• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.1
• /
• pp.62-67
• /
• 2005

Recently, polymer insulators that are used for high voltage applications have some advantages such as light weight, small size, vandalism resistance, hydrophobicity and easy making process. During outdoor service of polymer insulators, the surface of the insulating material is frequently subjected to moisture and contamination that lead to dry band arcing. Their tracking resistance, erosion resistance, end sealing and shed design are very important because dry band arcing causes degradation of polymer surface. Aging test to estimate life property of polymer insulator is executed through several international standard such as IEC 61109 and CEA tracking wheel test, but is not getting clear conclusion yet. There are two methods in the diagnosis method of polymer insulator such as off-line and on-line. The diagnosis methods in off-line are external condition analysis by the eye, contaminant analysis on surface, surface analysis, pollution withstand voltage test, power frequency flashover voltage test, lightning impulse flashover test, tensile fracture load test and flexural load test. Polymer material is also investigated it's tracking resistance by adding surface active agent in IEC 587. In this paper, the tracking performance of polymer insulator with salt solution which is added surface active agent. The diagnosis of insulator sample has been analyzed by leakage current and visual examination, STRI guide and thermal image camera.

• Polymer(Korea)
• /
• v.36 no.4
• /
• pp.500-506
• /
• 2012

In this study, we developed and optimized hydrophilic polymer based solid dispersion formulations (SDs) for enhancing the aqueous solubility of eprosartan, one of poorly soluble drugs, that has been broadly used for the treatment of high blood pressure. Poly(ethylene glycol) (PEG) and poly(vinyl pyrrolidone) (PVP) based SDs were prepared by hot melting and solvent evaporation methods and the drug/polymer composition varied in the range of 1:1~1:5 with or without poloxamer 407 (P407) as a polymeric surfactant. The SDs prepared by solvent evaporation showed more reduced crystallinity than ones by hot melting, and PVP based SDs showed more enhanced solubility and lower crystallinity than PEG based SDs. Furthermore, it was observed from DSC and PXRD analysis that the SDs with P407 (drug:polymer: P407 = 1:5:1) demonstrated no crystallinity and the most enhanced solubility (more than 3~4 times).

• Polymer(Korea)
• /
• v.32 no.2
• /
• pp.95-102
• /
• 2008

The $\alpha$,$omega$-diacrylate poly(dimethylsiloxane) (DA-PDMS) containing vinyl ester of versatic acid/vinyl acetate (Veova-10/VAc) was prepared by emulsion copolymerization of (DA-PDMS), Veova-10 (with VAc), and auxiliary agents at $85^{\circ}C$ in the presence of ammonium peroxodisulfate (APS) as an initiator. Sodium dodecyl sulfate (SDS) and nonylphenol ethylene oxide-40 units (NP-40) were used as anionic and nonionic emulsifiers, respectively. The resulting copolymers were characterized by using Fourier transform infrared spectroscopy (FT-IR). Thermal properties of the copolymers were studied by using thermogravimetric analysis(TGA) and differential scanning calorimetry (DSC). The morphology of copolymers was also investigated by scanning electron microscopy (SEM) and then the effects of variables such as temperature, agitation speed, surfactant kinds, molecular weights, initiator, and DA-PDMS concentrations on the properties of the silicone-containing Veova-10/VAc emulsions were examined. The calculation of monomer conversion versus time histories indicates that by increasing the DA-PDMS concentration the polymerization rate and the number of polymer particles decrease, respectively.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.7
• /
• pp.1891-1896
• /
• 2010

Submicron-sized polymeric colloidal particles can self assemble into 3-dimensional (3D) opal structure which is a useful template for photonic crystal. Narrowly dispersed polymer microspheres can be synthesized by emulsion polymerization in water using water-soluble radical initiator. In this report, we demonstrate a facile and reproducible emulsion polymerization method to prepare various polymeric microspheres within 200 - 400 nm size ranges which can be utilized as colloidal photonic crystal template. By controlling the amount of monomer and surfactant, monodisperse polymer colloids of polystyrene (PS) and acrylates with various sizes were successfully prepared without complicated synthetic procedures. Such polymer colloids self-assembled into 3D opal structure exhibiting bright colors by reflection of visible light. The colloidal particles and the resulting opal structures were rigorously characterized, and the wavelength of the structural color from the colloidal crystal was confirmed to have quantitative relationship with the size of constituting colloidal particles as predicted by Bragg equation. The tunability of the structural color was achieved not only by varying the particle size but also by infiltration of the colloidal crystal with liquids having different refractive indices.

