• 공업화학
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• 제9권1호
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• pp.71-75
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• 1998

LCD용의 재료로 사용하기 위하여 새로이 합성된 저분자 액정 중간체들을 이용하여 epoxy resin 구조를 근간으로 하는 측쇄형 선형액정 고분자 및 가교된 측쇄형 액정 고분자를 만들고 이 들의 액정특성에 대하여 조사하였다. Alkyl spacer의 길이가 다른 방향족 amine 말단의 방향족 저분자 액정(ALC(n))과 ethylene glycol diglycidylether로부터 합성된 선형 측쇄형 고분자액정은 DSC 및 편광현미경 관찰로부터 mesogen으로 쓰인 저분자 액정과 같이 네마틱 액정상을 보였으며 spacer $-(CH_2){_n}-$의 길이에 따라 액정상-등방상 전이온도($T_{NI}$)는 even-odd현상을 나타내었다. 선형 및 가교형 측쇄 액정고분자의 $T_{NI}$는 저분자 액정의 그것에 비해 더 낮은 온도에서 나타났으며 또한 가교형 측쇄 액정고분자의 경우에는 가교제인 1,10-diaminodecane 사용량에 따른 $T_g$및 $T_{NI}$의 변화폭이 그렇게 크지 않은 것이 관찰되었다.

• Composites Research
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• 제14권6호
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• pp.47-58
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• 2001

This paper describes applications of cure monitoring techniques by using embedded fiber optic strain sensors, which are extrinsic Fabry-Perot interoferometric (EFPI) and/or fiber Bra99 grating (FBG) sensors, to three kinds of molding methods of autoclave, FW and RTM molding methods. In these applications, internal strain of high-temperature curing resin was monitored by EFPI sensors. From theme experimental results, it was shown that strain caused by thermal shrink at cooling stage could be measured well. In addition, several specific matters to these molding methods were considered. As thor an autoclave molding of unidirectional FRP laminates, it was confirmed that off-axis strain of unidirectional FRP could be monitored by EFPI sensors. As for FW molding using room-temperature (RT) cured resin, it was found that the strain outputs from EFPI sensors represented curing shrinkage as well as thermal strain and the convergence meant finish of cure reaction. It was also shown that this curing shrinkage should be evaluated with consideration on logarithmic change in stiffness of matrix resin. As for a RTM melding, both EFPI and FBC sensors were employed to measure strain. The results showed that FBG sensors hale also good potential for strain monitoring at cooling stage, while the non-uniform thermal residual strain of textile affected the FBG spectrum after molding. This study has proven that embedded fiber optic strain sensors hale practical ability of cure monitoring of FRP. However, development of automatic installation methods of sensors remains as a problem to be solved for applications to practical products.

• 한국염색가공학회지
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• 제27권3호
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• pp.165-174
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• 2015

To develop automobile parts, the unsaturated polyester based matrix resin(PR)/reinforcement(randomly oriented chopped E-glass fiber, GF) composites were prepared using sheet molding compound(SMC) compression molding. The effects of GF length(0.5, 1.0 1.5 and 2.0inch)/content (15, 20, 25, 30wt%) and number of ply(3, 4 and 5) on the specific gravity and mechanical properties of PR/GF composites were investigated in this study. The optimum length of GF was found to be about 1.0inch for achieving improved mechanical properties(tensile strength and initial modulus). The tensile strength and initial modulus of composites increased with increasing GF content up to 30wt%, which is favorable content range for SMC. The specific gravity, tensile strength/initial modulus, compressive strength/modulus, flexural strength/modulus and shear strength increased with increasing the number of ply up to 5, which is the maximum number of ply range for SMC. The effectiveness of ply number increased in the flexural strength > shear strength > compressive strength > tensile strength.

• Restorative Dentistry and Endodontics
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• 제23권2호
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• pp.690-700
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• 1998

Rubber-toughened particles which are used in the field of chemical engineering are used to increase the fracture toughness of thermoset resin. The application of Core-Shell particles, one of rubber-toughened particles, as a filler for dental composite or restoration have not been examined. The purpose of this study was to evaluate possible use of Core-Shell particles for dental composite, and the hypothesis was that additional toughening mechanisms are activated by the addition of Core-Shell particles. After blending 50vol% quartz with Bis-GMA/TEGDMA resin matrix, the experimental resins were made by the addition of Core-Shell particles with varied content level as 0, 2.5, 5, 7.5, 10, 12.5, 15, and 20wt%. Fracture toughness was determined on three-point bending specimen with single-edge notch according to ASTM-E 399. Also, flexural properties, that is, strength and modulus were measured by three-point bending testing. Fractogragh of fracture toughness specimen was observed using SEM (JEOL 6400 SEM, MA). The following results from this study were obtained ; 1. Fracture toughness of composite resin added 2.5wt% Core-Shell particles was significantly higher than control group ($p{\leq}0.05$). 2. Flexural properties were decreased with increasing Core-Shell particle content, which showed a correlation statistically ($p{\leq}0.05$). 3. A toughening mechanism such as lamination and microcrack was observed in specimen determined high fracture toughness. 4. The dispersion of Core-Shell itself and quartz filler particles was limited present high content of Core-Shell particles, which decreased a resulting mechanical properties of composites. These results suggest that adequate Core-Shell particles can be used to enhance mechanical properties included toughening for dental composites.

