Preparation Of Super-hydrophobic Materials With Different Functions

Super-hydrophobic surfaces have been widely used in many applications, such as building, textile, and transportation. Different surface properties have been required in different applications. In this paper, three kinds of super-hydrophobic surfaces, which separately have excellent adhesion, anti-condensation/anti-frost properties and high transmittance, are successfully prepared.1. Preparation of super-hydrophobic coating with excellent adhesion.The super-hydrophobic coating, which is used as super-hydrophobic layer, is prepared by using epoxy-modified hydrophobic sol. To improve the super-hydrophobic coating’s adhesion, an adhesive layer of epoxy resin is coated on the substrate first and followed by a coating of super-hydrophobic layer. Thus, a two-side film with hydrophilic inner layer and hydrophobic out layer is prepared. The optimum conditions for preparing the hydrophilic-hydrophobic two-side film are investigated. Moreover, properties of the single hydrophobic layer film and the hydrophilic-hydrophobic two-side film are comparatively studied. The results show that the best volume ratio of the modified sol/hydrophobic sol and the optimum reaction time to prepare the hydrophobic layer are 1:1 and 20 h, respectively. Meanwhile, the optimal temperature to solidify the hydrophilic layer is 50°C for 3h. Compared the hydrophilic-hydrophobic two-side films with the single hydrophobic layer film, the contact angles decrease from 156 ° to 152.2 °. However, the adhesion strength increases from Grade 3 to Grade 0, the pencil hardness increases from HB to 3H. The scrub-resistance performance is also improved.2. Preparation of anti-condensation/anti-frost superhydrophobic copper and aluminum surfaces.A simple solution immersion method and surface modification are applied to create a super-hydrophobic copper and aluminum surfaces, respectively. Compared to untreated smooth surface, the treated surface can:(1) prevent the formation of large droplets from condensation. For copper etches for 90 min and modified, only several droplets with diameters of 1-2mm appear on it after 3h condensation. Most of the droplets cannot be observed by naked eyes. In contrast, almost all of the condensed droplets are more than 3mm in diameter on smooth copper surface without treatment. Droplets appear on the modified aluminum surface are mostly within the range of 1-2mm in diameter.(2) Delay the formation of frost. For the tests of anti-frost, most surface area of the untreated smooth copper is covered with frost after 20 min cooling. In contrast, only little frost emerge at the edge of the super-hydrophobic copper surface after cooling for 137 min. Tests on super-hydrophobic aluminum surface show that its anti-frost peformance is not as good as that of super-hydrophobic copper surface. Compared the anti-condensation/anti-frost properties of super-hydrophobic copper surface and super-hydrophobic aluminum surface, we can know that nano-sized roughness have better anti-condensation/anti-frost properties than micron-sized roughness.3. Preparation of super-hydrophobic materials with high transmittance.The transparent super-hydrophobic materials are prepared as the following depiction. Firstly, a hydrophobic sol is prepared by a sol-gel method. Secondly, 30 nm Si O2 is added to increase the roughness. Finally, the optimal solution is found by keeping a balance between hydrophobicity and transmittance. The contact angle and the light transmittance of the super-hydrophobic materials are measured. The results show that the contact angle is up to 158° and the light transmittance reaches 91%, which indicat that the super-hydrophobic materials have high transmittance.