Facile construction of robust super-hydrophobic coating for urea-formaldehyde foam: Durable hydrophobicity and Self-cleaning ability

A robust super-hydrophobic coating was constructed on the surface of urea-formaldehyde (UF) foams through a facile immersion process in SiO2 nanoparticle-dispersed ethanol solution with dodecyltrimethoxysilane (DTMS) as compatibilizer. By introduction of DTMS, strong hydrogen bonding interaction formed between SiO2 coating and UF foam. The UF-g-SiO2/DTMS foam showed a water contact angle (CA) of 157.2 degrees and a sliding angle (SA) of 3 degrees, and after long-term immersion, very slight change of CA and SA was observed, while the water absorption ratio was 36.89% lower than that of pristine sample, displaying durable super-hydrophobicity. The UF-g-SiO2/DTMS foam showed excellent self-cleaning ability. Introduction of DTMS improved the dispersion of SiO2 in solution and thus lots of bamboo shoot-shaped granular protrusions of SiO2 nanoparticles at micro/nano-scale formed on the foam surface during treatment process, while the strong interfacial interaction prevented SiO2 nanoparticles from falling off the foam after long-term immersion, and thus durable hydrophobicity was achieved.