• Tribology and Lubricants
• /
• v.35 no.5
• /
• pp.294-299
• /
• 2019

Most previous studies on water repellent surfaces using lasers rely on the use of pico- or femtosecond lasers. However, in industrial application, these methods have the disadvantages of high cost and low efficiency. In this study, we implement a hydrophobic surface using a high-power general-purpose diode laser. We have fabricated the microsurface using laser groove processing technology, and we present the correlation of wettability characteristics with space and width. The metal material is stainless steel (SUS 304), and the groove height during laser processing is set to $30{\mu}m$ to evaluate the wettability based on the gap and width of various grooves. Results show that the contact angle of the groove-shaped surface is increased by $40^{\circ}$ or more as compared with the surface without patterning, and the contact angle in the parallel direction is greater than that in the perpendicular direction. Results from contact angle hysteresis measurement experiments show that the groove width has a greater influence on the contact angle history than does the gap between grooves. In addition, the coating reveals that the contact angle can be increased using a chemical method and that the laser grooving process can further improve the wetting properties of the surface.

• Clean Technology
• /
• v.18 no.2
• /
• pp.170-176
• /
• 2012

A series of acrylic copolymers containing perfluoroalkyl acrylate were synthesized by 2-step emulsion polymerization of variety of acrylate monomers (ethyl acrylate, butyl acrylate or methyl methacrylate) with perfluoroalkyl ethyl acrylate (PFA) and glycidyl methacrylate (GMA) monomers. This study focused on effects of monomer compositions (the kind of acrylate monomer, contents of PFA and GMA) and composition of surfactants [(sodium dodecyl sulphate/nonylphenol 10mole ethoxylate (NP-10)] and initiator content on the contact angles and surface free energy. It was found that the copolymer having an optimum composition (BA : 87 wt%, GMA : 8.7 wt% and PFA : 4.3 wt%) was shown to be quite surface active [surface free energy : 19.89 mN/m and contact angles : $103.5^{\circ}$ (water) and $78.7^{\circ}$ (methylene iodide)] in the solid state. This result suggests that the optimal copolymer containing fluorinated monomer synthesized in this study have high potential as a low surface energy material, which may have high oil- and water-repellent surface and have been proposed as acrylic syntan for leather and also as soil-resistant/oil and water repellent coating for textiles and wood etc.

• KOMUNHWA
• /
• no.66
• /
• pp.87-112
• /
• 2005

Stain removal on ivory has been, for a long time, considered an undesirable treatment in conservation field because ivory is hygroscopic and anisotropic, having different physical properties in different directions. Cyclododecane, which sublimes at room temperature, has been investigated for its use in conservation field since 1995, as a reversible temporary consolidant, sealing agent or coating, water repellent, and barrier layer. This research aims to remove stains on ivory, temporarily protecting the none-stained area or painted area from methanol, acetone or the aqueous cleaning system using cyclododecane as a hydrophobic sealing agent. This research also aims to obtain information regarding whether cyclododecane can be safely and effectively used on archaeological wet ivory. Melted cyclododecane and saturated solutions of cyclododecane in mineral spirits, and hexanes were applied to ivory samples. Application methods, working properties of cyclododecane on ivory, and effect of cyclododecane coating on moisture content of wet ivory were evaluated. The sealing layer formed by molten cyclododecane or by saturated cyclododecane solution in hexane or saturated cyclododecane solution in mineral spirits did not form a secure contact with the surface of the highly polished ivory. The sealing formed with two different layers, in which saturated cyclododecane solution in hexane was applied initially and then molten cyclododecane was applied over the first layer, was found to securely protect the painted area. When the wet samples were kept in 100% RH environments for a month, active mold growths were observed except in the samples sealed with molten cyclododecane. In conclusion, cyclododecane was an efficient hydrophobic sealing agent to protect painting area while cleaning stains on ivory. It also prevented mold growing on wet ivory and wet bone. Evenness of cyclododecane film on ivory will be determined in UV light. Analytical techniques will include visual observation, polarized light microscopy, Scanning Electron Microscope, and Gas Chromatography.

