• 한국염색가공학회지
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• 제17권1호
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• pp.30-37
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• 2005

The tensile properties, acetic acid solubility and degree of swelling in distilled water of cellulose/chitosan and sericin/chitosan film blended by mixing chitosan acetic acid solution with cellulose solution or sericin solution were investigated and the effect of crosslinking agent on solubility and degree of swelling were also considered. From the experimental results, the model of intermolecular bond is proposed. Tensile modulus of 100% cellulose film is high but the tensile strength and elongation are low. The elongation of 100% chitosan film is high but tensile modulus and strength is low. But it is possible to make film having same or higher tensile strength and modulus compared to that of 100% cellulose film by mixing cellulose and chitosan or by mixing sericin and chitosan. Chitosan is solved in 5vol % acetic acid solution but cellulose and sericin are not solved. Degree of swelling of chitosan in distilled water is higher than that of cellulose and sericin. Lower than 40wt% chitosan content, the solubility of cellulose/chitosan film in 5vol % acetic acid solution shows lower expected value but higher in case of sericin/chitosan film.

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.278-283
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• 1999

Formaldehyde has widely been used for the cross-linking of polyvinyl alcohol polyvinyl alcohol polymer. The effects of formaldehyde on the water resistance of MDF cement composites were investigated as a function of types of catalyst, base or acid, and the amount of formaldehyde. The acetalization, reaction of OH group of PVA with aldehyde, was ended incompletely under base atmosphere. However, by addition of citric acid, the cross-linking of PVA polymer could be acheved through acetalization of PVA and formaldehyde. The effects of these different patterne according to the types of catalyst on the water resistance of MDF cement were studied by the preparation of PVA films and MDF composites. Thanks to the cross-linking reaction of PVA polymer chains by formaldehyde, the modified PVA films and MDF composites showed a good water-resistant propety. The modified MDF cement composite to which 3 wt% formaldehyde and 1 wt% cirtic acid were added showed 80% of initial flexural strength and good interfacial state between cement grain and polymer matrix. However, 4 wt% formaldehyde deteriorted the processing conditions, microstructures and eventually the flexural strength, causing sharp increase in the viscosity of sample dough during the mixing process. To study the relatins of flexural strength and interface of cement grain and polymer matrix, SEM and MIP measurement were performed.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.45.1-45.1
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• 2009

In this study, we investigated a calcium phosphate-calcium sulfate injectable bone substitute (IBS) with organic reinforcement of chitosan, citric acid and hydroxypropyl-methyl-cellulose (HPMC). The powder component of IBS consisted of tetra calcium phosphate (TTCP), dicalcium phosphate dihydrate (DCPD) and calcium sulfate dihydrate (CSD). The liquid component was a solution of citric acid and chitosan. The effect of HPMC in terms of setting time, compressive strength and apatite forming ability on this IBS was investigated. The mass content of HPMC in liquid phase was varied in array of 0%, 2%, 3% and 4%. The setting times obtained between 20 and 45 minutes. Compressive strength was achieved over 20 MPa after incubation at 370C and in 100% humidity for 28 days. Porosities were evaluated in relation with compressive strength. Elastic moduli of the 28 days after-incubation IBS were obtained around 4GPa

• Journal of Forest and Environmental Science
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• 제9권1호
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• pp.67-80
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• 1993

무공해 대체 펄프화법 개발의 일환으로 비교척 최근에 많은 연구가 이루어지고 있는 아세트산-물 용매 증해법을 이용하여 현사시나무와 소나무률 펄프화 하였다. 펄프 특성의 변화에서 현사시나무는 거의 모든 아세트산 충해초건에서 우수한 펄프화 경향을 보였지만 소나무는 저온에서 충해가 거의 일어나지 않았다. 현사시나무의 최적 중해조건은 중해농도 95%, 중해온도 $185^{\circ}C$, 증해시간 0.5hr이었다. 구성당 성분의 거동은 현사시나무와 소나무에서 glucose만이 소량 감소하는 반면 그외의 당성분들은 다량 용출되었다. 폐액중의 용출 아세트산 리그닌에 대한 기초척인 성질을 살펴본 결과 현사시나무의 아세트산 리그닌의 원소조성은 C가 63.88%, H가 5.45%, O가 30.67%이며 $C_9$의 formular는 $C_9H_{9.15}O_{3.24}$였고 소나무의 아세트산 리그닌의 조성온 C가 61.85%, H가 6.14%, O가 32.01% 이며 $C_9$의 formular는 $C_9H_{9.15}O_{3.50}$이었으며 두 수종의 아세트산 리그닌 중합 명균분자량은 현사시나무가 731이며 소나무는 725였다.

