• Journal of the Korean Electrochemical Society
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• v.9 no.3
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• pp.132-134
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• 2006

The main component governing selectivity in ion-selective electrodes and optodes is the ionophore. For this reason, a member of natural products that possess selective ion-binding properties have long been sought after. By applying this principle, the performance of tetracycline used as neutral carriers for cation selective polymeric membrane electrode was investigated. The cation ion-selective electrode based on tetracycline gave a good Nernstian response of 26.6 mV per decade for calcium ion in the activity range $1x10^{-6}M$ to $1x10^{-2}M$ with and without lipophilic additives. The optimized cation ion-selective membrane electrodes displayed very comparable potentiometric responses to various mono and di-valent cations of alkali and alkaline earth metal ions except $Mg^{2+}$.

• Journal of Pharmaceutical Investigation
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• v.16 no.1
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• pp.1-7
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• 1986

The influences of sodium chloride, polyethylene glycol 4000 and 20000 on 5-fluorouracil release from disk type silicone polymer devices were examined in isotonic phosphate buffer. These water soluble cosolvent and sodium chloride caused devices to swell in aqueous media. Sodium chloride exerted the greatest influence on drug release. The addition of water soluble cosolvent or sodium chloride to silicone polymeric devices permitted controlled release of 5-fluorouracil, presumably due to the change of the physical microstructure of silicone network, and the solubility and diffusivity of 5-fluorouracil. It seemed that the water soluble drug was released through the hydrophilic pores or pathways formed in the device by the incorporation of a water soluble cosolvent or sodium chloride.

• Membrane Journal
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• v.7 no.4
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• pp.191-198
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• 1997

Membrane formation mechanism by the phase inversion has been investigated in order to control the membrane morphology. It was found that finger-like structures were obtained when the heat of mixing between the solvent and non-solvent is exothermic, while sponge-like structures were obtained when they are endothermic in polystyrenes as well as in polyimides (Torlon and polyimide made frorn 3,3'4,4'-benzophenontetracarboxylic diahmydride and 1,4-phenylene diarnine) membranes. This concept was applied to control the morphology of polysulfone membranes simply by adding a solvent additive by adjusting the heat of mixing. A crude, but simple, relationship between the heat of mixing and the exchange rate of the solvent with non-solvent has been also developed.

• Journal of Biomedical Engineering Research
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• v.23 no.2
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• pp.139-145
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• 2002

Bis-GMA, 2.2-bis[p(2-hydroxy-3-methacryloyloxypropokyl)phenyl]Propane, is an essential component as a multifunctional methacrylate prepolymer in the light-curable polymeric dental composite resins. Two hydroxyl groups of the Bis-GMA molecule are considered to induce water sorption of the photocured composite resin in a mouth, resulting in gradual long-term deterioration of aesthetics and mechanical properties of the composite resins. In this study, some additives such as light stabilizer and antioxidant were added to composite resins to promote durability and storage stability of the last product. First of all, color change increased as a light stabilizer. Tinuvin P, was added to the composed resins and color stability was improved as an antioxidant, Irganox 245, was added to ones. In addition, when Tinuvin P and Irganox 245 were added together to the composed resins. the color stability was enhanced and mechanical properties such as diametral tensile strength before and after acceleration tests were also not greatly decreased. Therefore, when 0.5 weight Percent of Tinuvin P and 0.1 weight percent of Irganox 245 were added together to dental composite resins. the durability and color stability were enhanced, and furthermore the storage stability was also improved for the composed resins.

• Polymer(Korea)
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• v.26 no.5
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• pp.691-700
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• 2002

Interstitial therapy using biodegradable polymeric device loaded with anticancer agent can deliver the drug to the tumor site at high concentration, resulting in an increase of therapeutic efficacy. 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, carmustine) is most commonly used as chemotherapeutic agent for brain tumors. The design of implantable device is regarded as an important factor lot the efficient delivery of antitumor agent to targeting site. In order to control the release profile of drug, the release pattern of BCNU with the changes of various dimension and additives was investigated. The PLGA wafers containing 3.85, 10, 20 and 30% of BCNU were prepared in various shape (diameter of 3, 5 and 10 mm, thickness of 0.5, 1 and 2 mm) by direct compression method. In vitro drug release profile of BCNU-loaded PLGA wafers could be controlled by changing the dimension of wafers such as initial drug content, weight, diameter, thickness, volume and surface area of wafers, as well as PLGA molecular weight and additives. Drug release from BCNU-loaded PLGA wafers was facilitated with an increase of BCNU-loading amount or presence of poly(N-vinylpyrrolidone)(PVP) or sodium chloride (NaCl). The effects of various geometric factors and additives on the BCNU release pattern were confirmed by the investigation of mass loss and morphology of BCNU-loaded PLGA wafers.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.6
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• pp.406-413
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• 2012

Effect of three additives, chitosan, ferric chloride, and MPE50 on membrane fouling reduction was studied. They were introduced with various dosing rate into activated sludge, and changes in filtration resistance measured by the batch cell filtration test were evaluated. Both the filtration resistance and the specific cake resistance were minimized at 20 mg/g-MLSS with chitosan, 70 mg/g-MLSS with ferric chloride, and 20 mg/g-MLSS with MPE50 addition, respectively. Introduction of the additives into the activated sludge resulted in reduction of not only cake resistance, but also fouling resistance. However, the chitosan addition to three different activated sludge resulted in three different optimal dose of 10, 20, 30 mg/g-MLSS, respectively. This implies that the optimal dose is dependent on sludge characteristics rather than a constant value. Overdose above the optimal dosage always aggravated filterability in all cases. Zeta potential of sludge flocs, relative hydrophobicity, floc size distribution, soluble EPS concentration and supernatant turbidity were measured in order to analyze fouling reduction mechanism. Nearly neutral surface charge along with the largest particle size was observed at the optimal dose. This could be explained by particle destabilization and restabilization mechanism as positively charged additives were injected into sludge flocs of negative surface charge. Both soluble EPS concentration and supernatant turbidity also showed the lowest value at the optimal dose. These foulants are believed to be coagulated and entrapped in sludge flocs during flocculation. Chitosan and MPE50 which are cationic polymeric substances showed higher reduction in both soluble EPS and fine particles comparing with ferric chloride.

