Fabrication Of Superhydrophobic Hybrid Particles Based On Nano SiO₂ And Aligned Carbon Nanotube Bundles And Their Epoxy Composite Coatings

The superhydrophobic surface has the advantages of self-cleaning,anti-corrosion,antiicing,oil-water separation and so on,it has a wide application potential in real life.Generally,the superhydrophobic surface can be obtained by constructing micro/nanoscale hierarchical structure and introducing low energy surface material.However,due to the unique detailed structure of superhydrophobic surface,it can be easily damaged under external forces.The harsh environments raise strict requirements for the properties of superhydrophobic coatings.Therefore,the durable superhydrophobic coatings are needed.Although many strategies have been developed for durable superhydrophobic coatings,it is still a great challenge to construct durable coatings,because of the different chemical structure and properties of the coating.Aligned carbon nanotube bundle(ACNTB)is an aggregate that composed of many CNTs in a certain direction,which not only has a rich pore structure,but also has good flexibility,high strength and thermal properties.The special multi-pore structures of ACNTB are an ideal storage sites,which have special application in the construction of nanoparticles with complex hierarchical structures.Superhydrophobic SiO2 nanoparticles are often used to prepare superhydrophobic coatings.Epoxy resin(EP)is a commonly adhesive that has excellent adhesion,high thermal resistance and corrosion resistance.In the present work,a durable superhydrophobic EP coating with a stable hierarchical nanostructured surface is prepared by introducing SiO2 decorated ACNTB hybrid hydrophobic particles,for considering the main issues such as low stability of surface structure,poor adhesion of coating to substrate.The main research contents are as follows:First,two different sizes of hydrophobic nanoparticles MSiO2-KH570 and SiO2-KH570 were prepared by by hydrolyzing tetraethyl orthosilicate(TEOS)with silane coupling agent KH570 as the modifier in water and ethanol,respectively,and the effect of the content of KH570 on the structure of nanoparticles was discussed.Base on the optimization process of synthesis of MSiO2-KH570 and SiO2-KH570 particles,ACNTB hybrid particles decorated with MSiO2-KH570 and SiO2-KH570,coded as ACNTB-MSiO2-KH570 and ACNTB-SiO2KH570,were prepared,the particle size,dispersion state and hydrophobic ability of MSiO2KH570 and SiO2-KH570 particles were analyzed,and the structure and superhydrophobic properties of ACNTB-MSiO2-KH570 and ACNTB-SiO2-KH570 hybrid particles were invetigated.Results indicate that the particle size of MSiO2-KH570 that synthesized in water gradually increases with the content of KH570,and the particle size of SiO2-KH570 synthesized in ethanol solvent is basically not affected by the change of KH570 content.When the molar ratio of KH570 to TEOS is 0.25,the higest water contact angles(CA)on MSiO2-KH570 and SiO2-KH570 particles can be obtained,and they are 149.5 ± 2° and 152.7±3°,respectively.Because-OH on the surface of SiO2 particles can enhance the interface interaction between SiO2 and ACNTB,ACNTB-SiO2-KH570 hybrid particles have better structural stability than ACNTB-MSiO2-KH570 particles.The CA(166.3±1°)of water on ACNTB-SiO2-KH570 particle coating is higher than that on ACNTB particle coating,and even after the application of high pressure,CA can reach 147.4 ± 2.5°.The ACNTB-SiO2KH570 particles coating shows excellent repellency to different pH solutions and viscous liquids,as well as low surface energy liquids.Second,diglycidyl ether-terminated polydimethylsiloxane(DGETPDMS)modified EP coating with high curing volume shrinkage rate(9.64%)was prepared using laboratorysynthesized hyperbranched polysiloxane(HBPSi)as EP resin curing agent.Base on the formulation of the above-mentioned EP coating system and ACNTB-SiO2-KH570 particles,EP composite coatings with hierarchical nano structured surface were prepared by multistep dip-coating method at very low ACNTB-SiO2-KH570 content(4.3 wt%),the structure and hydrophobic properties of the coating are discussed,the self-cleaning performance,antifouling performance,abrasion resistance,thermal resistance,solvent resistance,self-healing properties of the coating were investigated.Results show that the prepared EP/ACNTB-SiO2-KH570 composite coating has a hierarchical surface nanostructure,the CA and the sliding angle(SA)of water on the coating can reach 158.8±2.5° and 2.5±0.5°,respectively,indicating significant superhydrophobic property.The coating also displays self-cleaning and anti-fouling performance.EP/ACNTBSiO2-KH570 composite coating can withstand the pressure of 1188 KPa from the water jet for 120s,and the high CA value(151.4 ± 1.5°)and low SA value(7.1 ± 1.5°)can still be obtained.After the coating is impacted by sand particles(impact energy of single particles is equal to 1.04×10-7 J/grain),the C A of water on the coating is still high(151.3 ± 1.6°)and SA value is also low(11.5±1.9°).After 60 abrasion cycles with 800 mesh sandpaper under a weight of 100 g,the CA of water on the coating can reach 150.5±1.5°.Evidently,the EP/ACNTB-SiO2-KH570 composite coating has excellent impact resistance and abrasion resistance,the main reason is the fact that the ACNTB-SiO2-KH570 particles have excellent mechanical properties and friction resistance.Additionally,the high curing volume shrinkage of the EP resin,and the rich amine and hydroxyl groups contained in EP polymers can strengthen the interface between the polymers and ACNTB-SiO2-KH570,which enhance the comprehensive mechanical properties of EP/ACNTB-SiO2-KH570 composite coating.The CA of water on EP/ACNTB-SiO2-KH570 composite coating formed on aluminum plates,wood,rubber,steel plates and glass substrates are as high as 156.3°158.2°,and the grid test shows that the adhesion ratings of coating to aluminum plates,wood,rubber,steel plates are all 4B.The folding tests indicate that after 25 folding times,the CA of water on the EP/ACNTB-SiO2-KH570 composite coating formed on rubber substrate is above 150°.Obviously,the adhesion of the coating to most substrates is strong.Mainly due to the high thermal resistance of ACNTB-Sio2-KH570,even after the EP/ACNTB-Sio2KH570 composite coating are treated at 200℃/48h,300 ℃/12h and 500℃/10min,the CA of the water on the coating is still high(161-158.9°),indicating the good thermal stability of the coating surface structure.When the damaged EP/ACNTB-SiO2-KH570 composite coating experiences the heat treatment process at 300℃ for 9h,the nano hierarchical structure of the damaged coating can be reconstructed,due to partial decomposition of the resin,the movement of molecular chain segments and the migration of nanoparticles,the superhydrophobic property of the coating can be recovered,the CA of water on the coating can improve for 123.1 ± 3° to 160.4 ± 2.5°,and SA can recover from 40.6±3° to less than 1°.After EP/ACNTB-SiO2-KH570 coatings are immersed in liquid nitrogen,DMF,ethanol,acetone,toluene,0.1MNaOH,0.1MNaCl and 0.1MHCl,CA of water on the coating is still high(151.3-156.9°),indicating the good solvent resistance of the coating.