• 대한치과교정학회지
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• 제25권3호
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• pp.341-353
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• 1995

이 연구는 부식농도가 전단결합강도와 법랑질 표면의 부식깊이에 미치는 영향을 관찰하기 위하여 표면을 편평하게 연마한 소의 법랑질을 $0%,\;5%,\;10%,\;20%,\;30%,\;40%,\;50%,\;60%,\;70%,\;80%$ 및 $85\%$ 인산용액으로 60초간 부식시키고, 브라켓 접착의 전단결합강도와 법랑질 표면의 부식깊이와 조도를 측정하고, 주사전자현미경으로 부식면을 검경하였으며, 이상에서 얻은 자료를 통계처리하고 평가하여 다음과 같은 결론을 얻었다. 법랑질 표면의 부식깊이는 인산액의 농도가 $40\%$ 내지 $50\%$에 도달할 때까지 증가하다가 그 이후의 농도증가와 함께 점진적으로 감소하였다. 법랑질 표면의 부식깊이와 부식면의 조도 사이에 상관성이 없었으며, 부식면의 조도와 전단결합강도 사이에 중등도의 상관성($\gamma$=0.63)을 보였다. 인산액의 농도가 $5\%$에서 $40\%$에 도달할때까지 균질의 편평한 부식면을 나타내는 소견을 보였으나 $50\%$와 $60\%$에서 불균질의 과도한 그리고 편평하지 못한 부식면소견을 보였으며, $10\%$에서 $60\%$까지의 인산액에 의한 법랑질 부식 후 레진 접착제의 전단결합강도 사이에는 유의차가 얼었으며, $5\%$와 $70\%$의 인산액에 의한 것은 전자보다 작았으나 구강내에서 교정력에 견딜수 있는 전단결합강도를 나타낼 것으로 추정된다.

• Restorative Dentistry and Endodontics
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• 제13권1호
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• pp.123-129
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• 1988

The purpose of this study was to evaluate the bond strength of glassionomer cement against cut dentin surface which was treated with various surface cleaning agents. 48 freshly extracted human 3rd molars were ground flat through the enamel into the dentin using 600 grit silicone carbide paper under a flow of water. The were divided into four groups by the following cleaning procedure on cut dentin surface; Group I : No surface treatment after grinding with 600 grit silicone carbide paper as control group Group II : Surface treatment with 50% citric acid for 30 seconds. Group III : Surface treatment with 37% phosphoric acid for 30 seconds. Group IV : Surface treatment with 10% poly acrylic acid for 30 seconds. The specimens in 4 groups were immersed in distilled water at $37^{\circ}C$ for 24 hours before testing after cleanising with water-spray and drying with air. Bond strength was measured with Instron Universal Testing Machine (Autograph S-100, Shimadzu, Kyoto, JAPAN). The results were as follows: 1. The bond strengths of group II, III & IV were not seemed to be shown more significant improvement than a group I. 2. The bond strengths in groups which were treated with 50% citric acid, 37% phosphoric acid and 10% polycrylic acid, were ranked 24.70kg/$cm^2$, 22.02kg/$cm^2$ and 31.13kg/$cm^2$, but its difference was not significant, statistically.

