Transparent, non-fluorinated, hydrophobic silica coatings with improved mechanical properties

Non-fluorinated, hydrophobic silica coatings were generated on soda lime glass substrates using dimethyldiethoxysilane (DMDEOS), tetraethoxysilane (TEOS) and a silylating agent hexamethyldisilazane (HMDS) using sol–gel process. To improve the mechanical properties of the coating, epoxy modified nanosilica particles were added to the sol of dimethyldiethoxysilane, tetraethoxysilane and hexamethyldisilazane followed by sonication prior to coating. Coatings were characterized for their water contact angles, thickness, UV–Vis transmission, pencil hardness and surface morphology. The concentrations of the nanosilica particles as well as the sonication times were optimized to obtain a transparent, hydrophobic coating with improved pencil scratch hardness. An optimized coating composition with 1: 0.5 M ratio of the nanosilica particles and sol synthesized from DMDEOS, TEOS and HMDS sonicated for 60 min yielded coatings that exhibited a water contact angle of 125±2° with a pencil scratch hardness of HB and average visible light transmittance of 89%.