The Control Of Surface Structure And Hydrophobility Of Flurosilicone-modified Silica Nano-coatings

The superhydrophobic surfaces have potential applications in self-cleaning, drag reduction of fluid delivery and other fields. The prerequisite to achieve superhydrophobility was that the surfaces with low surface free energy and a certain roughness. Fluorosilicone has low surface free energy, and silica nanoparticles(SiO2 NPs) could be used to build rough structure due to its excellent properties. So the fluorosilicone modified SiO2 nanoparticles(NPs) could be used to build micro-nano composite structure and introduce chemical materials with low surface free energy.The wettability of coating surfaces primarily has been influenced by surface free energy and microstructure. The introduction of alkoxy silane with different structures would change the arrangements of fluoro-containing chains, and influence the wettability of coating surfaces, thus the preparation of controlled structure and hydrophobility with silica nano-coating surfaces has higher difficulty. In this paper, fluorosilicone modified SiO2 NPs were prepared by sol-gel method. And then, the surface structure and hydrophobility of nano-coatings were studied. Following conclusions were obtained:1. Modified SiO2 NPs with different structures were prepared through sol-gel method. And the influences of different conditions on fluorosilicone modified SiO2 nano-coatings were studied.(1) Through Sol-gel method, SiO2 NPs were modified by methyltrimethoxysilane(MTMS), perfluorooctyl triethoxysilane(G617) and MTMS-G617 with different chemical structures and compositions. Modified SiO2 NPs which have better stability could reach more than 10 months, a narrow dispersion particle diameter, and better thermal stability.(2) The coatings were prepared by fluorosilicone-modified SiO2 NPs, and the film-forming conditions, substrates and hydrophobility were studied.① The substrate influenced the hydrophobility of coatings as the fluorine content changes. Coatings which coated on glass slides, the water contact angle(WCA) could reach 137.1 ° when G617 content in 6%, while coatings coated on aluminum plates could reach 138.6 ° when G617 content in 8%.② Hydrophobility of coatings differed from the prepared methods. For MTMS and MTMS-G617 coatings, the WCA of coatings by dip-coating and drop-coating were significantly improved. However, the WCA of G617 coatings prepared by spin-coating were obviously higher than other methods.③ The superhydrophobic coatings of MTMS and MTMS-G617 were prepared by surface-coating method, WCA were 150.4 ° and 150.2 ° and water hysteresis angles were 6.1 ° and 3.3 °, respectively.2. The surface morphology, composition and hydrophobility of fluorosilicone-modified SiO2 nano-coatings were studied.(1) The results of AFM showed that MTMS and G617 modified SiO2 coatings with bump and pore structure respectively, while the coatings of MTMS-G617 have composite structure with bump and pore, and its roughness could up to 27.436 nm. The surface morphology with bump, pore and composite structure were obtained by changing the contents of fluoro-containing.(2) The results of XPS showed that the contents of fluorine-containing segment gradually increased with the fluorine content of G617-SiO2 coatings.(3) The results of this studies showed that G617-SiO2 coatings were not existed enrichment of fluorine-containing segment. However, the co-modified coatings of MTMS-G617 have vast enrichments, indicating that the introduction of short-chain MTMS could fix the arrangement of fluorine-containing segment, so that the coatings exhibited better surface wetting performance.3. The superhydrophobic cotton fabrics were prepared by fluorosiliconemodified SiO2 NPs.(1) The hydrophobic cotton fabrics were successfully prepared through dipping-pad-dry method by using fluorosilicone modified SiO2 NPs. The factors were studied, which included baking temperature and time, the concentration of modified SiO2 NPs and the content of G617. The superhydrophobic cotton fabrics could be obtained in this work with the WCA could up to 156.4°.(2) The FE-SEM and XPS results showed that the superhydrophobic cotton fabrics of MTMS-G617 with good washing resistance and its surface contained uniform dispersion of SiO2 NPs. In addition, the fluorine content of finished cotton fabric could be as high as 13.14%.