Study On The Preparation Of Transparent Superhydrophilic Coating By Composite Multi-structure Nanoparticles

Because of its special wettability,the superhydrophilic surface has attracted wide attention in the fields of oil-water separation,medicine,architecture and so on.With the large-scale application of glass and transparent polymer materials,the problems of easy fogging and dirty resistance exposed have seriously affected the use of these transparent materials.The transparent superhydrophilic coating can maintain the transparency of the substrate material while achieving hydrophilic anti-fog and self-cleaning,which can well solve the problems exposed by the transparent material and has great application prospects.At present,there are two main ways to prepare transparent superhydrophilic coatings:one is the transparent photo-induced superhydrophilic coating based on TiO₂,but the hydrophilicity of this kind of coating will gradually decrease after leaving the light,resulting in its application field being limited.Second,inorganic nanoparticles based on SiO₂construct micro-nano structures on high surface energy materials to achieve superhydrophilicity.Such coatings are the focus of current research,but they often need to be prepared by layer-by-layer self-assembly,vapor chemical deposition,and high-temperature calcination.Such methods require high equipment and complex processes,and are not suitable for preparing transparent super-hydrophilic coatings for large-scale applications.Therefore,in this thesis,superhydrophilic coatings with high transparency and good mechanical properties suitable for large-scale applications were prepared by simple spraying or pulling process by studying composite nanoparticles with different structures.The specific work of the thesis is as follows:1.Transparent superhydrophilic coating was prepared by single structure nano-SiO₂.Firstly,the film-forming effect of the hydrolysate generated by tetraethyl orthosilicate（TEOS）in different PH environments was investigated,and the content of each component（TEOS,anhydrous ethanol,deionized water,acid）in TEOS hydrolysis was optimized.The results showed that the hydrolysate generated under acidic conditions had good bonding effect and uniform film formation.When PH=2.5,the mass ratio of TEOS,anhydrous ethanol and deionized water was 7:20:2,it was the best hydrolysis ratio.Then,using the hydrolysate as binder,different transparent superhydrophilic coatings were prepared by adding 30nm spherical and 39nm,89nm dendritic nano-SiO₂,respectively.The effects of different single structure nano-SiO₂on the surface morphology,transmittance and wettability of the coatings were investigated.The results showed that the hydrophilicity of the dendritic nano-SiO₂coating was better than that of the spherical nano-SiO₂,but the transmittance decreased.2.Transparent superhydrophilic coating was prepared by composite dual-structure nano-SiO₂.The transparent superhydrophilic coating with composite structure was prepared on the surface of glass by dip-coating method using the above TEOS hydrolysate as binder,10 nm spherical SiO₂and 89 nm dendritic SiO₂as nanofillers.The effects of nano-fillers with different mass ratios on the morphology,wettability and light transmittance of the prepared SiO₂coating were investigated.It was found that the comprehensive performance of the coating was the best when the spherical nano-SiO₂and dendritic nano-SiO₂were mixed at a mass ratio of 2g:6g,which avoided the problems of weak hydrophilicity of a single spherical SiO₂coating and poor transmittance of a single dendritic SiO₂.The contact angle of the coating can reach 2.2°,and the transmittance is about 92%in the wavelength range of 400-750 nm.It has certain anti-fogging properties in hot and cold water vapor environments,and has good adhesion and hardness.3.A self-cleaning transparent superhydrophilic coating suitable for glass curtain wall was prepared by composite modification of CNTs/dendritic nano-SiO₂.A black transparent superhydrophilic coating was prepared on the surface of glass by spraying method using TEOS hydrolysate as binder,natural polyphenol tannic acid（TA）modified carbon nanotubes（CNTs）and dendritic nano-SiO₂as nano-fillers.The effects of TA-CNTs and TEOS hydrolysate content on the wettability and transmittance of the coating were investigated.The results show that when the TEOS hydrolysate is 6g,the TA-CNTs is 0.16g,the dendritic nano-SiO₂is 2g,the coating has super-hydrophilic effect（CA,2.5°）,the transmittance decreases to 60%,and has good privacy.It is found that the coating has excellent self-cleaning effect at this time,and can withstand about 120 friction experiments still maintain superhydrophilicity,and has good adhesion and hardness.This method is suitable for large-scale production of self-cleaning curtain wall glass with privacy.