• 접착 및 계면
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• 제7권1호
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• pp.16-22
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• 2006

본 연구에서는 페놀수지 SMC 제조에 사용되는 수용성 레졸형 페놀-포름알데히드 수지의 열안정성과 경화 발열반응 피크의 변화에 미치는 경화온도 및 경화시간의 영향을 열중량분석기와 시차주사열량계를 사용하여 조사하였다. 수용성 페놀-포름알데히드 수지의 중량감소는 주로 $200^{\circ}C,\;400^{\circ}C$ 그리고 $500^{\circ}C$ 부근에서 세 단계로 발생하였다. 경화된 수지의 $750^{\circ}C$에서 탄화수율은 약 62%~65%이었다. 수용성 페놀수지의 열안정성은 경화온도와 경화시간이 증가할수록 증가하였다. 경화시 발열반응은 약 $120^{\circ}C{\sim}190^{\circ}C$ 사이에서 진행되며, 발열피크의 최대점은 약 $165^{\circ}C{\sim}170^{\circ}C$ 사이에서 관찰되었다. 발열반응 곡선의 형태와 발열피크의 최대점은 주어진 경화온도와 경화시간에 의존하였다. 경화되지 않은 수지에 포함되어 있는 $H_2O$ 및 휘발성분을 제거하기 위하여 경화 또는 성형 전에 적어도 $100^{\circ}C$ 이상에서 약 60분 이상의 열처리가 요구되었다. $130^{\circ}C$에서 120분 동안의 경화는 수용성 페놀-포름알데히드 수지의 발열피크를 사라지게 하며, $180^{\circ}C$에서 60분 동안이 후경화는 수지의 열안정성을 더욱 향상시켜 주었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1992년도 추계학술발표강연 및 논문개요집
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• pp.129-130
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• 1992

• 한국염색가공학회:학술대회논문집
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• 한국염색가공학회 2000년도 춘계학술대회 논문집
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• pp.145-149
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• 2000

• 한국재료학회지
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• 제9권5호
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• pp.467-472
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• 1999

Neopentyl glycoI(NPG) 의 함량변화에 따른 diglycidyl ether of bisphenol A (DGEBA)/4,4' -methylene dianiline (MDA) 계의 등온적 경화거동을 DSC를 이용하여 분석하였다. DGEBA/MDA 계의 경화속도를 증가시키기 위하여 NPG를 첨가하였다. NPG 함량에 관계없이 전화율 곡선이 s-자 모양이었으며, 이것은 DGEBA/MDA/NPG 계의 경화반응이 자촉매 반응 메커니즘에 따른다는 것을 의미한다. NPG의 함량이 증가함에 따라 경화속도가 증가하였으며, 이것은 NPG가 가지고 있는 두 개의 hydroxyl 기가 촉매로 작용하기 때문이다.

• Journal of Nutrition and Health
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• 제34권2호
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• pp.222-229
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• 2001

This study describes the application of the stages of change construct to fat intake by examining the associations of the stages of change with nutritional status and beliefs on health behavior. Data were obtained from apparently healthy 596 adults(326 females and 270 males) residing in large cities. Stages of change assessed by an algorithms based on 6 items were designed each subject into one of the 5 stages: precontemplation(PC), contemplation(CO), preparation(PR), action(AC) and maintenance(MA). Beliefs on health behavior were assessed by self efficacy as well as 4 belief scales from the Locus of Illness Control(LIC) developed using factor analysis such as internal disease cure and prevention and external disease cure and prevention. Energy and fat intakes were measured by a 39 item short form food frequency questionnaire. Regarding the 5 stages of change, MA stage comprised the largest group(37.9%), followed by Ac(30.7%), PC(11.4%), CO(10.4%) and PR(9.6%). Subjects who were females, older or healthier were more likely to belong to either AC or MA. Stage assignment of individuals was corroborated by their nutritional variables. Those in PC had the most energy and fat and those in MA ate the least for females. BMI was higher in PR than any other stages for both males and females. Those in PC were distinctive in that they were more externally oriented in terms of health control showing higher scores on external disease prevention(for males) and external disease cure(for females), and lower score on internal disease cure. On the other hand, those in MA received the highest scores on internal disease prevention and self efficacy, which suggested that they were more internally oriented. Canonical discriminant function analysis indicated that the 5 stages were importantly discriminated by BMI, self efficacy, internal disease prevention and external disease prevention for males and by fat intake, self efficacy and external disease cure variables for females. The results of our study confirm differences in stages of change in fat intake in terms of nutritional status and beliefs on heath behavior and indicate the need for taking these phases of change into account in nutrition advice. (Korean J Nutrition 34(2) : 222-229, 2001)

• 대한기계학회논문집A
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• 제24권10호
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• pp.2520-2528
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• 2000

Mechanical and physical properties of composite materials make a great difference due to their cure process condition. In order to clarify the effect of cure process condition on the microscopic damage behavior and failure mechanism of Carbon/Epoxy composites, three point bend test has been performed. For this purpose, two kinds of specimens with single adhesive and multiple adhesive layers were prepared. For single adhesive layer, four different types of specimen were used, that is, non-sanding, sanding, cocured, laminated specimens. Three different types of specimen were also used for the multiple adhesive layer, non-sanding, sanding, cocured specimens. Acoustic emission technique has also been employed to monitor the damage progresses associated with each micro-failure mechanism. The characteristics of AE parameters associated with micro-failure mechanism of each specimen were discussed.

