The wetting behavior of a hydrophobic rough surface is investigated on a surface fabricated by applying low surface tension materials such as silicone or fluoropolymer to polyester woven fabric consisting of multifilament yarns. The roughness factor of various woven fabrics can be calculated by Wenzel's and Cassie-Baxter's equations. For the fabrics treated with silicone or fluoropolymer, the Cassie-Baxter model was applied, showing a level of agreement for the fabric specimens non-textured filament fibers between the predicted contact angles and the measured values. More precisely, the fabrics treated with silicone or fluoropolymer represent the transitional state between the Wenzel type and the Cassie-Baxter type; that is, the fractional contact area between the water and air f 2 is greater than zero, and the sum of the fractional contact areas for solid-water f 1 and air-water f 2 is greater than 1. A surface with lower energy and higher roughness gave f 1 + f 2 close to 1 with smaller f 1 and larger f 2 , which resulted in a high contact angle. KeywordsHydrophobic, lotus effect, roughness factor, Wenzel model, Cassie-Baxter model Inspired by natural surfaces like the lotus leaf, surfaces with extreme water repellent properties have received considerable interest in the last decade. 1 The studies by Wenzel 2 and Cassie and Baxter 3 showed that the rough and porous structure of a surface combined with a low surface energy can contribute to the hydrophobicity of a surface. The surface of the lotus leaf is chemically made of wax and structurally has two levels of roughness consisting of nano-scale bumps on the surface of micro-scale protrusions that enables the trapping of air underneath water droplets, thereby contributing to a well-designed superhydrophobic surface. 4 Drops of water deposited on such superhydrophobic surfaces exhibit extremely high contact angles (>150 ) and roll off at slight inclinations. Potential applications range from non-wettable, quick-drying surfaces to anti-fouling or self-cleaning surfaces. 4-8 In view of the significant potential of such surfaces for numerous scientific and industrial applications, many strategies to create superhydrophobic surfaces have been published to date. [6][7][8][9] As a measure of the hydrophobicity of the fabric surface, the static contact angle is often used; a larger contact angle with a smaller contact angle hysteresis represents higher hydrophobicity. Wenzel 2 and Cassie and Baxter 3 suggested the theoretical models for contact angles of a liquid on a surface with certain geometry. 9 Different contact angles may result with the same roughness texture depending on how the liquid is configured on the surface. When a liquid completely fills all the spaces in the pores, the Wenzel model is applied to describe the contact angle W r as a function of the ratio of the liquid-solid contact area to the

No abstract

Superhydrophobic textile material having self-cleaning function was developed by employing carbon nanotubes (CNTs) and water-repellent agents. Hydrophobic fabrics were prepared on 100 % polyester woven fabrics with various yarn diameters and yarn types. The wetting behavior of fabrics with different treatments was compared for: siloxane repellent, fluorocarbon repellent, and CNT added fluorocarbon repellent. Drawn textured yarn (DTY) fabrics exhibited higher contact angle (CA) than filament yarn fabrics due to the larger surface roughness contributed by the textured yarn. Fabrics treated with fluorocarbon presented larger CA and lower shedding angle than those treated with siloxane, because of the lower surface energy of fluorocarbon repellent. Specimens made of 50 denier DTY and treated with CNT-Teflon AF ® showed the most superhydrophobic characteristics in the study, producing the static contact angle greater than 150° and the shedding angle smaller than 15°. CNT on fabric surface contributed to the nano-scale surface roughness to hold the air traps like papillae of lotus leaf, giving superhydrophobic characteristics.

The purpose of this study was to develop a warm-up suit that is comfortable as well as having a good thermal performance. Heat-insulating water vapor-permeable fabrics for warm-up suit were developed by applying ceramic powders to hydrophilic polyurethane films, which were then incorporated into textiles. Two types of ceramic compounds were used in this study: MU-4N and RT-3. The infrared emissivity was 92.6 for MU-4N and 94.8 for RT-3. In order to evaluate the effectiveness of using ceramics in a warm-up suit, we examined the effects of ceramics on selected variables: thermo-physiological properties of the clothing systems (using thermal manikin), and thermo-physiological responses and subjective sensations of human subjects. The infrared emissivity of textiles increased when ceramics were added to the film laminate. Ceramics slightly increased the thermal insulation value and decreased the water vapor transmission rate. The thermal manikin test also showed that ceramics enhanced the thermal insulation of the clothing system without increasing the evaporative resistance. The microclimate temperature was kept higher when subjects wore the warm-up suit with ceramics.

The purpose of this study was to develop the warm-up suit that is comfortable as well as has good thermal performance. The function of warm-up suit is to keep the body warm and thus to lose it’s weight by sweating. Ceramic powders, such as zirconium and magnesium oxide have been incorporated into the textile structures to utilize the far infrared radiation effect of ceramics, which heat substrates homogeneously by activating molecular motion. Thermal manikin tests were conducted to determine the clothing insulation and evaporative resistance of the selected warm-up suits. Also, the far IR emission effects of ceramics containing laminate on the body heat transfer were evaluated with the thermogram data using IR camera. The results showed that the ceramics inside laminate slightly increased the thermal insulation and the evaporative resistance. Thermogram showed that when the fabric was heated with the thermal manikin, surface mean temperatures of fabrics were increased as the ceramic incorporated, and the heat storage performance was confirmed.