Preparation And Application Of Superhydrophobic Alkylated Silica

Superhydrophobic surface is the surface with excellent hydrophobic properties on which the contact angle of water droplets is greater than 150°.Rough structure and low surface energy are two dominant factors for the construction of superhydrophobic surface.Superhydrophobic materials have a wide range of application prospects,such as anti-fogging coatings,anti-fouling coatings,anti-icing coatings,anti-corrosive coatings.In this work,pristine silica sol with mono-dispersion and good stability was prepared by sol-gel method.Superamphiphobic fluorinated silica was successfully prepared by surface modification of pure silica sol with 1H,1H,2H,2H-triethoxydsilane(FAS-17).An organic-inorganic composite coating was prepared by blending epoxy resin and fluorinated silica sol to serve as anti-corrosion coating.Superhydrophobic and oleophilic dodecylated silica sol was prepared by surface modification of pristine silica sol with dodecyl triethoxysilane(DTMS).Dodecylated silica/KH560/T-31 composite coating was prepared by using KH560as interface coupling agent and T-31 as curing agent.The work contained the following three parts:1.Preparation of monodisperse silica sol:Silica sol with different particle size were prepared by gel-sol method.The effect of solvent type,catalyst,reaction temperature and reaction time on particle size was investigated.The result shows that the best formula for the preparation of monodisperse and stable silica sol was deionized water:anhydrous ethanol:tetraethoxy-silane(TEOS):ammonia(1 mol/L)=2.0:20.0:2.0:0.3 under 50?for 4 h.2.Preparation and application of superamphiphobic fluorinated silica.Superamphiphobic fluorinated silica was successfully prepared by surface modification of pristine silica sol with 1H,1H,2H,2H-triethoxydsilane(FAS-17).The experimental results show that the optimal preparation concentration is 2.5 wt.%of modifier,96.5 wt.%of pristine silica sol(5.0 wt.%)and 1.0 wt.%of ammonia(1 mol/L)used as catalyst.According to XPS analysis,the atomic percentage of fluorine element in the surface of silica is 32.4%.The fluorinated silica has a diameter of ca.120 nm with a rougher surface.The spherical fluorinated silica was covered by layer of organic covering with a thickness of ca.10 nm with classic core-shell structure.The static water and hexadecane static CAs of the fluorinated silica coating were 161°and 156°respectively.At the same time,the slide angles of water and hexadecane are 1.2°and 2.1°,which indicates that the fluorinated silica coating is both superoleophobic and superhydrophobic.Epoxy/fluorinated silica composite coating was prepared by blending epoxy resin and fluorinated silica sol.The composite coating has good performance for anti-corrosion application.3.Preparation and application of superhydrophobic/superoleophilic dodecylated silica.Dodecylated silica was prepared by surface modification of pristine silica sol with dodecyl-triethoxysilane(DTMS).The experimental results show that the optimal concentration is3.0 wt.%of modifier,84 wt.%of CH₃CH₂OH,9 wt.%of H₂O,4.0 wt.%of NH₃·H₂O(1mol/L).The results of thermogravimetric(TGA)testing show that the graft rate of dodecyl chains on the surface of spherical silica is 65.8%.Dodecylated silica surface has a rough surface with a papillary structure.The static water and hexadecane CAs of the dodecylated silica coating were 158°and 9°respectively.Meanwhile,the water slide angles was 0.95°,which indicates that the dodecylated silica coating is superhydrophobic and oleophilic.Dodecylated silica/KH560/T-31 composite coating was prepared by using KH560 as interface modification coupling agent and T-31 was used as curing agent.PET fiber coated with dodecylated silica/KH560/T-31 composite coating has a good performance for oil-water separation.