• 대한화학회지
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• 제31권1호
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• pp.45-54
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• 1987

Calcon carboxylic acid[2-hydroxy-1-(2-hydroxy-4-sulfo-1-naphthylazo)-3-naphthoic acid;CCA)]를 이온교환시킨 Dowex 1-X8수지(CCA-Dowex 1-X8)와 2-methyl-8-hydroxyquinoline(MHQ)을 침윤시킨 Amberlite XAD-4 수지(MHQ-XAD-4)를 여러가지 매질중에 있는 철(Ⅲ)이온의 분리-농축에 사용하였다. 이들 수지의 안정성을 검토하고 철(Ⅲ)이온에 대한 흡착능을 측정하였다. 매트릭수의 주성분인 Al(Ⅲ), Ca(Ⅱ), 및 Fe(Ⅲ)들의 수지에 대한 흡착성을 pH를 변화시키며 조사하여 최적 pH범위를 결정하였다. 용리법으로 알루미늄호일과 초정약수중 미량의 철분을 매트릭스 이온으로부터 분리-농축하였다. 농축된 Fe(Ⅲ)는 소량의 강산으로 용리시켜 불꽃 원자흡광광도법으로 정량하였다. 초정약수중의 Fe(Ⅱ)와 Fe(Ⅲ) 이온들은 SP-Sephadex C-25컬럼으로 농축하고, ferrozine용액과 1% ascorbic acid-ferrozine용액으로 단계적 용리법에 의해 용리시킴으로써 각각을 분리할 수 있었다. 분리된 각 이온들은 Fe(Ⅲ)-ferrozine착물의 분석 파장인 562nm에서 분광 광도법으로 정량하였다.

• 한국염색가공학회지
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• 제29권2호
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• pp.77-85
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• 2017

The interfacial adhesion between fiber and matrix affects the physical properties of fiber reinforced composites. In this study, 3-(Methacryloyloxy)propyltrimethoxy silane(MPS) coupling agent was used to increase the interfacial adhesion between polyketone fiber and epoxy resin. The change of surface chemical composition of polyketone fiber treated with MPS was analyzed using a FTIR-ATR. The interfacial bonding between fiber and resin increased with silane coupling agent largely. Consequently, interfacial shear strength(IFSS) was enhanced with increasing concentration of MPS coupling agent and thus, the physical properties of the composites such as flexural properties and dynamic mechanical properties were changed. Flexural strength and modulus increased when the MPS concentration was higher than 0.5wt%. The dynamic storage modulus of Polyketone/Epoxy composites treated with MPS was higher than that of the untreated one. When the MPS concentration of 3wt%, the highest storage modulus was obtained.

• Restorative Dentistry and Endodontics
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• 제29권3호
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• pp.249-266
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• 2004

The purpose of this study was to determine whether pH and time has any influence on the degradation behavior of composite restoration by analyzing the leached monomers of dental composites qualitatively and quantitatively after storage in acetate buffer solution as a function of time using high performance liquid chromatography (HPLC) / mass spectrometer. Materials and Methods：Three commercial composite restorative resin materials (Z-250, Heliomolar and Aeliteflo) with different matrix structure and filler composition were studied. Thirty specimens (7mm $diameter{\times}2mm$ thick) of each material were prepared. The cured materials were stored in acetate buffer solution at different pH (4, 7) for 1, 7 and 45days. As a reference, samples of unpolymerized composite materials of each product were treated with methanol (10mg/ml). Identification of the various compounds was achieved by comparison of their mass spectra with those of reference compound, with literature data. and by their fragmentation patterns. Data were analysed statistically using ANOVA and Duncan's test. Results：1. Amounts of leached TEGDMA in Aeliteflo were significantly larger than those of UDMA in Z-250 and Heliomolar at experimental conditions of different storage time and pH variation (p<0.001). 2. As to comparison of the amounts of leached monomers per sorage time, amounts of leached TEGDMA in Aeliteflo and UDMA in Z-250 and Heliomolar were increased in the pH 4 solution more significantly than in the pH 7 solution after 1day, 7days and 45days, respectively (p<0.001). 3. In total amounts of all the leached monomers with storage times, the overall amounts of pH 4 extracts were larger than those of pH 7 extracts for all resin groups, but there was no significant difference (p>0.05).

