Study On Preparation Of Superhydrophobic Silica And Application In Coating

Superhydrophobic coating is widely used in anti-atomization, anti-corrosion,self-cleaning and other fields because of its special wettability.However,the inherent disadvantages of the superhydrophobic coating,such as fragile mechanical properties,expensive production equipment and environmentally unfriendly and expensive raw materials,severely limit the wide application of superhydrophobic surfaces in practical life.In this study,firstly,the blend coating method was used to prepare the superhydrophobic coating.The coating preparation method was simple and the raw material used was environmentally friendly and cheap.Then,the feasibility of improving the durability of hydrophobic coating by introducing different kinds of resins was explored.Finally,the superhydrophobic nano-silica modified by disilane coupling agent was designed and prepared by ourselves and applied in the epoxy resin coating,which further improved the practical application performance of the coating.1.The commercial gas-phase nano-SiO₂ particles（S-SiO₂）were doped with low surface energy polydimethylsiloxane（PDMS）in a certain proportion to construct S-SiO₂/PDMS composite superhydrophobic coating with micro-nano structure.Based on the contact angle and sliding angle of the coating surface and the wear resistance of the coating,the influence law of single factors such as the amount of S-SiO₂,coating thickness and curing time on the coating performance was explored.The optimal preparation process conditions were obtained,and the maximum contact angle of the surface water of the coating was 172°.In addition,it is found that with the increase of S-SiO₂ content,the contact angle increases first and then remains stable,while the sliding angle decreases first and then remains stable.Under the condition of 500 g load,the coating can still show superhydrophobicity after short distance wear of 600 mesh sandpaper,but the surface wear is serious.2.In order to improve the binding strength and wear resistance of the S-SiO₂/PDMS composite superhydrophobic coating,different kinds of resins（epoxy resin EP,thermoplastic acrylic resin PAA,polyurethane PU）were introduced to compose the S-SiO₂/PDMS/resin composite superhydrophobic coating.It is found that when the resin is added too much,the water contact angle of the coating decreases to a certain extent,the sliding angle even does not exist,and the coating appears adhesion to water droplets.After wear test,the coating can still maintain a high contact angle and a small sliding angle,the surface damage is small,the coating is relatively intact.The coating has been tested by grid adhesion method,and the epoxy resin and polyurethane modified coating has strong adhesion,and the ISO grade has reached the qualification standard of grade 0.The acid and alkali resistance test results show that the coating modified by epoxy resin and polyurethane can resist p H=2～14 strong acid and alkali solution environment.In addition,the epoxy resin coating showed better corrosion resistance in salt solution environment.3.The superhydrophobic nano silica powder（G-SiO₂）was successfully prepared in toluene system by the method of disilane coupling agent modification,and was added as filler to epoxy coatings to obtain epoxy coatings with different proportions.G-SiO₂ crystal is more stable,better thermal stability,better dispersion,less easy to agglomerate,can improve the coating surface hydrophobicity,can effectively make up for the coating surface holes,so that the coating surface smooth and compact.Through a series of mechanical properties tests（including adhesion,impact strength and tensile strength）,it is found that the addition of G-SiO₂ does not reduce the adhesion of the coating,and its tensile strength and elongation at break are superior to S-SiO₂,and even has a gain effect on elongation.Tafel polarization curve test shows that the corrosion current of G-SiO₂/EP coating is lower than that of S-SiO₂/EP coating.Electrochemical impedance spectroscopy test shows that the anticorrosion performance of G-SiO₂/EP coating gradually increases with the increase of G-SiO₂ addition amount,reaching the maximum value when the addition amount is 1.00%,and the resistance of the coating is 6.7 times of that of pure EP coating and 1.9 times of that of S-SiO₂/EP coating.