Preparation And Performance Study Of Durable Superhydrophobic Coatings Assisted By Epoxy Resin

In recent years,the’lotus effect’has been widely concerned by researchers and superhydrophobic surfaces with’lotus leaf effect’are very common in nature.Superhydrophobic surface is typically a solid surface with contact angle（CA）greater than150°and roll angle（SA）smaller than 10°when in contact with water.Due to its unique properties,the superhydrophobic surface exhibits self-cleaning,anti-fouling,anti-corrosion and anti-icing capabilities.As a result,it has been found that the superhydrophobic surface is highly versatile in various fields such as self-cleaning glass coating technology,marine anti-corrosion engineering,anti-icing and de-icing technology as well as liquid transportation.As research has progressed,it has been discovered that the two essential conditionsfor achieving and maintaining superhydrophobic properties are significant micro and nano-secondary rough structure on the surface and low surface energy characteristics.Various methods such as spraying,templating,etching and sol-gel techniques have been developed for preparing superhydrophobic materials.However,the current artificial preparation of superhydrophobic coatings is laborious and the raw materials required expensive or fluorine-contained.Moreover,the surface is easily distroyed by external environment factors during use,resulting in destruction of the micro-nano secondary structure or alteration of low surface energy substance,and lead to the loss of superhydrophobicity ultimately.Consequently,these seriously restrict the application of superhydrophobic coatings in practical production and daily life.Spraying is a commonly employed technique for the preparation of superhydrophobic coatings,which has a series of advantages such as ease of operation,broad applicability and substrate independence.In this study,hydrophobic silica（SiO₂）nanoparticle gel spray was incorporated into the epoxy resin binder,followed by preparation of superhydrophobic composite coatings via two-step and one-step methods.The coating surface properties were thoroughly tested and characterized to reveal the interplay between microstructure,chemical composition,mechanical stability and chemical durability,etc.The primary research aspects of this thesis are as follows:（1）Preparation and performance of EP@SiO₂/HDTMS durable superhydrophobic coating by two-step method:In the two-step process,E-51 epoxy resin and tetraethylene pentamine（TEPA）were mixed in proportion,scraped and coated onto the substrate surface as an intermediate bonding layer.Once it reached a semi-cured state,a spray containing hydrophobically modified SiO₂ nanoparticles by cetyltrimethoxysilane（HDTMS）was evenly sprayed onto the binder layer to create a superhydrophobic composite coating with exceptional durability.The wetting properties of coatings on various substrate were evaluated,with an average contact angle of 153.7°and a rolling angle of approximately 4.0°.Scanning electron microscopy（SEM）and attenuated total reflection Fourier transform infrared spectroscopy（ATR-FTIR）analyses revealed that the superhydrophobic composite coating prepared via a two-step method possessed a micro/nano secondary rough structure as well as successfully grafted low surface energy substances,which synergistically contributed to its superhydrophobicity.In addition,a series of performance tests were conducted on the coated surface,and the results demonstrated that the superhydrophobic composite coated steel sheet prepared by means of a two-step method exhibited excellent mechanical durability and chemical stability.Even after undergoing 2.1 meters of friction with 600 mesh sandpaper,its hydrophobicity remained intact.After being immersed in acid and alkaline solutions with varying p H values for 72 h,the coating remained hydrophobic as well.Upon testing its anti-icing performance at sub-zero temperatures,the freezing time of the surface was prolonged and the optimal result was observed at-4℃.（2）Preparation and performance of EP/SiO₂/HDTMS durable superhydrophobic coating by one-step spraying method:EP/SiO₂/HDTMS superhydrophobic composite coating was prepared via a simple one-step spraying method.Firstly,E-51 epoxy resin and tetraethylenepentamine（TEPA）were mixed to form a gel,and then dropped into the nano-SiO₂ sol with an ethanol solution of cetyltrimethoxysilane（HDTMS）simultaneously to produce a superhydrophobic spray containing epoxy binder.Furthermore,E-51 epoxy resin content and spraying time were optimized through controlling variable method,and the optimum preparation process was obtained.The optimal preparation process and wetting property test were employed to achieve a superhydrophobic composite coating with a contact angle of 154.7°and a rolling angle of 4.0°.Upon SEM and total reflectance infrared spectroscopy analysis,it was found that the superhydrophobic properties of the coating surface were constributed to the micro-nano secondary rough structure formed on it and the modification by alkyl long chains.Otherwise,the cluster structure formed by the aggregation of nano-SiO₂ particles is uniformly embedded in the epoxy binder,thereby enhancing its stability and durability.Even after being rubbed on 600 grit sandpaper for 3.6 m,the contact angle still remained greater than 150°.Furthermore,after soaking in acid-base solutions with varying p H values for different durations,there was little significant change observed in both contact and rolling angles.Subsequently,the oil-water separation experiment was conducted and,the efficiency of oil-water separation still maintained at 98.3%even after separation for10 times.