• 접착 및 계면
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• 제8권4호
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• pp.14-22
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• 2007

본 연구에서는 페놀수지의 열안정성 그리고 glass braid/페놀수지 복합재료의 동역학적 열특성에 미치는 유리분말 및 액상 니트릴고무(NBR)의 영향을 열중량분석기와 동역학적 열분석기를 이용하여 조사하였다. 수용성 페놀수지에 충진된 유리분말과 NBR은 페놀수지의 열안정성과 복합재료의 저장탄성률 그리고 tan ${\delta}$ 변화에 중요한 영향을 미쳤다. 유리분말의 충진은 페놀수지의 열안정성을 향상시키는 반면, NBR의 존재는 특정 온도영역에서 페놀수지의 중량감소를 초래하였다. 충진제의 유 무에 따른 페놀수지의 열안정성은 경화온도뿐만 아니라 경화시간에도 의존하였다. 스트립형태의 glass braid/페놀수지 복합재료의 저장탄성률과 tan ${\delta}$의 변화는 유리분말과 NBR이 혼합된 매트릭스의 도입과 경화조건에 의해 크게 영향을 받았다.

• Restorative Dentistry and Endodontics
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• 제48권2호
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• pp.13.1-13.11
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• 2023

Objectives: Natural extracts have been investigated as a biomimetic strategy to mechanically strengthen the collagen network and control the biodegradation of extracellular matrix. This study evaluated the effect of epigallocatechin-3-gallate (EGCG) on abfraction lesions prior to the composite resin. Materials and Methods: The sample consisted of 30 patients (aged between 28 and 60 years) with abfraction lesions located in 2 homologous premolars. The teeth were randomly assigned according to dentin treatment: 0.02% EGCG solution or distilled water (control). After enamel acid etching, the solutions were applied immediately for 1 minute. The teeth were restored with Universal Adhesive (3M) and Filtek Z350 XT (3M). Analyzes were done by 2 independent examiners using modified USPHS (retention, secondary caries, marginal adaptation, and postoperative sensitivity) and photographic (color, marginal pigmentation, and anatomical form) criteria at baseline (7 days) and final (18 months). The data analysis used Friedman and Wilcoxon signed-rank tests (α = 0.05). Results: At baseline, all restorations were evaluated as alpha for all criteria. After 18 months, restorations were evaluated as alpha for secondary caries, color, and marginal pigmentation. There was significant difference between baseline and 18 months (p = 0.009) for marginal adaptation and postoperative sensitivity (p = 0.029), but no significant difference were verified between treatments (p = 0.433). The EGCG group had a restoration retention rate of 93.3%, while the control group had 96.7%. Conclusions: The application of EGCG solution on abfraction lesions did not significantly influence the survival of the restorations based on clinical and photographic criteria.

• 방사성폐기물학회지
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• 제4권1호
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• pp.59-64
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• 2006

원자력 발전소의 증기발생기 슬러지 중에서는 이온교환수지가 발견되어서는 안 된다. 원자력 발전소의 증기발생기 슬러지 시료 중에서 발견되어 이온교환수지 입자로 의심되는 구형 입자들의 특성을 측정하였다. 미세조작기술을 이용하여 광학현미경으로 입자 크기 분포를, EPMA로 구형입자의 성분을, 그리고 IR 분광 스펙트럼 비교에 의하여 이온교환수지 여부를 조사하였다. 슬러지의 입자 크기는 1 내지 $200{\mu}m$이었으나 구형 입자는 $40-500{\mu}m$이었다. 슬러지의 주요 불순원소가 Si, Al, Mn, Cr, Ni, Zn, 그리고 Ti이었으나 구형 입자는 Si, Cu, Zn 이었다. 주성분은 두 경우 모두 철이었다. 구형 입자의 IR 분광스펙트럼은 증기발생기 취출수 정화계통에서 사용하는 이온교환수지의 스펙트럼과 비교했을 때 서로 일치하지 않음을 보여주었다. 이 결과들은 증기발생기 슬러지 시료 중에서 발견된 구형 입자가 이온교환수지는 아니며 일반적인 슬러지가 생성되는 과정에서 작은 슬러지 입자들이 크게 뭉쳐서 생성된 것임을 나타내고 있다.