• Journal of the Korean Wood Science and Technology
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• 제40권2호
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• pp.110-122
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• 2012

This study investigated the effects of layered clay on the thermal curing behavior and tensile properties of resole phenol-formaldehyde (PF) resin/clay/cellulose nanocomposites. The thermal curing behavior of the nanocomposite was characterized using conventional differential scanning calorimetry (DSC) and temperature modulated (TMDSC). The addition of clay was found to accelerate resin curing, as measured by peak temperature ($T_p$) and heat of reaction (${\Delta}H$) of the nanocomposite’ curing reaction increasing clay addition decreased $T_p$ with a minimum at 3~5% clay. However, the reversing heat flow and heat capacity showed that the clay addition up to 3% delayed the vitrification process of the resole PF resin in the nanocomposite, indicating an inhibition effect of the clay on curing in the later stages of the reaction. Three different methods were employed to determineactivation energies for the curing reaction of the nanocomposite. Both the Ozawa and Kissinger methods showed the lowest activation energy (E) at 3% clay content. Using the isoconversional method, the activation energy ($E_{\alpha}$) as a function of the degree of conversion was measured and showed that as the degree of cure increased, the $E_{\alpha}$ showed a gradual decrease, and gave the lowest value at 3% nanoclay. The addition of clay improved the tensile strengths of the nanocomposites, although a slight decrease in the elongation at break was observed as the clay content increased. These results demonstrated that the addition of clay to resole PF resins accelerate the curing behavior of the nanocomposites with an optimum level of 3% clay based on the balance between the cure kinetics and tensile properties.

• 한국임상보건과학회지
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• 제2권2호
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• pp.107-118
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• 2014

Purpose. to help them find mental rest and improve school life adjustment by way of a fine art cure program. Methods. two primary schools in Gyeongsangnam-do were chosen where there are plenty of multiple-family kids. 13 children from the families between Korean husbands and foreign wives were divided into 2 groups: experimental group (7, C School), control group (6, H School). The two groups took the KSD (Kinetic School Draw), while the experimental group received a fine art cure program (40 minutes, once a week, 10 times in total). After the program, the KSD was given again to both groups. To prove the effects of this study, the picture projection test KSD was given before and after the experiment. For comparison and analysis, the changes in each individual's attitude, behavior, responses, and emotions were observed and recorded. Results. The fine art treatment program had some effects on the psychological rest of the elementary school children from multiple-culture families. In the pretest before the art cure program, the subjects shrank and cared a lot about others. According to the progress of the program, however, their worries and anxiety began to be gone. They had confidence through mental ease and self-respect. Therefore, the fine art cure program had a positive effect on the improvement of self-respect and sociality of multiple-culture family kids. Their school life was influenced by the newly-attained confidence, achievement, and peer relationship. Conclusions. This research is of some significance in that the fine art cure program was held to reveal its effects on the school life adjustment of the elementary school kids from multiple-culture families, especially because worries grow about the possibility of their maladjustment in the era of multiple-culture families. In addition, this program is expected to give some basic information about the development of programs to make friendly relations and smooth communication among the multiple-culture parents and teachers as well.

• Macromolecular Research
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• 제10권1호
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• pp.34-39
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• 2002

Cure behavior of an epoxy resin was investigated at different cure temperatures (110, 120, 130, 140, and 150 $^{\circ}C$) and cure times in the presence of 2 wt% of an N-benzylpyrazinium hexafluoroantimonate (BPH) cationic catalyst by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The glass transition temperature ( $T_{g}$) and chemical conversion (x) at the different temperatures were determined from DSC thermograms. The $T_{g}$ and x vs. In time data were superposed up to $T_{g}$ = 10$0^{\circ}C$ and x = 0.70 by shifting horizontally at a reference temperature of $T_{g}$ = 13$0^{\circ}C$. It is interesting that the $T_{g}$ and x of the superposed data increase rather slowly in the early stage of cure and rapidly thereafter. Therefore, the increase of the $T_{g}$ and x can be divided into two regions; $R_{I}$= -18.4(= $T_{go}$ ) ~5$^{\circ}C$ and $R_{II}$ = 5 ~ 10$0^{\circ}C$ in $T_{g}$, and $R_{I}$ : 0~0.24 and $R_{II}$ : 0.24~0.70 in x. The $R_{I}$ is closely related to the initiation reactions between BPH and epoxy and between hydroxy group and epoxy in this epoxy/catalyst system. From the kinetic analysis of the $T_{g}$-shift, activation energy was 12.5 kcal/mol. The relationship between $T_{g}$ and x was also considered. The gelation and vitrification times for different cure temperatures were obtained from DMA curves.urves. DMA curves.urves.

• Composites Research
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• 제33권2호
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• pp.44-49
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• 2020

본 연구에서는 시차주사 열량계(differential scanning calorimetry, DSC)를 이용하여 진공백 성형 공정에 사용되는 탄소 섬유 프리프레그의 경화 거동을 연구하였다. 프리프레그를 이용한 동적주사 시험을 통해 전체 발열량(ΔH_total = 537.1 J/g)을 측정하였고, 130℃~180℃에서 등온주사 시험을 실시하였다. 등온주사 시험의 결과는 온도가 올라감에 따라 발열 반응이 증가되는 것을 확인하였다. 시험 결과를 토대로 수지의 경화 거동을 분석하기 위하여 Kratz 모델을 적용하였다. 서로 다른 경화 사이클로 제작된 평판의 경화도를 경화 예측 모델과 실험값을 비교하였다. 경화 예측 모델은 실험값 대비 3.4% 이하의 오차율을 보여 결과가 잘 부합하는 것을 확인하였다.