Superhydrophobic Surfaces On PVDF Based Composites Fabricated By Simple Methods And Its Stability Investigation

For the development of stable and durable superhydrophobic surfaces prepared via simple methods at low cost, two categories of polyvinylidene fluoride (PVDF) based composites were prepared using two simple methods. The first one made use of Polytetrafluoroethylene (PTFE) particles as low surface energy addition. The PVDF based composites were prepared by dry mixing the powder of PVDF, PTFE, and other filler Silicon dioxide(SiO2),Aluminum(Al),Carbon Black(CB),and then hot-pressing method. Subsequently, the prepared PVDF composites surfaces were ground with sandpaper and the superhydrophobic surfaces were obtained. The second superhydrophobic PVDF composites surfaces were prepared by roughening the SiO2, Al or CB particles filled PVDF composites surfaces with sandpaper, and then modified with1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS).Water contact angles (WCAs) and Water sliding angles (WSAs) of various PVDF based composites surfaces were meraured by An optical contact angle meter; The surface morphology was observed using a scanning electron microscopy; The surface chemical compositional analyses were performed by X-ray photoelectron spectroscopy (XPS); The stability of the superhydrophobic surfaces were evaluated by measuring their WCAs and WSAs on the surfaces after they suffered from various external environment. The surface’s durability to various inorganic aqueous solutions and organic solvents was evaluated by immersing it in a solution or solvent for2days at room temperature; Temperature stability was evaluated by cooling and heating the sample at various temperatures for2h. UV irradiation stability tests were performed using a home-made fluorescent UV exposure tester (fluorescent lamp); Accelerated UV weathering test were performed in an ultraviolet ageing oven.In summary, the composites containing PTFE particles can obtain superhydrophobicity by a simple sandpaper grinding method. When PTFE volume fraction is30%and sandpaper grade is320#, the composite surface possess optimum superhydrophobicity, with a WCA of163°, and a WSA of4.2°. All of the PVDF based composites surfaces without PTFE possess excellent superhydrophobicity after grinding with sandpaper and PFOTS modification, with WCAs higher than160°and WSAs lower than5°, regardless of the sandpaper grade. The survey XPS spectra indicated that the PFOTS coating is successfully self-assembled on the outermost surface after immersion in PFOTS ethanol solution and subsequent heat treatment. The composites containing PTFE particles possess excellent mechnical stability and easy repairability. Both of the PTFE filled and PFOTS modified PVDF composites surfaces have CAs>150°and SAs<5°to various aqueous solutions with a wide range of pH (1～11), and show superoleophilicity to various organic solvents. The stability investigation indicated that the superhydrophobicity of the composites surfaces without SiO2and Al incorporation show good stability to various aqueous solutions, various organic solvents, ultrasonic cleaning, temperature variation (-30～150℃), UV irradiation and accelerated UV weathering test.The composites filled with SiO2particles show poor superhydrophobicity stability with NaOH aqueous solution treatment, and the superhydrophobic surfaces of Al filled composites surfaces are volatile in acidic environment and accelerated UV irradiation. The stability of SiO2/PVDF and Al/PVDF composites superhydrophobic surfaces were better than that of the SiO2-PTFE/PVDF and Al-PTFE/PVDF composites, which was attributed to the protection of a fluorinated low surface energy film in the surface of the former composites.