Preparation And Properties Of Durable Superhydrophobic Nanocomposite Coating

Superhydrophobic material is a kind of special material with a surface contact angle greater than 150°and a sliding angle less than 10°.Because of its many unique properties,such as self-cleaning,anti-fog,anti-icing,anti-corrosion,oil-water separation,etc.,it has attracted widespread attention from scientific researchers.The research on superhydrophobic materials in nature manifests that the hydrophobicity of superhydrophobic materials is determined by their special rough structure and low surface energy substances.In this way,researchers have developed a variety of methods for artificially preparing superhydrophobic coatings,such as the template method,sol-gel method,deposition method,and etching method,and so on.However,most of methods are not suitable for large-scale production.Meanwhile,they present problems as poor mechanical stability and durability.This study aims to design and develop durable superhydrophobic coatings with simple preparation process,low cost,large-scale industrial production.The preliminary design,process preparation,sample characterization and application of superhydrophobic coatings are carried out.Meanwhile,the durability of superhydrophobic coatings when subjected to mechanical abrasion,extrusion,erosion by acid/alkali solutions and chemical solvents,and irradiation under UV light are investigated.The main research contents and results of the study are as follows:?1?Studies on the superhydrophobic nano-composite coating preparation based on the polydopamine?PDA?and SiO₂ nano-particles via two-step spraying method.Polydopamine was prepared by self-polymerization of dopamine?DA?firstly.And then was sprayed onto the surface of the substrate as an adhesion layer.Second,a superhydrophobic protective agent superhydrophobic was spray-coated onto the surface of the polydopamine adhesion layer while the superhydrophobic protective agent was prepared by protective agent of LB-S1modifying the nano-silica.Consequently,a superhydrophobic coating with a contact angle of153.6°and a rolling angle of less than 5°was obtained.Scanning electron microscopy?SEM?and total reflection infrared spectroscopy?ATR-FTIR?analysis showed that the surface of the prepared superhydrophobic coating had a micro-nanometer two-level multilayer rough structure composed of silicon dioxide?SiO2?particles while the surface is modified by the long hydrophobic alkyl chains.These combined effects endowed the coating with superhydrophobic performance,and which further made the coating present good self-cleaning performance.?2?The superhydrophobic PDA-SiO2 nano-composite coating was prepared by simple one-step spraying method.The effects of reaction temperature and the molar ratio of SiO₂ to DA on the wettability of the coating were investigated.The optimal preparation conditions were obtained.Under the optimal conditions,the superhydrophobic coating with contact angle of 155.0°and rolling angle of less than 5°was prepared.Results from SEM and ATR-FTIR analysis revealed that a stacked and protruding micro-/nano-composite rough structure,which were composited of PDA particles and SiO₂ particle,formed on the surface of the substrate.Meanwhile,the superhydrophobic coating was obtained after modified with the material with low surface energy.?3?The durability of superhydrophobic coatings prepared by two methods on various substrate surfaces was investigated under mechanical forces.The results showed that the superhydrophobic state of the coatings appeared on various substrate surfaces.When the coatings were damaged by dry friction,finger pressing,and tape adhesion,the mechanical stability of the coating surface was enhanced by the strong adhesion of PDA.As a result,the coating obtained good superhydrophobic performance under the action of mechanical force.It showed that the superhydrophobic coating had universality and good durability.?4?The stability and durability of the superhydrophobic coating under extreme conditions such as solution with various pH values,chemical solvents,ultraviolet irradiation,and outdoor environment were investigated.The results showed that the water droplets on the surface of the superhydrophobic coating were still round and spherical after immersed in extreme environment for a period or placed outdoor for 12 months.These results indicated that the superhydrophobic coating prepared by the two methods had excellent acid and alkali resistance,chemical solvent resistance,UV aging resistance,and weather resistance.?5?Two methods were used to prepare the superhydrophobic coating on the surface of polyurethane sponge.The application of the superhydrophobic sponge in the field of oil-water separation was investigated.The results showed that the adsorbed oil could reached 60 times of its own weight at most when the superhydrophobic sponge was used to adsorb different organic solvents.Moreover,the surface still presented superhydrophobic performance after 9cycles of oil absorption/drying.Therefore,the superhydrophobic coating prepared in this study also has good oil adsorption.The research above showed that the method for the preparation of the superhydrophobic coating in this research is simple,suitable for large-scale industrial production,and can be applied to a variety of substrate surfaces.Meanwhile,the resultant superhydrophobic coating has good durability in extreme environment,and has potential application prospects in the field of oil-water separation.