• Elastomers and Composites
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• 제36권3호
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• pp.195-200
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• 2001

UV조사 하에서 아크릴산의 그라프팅을 이용한 LDPE의 표면개질을 XPS와 접촉각을 이용하여 살펴보았으며, 이에 따른 알루미늄/LDPE 라미네이트의 접착력 변화를 살펴보았다. 접촉각은 UV조사시간이 증가함에 따라 초기에 급격히 감소하다가 점차 일정한 값을 나타내었다. 이는 초기에는 LDPE 표면에 그라프트된 아크릴산에 의해 친수성이 급격히 증가하다가 표면의 아크릴산 농도가 증가함에 따라 친수성의 변화가 상대적으로 감소하기 때문으로 생각된다. 이러한 결과는 XPS를 이용한 O1s/C1s 비의 증가로도 확인할 수 있었다. 아크릴산이 그라프트된 LDPE와 알루미늄의 접착력은 순수한 LDPE를 이용하였을 때에 비하여 약 30배치 증가를 나타내었으며 이는 아크릴간의 그라프트에 의해 LDPF의 표면 극성기가 증가하였기 때문이다. 황산/isodium dichromate를 이용하여 알루미늄 표면을 처리한 경우 보다 뛰어난 접착력을 나타내었다. 아세트산의 존재하에서 LDPE/알루미늄 라미네이트의 계면접착력은 급격히 감소함을 알 수 있었다.

• KSBB Journal
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• 제10권2호
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• pp.149-158
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• 1995

각종 CD와 여러 종류의 화합물, pH indicator, biostain, 아미노산, 천연배당체, 그리고 fatty acid 간의 inclusion complex 형성능을 비교하였다. Fatty acid가 각종 CD에 대한 포접형성능과 선택성 이 높아 CD 분리용 ligand로 적합함을 알았다. Fatty acid의 포접능과 선택성은 탄소쇄의 길이와 밀접한 상관관계를 나타내어 capric acid는 ${\alpha}$- CD와 palmitic acid는 ${\beta}$-CD와 높은 선택성을 보였다. Complex형성에 미치는 반융조건인 흔합 농도비, pH, ionic strength, 그리고 온도의 영향을 검토하였다. 적정 혼합 농도비는 CD가 50mM 그리고 lig and 인 fatty acid가 50mM 일 때 였으며 , 온도가 중 요한 형성조건으로 작용하였다. 포접되지 않은 CD 와 fatty acid가 포접 된 CD의 분자구조를 X-ray diffraction과 IR spectrum을 사용하여 비교 검토하였으며, DSC로 inclusion complex 형성반응의 en­t thalpy의 변화값(${\gamma}H$)을 측정하여 발열반응임을 확인하였다.

• 한국염색가공학회지
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• 제17권4호
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• pp.35-40
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• 2005

Researches to preserve and restore the excavated cellulose fabrics as costume heritages have been carried out. In this study, in order to artificially restore an excavated cellulose fabrics, acid-treated cellulose fabrics were prepared. Three kinds of cellulose fabrics were used for an experiment. Three kinds of cellulose fabrics were treated by the acid aqueous solution for the various strength retention ($100\%,\;80\%,\;60\%,\;40\%,\;20\%$). The fine structure and physical properties of acid treated cellulose fabrics were investigated with various techniques such as wide-angle X-ray diffraction, tensile test, weight loss, shrinkage, SEM etc. Tensile strength and strain of cellulose fabrics decreased with increasing acid treatment time. However, weight loss and shrinkage increasing slightly. The crystal diffraction intensity was not changed. SEM results of acid-treated cellulose fabrics show that the surface was damaged.

• Geomechanics and Engineering
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• 제34권5호
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• pp.473-480
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• 2023

Acid rain of soils has a significant impact on mechanical properties. An X-ray diffraction test, scanning electron microscope (SEM) test, laser particle size analysis test, and triaxial unconsolidated undrained (UU) test were carried out in red clay soils with different compaction degrees under the effect of different concentrations of acid. The experiments demonstrated that: the dissolution effect of acid rain on colluvium weakened with the increase in the compacting degree under the condition of certain pH values, i.e., the damage to the structure of red clay soil was relatively light, where the number of newly increased pores in the soil decreased and the agglomeration of soil particles increased; for the same compacting degree, the structural gap decreased, and the agglomeration increased with the increase in the pH value (acidity decreases) of the acid rain; the dissolution rate of Si, Al, Fe, and other elemental minerals and cement in red clay soil was found to be higher under the effect of acid rain, in turn destroying the original structure of the soil body and producing a large number of pores. This is macroscopically expressed as the decrease of the soil cohesion and internal friction angle, thereby reducing the shear strength of the soil body.