• Journal of Korean Society of Environmental Engineers
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• v.39 no.9
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• pp.542-547
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• 2017

This paper was to analyze the membrane characterization of hydrophilicity, surface morphology and membrane chemical anlysis of three commercial microfiltration/ultrafiltration membranes, and evaluate the filtration performance of a seawater to assess the availability for pretreatment of desalination process. From the results of contact angle, Mem-3, fabricated with polyacrylonitrile, was highly hydrophilic. It find out that Mem-3 has more anti-biofouling property. In Field emission scanning electron microscope (FESEM), Mem-1 (polyethylene) and Mem-2 (Polyvinylidenefluoride) showed the sponge-like shape and Mem-3 showed finger-like shape. Membrane chemical analysis by energy dispersive spectrometer (EDS) presented that Mem-2 was mostly fluoride and Mem-3 had s high ratio of N (32.47%) due to the nitrile group. The permeation flowrate per time on suction pressures using deionized water (D.I. water) tends that permeation rate of Mem-3 more increased when the pressure was increased compared to other membranes. From the results of turbidity and total suspended solids (TSS) removal, turbidity of permeate was 0.191 NTU to 0.406 NTU and TSS was 2.2 mg/L to 3.0 mg/L in all membranes, indicating that it was not suitable for the pretreatment of seawater desalination by short-term experiments.

• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.584-594
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• 2014

To increase of surface hydrophilicity of polymeric thin films is an important approaching technique for introduction of self-cleaning and/or antifogging properties on the surfaces of those films. In general, hydrophilic surface can be produced by coating non ionic surfactants or by increasing surface energy. Various non-ionic surfactants, such as Tween, Span, and PEG-PPG block copolymers were selected for our experiments, because they are cheap and well soluble in toluene system as well as they contain several reactive hydroxy fuctional groups with coupling agents. Blending conditions influence the PET film surface hydrophilicities. However, the introduction of only these surfactants on the surface of PET films did not show the high durability of hydrophilic properties after washing with water. To improve the durability two types of coupling agents such as epoxide and diisocyanate were adopted. Contact angle of water on hydrophilically coated PET film surface with 6 wt% of isophrone diisocyanate(IPDI) containing coating solution was reached to $8.7^{\circ}$, which was an indirect evidence for very high surface hydrophilicity. A light(500 nm of wavelength) transmittance value of coated PET film was changed only from 87% to 85% with keeping a good transparent property. This film can be usable for self-cleaning film industries.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.174-180
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• 2014

A plasma hydrophobic coating on commercial fish feed was conducted to prolong the floating time of feed, thereby enhancing the feed consumption rate and reducing the contamination of water in fish farms. The hydrophobic coating on the fish feed was prepared using an atmospheric-pressure dielectric barrier discharge (DBD) plasma with hexamethyldisiloxane (HMDSO), toluene and n-hexane as the precursors. The effect of the parameters such as input power, precursor type and coating time on the coating performance were examined. The physicochemical properties of the coating layer were analyzed using a Fourier transform infrared (FTIR) spectrometer and a contact angle (CA) analyzer. The water CA increased after the coating preparation, indicating that the surface changed from hydrophilic to hydrophobic. The FTIR characterization revealed that the hydrophobic layer was comprised of functional groups such as $CH_3$, Si-O-Si and Si-C. As a result of the hydrophobic coating, the floating time of the fish feed increased from several seconds to 3 minutes, which suggested that the plasma coating method could be a viable means for practical applications. Compared to the water CA measured as soon as the coating layer was prepared, the 6-day aged sample exhibited a substantial CA increase, confirming the aging effect on the improvement of the hydrophobicity.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.74-80
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• 2019

$Nafion/TiO_2$ composite membranes were prepared via an in-situ sol-gel process with different immersing periods from 1 day to 7 days for the low humidifying proton exchange membrane fuel cell. As the immersing time increased, the $TiO_2$ content within the Nafion membrane increased. The contact angle decreased with the increased $TiO_2$ content in the composite membrane due to the increased hydrophilicity. The water uptake and proton conductivity reached to the highest level for 4 day immersing period, then decreased as the immersing period increased. A 7 days of immersing time was shown to be too long because too much $TiO_2$ aggregates were formed on the membrane surface as well as interior of the membrane, interfering the proton transfer from anode to cathode. Cell performance results were in good agreement with those of the water uptake and proton conductivity; current densities under a relative humidity (RH) of 40% were 0.54, 0.6, $0.63A/cm^2$ and $0.49A/cm^2$ for the immersing time of 1, 3, 4 and 7 days, respectively at a 0.6 V. The composite membrane prepared via the in-situ sol-gel process exhibited the enhancement in the cell performance under of RH 40% by a maximum of about 66% compared to those of using the recasting composite membrane and Nafion 115.

