Preparation And Studies Of Durable Biomimetic Underwater Superoleophobic Functional Coatings

Due to the excellent hydrophilic and oleophobic properties,underwater superoleophobic coatings have wide applications in the fields of crude oil transportation,anti-oil adhesion,anti-bioadhesion,self-cleaning,oil-water separation,and droplet manipulation.At present,most underwater superoleophobic coatings suffer from complex preparation processes,poor mechanical stability,and insufficient chemical durability.In this study,E44 epoxy resin adhesive with strong chemical durability was used as the glue to compound hydrophilic nanoparticles/polymers.The durable underwater superoleophobic coating and underwater lubricating superoleophobic coating were prepared by a simple method of spraying,respectively,which are as follows:（1）The durable underwater superoleophobic coatings were prepared by pressing various nano-particles into the pre-cured E44 epoxy resin coating.The prepared coatings exhibited excellent underwater superoleophobic properties,mechanical stability,chemical durability and corrosion resistance.The coating still had stable underwater superoleophobic properties after being rubbed by sandpaper loaded with 10 N for 1000 times and soaked in strong acid and alkali with p H=2 and p H=12 for one month.The coating exhibited excellent anti-corrosion properties in the electrochemical tests.Besides,the prepared E44-Ti O₂ coating exhibited excellent self-cleaning properties of degrading organic pollutants and transforming wettability of water droplets under oil.When the E44-Ti O₂ coating was applied on the stainless steel mesh,the oil-water emulsion could be separated with an oil-water separation efficiency of 99.8%and high flux（>1700 L/m²h）,which showing excellent oil-water separation performance.（2）The durable underwater lubricating superoleophobic coatings were prepared by spraying the composition of polyethyleneimine（PEI）and Ti O₂ on the surface of pre-cured E44epoxy resin.The prepared underwater superoleophobic coating had excellent mechanical stability,lubricating drag reduction,chemical durability,anti-crude oil and anti-corrosion.The E44/PEI/Ti O₂ coating maintained stable underwater superoleophobic properties after being rubbed by 2 N loaded sandpaper for 225 times and after being immersed in 1 M/2 M strong acid and strong alkali solution,artificial seawater and distilled water for 10 h.Importantly,when the E44/PEI/Ti O₂ coating was under water,PEI would absorb water and swelled to wreathe the nanoparticles.At this time,a large number of hydration layers around PEI molecules would reduce the friction coefficient of the coating under water,which made the coating had lubricating and drag-reducing effect under water.The E44/PEI/Ti O₂ coating also had excellent anti-crude oil performance.When the coating was contaminated by crude oil,the crude oil could be well peeled off from the coating surface when it was put into water.Compared with commercially available hydrophilic coatings,E44/PEI/Ti O₂ coatings have better anti-corrosion properties.In addition,when E44/PEI/Ti O₂ coating was applied to stainless steel mesh,it could separate different kinds of oil-in-water emulsions（petroleum ether-water,n-hexane-water,cyclohexane-water,kerosene-Water）with a separation efficiency of 99.7%,the separation flux could reach up to about 1500 L/m²h,showing excellent oil-water separation performance.