• Korean Chemical Engineering Research
• /
• 제56권4호
• /
• pp.461-468
• /
• 2018

Poly-L-lactic acid (PLLA)를 출발물질로 하여 용매증발법에 의해 마이크로스피어를 제조하고, 제조 변수가 형성된 마이크로스피어의 형상 및 평균 입경에 미치는 영향을 살펴보았다. PVA 수용액의 농도가 1~5 wt%로 증가함에 따라 평균입경이 $370{\sim}160{\mu}m$으로 감소하다가 7 wt%에서다시 $240{\mu}m$으로 증가하였다. 그리고 PVA의첨가부피가 10~50 mL로 증가함에 따라 평균 입경은 $370{\sim}220{\mu}m$으로 감소하였다. 또한 교반속도가 500~1,500 rpm으로 증가함에 따라 평균 입경은 $370{\sim}110{\mu}m$으로 감소하였다. 유기용매로써 dichloromethane과 chloroform을 각각 사용한 경우 평균 입경은 큰 차이를 보이지 않았으며, dichloromethane을 사용한 경우 표면에서 공극이 확인되었으나 chloroform을 사용한 경우 매끈한 형상의 구형입자가 얻어졌다.

• 전기화학회지
• /
• 제10권2호
• /
• pp.82-87
• /
• 2007

New porous separators based on non-polyolefin materials including the blend of poly (vinyl chloride) (PVC)/poly (vinylidene fluoride-co-hexafluoropropylene) (P(VdF-co-HFP)/poly(methyl methacrylate) (PMMA), and the porous separator based on poly (vinylidene fluoride) (PVdF) were prepared by phase inversion method. The porosity and morphology were controlled with phase inversion rate, which is governed by the relative content of non-solvent and solvent in coagulation bath. To enhance tensile strength, the solvent pre-evaporation and uni-axial stretching processes were applied. The ionic conductivity was increased with increasing stretching ratio, and tensile strength was increased with increasing solvent pre-evaporation time and stretching ratio. The 200% stretched PVdF separator showed 56 MPa of tensile strength, and the ionic conductivity of the stretched PVdF separator was $8.6{\times}10^{-4}\;S\;cm^{-1}\;at\;25^{\circ}C$.

• Nuclear Engineering and Technology
• /
• 제39권6호
• /
• pp.731-736
• /
• 2007

Radioactive organic wastes containing acetone, alcohol, and particularly tributyl phosphate (TBP)/dodecane contaminated with uranium are extracted from the PUREX process and the decontamination of related equipment. An evaporation method that utilizes existing DU oxidation apparatuses and ventilation systems and a typical muffle furnace installed with an aspirating system are adopted. A separation method using phosphoric acid especially for the TBP/dodecane waste is also studied and evaluated. The results show that a simple evaporation process is utilizable for wastes containing acetone or alcohol with a lower boiling point. A modified muffle furnace is more appropriate to dispose directly of organic wastes having a higher boiling point, such as TBP/dodecane, without generating a condensed waste solution. It is recommended that, when the uranium concentration of TBP/dodecane waste is much higher than stipulated levels, separation technology should be applied to remove uranium from the mixture. Each type of solvent after separation can then be considered disposable below the regulatory limit in the modified furnace discussed in this study.

• Korean Chemical Engineering Research
• /
• 제60권2호
• /
• pp.237-242
• /
• 2022

본 연구에서는 정제된(+)-dihydromyricetin로부터 잔류 용매를 효과적으로 제거할 수 있는 건조 방법을 개발하였다. 에탄올 전 처리를 통한 회전 증발(rotary evaporation)에 의해 잔류 아세톤 농도를 ICH 규정치(5,000 ppm) 이하로 효율적으로 제거하였다. 또한 잔류 에탄올 역시 물 첨가를 통한 회전 증발로 ICH 규정치(5,000 ppm)를 충족시켰으며 잔류 수분 함량은 4% 이내였다. 모든 건조 온도(35, 45, 55 ℃)에서 잔류 용매는 건조 초기에 급격히 제거되었으며 건조 효율은 건조 온도가 높을수록 증가하였다. 건조 메커니즘 조사 결과, 에탄올 전 처리에 의한 잔류 용매 제거는 아세톤-에탄올 혼합물의 높은 증기압과 아세톤-에탄올 간의 수소 결합과 연관됨을 알 수 있었다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집B
• /
• pp.59-64
• /
• 2001

The fluid flow, mass transfer and film thickness variation during a wafer spin coating process are numerically studied. Governing equations for the cylindrical coordinates are simplified using the similarity transformation and solved efficiently using the finite difference method. Concentration dependent viscosity and the binary diffusivity of the coating liquid are used in the analysis. The time variational velocity components of the coating liquid and the film thickness are analyzed according to the various spin speed. When the evaporation is considered, the flow decease in the early times due to the increase of the viscosity and the resultant flow resistance. Effects of the two film thinning mechanism, the flow-out and evaporation are also considered in the analysis.

