental composite resins were linearly increased as the number of cycles increased. It was observed that the wear resistances of these specimens were in the order of Dyract AP > Surefil > Compoglass > Z100 > Fuji II LC. On the morphological observations by SEM, the large crack formation on the sliding track of Fuji II LC specimen was the greatest among all resin composites. Dyract AP showed less wear with few surface damage. There is no significant difference in wear performance between conventional halogen light curing and light emitting diodes curing sources. It indicates that a light emitting diodes (LED) source can replace a halogen light source as curing unit for composite resin restorations.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.965-968
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• 2008

현재 국내현장에서 공사기간 중 구조물의 압축강도를 확인하는 방법으로는 KS F 2403에 의한 시험용 공시체의 압축강도를 구조체 콘크리트의 압축강도로 정하고 있으며, 이 규정의 내용에는 시험용 공시체의 양생방법으로 표준수중양생(20$\pm$2$^{\circ}$C)을 하도록 규정되어 있다. 그러나 현장 타설된 콘크리트의 경우 일반 대기환경에 노출되어 사계절 온도변화의 환경하에서 양생되고 있어 실 구조물의 콘크리트 압축강도와는 큰 차이를 나타내게 된다. 따라서 본 논문에서는 현재 KS에 규정되어 있는 압축강도용 시험체의 양생방법과 현장에서 구조체의 강도 및 거푸집 탈형시기 판정 등의 품질관리를 위해 사용하는 기중양생, 봉함양생, 구조체의 코어강도, 그리고 본 연구에서 제안하는 구조체의 내부환경 조건을 양생조건으로 적용한 양생방법을 적용하여 고강도 콘크리트의 강도발현특성을 파악하여 구조체 콘크리트의 강도에 가장 근접하는 공시체 양생방법을 제안하고자 한다.

• 한국지반환경공학회 논문집
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• 제21권11호
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• pp.11-20
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• 2020

연약지반 차수 및 보강용 그라우트에 대하여 다양한 양생조건에서 초기 및 장기재령에 걸쳐 내구성에 대한 검토를 수행하였다. 그라우트는 물유리계, 급결광물계 및 아크릴고분자계를 대상으로 하였으며, 양생조건은 수도수(청수) 양생, 인공해수 양생 및 대기 양생으로 하고, 시험은 재령별 일축압축강도와 길이변화량 및 중량변화량에 대하여 수행하였다. 인공해수는 MgCl₂와 MgSO₄ 수용액을 각각 제조하여 사용하였다. 급결광물계와 아크릴고분자계는 수도수와 인공해수에서는 내구성에 큰 변화가 없이 안정적으로 양생되는 반면 물유리의 경우 수도수에 비해 인공해수조건에서 매우 급격한 내구성 저하가 발생되었다. 대기 양생조건에서는 모든 경우에서 수도수 양생에 비해 내구성이 저하되는데, 특히 급결광물계와 물유리계에서 중량감소가 각각 약 62% 및 60%로 큰 내구성 저하가 발생되었다.

• 한국추진공학회지
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• 제24권6호
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• pp.101-107
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• 2020

본 논문에서는 HTPB/AP 계열의 추진제의 경화 온도를 변화시키는 Step 경화 방법으로 경화일 단축 연구를 진행하였다. 이 연구는 HTPB/AP 계열의 추진기관 제작 시 생산성 향상(제작기간 단축 및 치구회수율 증대)을 목적으로 한다. 정상 경화 대비 추진제의 기계적 물성을 비교하여 정상 경화 시 60℃ 5일 소요되는 경화일을 Step 경화로 4일(60℃ 1일 / 65℃ 3일)로 설정하였다. 경화일 단축을 적용 시 추진제 노화 특성을 알아보기 위해 Step 경화 후 후경화(Post-cure) 시험을 진행하였다. 이를 통해 기계적 물성 및 열팽창 계수를 측정하여 추진제의 후경화 특성을 분석하였다. 또한, Step 경화 후 가속 노화 시험을 진행하여 12주차 경과 후 인장시험을 수행하였다. 그 결과, Sm(bar)은 8 bar 이상, Em(%)은 40%이상으로 요구되는 우수한 기계적 물성을 가지는 것을 알 수 있었다.

