Research And Application Of Self-Cleaning Coating Preparation Process

The self-cleaning coatings are widely used in the protection of buildings,ships,ports and other facilities due to their unique advantages in cleaning,waterproofing,anti-fouling,anti-fog and other aspects.Generally speaking,the self-cleaning coating can be divided into two types:one is a super-hydrophobic self-cleaning coating;the other is a superhydrophilic self-cleaning coating.Both are functional coatings,but there are differences in the expression effect.The superhydrophobic coating has a surface contact angle of more than 150°,and self-cleaning is achieved by the water droplet rolling on the surface;the superhydrophilic coating has a surface contact angle of less than 10°,and self-cleaning is achieved by the formation of a liquid film on the surface of the superhydrophilic coating that penetrates under the dirt.This article starts from the preparation process and uses different methods to prepare the superhydrophobic/superhydrophilic self-cleaning coating.The research content is as follows:?1?Using silicon dioxide substrate and polydimethylsiloxane?PDMS?as experimental materials,the superhydrophobic coating was prepared by a casting/peeling process.By detecting the wettability of the surface before and after pouring/peeling of different materials,it was found for the first time that no chemical treatment or additional chemical reagents are needed,PDMS has adhesiveness to the silicon dioxide substrate only through the casting/peeling process at room temperature.AFM,EDS,ellipsometry and other instrumental tests were used to confirm the existence of PDMS adhesion layer,and the cause of its adhesion was analyzed and interpreted from a microscopic perspective.According to this result,the silicon dioxide substrate having a microstructure was combined with the low energy material PDMS adhesion layer.The results show that the PDMS adhesion layer can improve the surface contact angle of the silicon dioxide substrate with microstructure,and thus form the superhydrophobic surface.?2?The self-cleaning coating for building wall protection was proposed,which was mainly the compound of the PDMS and hydrophobic SiO₂.The prepared coating was sprayed on the building wall and cured at room temperature to form the self-cleaning coating.Through the analysis of the combination mechanism of the coating and building wall,it showed that the coating has a strong adhesion to the wall.Due to the super-hydrophobic property of the coating,the particulate pollutants and the liquid contaminants attached to the wall were easily cleaned through water flow.Furthermore,the experiments also showed that the self-cleaning effect of the coating did not change significantly even after five months in the outdoor environment.?3?In the traditional sense,electrical wettability changes caused by the accumulation of electric and liquid-gas interfaces driven by electric field.This is the first time that the electric charge is injected and accumulated on the surface of the solid driven by an electric field,which leads to the wettability change.Waterborne varnish and hydrophobic SiO₂ were used as experimental materials,and the superhydrophobic coating was prepared by spraying.The superhydrophobic coating was converted into the superhydrophilic coating by applying an electric field and temperature,and the wettability was restored to superhydrophobicity by heating,and a superhydrophobic-superhydrophilic reversible conversion was completed.The testing of coatings by SEM,KFM,EDS,etc.,verifies that the change of the wettability of the coating is caused by the injection and accumulation of charges on the coating surface,forming the surface potential and thus affecting the wettability of the coating surface.At the same time,the influence of the energization voltage,the energization time and the heating temperature on the wettability of the coating surface was also investigated.The results show that the change of wettability of the coating surface is influenced by three factors:voltage,temperature,and time.