Studies On Fabrication And Properties Of Low-Adhesion Superhydrophobic Surface Coatings

Wettability of a solid surface is an important property as well as one ofthe most common interfacial phenomena in nature. Because of the specialsurface wetting properties and the potential market value,superhydrophobicity is expected to be applied in various fields such as waterrepellency, anti-fouling, anti-frost, anti-icing, acid and alkali resistance,liquid transmission and optical reflection. Therefore, both academic andpractical research attention has been focused on superhydrophobic surfaces.It has been revealed that the surface wettability depends on the chemicalcomposition and the morphology of the surface. Accordingly, artificialsuperhydrophobic surfaces have been fabricated by the means of constructinghierarchical roughness on materials with low free energy or modifying roughsurfaces using materials with low free energy. However, the practicalapplication of these approaches is greatly restricted due to their difficulty of large-scale production, complicated process, high production cost and shortservice life.This dissertation concentrates on developing a low-adhesionsuperhydrophobic coating which is easy to be realized and applied in largescale industrial production. The superhydrophobic coating is prepared bythe means of applying modified water-based overprint varnish onto the papersurface. And the properties of the superhydrophobic coatings have beenstudied, such as water repellency, anti-fouling, anti-frost, anti-icing, acid andalkali resistance, and scratch resistance.1. Commercially available water-based varnish is hydrophobically modifiedwith modifying agent which consists of silica nanoparticles,decamethylcyclopentasioxane, polydimethylsiloxane and nonionicsurfactant p-Octyl polyethylene glycol phenyl ether. The modifiedvarnish is coated on paper surface with a simple coat-dry method in orderto fabricate the low-adhesion superhydrophobic coatings. The stablesuperhydrophobic coatings are obtained when the modifying agent in thevarnish is above30wt%, the water contact angle on the surface reachingover150°. The superhydrophobic coatings show satisfactory waterrepellency, anti-fouling, anti-frost and scratch resistance properties.2. The influence of different particle size and specific surface area of silica nanoparticles on the surface wettability is investigated. The hydropho-bicity of the modified varnish coatings are enhanced with the decrease ofthe particle size and the increase of the specific surface area.3. The hydrophobically modifed water-based overprint varnish displays asubstantial shear thinning effect, which makes it suitable for a variety ofprinting applications.4. With a simple coat-dry method, the hierarchical micro-/nano-structuredsuface is obtained, the contact angle above159°, by introducing SiO2microparticles and nanoparticles simultaneously into the modifying agent.The waterproof porperty of the varnish coating is enhanced with theincrease of the mixed particles (SiO2microparticles and nanoparticles).And the acid and alkali resistant property has been improved as well.5. Polytetrafluoroethene (PTFE) Teflon microparticles are used with SiO2nanoparticles in the modifying agent to prepare the modified varnish.The hierarchical micro-/nano-structured suface is obtained as well, and thesuperhydrophobic property is maintained, contact angle reaching151°.At the same time, the stability and mechanical strength is enhanced.