• Journal of Adhesion and Interface
• /
• v.7 no.1
• /
• pp.16-22
• /
• 2006

In this work, the effect of cure temperature and time on the thermal stability and the exothermic cure reaction peak of a waterborne resol-type phenol-formaldehyde resin, which may be used for preparing phenolic sheet molding compounds (SMC), has been investigated using a thermogravimetric analyzer and a differential scanning calorimeter. The weight loss of waterborne phenol-formaldehyde resin was mainly occurred at three temperature stages: near $200^{\circ}C,\;400^{\circ}C$, and $500^{\circ}C$. The carbon yield at $750^{\circ}C$ for the cured resin was about 62%~65%. Their thermal stability increased with increasing cure temperature and time. Upon cure, the exothermic reaction was taken placed in the range of $120^{\circ}C{\sim}190^{\circ}C$ and the maximum peak was found in between $165^{\circ}C$ and $170^{\circ}C$. The shape and the maximum of the exothermic curves depended on the given cure temperature and time. To remove $H_2O$ and volatile components, the uncured resin needed a heat-treatment at $100^{\circ}C$ for 60 min at least prior to cure or molding. Curing at $130^{\circ}C$ for 120 min made the exothermic peak of waterborne phenol-formaldehyde resin completely disappeared. And, post-curing at $180^{\circ}C$ for 60 min further improved the thermal stability of the cured resin.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.10
• /
• pp.339-345
• /
• 2018

We investigated the curing properties of cured coatings for a multi-focal UV-LED. The coatings are for LEDs that operate at multiple UV wavelengths, unlike conventional single-wavelength UV-LEDs. Using UV-LED light sources with wavelengths of 365, 395, 420, and 450 nm, we analyzed the optical characteristics such as the direction of light flux and light source. We also analyzed the curing characteristics at each UV-LED wavelength to optimize the LED for composite wavelengths. The curing performance state was predicted through computer simulation for when the multiple wavelengths of UV light sources are superimposed, and then actual LEDs were designed and fabricated. To improve the internal high-speed curing, a multi-spot module was fabricated, in which each LED is condensed, and multiple wavelengths are synthesized and condensed at the same position. The adhesive strength, surface hardness, and internal hardness of the curing agent were tested by varying the wavelength combination conditions. The surface hardening and internal hardening were compared and analyzed using a hardness tester and FT-IR analyzer. As a result, the characteristics of the surface and internal hardness were improved by a multi-spot method in which four wavelengths were overlapped in a UV-LED rather than a single wavelength.

• Polymer(Korea)
• /
• v.37 no.5
• /
• pp.557-562
• /
• 2013

The thermal expansion and mechanical properties of diglycidyl ether of bisphenol A (DGEBA) with mercaptan hardeners were studied by a comparative method with an amine-adduct type hardener. Thermal expansion and dynamic mechanical properties were measured by thermo mechanical analysis (TMA) and dynamic mechanical ananlysis (DMA), respectively. The $T_g$ and the coefficient of thermal expansion (CTE) of epoxy/amine-adduct type hardener system were $82.6^{\circ}C$ and 71.2 $ppm/^{\circ}C$, respectively. As the number of -SH functional group of mercaptan hardener increased, the $T_g$ rapidly decreased and gradually increased up to ca. $80^{\circ}C$ and the CTE under the $T_g$ rapidly increased to ca. 200 $ppm/^{\circ}C$ from 80 $ppm/^{\circ}C$ and decreased to ca. 100 $ppm/^{\circ}C$. The crosslinking density of epoxy with amine-adduct type hardener was ca.1.5 $mol/cm^3$, while that of epoxy with mercaptan hardeners increased from 1.0 to 1.7 $mol/cm^3$, as the number of -SH functional group increased. The storage modulus can increase up to 2700MPa at $30^{\circ}C$.

• Journal of Chest Surgery
• /
• v.34 no.3
• /
• pp.231-234
• /
• 2001

배경: 하지 정맥률의 치료법중의 하나인 압박경화요법의 치료효과를 알아보고자 하였다. 대상 및 방법: 영동세브란스병원에서 1997년 8월부터 1999년 8월까지 복대-대퇴정맥판막 부전이 없는 하지정맥류 환자 중 압박경화용법을 시행 받은 94명을 대상으로 하였다. 병역 및 이화학적 검사결과, 압박경화용법의 치료효과와 합병증 등을 살펴보았다. 결과: 환자의 연령은 20대에서부터 70대까지 있었으며, 평균 43.4세였고 성별은 남자가 28명 여자가 66명 이었다, 정맥의 돌출 이외에 다른 증상은 없는 환자가 87명이었으며, 다리가 무거운 증사, 피로, 통증도 각각 1예, 2예, 2예가 있었다. 대상 환자 중에서는 소복재정맥에 이환된 사람이 83예이었다. 50명환자에서 1회의 시술만으로 만족할 만한 결과를 보였으며, 시술 후의 합병증으로 부분적인 열감, 정맥염, 괴사가 있었다. 결론: 복재-대퇴정맥판막 부전이 없는 하지정맥류의 치료에 있어 경화요법은 미용적으로 우수한 효과적인 치료법으로 생각된다.