• Journal of the Mineralogical Society of Korea
• /
• v.18 no.2
• /
• pp.83-92
• /
• 2005

Dissolution rate of minerals may differ from climates configuration, but weathering rate of feldspars is generally proved to be relatively higher The result of geochemical reaction modeling indicates the acid water of pH 4.5 excluding any other variables, was 2.3 times higher than that in ordinary rain of pH 5.7. This result proved that pH is very important factor in preservation of granite cultural properties. To prevent the weathering of stone cultural properties, weathering characteristics of stones should be studied first and constitution of dry environments, using water repellent or oil coating, isolating water which cause chemical weathering reaction like hydration and oxidization should be considered. Considering the long-term reactions between granite and rain, selection of materials, which can bring neutralization and non-oxidization conditions, are very important in using cleaning agents and biological controls.

• Journal of Adhesion and Interface
• /
• v.16 no.3
• /
• pp.116-121
• /
• 2015

In this study, octadecyltrichlorosilane (OTS) has been used to replace fluoro-silanes which are much more expensive than OTS. In order to improve the mechanical and adhesive properties of coating layers, inorganic binders were separately synthesized based on sol-gel reaction in acidic condition. Since the synthesized silica nanoparticles gave only nano-scaled roughness, superhydrophobicity is not well obtained. Here, we present a new simple approach by intentionally inducing particle aggregation in the solution which is controlled by adjusting solvent amount. With selecting suitable sizes of silica nanoparticles, superhydrophobic surfaces were obtained with increasing the amount of organic solvents after surface hydrophobization using OTS, and an extremely water-repellent behavior was observed with zero sliding angle. This superhydrophobicity was achived only for the dielectric constant lower than 25, regardless of the composition of solvent, meaning that the dielectric constant could be an excellent indicator for fabricating superhydrobic surfaces induced by particle aggregation in the solution.

• Journal of the Korean Applied Science and Technology
• /
• v.35 no.2
• /
• pp.502-508
• /
• 2018

The acrylate copolymer having good coating, water-repellent and adhesion properties was designed and prepared. We prepared copolymers with high yield of > 95% using methyl methacrylate(MMA), 2,2,2-trifluoroethyl acrylate (FMA) and 2-hydroxyethyl methacrylate monomers(HEMA) by either bulk or emulsion polymerization techniques. The $^1H-NMR$ spectrum was used to identify chemical structure and DSC and DMA analysis were conducted. As a result, the glass transition temperature decreased by $3^{\circ}C$ as FMA content increased from 5% to 10%, and decreased by $2{\sim}8^{\circ}C$ when HEMA content increased from 5 % to 10 %. The physical properties were measured using Instron and TGA. As FMA or HEMA content increased by 10%, tensile strength decreased from 29 MPa to 22 MPa and Td decreased from $200^{\circ}C$ to $180^{\circ}C$ in both bulk and emulsion. The contact angle relatively decreased as hydrophilic HEMA content increased.

• Clean Technology
• /
• v.17 no.3
• /
• pp.259-265
• /
• 2011

The textile industry is suffered from air pollution problems which must be resolved. In particular, white smoke and odor after the tenter process require abatement. The major air pollution problem in the textile industry occurs during the finishing stages, where various chemicals are used for coating the fabrics. Lubricating oils, plasticizers, and water repellent chemicals are the fabric treatment chemicals. The coated fabrics are cured by heating in tenter facility. In this process, most of air pollutants emitted into the air. White smoke is basically made up of tiny solid or liquid particles of VOCs less than one micron in size. The oil mist can be carried over long distance from their point of origin. The most effective method of removing odor from tenter process is to get rid of tiny oil mist at the emitted gas. For this reason, the full-scale EFC (Electric Fume Collector) of 700 CMM was tested for removing odorous substances emitted from tenter facility. As a result of this study, odor and white smoke can be eliminated effectively and quite large amounts of oil can be recovered.