Decorative, hydrophobic sol–gel coatings densified using near-infrared radiation

Decorative, hydrophobic coatings were generated using sols synthesized from hydrolysis and condensation of methyltriethoxy silane, tetraethoxy silane and 1H,1H,2H,2H-perfluorooctyltriethoxysilane, in combination with nanosized and submicron-sized inorganic black pigment particles. Coatings were densified at 250 °C using near-infrared radiation as well as by a conventional curing method. The densified coatings were characterized for their thickness, roughness, contact angles and adhesion. The properties of the near-infrared radiation cured pigmented coatings were found to be comparable with those of the conventionally cured coatings. The pigmented coatings generated using nanosized pigments, whether near-infrared radiation cured or conventionally cured were seen to exhibit improved hydrophobicity with contact angles ranging from 130 to 145° when compared to their transparent unpigmented counterparts, that showed water contact angles from 93 to 97°. The improved hydrophobicity was explained on the basis of presence of a possible double length scale roughness of the coatings.