• Textile Coloration and Finishing
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• v.29 no.2
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• pp.55-61
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• 2017

A non-fluorinated polystearyl methacrylate water repellent was synthesized by emulsion polymerization. The number and weight averaged molecular weights were obtained at around 137,277 and 237,754g/mole. The melting point was observed at $32^{\circ}C$. The contact angle of water droplet on fabrics treated with the water repellent was $140{\sim}145^{\circ}$ for cotton and polyester, and $125{\sim}130^{\circ}$ for wool and nylon. Since the critical surface tension was estimated at 20.7mN/m, even though relatively not so strong as fluorinated water repellent, it is considered to be used as a good water repellent practically.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.124-132
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• 2019

Water-repellent coating solutions were synthesized by hydrolysis and polycondensation reactions with water using tetraethoxysilane (TEOS) and chlorotrimethylsilane (CTMS) as precursors. The solutions were coated on a PMMA sheet and thermally cured to prepare non-fluorinated water-repellent coating films. Coating films were characterized by water contact angles, UV-Vis transmittance and surface morphology. The contact angle of coating films prepared by varying the molar ratio of CTMS/TEOS to 0.6~1.0 exhibited a maximum value of $107^{\circ}$ when the CTMS/TEOS molar ratio was 0.8. The coating films showed a high transmittance over the visible range up to 90% when the CTMS/TEOS molar ratios were 0.6~0.8. However, when the molar ratios of CTMS/TEOS were 0.9~1.0, the transmittance of coating films was lower than 70% due to an uneven shape of the rough surface.

• Textile Coloration and Finishing
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• v.30 no.4
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• pp.275-287
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• 2018

In recent years, research on the development of eco-friendly synthetic suede based on water-dispersed polyurethane resin and non-fluorine water repellent has been conducted. Synthetic suede has a problem that the fastness to dyeing is greatly lowered after the water-repellent processing at a high temperature of $160^{\circ}C$ because the polyester is dyed with a disperse dye. Therefore, in this study, silica was added to water-dispersed polyurethane resin to improve dye fastness. To distribute the $PUD-SiO_2$ mixture evenly in the water-dispersed polyurethane resin, sufficient stirring was done for a period of time. When the $PUD-SiO_2$ mixture(PUD 1-5%) is applied to the substrate, it is confirmed through SEM that the mixture is uniformly applied without particle condensation. The results showed that silica with a diameter of 4~12nm and BET of $200{\sim}380g/m^2$ had the ability to improve dispersibility and fastness.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.177-184
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• 2019

Non-fluorinated water repellent coating solutions were obtained using methyltrimethoxysilane (MTMS) and trimethylethoxysilane (TMES) as precursors. The solutions were spin-coated on a cold-rolled steel sheet and cured thermally to prepare water repellent coating films. During this process, the effect of molar ratio of TMES/MTMS was studied for the hydrophobic properties of the coating films. Hydrophobic properties of coating films were characterized using contact angle measurement, surface morphology analysis and infrared spectroscopy. When the molar ratio of TMES/MTMS was varied from 0 to 30, the contact angle of the un-coated cold-rolled steel sheet was $30^{\circ}$, whereas when the molar ratio of TMES/MTMS was 1, the contact angle increased to $104^{\circ}$ and water repellency was significantly improved. In the case of TMES/MTMS molar ratios of 10, 15, 25 and 30, the contact angles of coating films showed $109^{\circ}$, $114^{\circ}$, $117^{\circ}$ and $144^{\circ}$, respectively. At this time, the hydrophobicity of the coating films was improved by the increase of the surface roughness and the content of the methyl component at the coating surface. In particular, when the molar ratio of TMES/MTMS was 30, the overall surface roughness was greatly increased due to the presence of surface particles as well as the water repellency due to methyl groups of TMES, resulting in super hydrophobicity of $144^{\circ}$.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.749-757
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• 2019

Methyltrimethoxysilane (MTMS) and trimethylethoxysilane (TMES) as starting materials were dissolved in various types of solvents, and hydrolysis with water and polycondensation reaction were carried out using various types of catalysts to prepare non-fluorinated water-repellent coating solutions. The coating solutions were spin-coated on cold-rolled steel sheets, and thermally cured to prepare water-repellent coating films. The effect of types of catalysts and solvents on the water repellency of the resulting coating films was investigated during this process. When hydrochloric acid and nitric acid, which are strong acids, were used as catalysts, the solutions showed a white opaque state due to the aggregation of siloxane polymers. On the other hand, when acetic acid, phosphoric acid, and oxalic acid, which are weak acids, were used, they were in a stable and transparent state without precipitation. As a result, the contact angles of the coated films, prepared from hydrochloric acid and nitric acid, were $58^{\circ}$ and $92^{\circ}$, respectively, showing low water repellency. On the other hand, when acetic acid, phosphoric acid, and oxalic acid were used, the contact angles of the coated films were $101^{\circ}$, $103^{\circ}$ and $116^{\circ}$, respectively, showing high water repellency. In addition, when isopropanol and ethanol were used as solvents, phase separation occurred in the solutions due to the aggregation of siloxane polymers. On the other hand, when methanol, ethyl acetate, and methyl ethyl ketone were used as solvents, the solutions were transparent and showed a stable state without sedimentation.