• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.8
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• pp.696-701
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• 2005

This paper was investigated the changes of surface properties of high-temperature-vulcanized (HTV) semiconductive silicone rubber due to oxygen plasma discharge. The modifications produced on the silicone rubber surface by oxygen plasma were accessed using Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS), contact angle and Surface Roughness Tester. The results of the chemical analysis Showed that C-H bonds were broken due to plasma discharge and Silica-like bonds (SiOx, x=$3\~4$) increased. It is thought that the above changes lead to the increase of surface energy of high-temperature-vulcanized (HTV) semiconductive silicone rubber also, Surface roughness was increased with cleavage of side-chains and oxidation process, it confirmed change as the SEM. The micromorphology of surface and hydrophobicity due to plasma discharge based on our results were discussed.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.4
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• pp.353-358
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• 2014

This paper reports a simple, yet effective 1-step surface modification method for stainless steel. Electrochemical etching in dilute Aqua Regia forms hierarchical micro and nanoscale structure on the surface. The surface becomes highly hydrophobic (${\sim}150^{\circ}$) as a result of the etching in terms of static contact angle (CA). However the liquid drops easily pinned on the surface because of high contact angle hysteresis (CAH), which is called a "petal effect": The petal effect occur because of gap between surface microstructures, despite of intrinsic hydrophobicity of the base material. The pore size and period of surface structure can be controlled by applied voltage during the etching. This method can be applied to wide variety of industrial demand for surface modification, while maintaining the advantageous anti-corrosion property of stainless steel.

• Journal of Environmental Science International
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• v.11 no.12
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• pp.1315-1320
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• 2002

Since the enzymatic degradation of microbial poly[(R)-3-hydroxybutyrate-co-3-hydroxyvalerate] (P(3HB-co-3HV)) initially occurs by a surface erosion process, a degradation behavior could be controlled by the change of surface property. In order to control the rate of enzymatic degradation, plasma gas discharge and blending techniques were used to modify the surface of microbial P(3HB-co-3HV). The surface hydrophobic property of P(3HB-co-3HV) film was introduced by CF$_3$H plasma exposure. Also, the addition of small amount of polystyrene as a non-degradable polymer with lower surface energy to P(3HB-co-3HV) has been studied. The enzymatic degradation was carried out at 37 $^{\circ}C$ in 0.1 M potassium phosphate buffer (pH 7.4) in the presence of an extracellular PHB depolymerase purified from Alcaligenes facalis T1. Both results showed the significant retardation of enzymatic erosion due to the hydrophobicity and the enzyme inactivity of the fluorinated- and PS-enriched surface layers.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.75-78
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• 2002

In this paper, we investigated the change of wettability, surface potential decay and surface resistivity caused by thermal-treated and plasma-treated FRP respectively for finding out the influence of electrical characteristics on the surface of polymer composites. For the change of wettability, the contact angle of thermal-treated specimen with the high temperature of 200$^{\circ}C$ increased. But that of plasma-treated specimen decreased. The characteristic of surface potential decay shows the tendency of the remarkable decrease on plasma-treated specimens, but no difference on thermal-treated specimen compared with untreated one. Also, for the surface resistivity, it shows the same trend compared with the change of contact angle. We can conclude that the degradation phenomena of epoxy surface are dominated by the induction of hydrophilicity and hydrophobicity.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.355-363
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• 2015

HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano $Al(OH)_3$ filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nano-filler concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.8
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• pp.737-742
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• 2016

An elastomer (especially PDMS) sponge is considered to be a promising selective absorber in cleaning up oil spills. The performance of a PDMS sponge in capturing and separating oil from (sea) water depends on several parameters such as surface roughness, physicochemical treatments, and hydrostatic stability. Here, we first present a method of fabricating the PDMS sponges having numerous micro-sized pores that act as absorption and storage spaces for the target material, and then we report an experimental effort undertaken to control the surface physicochemistry (i.e., hydrophobicity or hydrophilicity) of the PDMS sponges by adjusting the size of the pores and the concentration of the surfactant (i.e., silwet L-77). From the experimental results, we develop an in-depth understanding of the mechanism for controlling the surface physicochemistry of PDMS using water-soluble micro-sized particles and a surfactant. The surface energy and absorbing behavior of the PDMS sponges are also extensively discussed.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.377-383
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• 2003