• Polymer(Korea)
• /
• v.24 no.1
• /
• pp.65-71
• /
• 2000

The latent properties and cure kinetics of an acid anhydride-cured epoxy resin have been investigated by a near-infrared (NIR) reflection spectroscopy. The assignments of the latent properties and cure behaviors were performed by the measurements of the NIR reflectance for epoxide and hydroxyl groups at different temperatures. A comprehensive analysis of the origin, location, and shifts during reaction of all major NIR absorption peaks in the spectral range from 4000 to 7100 $cm^{-1}$ / was provided. The extent of reaction was determined from NIR absorption band at the 4530 $cm^{-1}$ / depending on epoxide concentration and cure temperature.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.6
• /
• pp.28-33
• /
• 2022

In this study, the curing characteristics of commonly used Hydroxyl terminated polybutadiene(HTPB)-based solid propellant according to the curing temperature and Equivalent ratio change were investigated. In addition, the effect of curing reaction according to their ratio and content in the Triphenyl bismuth(TPB), Maleic anhydride(MA) and Magnesium oxide(MgO) catalyst systems was confirmed. Finally, moisture was added for each propellant mixing process to check the effect of moisture on propellant curing.

• Proceedings of the KIEE Conference
• /
• 2008.04a
• /
• pp.125-126
• /
• 2008

현재, 우리나라 당뇨병의 유병률은 빠른 속도로 증가하고 있으며 당뇨병의 유병기간이 길수록 각종 합병증이 발생하며 더욱 심각한 증세를 나타내기도 한다. 그 중, 비만 및 고혈당, 당대사장애로 인한 당뇨병성 혈관 합병증과 말초 혈관 경화증이 많이 발병하고 있는 실정이다. 본 연구에서는 광혈류량 측정법(Photoplethysmograaphy)으로 손가락에서 얻어진 맥파의 2차 미분 분석을 통해 당뇨병으로 확진된 36명의 당뇨병 환자에 대해 말초혈관 경화도를 연령별로 비교하고자 하였다. 이때 사용한 PPG 파형의 2차 미분 분석 평가 인자는 a와 d이고, d/a는 혈관의 경화도를 의미하며 경화도가 클수록 d/a의 값은 감소하게 되고, 연령이 증가할수록 경화도는 증가하게 된다. 50대 미만의 당뇨병 환자의 d/a값은 $-0.32{\pm}0.12$, 50대는 $-0.48{\pm}0.13$, 60대는 $-0.55{\pm}0.16$, 70대 이상에서는 $-0.59{\pm}0.19$로 연령이 높아질수록 d/a값이 감소하는 것을 확인하였다. 또한, SPSS 13.0 for Windows(SPSS Inc, USA)의 Oneway ANOVA 분석 결과, 연령과 경화도는 통계적으로 유의한 차이를 보였다(p<0.05). 하지만 70대 이상의 당뇨병 환자 그룹에서는 유의한 차이를 확인할 수 없었다. 본 연구에서는 PPG 파형의 2차 미분 분석을 통하여 연령별 당뇨병 환자의 말초혈판 경화도를 비교하였으며, 향후 보완 연구를 통해 비침습적이고 간단한 방법으로 당뇨병 환자의 말초혈관 경화도를 객관적으로 평가하고 진단할 수 있는 시스템 개발로 당뇨병 환자들의 심혈관계질환 사전예방과 치료효과 판정에 도움을 줄 것으로 기대한다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.31 no.1
• /
• pp.53-61
• /
• 2018

Ballast track requires constant maintenance work due to progress of track irregularity. Fast Hardening Track(FHT) has been developed to reduce the maintenance effort done by injecting fast hardening mortar in aged ballast to convert slab track. For the application of FHT to a railway bridge, post-installed anchors should be placed at center of the track segment to fix it on bridge. This paper presents track-bridge interaction analysis results with FHT considering stiffness and strength of post-installed anchor, age of FHT concrete and friction between FHT and bridge deck surface. Based on the analysis results, this study suggests when is good to install the anchors and allow normal operation of passing train.

• Polymer(Korea)
• /
• v.24 no.6
• /
• pp.837-844
• /
• 2000

The cure behavior of commercial epoxy molding compounds (EMC) commonly used for IC package was studied at constant cure temperatures as well as at constant heating rates using differential scanning calorimetry (DSC), rheometer, and dielectric analyzer (DEA). The cure kinetics were obtained using autocatalytic reaction model according to the Ryan Dutta method after assuming m+n equal to 2. The prediction of reaction rates by the model equation corresponded well to experimental data at all temperatures except for 10$0^{\circ}C$. The phase transitions such as gelation and vitrification occurred during network formation. At each isothermal cure temperature, $T_{g}$ was measured in accordance with cure time, and the vitrification point was attained when $T_{g}$ was equal to $T_{cure}$. The temperature dependence of gel points and vitrification points showed good agreement with Arrhenius relation. DEA using parallel plate electrode was effective for the monitoring of EMC cure. we knew that if the resin systems are materials of comparable quality, $_{gel}$$T_{g}$ is constant regardless of accelerator concentration in TTT (Time-Temperature-Transformation) diagram.

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