Preparation and UV aging of nano-SiO2/fluorinated polyacrylate polyurethane hydrophobic composite coating

Hydrophobicity and anti-aging are two key features being sought in coating industry in light of their great importance in the development of self-cleaning materials for outdoor applications. The current study reports a nano-SiO2/fluorinated polyacrylate polyurethane (SiO2-FPEAU) composite coating that shows both good hydrophobicity and good anti-aging properties. Nano-SiO2 was first modified with γ-methacryloxypropyltrimethoxysilane (Kh570) to be well dispersed in fluorinated and hydroxyl acrylate monomers, where from copolymerization was carried out to form a nano-SiO2/ fluorinated polyacrylate composite resin (SiO2-FPEA). Cured with an isocyanate prepolymer (N3390) at room temperature, the SiO2-FPEA was cross-linked into the polyacrylate polyurethane (SiO2-FPEAU) composite coating. Numerous nano-SiO2 particles were observed on the film forming a surface nano-roughness, which was most likely driven by the surface self-segregation of surrounding fluorinated polymer chains. The nano-rough structure together with the fluorine enrichment on the film surface gave the composite coating a water contact angle of 116°. Moreover, the surface coverage of silica layer and the cross-linking structure in polyurethane greatly enhanced the anti-aging properties of the composite coating as demonstrated by less than 30 % of gloss loss after an artificial UV irradiation for 720 h. Besides, both chemical resistance and mechanical properties of the composite coating were improved thanks to the synergistic effect of the fluorine segments, the cross-linking in polyurethane and the nano-SiO2 particles. These findings indicated that the composite coating could be a very attractive solution for many practical areas, especially for outdoor applications.