The Study On Preparation And Properties Of Biomimetic Superhydrophobic Coating

In nature, many animals and plants have superhydrophobic, such as the lotus leaf surface,the water strider legs, butterfly wings. By studying these natural superhydrophobic surfaces,found that these superhydrophobic properties mainly depended on the roughmicro-nanostructure and waxy layer of the surface. Therefore, controlling the surfacechemical composition and morphology of material can control the hydrophobic of the surfaceof the material effectively. It provided theoretical basis and design ideas for the preparation ofartificial superhydrophobic coatings.According to the characteristics of lotus leaf superhydrophobic surface structure,dispersion solution was prepared by biomimetic method using silica (SiO2), titanium dioxide(TiO2), polyurethane (PU), polysiloxane as raw materials. SiO2/PU superhydrophobic coating,wettability can shift of TiO2/PU superhydrophobic coating, silica/polysiloxane transparentsuperhydrophobic coating with rough surface similar to lotus leaf, which built by using thespraying process combining phase separation and self-assembly technology. The coatingsurface contact angle (CA) and sliding angle (SA) of water droplets were determined bycontact angle tester. Microscopic structure of the coating surface was observed by fieldemission scanning electron microscopy (SEM). Stripping experiments of different coatingswere carried out by3M610type test tape, the change of the CA and SA were observed, andthe stability of the coating was analyzed. Silica/polysiloxane coating transparent rate wasinvestigated by UV visible spectrophotometer. The hydrophobic property of the coating ondifferent materials was studied, and the self-cleaning and anti freezing effect of SiO2/PUcoating surface were studied.SEM photos and contact angle test showed that the prepared SiO2/PU coating had roughmicro-nanostructure similar to the lotus leaf surface, and had superhydrophobic property. The dosage and ratio of each component in the coating, and the coating process had greatinfluence on the hydrophobic of the coating surface. When m(SiO2):m(PU)=3:5~4:5, andorganic silicon content was not less than15%, using the spraying process, the preparedcoating had superhydrophobic property, the water contact angle of coating can reach to158°,and sliding angle was3°. The stability of SiO2/PU coating was analyzed, the coating wasprepared by SiO2with different particle size. The results showed that the coating wasprepared by7nm SiO2had good bonding strength and stable structure. The contact angle ofcoating was153°, and sliding angle was9°after7times tape stripping test, the coating stillhad superhydrophobic property. For many materials, the coating showed goodsuperhydrophobic property, and SiO2/PU superhydrophobic coating had self-cleaningproperty and anti freezing property.SEM photos and contact angle test showed that the prepared TiO2/PU coating had roughmicro-nanostructure similar to the lotus leaf surface, and had superhydrophobic property. Thedosage and ratio of each component in the coating had great influence on the hydrophobicproperty of the coating surface. When m(TiO2):m(PU)=3:5~4:5, and organic silicon contentwas not less than15%, the prepared coating had superhydrophobic property, the water contactangle of coating was156°, and sliding angle was3°. TiO2/PU superhydrophobic coating hadgood bonding strength and stable structure. The contact angle of coating was151°, and slidingangle was9°after6times tape stripping test, the coating still had superhydrophobic property.For many materials, TiO2/PU coating showed good superhydrophobic property. Because thephotosensitive properties of TiO2, under UV light irradiation for3~4h, the contact angle of thecoating surface from156°reduced to3°, the superhydrophobic surface turned intosuperhydrophilic surface. Then the superhydrophilic surface was placed in dark for20d, thecoating surface restored to hydrophobic property, the contact angle was120°.SEM photos and contact angle test showed that the prepared silica/polysiloxane coatinghad rough micro-nanostructure similar to the lotus leaf surface, and had superhydrophobicproperty. Quality ratio of silica and polysiloxane had great influence on the hydrophobicproperty of silica/polysiloxane coating surface. When the quality ratio of silica to polysiloxane was from1:5to1:6, the prepared coating had superhydrophobic property, thewater contact angle of coating was156°, and sliding angle was4°. In the quality ratio range,the coating was prepared by7nm SiO2except had superhydrophobic, and had goodtransparency, the average transparent rate in visible light range higher than75%.Silica/polysiloxane superhydrophobic coating had good bonding strength and stable structure.The contact angle of coating was still greater than150°, and sliding angle was less than10°after5times tape stripping test, the coating still had superhydrophobic property. For manymaterials, silica/polysiloxane coating showed good superhydrophobic property.