Study On The Preparation And Properties Of Super-hydrophobic Silica Surface

Superhydrophobic surface has attracted more and more attention due to the application of clean technology such as maintaining high architectural glass and automotive glass cleaning and consumer applications such as waterproof textile, protective coating for communication antenna. Superhydrophobic surface with self-cleaning function can reduce the energy and clean water, decrease environmental pollution caused by chemical cleaning agent. This paper studied the preparation and properties of super hydrophobic surface, provided a simple and low cost preparation method of self cleaning surfaces.With trimethylchlorosilane(TMCS) and hexamethyldisilazane(HMDS) as hydrophobic agent for preparing hydrophobic modification. Because of the steric effect of TMCS is smaller than HMDS, and reaction mechanism of TMCS is relatively simpler, so the contact angle of film prepared by TMCS is larger than HMDS. Through studying the reaction conditions of modified silica sol, we found that when the reactive temperature was 50?and the reactive time was 5hours, the contact angle of prepared silica film modified by TMCS can reach 131.8°. If we continue to increase the reaction time and temperature, due to the self polymerization of silanol, the number of hydroxyl will reduce, thereby reducing the number of hydrophobic groups which introduced to sol, so that the contact angle of the films will decrease. The transmittance of SiO2 films modified by TMCS and HMDS are all above 80%. But when the reaction time is too long or modification temperature is too high, uniform film will not be obtained. Whereas when we modified directly the surface of silica films with TMCS, the contact angle of modified films can further increase to more than 150°. Studying the corrosion of hydrophobic surface cause ammonia solution and acid solution, we found that acid solution caused greater damage than ammonia to the the hydrophobicity of films.Using ammonia as catalyst, because of the spontaneous aggregation of nanoparticles into large particles, the obtained SiO2 powders can be charactrized by a spherical shape and a nano/micron binary structure with a micron-scale diameter and a nano-scale surface roughess. So the contact angle of obtained powders without modifying by TMCS can reach 121°, and after modifying by TMCS, the superhydrophobic powders can further increase to 165°. Using mechanical force of ultrasonic dispersed the superhydrophobic powders, powders can be dispersed into submicron-particles but can not be dispersed into into nano-particles. And study on powder morphology and the contact angle have found that the contact angle of powder was not dependent on the silica particle size. Research of super hydrophobic powder by infrared spectroscopy has found that the hydrophobic group of powders have replaced by methyl. These indicated that hydrophobicity depended on both low surface energy and roughness.