• 한국세라믹학회지
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• 제44권10호
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• pp.574-579
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• 2007

Porous $Al_2O_3$ ceramics were prepared by the gelcasting foams method (a slurry foaming process) with acrylamide monomer. The foaming and gelation behavior was investigated with the parameters such as the type and concentration of surfactant, solid loading of slurry, and the concentrations of initiator and catalyst. Density, porosity, microstructure, and strength of the green and sintered samples were characterized. Of the four kinds of surfactants tested, Triton X-114 showed the highest foaming ability for the solid loading of 55-30 vol%. The gelation condition giving the idle time off min was found to set the foamed structure without significant bubble enlargement and liquid lamella thinning. The green samples were fairly strong and machinable and showed maximum strength of 2.4 MPa in diametral compression. The sintered samples showed densities of 10-36% theoretical (i.e. porosity 90-64%) with a highly interconnected network of spherical pores with sizes ranging from 30 to $600{\mu}m$. The pore size and connectivity increased but the cell strut thickness decreased with decreasing the solid loading. Flexural strength of 37.8-1.7 MPa was obtained for the sintered samples.

• 한국응용과학기술학회지
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• 제13권1호
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• pp.11-19
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• 1996

The liposomes have been developed in many drugs and cosmetics fields. The liposomes prepared with main compounds of the intercellular lipids and lecithin. Amphiphile nonionic surfactants used for (PEG) n-sitosterol(n=5), diethanolamine cetylphosphate. The effect of gelation for liposomes have been on swelling reaction which have been mixed phospholipid with polyol-group at the high temperature. There were very good encapsulated properties of the active ingredients whether hydrophilic-group(magnesium ascorbyl phosphate, allantoin, sodium hyaluronate) and hydrophobic-group(vitamin-E acetate, vitamin-A palmitate). Optimum condition of liposomes were passed five times in the microfluidizer(700bar), wetting reaction temperature was at $95{\pm}5^{\circ}C$ for a hours. Particle size distribution of the vesicles should be within range 50-560nm(mean 200nm). The stability of liposomes for the course of time was stabilized for six months at $45^{\circ}C$. Application of the cosmetic was prepared moisturizing cream with liposomes of the phospholipid base.

• 대한치과보철학회지
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• 제41권6호
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• pp.732-746
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• 2003

Statement of problem. Soft lining materials, also referred to as tissue conditioning materials, tissue heating materials, relining materials, soft liners or tissue conditioners, were first introduced to dentistry by a plastic manufacturer in 1959. Since the introduction of the materials to the dental field, their material properties have been continually improved through the effort of many researchers. Soft lining materials have become widely accepted, particularly by prosthodontists, because of their numerous clinical advantages and ease of manipulation. Unfortunately, few reports have been issued upon the topic of increasing the bond strength between the base metal alloy used in cast denture bases and PMMA soft liner modified with 4-META, nor upon the pattern of debonding and material change in wet environment like a intra oral situation. Purpose. The purposes of this study were comparing the bond strength between base metal alloy used for the cast denture bases and PMMA soft liner modified with 4-META, and describing the pattern of debonding and material property change in wet environment like the intraoral situation. Material and Methods. This study consisted of four experiments: 1. The in vitro measurement of shear bond strength of the adhesive soft liner. 2. The in vitro measurement of shear bond strength of the adhesive soft liner after 2 weeks of aging. 3. A comparison of debonding patterns. 4. An evaluation the Relation time of modified soft liner. The soft liner used in this study was commercially available as Coe-soft (GC America.IL.,USA), which is provided in forms of powder and liquid. This is a PMMA soft liner commonly used in dental clinics. The metal primer used in this study was 4-META containing primer packed in Meta fast denture base resin (Sun Medical Co., Osaka, Japan). The specimens were formed in a single lap joint desist which is useful for evaluating the apparent shear bond strength of adhesively bonded metal plate by tensile loading. Using the $20{\times}20mm$ transparent grid, percent area of adhesive soft liner remaining on the shear area was calculated to classify the debonding patterns. To evaluate the change of the initial flow of the modified adhesive soft liner, the gelation time was measured with an oscillating rheometer (Haake RS150W/ TC50, Haake Co., Germany). It was a stress control and parallel plate type with the diameter of 35mm. Conclusion. Within the conditions and limitations of this study, the following conclusions were drawn as follows. 1. There was significant increase of bond strength in the 5% 4-META, 10% 4-META containing groups and in the primer coated groups versus the control group(P<0.05). 2. After 2 weeks of aging, no significant increase in bond strength was found except for the group containing 10% 4-META (P<0.05). 3. The gelation times of the modified soft liner were 9.3 minutes for the 5% 4-META containing liner and 11.5 minutes for the 10% 4-META liner. 4. The debonding patterns of the 4-META containing group after 2 weeks of aging were similar to those of immediaely after preparation, but the debonding pattern of the primer group showed more adhesive failure after 2 weeks of aging.

