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Abstract Cotton fabric surface was treated with combinations of silica nanoparticles, silane hydrophobes, and silane crosslinkers to obtain durable hydrophobicity. Performance analysis was done by measuring the contact angle of water on the treated fabric surface. To evaluate the durability of the surface hydrophobicity, AATCC crocking and laundering tests were performed. Cotton fabrics with good hydrophobicity (contact angle = 139. G) and excellent durability (e.g. 95% recovery of contact angle after laundering) were obtained when treated with Aerosil® 90 nanoparticles, n-octyltrimethoxysilane, and bis(triethoxysilyl)ethane. This study demonstrated that the surface treatment using silica nanoparticles and mixed silanes is a promising alternative to fluoropolymer chemistry for achieving durable hydrophobic fabrics.
Key words fabric finishing, hydrophobicity, nanotechnology, silane, silica
Textiles with hydrophobic surfaces have many uses in industrial, consumer, and apparel markets. These surfaces are mostly produced on commercial textiles by creating a coating with fluoropolymers. Recently, fluoropolymers have come under scrutiny due to their environmental persistence and potential human-health issues, and hence non-fluorine silane chemistry (e.g., alkyltrialkoxysilanes) has become of particular interest in both academy and industry [1-9]. Non-fluorine silane-based hydrophobic textiles are typically made by surface-treating textile materials using mixtures of silane hydrophobes (such as long-chain alkyltrialkoxysilanes) and silane crosslinkers. For example, Daoud et al. [6] used a mixture of hexadecyltrimethoxysilane, tetraethoxyorthosilicate, and 3-glycidyl-oxypropyltrimethoxysilane to treat cotton surface and obtained a water contact angle of 141°.
Currently, one major barrier to widespread commercial use of non-fluorine silane chemistry is the poor durability of the resultant hydrophobic surfaces. Our approach to create durable hydrophobic surfaces is to introduce silica nanoparticles into the mixture of silane hydrophobes and silane crosslinkers. Figure 1 shows a possible schematic presentation of the surface chemistry after applying silica nanoparticles, silane hydrophobes, and silane crosslinkers onto a cotton fabric. Silica nanoparticles have large amounts of surface hydroxyl groups and are covalently linked to the fabric surface by silanes through -O-Si-O- or -CH^sub 2^-O-Si-O- groups. Silica nanoparticles can also significantly improve the water repellence by increasing the amount of attached alkyltrialkoxysilanes, because these nanoparticles have large amounts of surface hydroxyl groups [1O]. In addition, silica nanoparticles on fabric surface can increase the surface roughness, and hence improve the finishing durability to laundering and abrasion [11, 12]. Silane hydrophobes, such as hydrophobic alkyltrialkoxysilanes, provide...