• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
• /
• pp.214-217
• /
• 2004

The cure kinetics of blends of epoxy(tetraglycidyl-4,4'-diaminodiphenylmethane ; TGDDM)/curing agent(diaminodiphenyl sulfone ; DDS) resin with amine terminated polyetherimide-CTBN-amine terminated polyetherimide triblock copolymer(ABA) were studied using differential scanning calorimetry under isothermal conditions to determine the reaction parameters such as activation energy and reaction constants. By increasing the amount of ABA in the blends, the final cure conversion was decreased. Lower values of the final cure conversions in the epoxy/ABA blends indicated that ABA hinders the cure reaction between the epoxy and curing agents. 1be value of the reaction order, m, for the initial autocatlytic reaction was not affected by blending ABA with epoxy resin, and the value was approximately 1.0. The value of n for the nth order component in the autocatalytic analysis was increased by increasing the amount of ABA in the blends, and the value increased from 2.0-3.4. A diffusion controlled reaction was observed as the cure conversion increased and the rate equation was successfully analyzed by incorporating the diffusion control term for the epoxy/DDS/ABA blends.

• Journal of Korean Neurosurgical Society
• /
• 제37권5호
• /
• pp.357-363
• /
• 2005

Objective: The microvascular decompression(MVD) for trigeminal neuralgia(TN) is known as an effective surgical technique. But the failed MVD cases have been reported in long term follow-up studies. This study is to evaluate the efficacy of MVD through our operative techniques, offending vessels in operative field, failed cases with the review of the literatures. Methods: We analyzed total 63 cases of TN which underwent MVD from 1955 to 2003 according to characters of pain, operative findings, operative results related to causative vessel compression and operative method, progonotic factor. Statistical analysis was performed using paired t-test with SPSS Ver 11.0. Results: In TN, the most common offending vessel was superior cerebellar artery(45.0%). In compression group of nerve root by offending vessel, the cure rate was 91.7%. However, the cure rate of the contact group was 64.7% and the cure rate of the negative group was 37.5%. There was no statistical significance between the degree of compression by vessel and the operative result(p=0.076). In 51 cases with MVD only, the cure rate was 84.3% and in 3 cases with PSR only, 42.8% and in 2 cases with PSR(partial sensory rhizotomy) with MVD, 50.0%. TN recurred in 7 cases within the follow-up period and reoperations(PSR) were added in 2 cases of them. Conclusion: This study shows that MVD provided a high rate of success with a minor risk of complications, which has been regarded as the most safe and effective procedure for trigeminal neuralgia. Additional MVD in recurred TN by severe adhesion of teflon showed poor outcome. But, revisional operation(PSR) in recurred TN showed relatively good outcome. PSR should be considered for treatment of recurrent TN after MVD.

• 폴리머
• /
• 제25권1호
• /
• pp.63-70
• /
• 2001

대표적 가교형태 변화에 따른 유사한 stress-strain 특성을 나타내는 조건하에서 공정특성 및 전반적 물성에 미치는 영향을 조사하였다. 천연고무 기본 배합에서 촉진제나 황 공여체(sulfur donor) 증가에 따라 induction time은 길어지나, 가류속도는 빨라졌다. 가교계 변화에 따른 인장강도의 영향은 매우 적은 반면 신장율은 conventional vulcanization (CV)계에서 efficient vulcanization (EV)계로 갈수록 감소하는 경향을 보여 주었다. Blow-out이 발생하는 시간을 가교형태에 따라 비교하여 보면 CV

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1999년도 제30회 추계학술대회
• /
• pp.49-56
• /
• 1999

A material was formulated with Phenol novolac and HEXA only. The cure kinetics and thermal characteristics of phenol novolac with various HEXA contents were peformed by differential scanning calorimetry and thermal gravimetric analysis. All kinetic parameters of the curing reaction including the reaction order, activation energy, and rate constant were calculated and reported. The results indicate that the curing reaction goes through an autocatalytic kinetic mechanism. The friction and wear characteristics of this material were determined using friction material testing machine. The friction coefficient of phenol novolac with various HEXA contents was determined using the PV(pressure & velocity) factor. The most stable and highest friction coefficient with a various pressure and velocity condition was found at HEXA 10 wt.% material. The specific wear rate per unit sliding distance with a various HEXA contents was reported.

• 한국마이크로전자및패키징학회:학술대회논문집
• /
• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
• /
• pp.152-157
• /
• 2002

The cure and rheological behavior of Diglycidyl ether of bisphenol F, catalyzed by four kinds of imidazoles and a Nadic methyl anhydride curing agent were studied using a differential scanning calorimeter (DSC) and rheometer. The isothermal traces were employed to analyze cure reaction. The DGEBF/anhydride conversion profiles showed autocatalyzed reaction characterized by maximum conversion rate at 20~40 % of the reaction. The rate constants obtained from isothermal test showed temperature dependance, but reaction order did not. The order of reaction (m+n) was calculated to be close to 3. The measurements of viscosity and relation time in the presence of inorganic fillers were carried out at different isothermal curing temperatures. The viscosity and gelation time increased with filler content at the same isothermal temperature.