• Journal of Pharmaceutical Investigation
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• 제30권3호
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• pp.167-172
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• 2000

The purpose of this study is to develop a transurethral liquid suppository containing prostaglandin $E_1\;(PGE_1)-loaded$ microemulsion, which undergoes a phase transition to gels at body temperature. The effects of oils, ethanol as solvent and HCl as pH-controlling agent on the physicochemical properties of liquid suppositories composed of poloxamer P 407, P 188 and carbopol was investigated. The stability of $PGE_1$ and release of $PGE_1$ from liquid suppository were evaluated. Oils such as Neobee and soybean oil significantly decreased the gelation temperature but increased the gel strength of liquid suppository due to their strongly binding with the components of liquid suppository base. However, ethanol slightly did the opposite. The pH of liquid suppositories hardly affected the gelation temperature and gel strength due to addition of very small HCl (0.005-0.01%). A liquid suppository [$PGE_1/P$ 407/P 188/carbopol/Neobee/ethanol/HCl (0.2/14/14/0.4/7/2/0.005%)], which had the gelation temperature $(34.2{\pm}0.6^{\circ}C)$ and gel strength $(31.35{\pm}4.37\;sec)$ suitable for liquid suppository system, was easily administered and not leak out from the body. About 60% of $PGE_1$ was released out within 2 h from this formulation. It was shown that the release of $PGE_1$ was proportional to the square root of time, indicating that $PGE_1$ might be released from the suppository by Fickian diffusion. It was stable at $4^{\circ}C$ for at least 2 months. The results suggest that transurethral liquid suppository containing prostaglandin $E_1-loaded$ microemulsion is thought to be a convenient, safe and effective dosage form for $PGE_1$. However, it should be further developed as a more convenient and stable dosage form for $PGE_1$.

• 한국세라믹학회지
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• 제26권5호
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• pp.677-681
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• 1989

On the preparation of silica glass by sol-gel process, we used fine powder of silica gel to prevent cracking. In this case, the best condition of silica glass preparation is the contents of 10~40wt% seed and the gelation time of solution in contract. The dried gels conversed to silica glass by heat treatment up to 125$0^{\circ}C$.

• 한국세라믹학회지
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• 제28권4호
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• pp.324-328
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• 1991

Monolithic silica gel and glass were prepared from TMOS solution with high concentration of HCl. Appearance of the dried gels and gelation time varied with content of HCl and H2O were observed in the TMOS-CH3OH-HCl-H2O system. The conversion from gel to glass during heat treatment stage was investigated using TG-DTA, XRD, IR and SEM and characteristics of the gel were examined by measuring bulk density, linear shrinkage and Vicker's hardness. A transparent silica glass was prepared from the gel after heat treatment at 1050℃.

• 대한화학회지
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• 제9권1호
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• pp.16-22
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• 1965

Sodium alginate-$CaSO_4{\cdot}$1/2 $H_2O$의 gel에 미치는 alkali鹽의 遲延효果를 Miyake date와 比較하고, Schwedoff法을 改良한 連續的 測定方法을 써서, 金屬酸化物의 添加에 依한 彈性 gel의 生成速度 및 彈性의 變化를 硏究하였다. 즉 (1) sample의 張力變化를 連續的으로 測定하여, sodium alginate와 $CaSO_4{\cdot}$1/2 $H_2O$ aqueous sol의 gel化 過程을 觀察하였다. (2) 彈性 gel의 生成速度에 미치는 $Na_3PO_4$의 遲延효果는 $Na_2CO_3$보다 크다는 點에서는 Miyake 報告와 一致하였으나, Miyake date처럼 兩者間에 그리 큰 差가 없었다. (3) 金屬酸化物이 彈性 gel生成速度에 미치는 影響에 어떤 規則性은 없었지마는 $SiO_2$와 MgO는 比較的 큰 速度增大효果를 나타내고 ZnO는 比較的 적었다. 그러나 $Al_2O_3$, $Sb_2O_3$와 $TiO_2$는 速度低下효果를 나타냈다. 結果的으로 酸化物의 種類나 그 添加量에 따라 어떤 明確한 規則性을 觀察하지 못하였다. (4) 彈性率과 生成速度에 미치는 효果사이에 比例關係는 없없으나 金屬酸化物을 添加하면 一般的으로 彈性率이 增加하였다. 이들 酸化物 中에서 彈性率增大효果가 가장 큰 것은 MgO였다.

