Superhydrophobic fabrics from hybrid silica sol-gel coatings: Structural effect of precursors on wettability and washing durability

Particle-containing silica sol was synthesized by co-hydrolysis and co-condensation of two silane precursors, tetraethylorthosilicate (TEOS) and an organic silane composed of a non-hydrolyzable functional group (e.g., alkyl, fluorinated alkyl, and phenyl), and used to produce superhydrophobic coatings on fabrics. It has been revealed that the non-hydrolyzable functional groups in the organic silanes have a considerable influence on the fabric surface wettability. When the functional group was long chain alkyl (C16), phenyl, or fluorinated alkyl (C8), the treated surfaces were highly superhydrophobic with a water contact angle (CA) greater than 170°, and the CA value was little affected by the fabric type. The washing durability of the superhydrophobic coating was improved by introducing the third silane containing epoxide group, 3-glycidoxypropyltrimethoxysilane (GPTMS), for synthesis. Although the presence of epoxide groups in the coating slightly reduced the fabrics' superhydrophobicity, the washing durability was considerably improved when polyester and cotton fabrics were used as substrates.