• Membrane Journal
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• v.33 no.6
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• pp.427-438
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• 2023

In this study, in order to improve the performance of the reverse osmosis membrane with high water flux and high salt rejection, a study was conducted on the evaluation of characteristics according to the curing temperature and time during various additives and interfacial polymerization. The morphology of the membrane with no additives and the membrane with additives both showed a "rigid-and-valley" structure, confirming that the polyamide layer was successfully polymerized on the surface of the porous support layer. In addition, the additive of 2-Ethyl-1,3-hexanediol (EHD) had improved hydrophilicity and water flux, which was confirmed by measuring the contact angle. Finally, a highly permeable TFC membrane with NaCl and MgSO₄ salt rejection of 97.78% and 98.7% and a high water flux of 3.31 L/(m²⋅h⋅bar) was prepared.

• Journal of the Korean Geotechnical Society
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• v.40 no.4
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• pp.7-18
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• 2024

Because of their mineral composition, tire chips have very low thermal conductivity compared with natural geomaterials, leading to the use of sand-tire rubber mixtures in thermally insulating applications. However, systematic studies evaluating factors affecting the thermal conductivity of sand-tire rubber mixtures have been very limited. Thus, this study investigated the thermal conductivity of sand-tire rubber mixtures with varying size ratios and tire chip fractions according to the degree of saturation (S). Specimens were prepared in insulated cells, and thermal needle probe tests were performed. In addition, the contact angle and solid surface free energy of sand-tire rubber mixtures were investigated. The results of this study revealed that the thermal conductivity decreased with increasing tire chip fraction but increased with increasing water content (or S). However, the trend of increasing thermal conductivity with S varied with the tire chip fraction, and the specimens with tire chip fraction > 0.4 clearly showed a delayed increase in thermal conductivity with increasing S. This reflected that hydrophobic particles (tire chip) affected the dependency of thermal conductivity on S because of the delayed formation of capillary water bridges, which served as additional thermal conduction paths with increased moisture content.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.589-604
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• 2021

Waterjets for rocks have various advantages of the non-contact and eco-friendly excavation using only water and abrasive. To overcome the problems (e.g., dust and noise occurrence) of the conventional drilling methods, waterjet excavation methods are broadly used. It is advantageous to operate a couple of nozzles in order to increase the waterjet excavation efficiency. When multiple nozzles are used, it is essential to analyze the excavation performance and shape according to the nozzle operation method. In this study, nozzle angle, horizontal distance between nozzles, and standoff distance were defined as nozzle operating parameters and the excavation performance and shape were analyzed. As a result of the experiment, when the nozzle angle and standoff distance are increased, the excavation depth is decreased and the effective depth tends to be increased. In addition, based on the experimental results, the excavation shape criteria required for nozzle insertion were proposed and optimal nozzle operating parameters were derived according to the criteria. This study result is expected to be used as useful basic research in the future development of multiple waterjet nozzles for rock drilling.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.1
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• pp.27-34
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• 2006

We investigated the question whether the efficacy of cleaning tear components on RGP lens and preserving the superior wettability of RGP lens depended on the different type of contact lens care system - RGP lens care solution, SCL care solution, combined solution both for SCL and RGP lens or saline solution. The removal efficacy of the deposited protein was examined by Lowry protein assay and Scanning Electro Microscope(SEM) and residual lipid concentration on RGP lens was determined by High Pressure Liquid Chromatology(HPLC). Wettability was assessed with an equilibrium water-in-air contact angle method. When cared by RGP lens solution, it was demonstrated that 62 percent out of the adhered protein on RGP lens were removed and the removal efficacy of RGP lens solution was not only 4 times than saline solution and the alternative but also higher twice than SCL solution. Contrarily, the SCL solution had the most excellent removal efficacy of the adhered protein on SCL. These results suggest that the cleaning efficacy is thought to be affected by the other factors like the viscosity of care solutions, which mutual contact between RGP lens and care solutions is on the increase due to the viscosity enhancer in RGP lens care solution. RGP lens solution had the greatest removing efficacy to cholesterol and the residual cholesterol concentration was decreased to 50%. It is significant for RGP lens to preserve the superior wettability which means the predictive value for comfortable wearing and it showed that the RGP lens solution offered the most excellent efficacy to maintain the surface wettability. Combined solution both for SCL and RGP lens had weak efficacy of cleaning and maintaining wettability for RGP lens compared to RGP lens care solution.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.39-42
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• 1999