• 한국세라믹학회지
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• 제34권2호
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• pp.216-224
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• 1997

TEOS와 에탄올의 양을 고정하고 H2O/TEOS의 몰비가 2.6-59.0이 되는 범위에서 염산촉매를 사용하여 다공성 실리카 세라믹을 제조하였다. 서로 다른 조성의 솔 9종을 만든 후 젤화시간 측정, TG/DTA에 의한 건조시료의 열분석 및 FT-IR과 X-ray diffractometer에 의한 중간생성물의 특성분석을 수행하였고 50$0^{\circ}C$까지 열처리한 시료의 FT-IR에 의한 SiO2폴리머 분석, N2-adsorption isotherm을 이용한 비표면적과 기공크기분포 조사 및 TEM에 의한 SiO2폴리머의 형태와 기공의 변화를 조사하였다. 적용된 조성 및 촉매의 농도에서 최소 젤화반응시간은 TEOS1몰달 물의 양이 약 11몰에서, 가장 높은 중합도는 약 8-18몰에서, 그리고 가장 큰 비표면적값은 약 11몰에서 보였다. 이것은 물의 양이 약 11몰일 때 중합반응이 가장 빠르게 진행하였음을 의미한다. 결론적으로, 물의 양이 증가함에 따라서 약 11몰까지는 반응이 빠르게 진행되나 그 이상의 물이 사용될 경우 과잉의 물이 반응저해요인으로 작용하여 젤화시간의 지연 및 비표면적의 감소를 보인다.

• 폴리머
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• 제25권2호
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• pp.168-176
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• 2001

새로운 열잠재성 개시제로서 N-crotyl-N,N-dimethyl-4-methylanilinium hexafluoroan-timonate (CMH) 촉매가 diglycidylether of bisphenol A (DGEBA) 에폭시 양이온 중합계의 열적, 유변학적 특성 및 열정성에 미치는 영향에 대해 연구하였다. DSC에 의한 DGEBA/CMH 경화계의 열분석 결과, 본 경화계는 일정 온도까지 우수한 잠재성을 지닌 반응 기구임을 확인할 수 있었으며, 특히 개시제의 함량이 증가할수록 CMH의 높은 활성에 의해 DGEBA의 전환율 및 경화반응 속도가 증가하였다. 유변학적 특성은 레오미터를 사용하여 등온 조건 하, 저장 탄성율(G'), 손실 탄성율(G") 그리고 damping factor (tan $\delta$)를 구한 후 이들 데이터로부터 겔화 시간을 측정하였다. 실험 결과 경화 온도 및 CMH의 증가에 따른 활성의 차이로 인하여 에폭시 양이온 중합의 네트워크 구조 형성에 영향을 미쳐 겔화 시간이 단축됨을 알 수 있었다. 형성된 네트워크 구조의 열안정성은 TGA 분석을 통해 분해 활성화 에너지 및 열안정성 인자 등의 측정으로 고찰하였다.찰하였다.

• 분석과학
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• 제26권3호
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• pp.205-210
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• 2013

졸-겔법에 의한 LAS계 결정화 유리합성공정에서 출발물질로 사용된 금속 알콕사이드의 조성비, 조핵제의 첨가량 및 열처리조건이 생성된 유리의 결정화 특성에 미치는 영향을 조사하였다. LAS 유리전구체의 겔화시간은 $TiO_2$의 첨가량이 늘어남에 비례하였고, 금속 알콕사이드 중의 TEOS의 몰비가 증가함에 따라서 폭발적으로 증가하였다. 또한 TEOS의 조성비가 커지면 LAS계 유리의 결정화 온도는 증가 하였지만, $TiO_2$ 첨가량의 영향은 미미하였다. 그리고 $TiO_2$의 첨가량이 늘어나면 낮은 온도에서도 결정성이 증가하는 것으로 나타나 이는 조핵제가 LAS계 결정화 유리의 결정성을 향상시키는 것으로 판단되었다.