• Journal of Life Science
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• v.19 no.4
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• pp.538-542
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• 2009

In this study, we confirmed water content and oxygen permeability of new polymeric materials synthesized from itaconic acid used for soft contact lenses. In this study, we polymerized materials for soft contact lenses using HEMA (2-hydroxyethyl methacrylate), the based-monomer of soft contact lenses, EGDMA (ethylene glycol dimethacrylate) as a cross linkage agent, and the new additives mono-ester or di-ester derived from itaconic acid commercially produced by the fermentation of A. itaconicus. New polymer materials for contact lenses were synthesized with the mixture of HEMA and mono- or di-ester at different ratios and water content and oxygen permeability (Dk) was analyzed. In polymerizing HEMA and mono-ester (15%), the water content and oxygen permeability of contact lenses were found to be of good value at 57.7% and 28.6 Dk respectively. The mixture of HEMA and mono-ester is more excellent than HEMA/di-ester in regards to water content and oxygen permeability. The water content and oxygen permeability of soft contact lenses made by new polymeric materials were highly represented.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.19-26
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• 2012

SEI (solid electrolyte interphase) layers are generated on a graphite negative electrode from three different electrolytes and low-temperature ($-30^{\circ}C$) charge/discharge performance of the graphite electrode is examined. The electrolytes are prepared by adding 2 wt% of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) into a standard electrolyte solution. The charge-discharge capacity of graphite electrode shows the following decreasing order; FEC-added one>standard>VC-added one. The polarization during a constant-current charging shows the reverse order. These observations illustrate that the SEI film resistance and charge transfer resistance differ according to the used additives. This feature has been confirmed by analyzing the chemical composition and thickness of three SEI layers. The SEI layer generated from the standard electrolyte is composed of polymeric carbon-oxygen species and the decomposition products ($Li_xPF_yO_z$) of lithium salt. The VC-derived surface film shows the largest resistance value even if the salt decomposition is not severe due to the presence of dense film comprising C-O species. The FEC-derived SEI layer shows the lowest resistance value as the C-O species are less populated and salt decomposition is not serious. In short, the FEC-added electrolyte generates the SEI layer of the smallest resistance to give the best low-temperature performance for the graphite negative electrode.

• Tribology and Lubricants
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• v.28 no.2
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• pp.47-55
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• 2012

Generally, to product multi-grade oil like engine oil, a sort of mineral base oil is mixed with a fundamental additive package liquid and a polymer liquid as viscosity index improver in order to improve the lubricating property of base oil. That is, engine oil is the mixture of more than two fluids. Specially, a polymeric type liquid cannot be seen as the linear viscosity like Newtonian fluids. In this research, by using the governing equation describing non-Newtonian hydrodynamic lubrication related with the mixture of incompressible fluids based on the principle of continuum mechanics, it will be compared the bearing performance between the mixture of each liquid to be blended and multi-grade engine oil as a single fluid in a high speed hydrodynamic journal bearing. Further, it is to be found the way estimating the performance of the blended multi-grade engine lubricant in a journal bearing in advance before blending by using the physical properties of mineral base oil, fundamental additive liquid and polymer liquid of viscosity index improver. So, it can be reduced the number of trial and error to get the wanted lubricant by selecting the proper volume fraction of each liquid to satisfy the expected performance and estimating in advance the performance of various multi-grade oils before blending. Therefore, it can be shorten the developing time and saved the developing cost.

• Journal of the Korean Applied Science and Technology
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• v.23 no.3
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• pp.207-214
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• 2006

$Y_{2-x}Gd_xO_3:Eu$, phosphors for plasma display panel(PDP), were prepared by Pechini method which use yttriun chloride, gadolinium chloride, and europium oxide as starting materials. This method is a different way to the synthesis of europium(Eu)-doped phosphors, and it consists of the formation of a polymeric resin obtained by polyesterification between metal chelate compounds and a polyfunctional alcohol. This needs lower temperature than solid-state synthetic method. The prepared $Y_{2-x}Gd_xO_3:Eu$ phosphor particles had spherical shape and coherence. The luminescence intensity of $Y_{2-x}Gd_xO_3:Eu$ phosphor particles increased according to the increase of gadolinium(Gd) content(to 0.8mol%), and $Y_{1.2}Gd_{0.8}O_3:Eu$ phosphors had the highest luminescence intensity under vacuum ultra violet(VUV) excitation. The optimum concentration of Eu in the phosphor and optimum calcination temperature was 3wt% and $1100^{\circ}C$. The prepared phosphors were consist of particle, and its size was between 100nm and 150nm. Among the different polyfunctional alcohols, diethylene glycol(DEG) improved the luminescence intensities of phosphors more than other additives. The Pechini method proved that it is demonstrated to be suitable for the synthesis of phosphors used in PDP.