Waterborne fluorinated emulsion/F-SiO2 amphiphobic coatings for cementitious substrates: Wettability, interfacial adhesion and durability

Cementitious substrates are porous, rough, and alkaline. These characteristics make amphiphobic coatings prone to interfacial failure and make it difficult to simultaneously maintain liquid repellency, adhesion, and functional stability. Existing fluorinated, fluorine-free, and organic–inorganic hybrid amphiphobic coatings can achieve high contact angles on smooth substrates, but their engineering adaptability to rough, porous, and highly alkaline cementitious substrates still needs to be improved. In this study, a waterborne fluorinated emulsion (WFE) was used as the film-forming matrix. Fluorinated SiO 2 (F-SiO 2 ) was introduced to build a micro/nano rough structure. KH-560 and a water-dispersible isocyanate were also added to strengthen the interface and the bulk phase. Unlike previous studies that mainly focused on static contact angles, this work establishes a formulation-structure-adhesion relationship for waterborne amphiphobic coatings on porous and alkaline cementitious substrates. As the ratio of m(binder):m(F-SiO 2 ) changed from 1.0:0–0.2:1.0, the water contact angle increased from 78.0° to 152.3°, and the oil contact angle increased from 40.0° to 143.1°. This indicates a transition from a Wenzel-dominated state to a Cassie–Baxter composite wetting state. A clear transition region appeared near 1.0:0.5. The ratio of 0.5:1.0 was selected as the most balanced formulation among the tested groups because it achieved comparable liquid repellency with better adhesion balance and lower filler loading. After KH−560 and isocyanate were added, the pull-off adhesion strength increased from 1.52 MPa to 2.03 MPa. After immersion in acid/alkali solutions for 48 h, immersion in deionized water for 7 d, 100 cycles of mechanical abrasion, and UV aging for 7 d, the optimized coating still maintained high water and oil repellency, indicating short-term functional retention under laboratory exposure conditions. These results provide an effective strategy for preparing waterborne amphiphobic coatings with balanced liquid repellency, interfacial adhesion, and short-term functional stability on cementitious substrates.