Research On The Preparation And Durability Of Superhydrophilic Anti-fog Coating

Transparent materials have been widely used in industrial and civil fields due to their excellent optical properties.However,the fogging phenomenon will significantly affect their use effect.The superhydrophilic anti-fog coating is considered to be the most potential method due to their convenience,versatility,economy and environmental friendliness.In recent years,great progress has been made in the research of superhydrophilic anti-fog coatings,but there are still challenges that need focus on,such us poor abration resistance,which are insufficient to cope with the actual environment.In response to the problem of insufficient durability,the long-lasting durability mechanisms of the superhydrophilic anti-fog coating were revealed by studying the anti-fog properties,abration resistance and boiling resistance of the coating in this paper.Finally,a longlasting superhydrophilic anti-fog coating with simple preparation process,low cost,non-toxic and excellent performance was successfully prepared.First,an inorganic superhydrophilic anti-fog coating with dense structure was prepared by Solgel method using Si O2 nanoparticles,Sodium alkenyl sulfonate(AOS)and tetraethoxysilane(TEOS).By adjusting the proportion of components,it was found that when AOS was added at 1.6 wt.%,Si O2 nanoparticles at 0.5 wt.%,and cross-linking agent TEOS at 1.8 wt.%,the coating had the best abration resistance and boiling resistance.The analysis results show that the multi-component synergy of the components at this ratio endows the coating with high hydrophilicity,high hardness and dense surface microstructure,thereby significantly improving the abration resistance of the coating.At the same time,the coating of this composition is rich in hydrophilic groups,which enhances the boiling resistance of the coating.On the basis of this component ratio,the anti-fog coating with micron thickness was efficiently prepared by spraying method,and the effect of thickness on the durability and optical properties of the coating was compared and studied.The final prepared coating has thickness of 3.4 ?m and transmittance of 90.5%,which can withstand abration for 220 cycles with Taber abraser at 250 g and boiling for 20 minutes.However,the adhesion between the coating and the substrate is poor,only 2.59 MPa,so it is difficult to withstand longer abration and boiling.In order to further improve the adhesion between the above coating and the substrate,organicinorganic hybrid superhydrophilic antifogging coatings were successfully prepared by blending hydrophilic transparent resin in the system.The results showed that the adhesion between the coating and the substrate was the highest(4.21 MPa)by blending aqueous polyacrylic acid(PAA)resin,which effectively alleviating the particle detachment after long-term abration and boiling.At the same time,the introduction of resin will aggravate the agglomeration of particles and reduce the transmittance of the coating.In order to balance the durability and optical properties,3 wt.% PAA resin is preferred to be blended,and the transmittance of the coating is 90%.At the same time,it can withstand abration for 220 cycles with Taber abraser at 250 g and boiling for 40 minutes.After further analysis of the failure mechanism of the coating,it is found that the structural stability of the coating plays an important role in the abration resistance and boiling resistance of the coating.Therefore,the content of TEOS was increased to 2 wt.%,and the densified network structure was formed to further improve the durability of the coating.The finally prepared organic-inorganic hybrid coating can withstand abration for 300 cycles with Taber abraser at 250 g and boiling for 60 minutes.Based on the above organic-inorganic hybrid coating,in order to further enhance its boiling resistance,a superhydrophilic antifogging base on porous layer protection was designed and prepared.A porous layer constructed by inorganic nanoparticles was added on the surface of the organicinorganic hybrid coating.The nano-scale pores in the porous layer can increase the movement resistance of the surfactant AOS migrating from the anti-fog layer to the aqueous solution,which significantly slowing the loss speed of AOS.The EDS data show that the porous layer composite superhydrophilic anti-fog coating retains more hydrophilic substances after boiling,and the boiling resistance of the coating is enhanced.UV spectrophotometer test results show that the coating with porous layer still has transmittance of 90 %.Finally,by dip-coating L-type silica sol twice and curing at 220°C for 1 hour,the boiling resistance of the coating was improved to 80 minutes.