Perfluoropolymers represent the ultimate resistance to hostile chemical environments and high service temperature, attributed to the presence of fluorine in the polymer backbone, i.e. to the high bond energy of C-F and C-C bonds of fluorocarbons. Copolymers of Tetrafluoroethylene (TEE) and 2, 2, 4Trifluoro-5Trifluorometoxy- 1, 3Dioxole (TTD), commercially known as HYFLON AD, are amorphous perfluoropolymers with glass transition temperature (Tg)higher than room temperature, showing a thermal decomposition temperature exceeding 40$0^{\circ}C$. These polymer systems are highly soluble in fluorinated solvents, with low solution viscosities. This property allows the preparation of self-supported and composite membranes with desired membrane thickness. Symmetric and asymmetric perfluoropolymer membranes, made with HYFLON AD, have been prepared and evaluated. Porous and not porous symmetric membranes have been obtained by solvent evaporation with various processing conditions. Asymmetric membranes have been prepared by th wet phase inversion method. Measure of contact angle to distilled water have been carried out. Figure 1 compares experimental results with those of other commercial membranes. Contact angles of about 120$^{\circ}$for our amorphous perfluoropolymer membranes demonstrate that they posses a high hydrophobic character. Measure of contact angles to hexandecane have been also carried out to evaluate the organophobic character. Rsults are reported in Figure 2. The observed strong organophobicity leads to excellent fouling resistance and inertness. Porous membranes with pore size between 30 and 80 nanometers have shown no permeation to water at pressures as high as 10 bars. However high permeation to gases, such as O2, N2 and CO2, and no selectivities were observed. Considering the porous structure of the membrane, this behavior was expected. In consideration of the above properties, possible useful uses in th field of gas- liquid separations are envisaged for these membranes. A particularly promising application is in the field of membrane contactors, equipments in which membranes are used to improve mass transfer coefficients in respect to traditional extraction and absorption processes. Gas permeation properties have been evaluated for asymmetric membranes and composite symmetric ones. Experimental permselectivity values, obtained at different pressure differences, to various single gases are reported in Tab. 1, 2 and 3. Experimental data have been compared with literature data obtained with membranes made with different amorphous perfluoropolymer systems, such as copolymers of Perfluoro2, 2dimethyl dioxole (PDD) and Tetrafluorethylene, commercialized by the Du Pont Company with the trade name of Teflon AF. An interesting linear relationship between permeability and the glass transition temperature of the polymer constituting the membrane has been observed. Results are descussed in terms of polymer chain structure, which affects the presence of voids at molecular scale and their size distribution. Molecular Dyanmics studies are in progress in order to support the understanding of these results. A modified Theodoru- Suter method provided by the Amorphous Cell module of InsightII/Discover was used to determine the chain packing. A completely amorphous polymer box of about 3.5 nm was considered. Last but not least the use of amorphous perfluoropolymer membranes appears to be ideal when separation processes have to be performed in hostile environments, i.e. high temperatures and aggressive non-aqueous media, such as chemicals and solvents. In these cases Hyflon AD membranes can exploit the outstanding resistance of perfluoropolymers.

• Journal of the Korean Society of Clothing and Textiles
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• v.29 no.12 s.148
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• pp.1546-1553
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• 2005

The wetting behavior and liquid transport of nonionic surfactant solutions; Span 20 and Tween 20, 40, 60, 80, 21, 61, 81, 65 & 85: in polyethylene terephthalate(PET) fabrics are reported. Five different PET fabrics are used in this study. PET 1, 2 & 3 have different compactness in structure. PET 4 & 5 have similar physical properties to PET 2, however, PET 4 has heat set finish and PET 5 with rewetting agent. The wetting and water retention properties of PET fabrics are greatly improved by addition of nonionic surfactants. The aqueous liquid retention(W) vs. cosq and W vs. adhesion tension has positive linear relationship. Hydrophilic surfactants which have short hydrophobes and surfactants with unsaturated hydrophobe structures are more efffctive in improving the wetting properties of PET fabrics. PET fabric which has larger thread spacing shows greater value of water retention ratio(W/H) than PET fabric with smaller thread spacing if there are no surfactants present in the system, however, W/H values become very similar among these PET fabrics when the surfactants are added. If there are no surfactants present in the system, PET with heat set finish has smaller value and PET with rewetting agent has greater value of W/H than PET without finish even though the fabrics have the similar physical properties.