• Journal of the Korean Applied Science and Technology
• /
• v.19 no.4
• /
• pp.265-272
• /
• 2002

$CaCO_{3}$ absorbed sodium lauryl sulfate (SLS) surfactant was prepared, Core-shell polymers of inorganic/organic pair, which have both core and shell component, were synthesized by sequential emulsion polymerization using styrene(St) as a shell monomer and potasium persulfate (KPS) as an initiator, We found that when $CaCO_{3}$; core prepared by adding 2,0 wt% SLS, $CaCO_{3}$ core/PSt shell polymerization was carried out on the surface of $CaCO_{3}$ particle without forming the new PSt particle during St shell polymerization in the inorganic/organic core-shell polymer preparation, The structure of core-shell polymer were investigated by measuring the degree of decomposition of $CaCO_{3}$ using HCl solution, thermal decomposition of polymer composite using thermogravimetric analyzer and morphology by scanning electron microscope.

• Polymer(Korea)
• /
• v.25 no.4
• /
• pp.528-535
• /
• 2001

Polyurethane specimens were mainly composed of polyol, MDI, silicone surfactant, and water. The effects of ethylene glycol on the cell size, forming magnification, cream time, gel time, take free time, final free rising height, and reactive temperature were investigated. The cyclopentane was used for PU foam as a physical blowing agent. The components were hand-mixed at about 5000 rpm within 4 seconds at room temperature. The mixtures with various ethylene glycol contents were foamed in the wood mold. When the index of isocyanate was fixed, as the amount of ethylene glycol increased, cell size and thermal conductivity were decreased by about 5.1% and 14%, respectively.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.36 no.2
• /
• pp.93-97
• /
• 2010

In this study, cationic guar polymer was selected from many cationic polymers currently using in shampoo and then was newly developed having 0.7 % above of nitrogen content and 190~200 cps of viscosity through various performance measurements. Wet combing ability, polymer substantivity, silicone deposition and panel test were evaluated for performance measurements. Cationic guar polymer that was invented from this study can optimize conditioning effects in shampoo.

• Archives of Pharmacal Research
• /
• v.21 no.4
• /
• pp.418-422
• /
• 1998

Aim of this work is to prepare poly(DL-lactide-co-glycolide) (PLGA) nanoparticles by dialysis method without surfactant and to investigate drug loading capacity and drug release. The size of PLGA nanoparticles was 269.9 $\pm$118.7 nm in intensity average and the morphology of PLGA nanoparticies was spherical shape from the observation of SEM and TEM. In the effect of drug loading contents on the particle size distribution, PLGA nanoparticles were monomodal pattern with narrow size distribution in the empty and lower drug loading nanoparticles whereas bi- or trimodal pattern was showed in the higher drug loading ones. Release of clonazepam from PLGA nanoparticles with higher drug loading contents was slower than that with lower loading contents.

• Journal of Pharmaceutical Investigation
• /
• v.37 no.6
• /
• pp.339-347
• /
• 2007

SMEDDS is mixture of oils, surfactants, and cosurfactants, which are emulsified in aqueous media under conditions of gentle agitation and digestive motility that would be encountered in the gastro-intestinal(GI) tract. The main purpose of this work is to prepare self-microemulsifying drug delivery system(SMEDDS) for oral bioavailability enhancement of a poorly water soluble drug, atorvastatin calcium. Solubility of atorvastatin calcium was determined in various vehicles. Pseudo-ternary phase diagrams were constructed to identity the efficient self-emulsification region and particle size distributions of the resultant micro emulsions were determined using a laser diffraction sizer. Optimized formulations for in vitro dissolution and bioavailability assessment were $Capryol^{(R)}$ 90(50%), Tetraglycol(16%), and $Cremophor^{(R)}$ EL(32%). The release rate of atorvastatin from SMEDDS was significantly higher than the conventional tablet ($Lipitor^{(R)}$), 2-fold. Our studies illustrated the potential use of SMEDDS for the delivery of hydrophobic compounds, such as atorvastatin calcium by the oral route.

• Polymer(Korea)
• /
• v.35 no.6
• /
• pp.543-547
• /
• 2011

A study has been done to enhance the mechanical properties and processability of electrically conductive polyaniline(PANI) without the polymer's structural alternation. Functionalized acid doped PANI (PANI-DBSA) was prepared by an emulsion polymerization, and dodecylbenzenesulfonic acid (DBSA) played both roles of surfactant and dopant. Also, PANI-DBSA was solution cast blended with high impact polystyrene (HIPS) to produce PANI-DBSA/HIPS blend film. The structure and electrical properties of the conducting polymer blends were observed through UV-vis and FTIR/ATR spectroscopy. A study of the blend was carried by focusing on observation of mechanical and electrical properties based on dispersibility and changes in polymer morphology. The conductivity of the blends was increased by increasing the content of PANI-DBSA, and the sudden increase of conductivity to $3.5{\times}10^{-4}$ S/cm was observed even under a low content of 9 wt%. There was a strong association of continuous network formation with percolation and conductivity in the conducting polymer blends.