Physicochemical properties of a series of PC monolayers with different alkyl chains (C24, C20, C16, and C8), at the air/water interface were investigated. The surface pressure is influenced mainly by the hydrophobicity of the PCs, which is confirmed by the curve shape and the on-set value of π-A isotherms at the air/water interface by increasing the number of alkyl chain. The on-set values of surface pressure were 125 Ų/molecule for DOPC(C8), 87 Ų/molecule for DPPC(C16), 75 Ų/molecule for DAPC(C20), and 55 Ų/molecule for DLPC(C24), respectively. The orientations of alkyl chains at the air/water interface are closely connected with the rigidity of the monolayers, and it was confirmed by the tendency of monolayer thickness in ellipsometry data. The temperature dependence of a series of PCs shows that the surface pressure decreases by increasing temperature, because the longer the alkyl chain length, the larger the hydrophobic interaction in surface pressure. The temperature effects and the conformational changes of unsaturated and saturated PCs were confirmed by the computer simulation study of the cis-trans transition with POPC and DPPC(C16). The cistrans conformational energy difference of POPC is 62.06 kcal/mol and that of DPPC(C16) is 6.75 kcal/mol. Due to the high conformational energy barrier of POPC, phase transition of POPC is limited in comparison with DPPC(C16).

• Polymer(Korea)
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• v.27 no.6
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• pp.555-561
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• 2003

The self-assembled monolayer coating of octadecyltrichlorosilane (OTS) on the silicon based MEMS was investigated and surface characteristics were considered as a function of coating conditions and reagent composition. The sulfuric peroxide mixture (SPM) solution was used to form -OH group which caused the hydrophilic characteristic on silicon surftce. Highest hydrophilicity was obtained by SPM solution with 85% acid content at room temperature. OTS was applied on the silicon surface by means of self-assembled monolayers (SAMs) coating. It was found that sol-gel reaction was took place between -OH group on the silicon surface and -Cl group in OTS. As a result, the contact angle increased due to the increase of hydrophobicity by Si-O bonding of SAMs. Sol-gel reaction could be controlled by coating conditions as well as reagent composition in OTS coating solution.

• Journal of Sensor Science and Technology
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• v.25 no.3
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• pp.213-217
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• 2016

The superhydrophobic and superoleophobic meshes surfaces have been used in various applications such as self-cleaning, anti-icing, gas exchange, oil-water separation, sound-wave penetrable anti-wetting structures, etc. In particular, there are many studies for oil-water separation with environmental issues. Because of high pressure and dynamic environment, oil-water separation filters must have stable surface properties as super-hydrophobicity and superoleophobicity. The oleophobicity of surface depends on the surface chemistry and roughness of the surface. The roughness of oleophobic surface enhances its static contact angle and stability. The multi-scale hierarchical structure provides a stable superhydrophobic state by maintaining a Cassie state. In this research, we fabricated a superoleophobic mesh with a multi-scale hierarchical structure to increase the pressure resistance and adjusted a size of the mesh hole.

• Journal of the Korean institute of surface engineering
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• v.51 no.1
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• pp.11-20
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• 2018

Hydrophobic and Superhydrophobic surfaces are promising technology for the surface finishing of metallic materials due to its water-repellency. Realization of highly water-repellent surface on aluminum and its alloys provides various functionalities for real application fields. In order to realize the hydrophobic/superhydrophobic surfaces on aluminum and its alloys, various technologies have been demonstrated. Especially, traditional anodic oxidation for aluminum has been widely employed for the morphological texturing of surfaces, which is essential to enhance the hydrophobic efficiency. De-wetting superhydrophobic surface on aluminum provides various exceptional properties, such as anti-corrosion, anti-/de-icing, anti-biofouling, drag reduction, self-cleaning and liquid separation. Nevertheless, the durability and stability of superhydrophobic surfaces still remain challenges for their actual applications in engineering systems and industry. In this review, the theoretical/experimental studies and current technical limitations on the hydrophobic and superhydrophobic surface using anodic oxidation of aluminum have been summarized.