Abstract:
Transparent superhydrophobic coatings have potential applications in optical devices, solar panels, automobile windshields and glass building facade. However, their real-world applications are restricted by low transparency, poor durability, and the complex preparation processes. Hybrid silica sol is commonly prepared by the sol-gel process using fumed silica, tetraethoxysilane (TEOS) and hexamethyl-disilazane (HDMS) as raw materials. In this study, transparent superhydrophobic composite coatings were obtained via incorporating the hybrid silica sol with organosilicon oligomer synthesized from 2,3-epoxypropoxy propyltrimethoxysilicane (KH560) and alkyl siloxane as precursors. The influence of loading of fumed silica and HDMS on the hydrophobic property of the hybrid silica sol coatings was investigated, and the effects of KH560 , organosiloxane diversity and organosilicon oligomer loading on the properties of composite coatings were studied. The optimal performance of hybrid silica sol coatings was obtained with a water contact angel (CA) of 166° and sliding angel (SA) of less than 3° when the mass ratio of nano-fumed silica to TEOS was 0.075, and the mass ratio of HMDS to TEOS was 0.75, respectively. When the molar ratio of KH560 to MTES was up to 0.50, and the mass ratio of organosilicon oligomer to hyrid silica sol was 0.100, the composite coating remained superhydrophobic with water contact angle being 138° even after ultrasonic treatment for 5 min. Scanning electron microscopic showed a continuous porous network with a large amount of micro-nano composite rough structures on the surface of the composite coating. Furthermore, the optical transmittance of the hybrid silica superhydrophobic composite coating reached 85.4% at 550 nm.