Fluorine-free anti-droplet surface modification by hexadecyltrimethoxysilane-modified silica nanoparticles-coated carbon nanofibers for self-cleaning applications

Abstract

In daily life, many surfaces become contaminated owing to dust/dirt accumulation via air pollution. Selfcleaning surface modification is one of the best ways to address this problem. Therefore, ultra-hydrophobic coatings have garnered significant attention owing to their potential applications featuring water resistance and self-cleaning ability. In this study, a simple, fluorine-free, as well as eco-friendly technique was utilized to fabricate durable self-cleaning coatings. This coating material consists of fluorine-free hexadecyltrimethoxysilane-altered SiO2 nanoparticle (NPs)-coated carbon nanofibers (CNF/SiO2-HDTMS) and a commercial gelatin based adhesive emulsion. Owing to the presence of the hydroxyl (-OH) functional groups of CNFs, SiO2 NPs could accumulate on CNFs surface, hence creating hierarchical microstructures that generate air pockets for improved hydrophobicity. In this study, the developed coating was applied onto a polyethylene sheet, glass fiber membrane, and glass via dip coating. These surfaces were targeted due to over-use in day-to-day life as well as in industrial applications such as plastic tents, umbrellas, windshields of vehicles, window and door glasses, skyscrapers, membranes, fabrics, papers and the list is endless. Interestingly, after the introduction of the adhesive based CNF/SiO2-HDTMS coating, the superhydrophilic microfiber filter became highly hydrophobic, with a water contact angle of 125 degrees. Similar effect can be seen in case of the modified glass, where the average contact angle was determined to be around 141 degrees. The CNF/SiO2-HDTMS coated poly bag exhibited excellent anti-droplet behavior with water contact and rolling angles of 136 degrees and 12 degrees, respectively. The self-cleaning coatings maintained anti-droplet behavior even after tests such as sand impact abrasion, and finger touch. This study explores the possible industrial applications of self-cleaning coatings at ambient temperature to improve the feasibility of their usage.