• 한국정밀공학회지
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• 제21권1호
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• pp.46-50
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• 2004

The curing characteristics of a liquid photopolymer during microstereolithography and the shape accuracy of thereby fabricated microstructures were investigated experimentally. A He-Cd laser with a wavelength of 442nm and a photopolymer consisted of a commercial resin from SK chemical and a photoinitiat or were used for the experiment. By varying the laser beam power and scanning speed of the focused laser beam, minimum curing thickness of 50 ${\mu}ㅡ$ was obtained. The distortion of solidified structure due to adhesion force was measured and the optimum fabrication conditions were determined. Also, the feasibility of direct fabrication of three-dimensional microstructures by Super IH process was examined.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.589-594
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• 2003

The pi-cell [1] is known as one of the candidates for a fast response time and a good viewing angle characteristics due to a self-compensated configuration and can be a replaceable mode instead of the current TN mode and the IPS mode for moving picture in future. This paper shows the optimized condition to maintain bend state instead of splay state, which is mortal demerit for good optical properties in a pi-cell, by using the polymer stabilized method [2]. The good electro-optical characteristics are also obtained by optimizing the various factors, which are monomer concentration in a LC, UV intensity, curing time, curing voltage, and curing temperature, and by using retardation film. We use a scanning electron microscope to study the structures of the polymer stabilized polymer network in a pi-cell as a key to figure out why bend state is occurred.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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• pp.259-262
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• 2012

Recently, as the national policy of green growth is promoted, construction field also makes an effort to reduce CO₂ gas released when producing cement continuously. In other words, as the method solving environmental pollution and resources exhaustion, lots of mineral material compounds such as blast furnace slag powder which is industrial by-product, fly ash, red mud, etc. are examined to bo used as the substitute good of cement Therefore this study is to investigate the hardening characteristics of alumino-silicate inorganic binder using red-mud used as a accelerator of industrial by-product such as fly ash and blast furnace slag powder according to curing temperature. As a result, it is effective to use red-mud as the accelerator of inorganic binder with other additory accelerators.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.147-148
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• 2006

A research on scaffold fabrication has been progressed in many research groups. However, the mechanical properties of existing biodegradable materials are still not satisfactory. But, PPF (poly (propylene fumarate)) has a good mechanical property in comparison to other biodegradable materials. Nevertheless, the viscosity of the synthesized PPF is too high to fabricate structures using micro-stereolithography. Therefore, the viscosity of the resin was made low by adding the diethyl fumarate and this material could be used in micro-stereolithography apparatus. Then, a photoinitiator was added for photo crosslinking of the DEF/PPF resin. 2.5D and 3D scaffolds were fabricated our system and curing characteristics of the resin were analyzed through the experiment.

• Elastomers and Composites
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• 제53권2호
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• pp.67-74
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• 2018

Magneto-rheological elastomers (MREs) are smart materials in which the inherent stiffness and damping properties can be changed by the influence of an external magnetic field. The magneto-rheological (MR) effect depends on the orientation characteristics of the dispersed magneto-responsible particles (MRPs) in the matrix. In this study, natural rubber (NR) and ethylene propylene diene rubber (EPDM) were blended and used as a matrix of an MRE. EPDM was pre-cured before blending with NR. The Mooney viscosity, curing characteristics, and mechanical properties were analyzed with various pre-curing conditions of EPDM and the NR/EPDM blend. The results show that excellent mechanical properties of the NR/EPDM blend-based MRE were obtained when the pre-curing time of EPDM was 60 min. The aging property of the NR-based MRE was improved by the introduction of pre-cured EPDM. Also, the anisotropic MRE showed a higher MR effect than that of the isotropic MRE.