Preparation And Performances Of Durable Superhydrophobic Polyvinylidene Fluoride(PVDF) Composite Coatings

Recently,lotus effect-inspired superhydrophobic surfaces with special wettability have aroused considerable interest of the scientific researchers.The superhydrophobic coatings are endowed with the excellent hydrophobic,self-cleaning,anti-corrosive and anti-icing performances by the special wettability,which demonstrate great application values in production and life.However,the artificial superhydrophobic coatings still suffer the weak mechanical strength,the low chemical stability of the low surface energy materials and the poor hydrophobic durability,which hinder the practical application of superhydrophobic coatings seriously.In this paper,aiming at the above problems,we took the interface strength and microstructure design as the breakthrough points to enhance the interface interaction between coating and substrate,among the resin materials or the nano fillers.The durable superhydrophobic coatings with reticular nano/micro structures,double-layer gas film structures,self-healing ability or gas compensation function were successfully prepared.The main properties of the prepared coatings were tested and analyzed.Finally,the effects of surface roughness and chemical composition on the hydrophobic durability of coatings were further studied.The main contents and results of this paper are listed as follows:(1)The nano/micro hierarchical structures with vast hydroxyl groups on aluminium surface were constructed by chemical etching in hydrochloric acid(HCl)solution and boiling water.It can increase the contact area between coating and substrate,and form hydrogen bonding to enhance the adhesion of coating.The robust wear/corrosion-resistant superhydrophobic polyvinylidene fluoride(PVDF)/fluorinated ethylene propylene(FEP)/carbon nanofibers(CNFs)composite coating with interpenetrating network nano/micro structures has been fabricated by a simple spray method.Effects of FEP and CNFs content on the surface wettability were investigated.In addition,the wear/corrosion-resistance and adhesion of the prepared coating were also studied.FT-IR results indicated that the dehydrofluorination of PVDF occurred during the high temperature treatment,which was beneficial to promote the cross-linking reaction and enhance the adhesion between coating and substrate.The wear-resistance of the prepared superhydrophobic coating was approximately 5 times higher than that of the pure PVDF coating and the commercial fluorocarbon coating.Moreover,the acid/base immersion and Tafel curve test results showed that the prepared superhydrophobic coating also possessed highly corrosion resistance.(2)The superhydrophobic and high oleophobic epoxy resin(EP)/MPVDF composite coating with reticular mastoid nano/micro structures was prepared by a spraying method,using EP and MPVDF as the mian coating materials,nano-SiO2 and carbon nanotubes(CNTs)for constructing surface roughness,FEP as the low surface energy material.The prepared EP/MPVDF composite coating demonstrated high contact angles(166°,155°)to water and glycerol,respectively.Researches revealed that the reticular mastoid nano/micro structures can improve the surface oleophobicity and overcome the weak superhydrophobic stability in oil-water mixture.In addition,because the MPVDF surface possesses a large number of hydroxyl groups,there will exist chemical bonding between EP and MPVDF under high temperature,which can improve the interface strength and enhance the mechanical properties and chemical stability of the coating.Bending test results demonsrated that the brittleness of EP was avoided by introducing the malleable MPVDF and CNTs.Moreover,The EP/MPVDF composite coating showed excellent wear resistance and the wear life was 18 times higher than the pure EP coating.Simultaneously,the EP/MPVDF composite coating also possessed excellent hydro-oleophobic stability and corrosion resistance.(3)The 3D porous RGO-SiO2 particles were fabricated by the combination of the dopamine modification and TEOS sol-gel process to enhance the interface adhesion strength between RGO and SiO2.The healing agent of 1H,1H,2H,2H-perfluorooctyltriethoxysilane(POTS)with low surface energy was stored in the porous RGO-SiO2 particles by chemical grafting and physical absorption.After mixing the modified RGO-SiO2 particles into PVDF solution,we successfully fabricated a self-healing superhydrophobic PVDF/RGO-SiO2 coating by a simple spray method.Effect of sol-gel time on the microstructure of the RGO-SiO2 particles was investigated.In addition,the self-healing,wear-resistant and drag reduction properties of the prepared superhydrophobic coating were also studied.The test results demonstrated that the PVDF/RGO-SiO2 coating can retain its superhydrophobicity after 9 cycles of the rubbing/healing treatment due to the migration of the prestored POTS to the rubbed coating surface.Moreover,the wear life of the prepared coating was 10 times longer than the pure PVDF coating and the sliding energy consumption of water drop on the prepared coating was only 25.3%,which was far below that of pure PVDF coating(>99.9%).(4)The novel bistratal gas layer structure comprised of the underlying TiO2 nanorod arrays and the superficial PVDF microfiber network structures has been designed by the combination of a hydrothermal process and electrospinning technique,using FTO conductive glass as a substrate,butyl titanate and PVDF as the main materials.The durable superhydrophobic surface with bistratal gas layer structure was successfully prepared by the subsequent heat treatment and modification with POTS.Effects of hydrothermal process and electrospinning time on the morphology of the bistratal gas layer structure were investigated.In addition,the effect of the bistratal gas layer structure on the surface hydrophobic durability was also studied.The prepared surface with the bistratal gas layer structure demonstrated highly superhydrophobic stability under continuous contact with dynamic(250 kPa)or static(0.8 MPa)high pressure water.This can be mianly attributed to the excellent airtightness of the nanoarray and the mechanical cushioning of the superficial microfiber network structure.Additionally,the prepared surface also possessed excellent self-healing capability and superhydrophobic stability toward hot water.The water contact angle of the prepared surface can remain above 150°even after 10 cycles of jetting/healing treatment or contact with hot water(100?).(5)The durable superhydrophobic PVDF/PMSR/Na2CO3@SiO2 coating with gas compensation function was prepared by sol-gel and spraying method,using PMSR and PVDF as the main materials,Na2CO3@SiO2 particles for constructing roughness and POTS as low surface energy material.Effects of sol-gel time and PMSR content on the microstructure of Na2CO3@SiO2 particles and the adhersive strength of the prepared coating were investigated,respectively.The self-healing property,wear resistance,gas compensation function,acid/base resistance and weatherability of the prepared superhydrophobic coating were also studied.Results showed that the Na2CO3@SiO2 particles on the coating surface can react with the acidic solution to generate CO2,which can repair the damged gas film and extend superhydrophobic duration by 400%.In addition,the wear life of the prepared superhydrophobic coating was 6 times higher than that of pure PVDF coating,and the prepared coating can maintain its superhydrophobicity after 10 rubbing/healing test cycles,indicating the excellent self-healing ability.Furthermore,the prepared coating also possessed prominent superhydrophobic stability under the conditions of acid/alkaline solution(pH=1-14)or strong UV exposure(14 days).