• 한국재료학회지
• /
• 제5권6호
• /
• pp.667-672
• /
• 1995

DGEBA (diglycidyl ether of bisphenol A )/MDA(4,4'-methylene dianiline)/SN(succinonitrile)계와 DGEBA/MDA/SN/HQ(hydroquinone)계의 경화반응 속도론을 Kissinger equation 및 Fractional life 법에 의해 85~15$0^{\circ}C$에서 DSC를 이용하여 연구하였다. 경화반응 온도가 높아짐에 따라 반응속도는 증가하는 반면, 반응차수는 거의 일정하였다. 또한 촉매로 HQ를 첨가한 계가 첨가하지 않은 계보다 반응속도는 크게 증가했으며, 활성화 에너지 값은 약 20% 정도 감소하였다 또한, 경화반응 시작온도는 3$0^{\circ}C$ 정도 낮아졌다.

• Macromolecular Research
• /
• 제11권4호
• /
• pp.267-272
• /
• 2003

The isothermal cure reactions of blends of epoxy (DGEBA, diglycidyl ether of bisphenol A)/anhydride resin with polyamide copolymer (poly(dimmer acid-co-alkyl polyamine)) or PEI were studied using differential scanning calorimetry (DSC). Rheological measurements have been made to investigate the viscosity and mechanical relaxation behavior of the blends. The reaction rate and the final cure conversion were decreased with increasing the amount of thermoplastics in the blends. Lower values of final cure conversions in the epoxy/thermoplastic blends indicate that thermoplastics hinder the cure reaction between the epoxy and the curing agent. Complete miscibility was observed in the uncured blends of epoxy/thermoplastics up to $120^{\circ}C$ but phase separations occurred in the early stages of the curing process at higher temperatures than $120^{\circ}C$. According to the rheological measurement results, a rise of G' and G" at the onset of phase separation is seen. A rise of G' and G" is not observed for neat epoxy system since no phase separation is seen during cure reaction. At the onset of phase separation the rheological behavior was influenced by the amount of thermoplastics in the epoxy/thermoplastic blends, and the onset of phase separation can be detected by rheological measurements.

• Korean Chemical Engineering Research
• /
• 제40권6호
• /
• pp.681-686
• /
• 2002

산업 현장에서 이론적인 건조방법이 실제와는 차이가 많고 또한 배기가스의 재순환이 폐열을 이용하는 목적으로 열원의 절감에는 경제적이지만 이들 파라미터에 따른 요소수지 성형화에 미치는 영향을 연구한바가 없다. 따라서 요소 수지 성형재료의 경화 특성을 건조와 성형 공정 중의 건조온도와 시간, 배기가스 재 순환률 및 성형온도에 따라 실험하여 다음과 같은 결과를 얻었다. 성형재료의 수분함량은 건조 시간과 건조 온도가 증가함에 감소하고, 건조속도는 배기가스 재 순환률이 증가하면 감소한다. 특히 경화유동도는 배기가스의 재 순환량, 건조온도 및 성형온도가 증가하면 감소한다. 또한 건조온도, 건조시간, 배기가스의 재 순환량 및 성형온도에 따라 수분함량과 경화유동도에 대한 상관식을 구하여 재현성있는 최적의 조건을 구명하였다.

• Elastomers and Composites
• /
• 제55권4호
• /
• pp.314-320
• /
• 2020

This study focused on experiments with polyethylene glycol (PEG) and glycidyl methacrylate (GMA), which are functional additives for water-expandable rubber. Polychloroprene rubber (CR)/superabsorbent polymer (SAP) composites were prepared and their cure behaviors, mechanical properties, water absorption rates, and surface morphology were measured based on the functional additives applied. When PEG and GMA were applied to the composites, the water absorption rate increased-including the initial rate-compared to that measured when functional additives were not used. The results also show that PEG has a hydrophilic functional group, which allows it to absorb more water, and GMA acts as a coupling agent between CR and SAP. However, with the introduction of functional additives, the cure rate slowed down and the mechanical properties also decreased.

• 응용통계연구
• /
• 제9권2호
• /
• pp.95-108
• /
• 1996

의약학 분야에 있어서 임상시험(clinical trial)을 하는 도중에 약의 독성이 발견되거나 연구 초기에 두 처리군간의 차이가 크게 나타난다면 임상시험의 종료를 신중하게 고려하는 것이 바람직할 것이다. 따라서 요즈음에는 일정시간이 경과할 때마다 실험 결과를 중간점검(interim monitoring)하는 것이 점점 요구되어지고 있는 추세다. 본 논문에서는 두 치료법의 치료율을 비교하는 경우에 비모수검정통계량에 집단축차검정법을 적용하여 생존분포, 치료율, 중도절단율, 오류분배율함수(error spencing rate function) 등을 다양하게 변화시키면서 모의실험을 실시하여 Gray-Tsiatis 통계량, logrank 통계량, Gehan 통계량 각각에 대한 검정력과 유의수준을 비교하였다.