Study On The Preparation And Properties Of Superhydrophilic Sols And Coatings Based On Silica

Base on the superhydrophilic principle of material,two kinds of silica sols and superhydrophilic coatings,together with their modified hybrid sols and superhydrophilic hybrid coatings,were prepared vis sol-gel method,and the properties of sols and coatings were studied.The main work is as follows:1.Using tetramethyl orthosilicate(TMOS)or tetraethyl orthosilicate(TEOS)as precursor,ammonia(NH3·H2O)as the catalyst,silica sols with different sizes were prepared through hydrolysis and condensation by sol-gel method,which can keep stable for about 30 days at room temperature.The superhydrophilic coatings based on the above sols were prepared on glass substrates using spin coating technique,and their water contact angles(WCAs)reached at as low as 5° and maintained for 30 days at room temperature.The coatings with cracks had high transparency,their hardness was not less than B degree,and the adhesion to the surface of glass was not higher than the 2nd level.2.The modified hybrid sols and mixed hybrid sol with different sizes were obtained from the silica sols prepared above using silane coupling agent(KH-570)and surfactant(SDS)as modifiers,and they were stable within 30 days at room temperature.The superhydrophilic hybrid coatings were prepared from the hybrid sols and mixed hybrid sol on glass substrates using spin coating technique,and their water contact angles(WCAs)declined to 00 within 5 s and the superhydrophility could maintain for 60 days at room temperature.The hybrid coatings and mixed hybrid coating with no crack were transparent.Their hardness was not higher than 2B degree,and adhesion to the surface of glass was not lower than the 2nd level.After modification,the hardness of the hybrid coatings decreased and the hardness of the mixed hyrid coating reached 3B degree.3.The modified hybrid sols and mixed hybrid sol with different sizes were obtained using functional polysiloxane(Di-10)as modifiers based on the silica sols prepared above,and they could maintain stability about 60 days at room temperature.The superhydrophilic hybrid coatings were prepared from the hybrid sols and mixed hybrid sol on glass substrates using spin coating technique,and their water contact angles(WCAs)could be as low as 50 and the superhydrophility could maintain for 30 days at room temperature.The hybrid coatings with no crack had high transparency.Their hardness was not higher than 2B degree,and adhesion to the surface of glass was not lower than the 2nd level.After modification,the hardness of hybrid coatings decreased,and the hardness of mixed hybrid coating reached 3B degree.In the thesis,the particle size,stability,transparency of the sols,and the chemical composition,surface morphology,hydrophilicity and stability of the coatings were investigated by the particle size,WCA,UV-Vis,FT-IR,SEM and coating hardness and adhesion test,respectively.Meanwhile,hybrid sols were compared with original sols in terms of particle size and distribution,transparency and stability,while the hybrid coatings were compared with the silica coatings in terms of stability,hydrophilicity and membrane properties.It can be concluded that the hybrid sols modified with functional polysiloxane and their superhydrophilic hybrid coatings had obvious advantages in the aspects mentioned above,possessing promising potential in the applications of optical,biological and daily life.