• Restorative Dentistry and Endodontics
• /
• 제35권5호
• /
• pp.321-334
• /
• 2010

연구목적: 본 연구는 상아질 접착제의 잔류 용매가 접착 효율에 미치는 영향을 평가하고자 하였다. 연구 재료 및 방법: 본 연구에서는 5세대 2단계 산부식형 접착제와 7세대 단일과정 자가부식형 접착제를 사용하였다. 상아질 접착제의 증발률과 전환률, 적용 후 용매의 공기건조 방법에 따른 미세인장결합강도를 측정하였으며 접착 계면을 FE-SEM을 이용하여 관찰하였다. 결과: 1. 시간에 따라 접착제의 증발률은 증가하나 접착제의 종류에 따라 증가 양상이 서로 달랐다. 2. 대부분 전환률은 증발률에 비례하는 경향을 나타내었다. 3. 공기건조 방법에 따라 결합강도는 대부분 under군, control군, over군 순으로 증가하는 양상을 나타내었다. 4. FE-SEM에서 아세톤을 용매로 사용하는 접착제는 공기건조 방법에 따라 droplet이나 gap이 관찰되었다. 결론: 상아질 접착제의 잔류 용매는 접착 효율에 부정적인 영향을 미치기 때문에, 상아질 접착제의 선택과 사용 시 용매의 종류와 특징에 대한 적절한 이해가 필요할 것이다.

• 약학회지
• /
• 제41권3호
• /
• pp.305-311
• /
• 1997

Sustained release-microspheres and immediate release-pellets were prepared to develop a controlled release multiparticulate system containing both water soluble and insoluble dr ug. Pseudoephedrin.HCl (EPD) and terfenadine (TRF) were used as model drugs, respectively. Sustained release-EPD microspheres were prepared by solvent evaporation method using Eudragit RL or RS as a matrix combined with pH-insensitive film coating. Smaller EPD microspheres were obtained when smaller amount of Eudragit as a matrix material or larger amount of magnesium stearate as a dispersing agent was used. However the obtained microspheres did not show syfficient sustained release characteristics. About 97% of EPD was released after 1 hr irrespective of matrix material used. Subsequent coating of the microspheres with pH-insensitive polymer such as Eudragit RS or ethylcelulose (EC) resulted good sustained in 37.5, 73.3 and 92.0% release of encapsulated EPD in distilled water after 1, 3 abd 7 hr, respectively. It corresponds to mean dissolution time (MDT) of 2.3 hr, which is much larger than that of un-coated EPD microspheres (0.0048 hr). Immediate release TRF pellets were prepared by spherically agglomerated crystallization using Eudragit E as an inert matrix and methylene chloride as a liquid binder. Using Eudragit E alone as a matrix resulted in satisfactory physical properties of the pellets such as sphericity, surface texture and flowability, but led to slower release of TRF from pellets than un-modified TRF powder (MDT of 1.70 vs 1.43 hr in pH 1.2 dissolution medium). Introducing propylene glycol or sodium lauryl sulfate as an emulsifier brought about faster release of TRF from pellets (MDT of 1.14 and 0.95 hr, respectively). In conclusion, microencapsulation by solvent evaporation combined with film coating and spherically agglomerated crystallization were successfully utilized to prepare controlled release multiparticulate system composed of sustained release EPD-microspheres and immediate release TRF pellets.

• Bulletin of the Korean Chemical Society
• /
• 제30권12호
• /
• pp.3066-3068
• /
• 2009

• Journal of Pharmaceutical Investigation
• /
• 제35권2호
• /
• pp.95-99
• /
• 2005

Mucoadhesive microspheres were prepared by interpolymer complexation of chitosan with poly(acrylic acid) (PAA) and solvent evaporation method to increase gastric residence time. The chitosan-PAA complex formation was confirmed by differential scanning calorimetry and swelling study. The DSC thermogram of chitosan-PAA microspheres showed two exothermic peaks for the decomposition of chitosan and PAA. The swelling ratio of the chitosan-PAA microspheres was dependent on the pH of the medium. The swelling ratio was higher at pH 2.0 than at neutral pH. The results indicated that the microspheres were formed by electrostatic interaction between the carboxyl groups of PAA and the amine groups of chitosan. The effect of various process parameters on the formation and morphology of microspheres was investigated. The best microspheres were obtained when 1.5% of the high molecular weight chitosan and 0.3% of PAA were used as an internal phase. The optimum internal phase volume was 7%. The com oil was used as the external phase of emulsion, and span 80 was used as the surfactant. The prepared microspheres had spherical shape.

• Macromolecular Research
• /
• 제10권5호
• /
• pp.246-252
• /
• 2002

In order to the development of the delivery device of long-acting local anesthetics for postoperative analgesia and control of chronic pain of cancer patient, fentnyl-loaded poly (L-lactide-co-glycolido) (PLGA, molecular weight, 5,000 g/mole; 50 : 50 mole ratio by lactide to glycolide) microspheres (FMS) were studied. FMS were prepared by an emulsion solvent-evaporation method. The influence of several preparation parameters such as initial drug loading, PLGA concentration, emulsifier concentration, oil phase volume, and fabrication temperature has been investigated on the fentanyl release profiles. Generally, the drug showed the biphasic release patterns, with an initial diffusion followed by a lag period before the onset of the degradation phase, but there was no lag time in our system. Fentanyl was slowly released from FMS over 10 days in vitro with a quasi-zero order property. The release rate increased with increasing drug loading as well as decreasing polymer concentration with relatively small initial burst effect. From the results, FMS may be a good formulation to deliver the anesthetic for the treatment of chronic pain.