Preparation And Mechanism Of Superhydrophobic Wood Based On Surface Micro/nano Structure Design

Biomimetically fabricating the superhydrophobic coating on wood surface,which can effectively decrease the interaction between wood and moisture,thus avoiding a series of problems such as deformation,cracking,decay,mildew,discoloration and degradation caused by water absorption.Meanwhile,it can endow superhydrophobic wood with antibacterial,flame retardant,conductive,magnetic,microwave absorption and other functions,which has important research value and practical significance for the high value-added utilization and functional extension of wood.However,the poor mechanical and chemical stability of superhydrophobic coatings are key factors for limiting the practical application of superhydrophobic wood.Based on the "lotus-leaf effect" bionic principle,the different micro-/nano-hierarchical rough structures were constructed on original wood surface through the reasonable structural design and interface control,and prepared the superhydrophobic wood with excellent mechanical resistance and chemical durability.The interface bonding and adjusting mechanisim between superhydrophobic coating and wood matrix,as well as the construction method of robust micro-/nano-hierarchical rough structures,were studied.The effects of different micro-nano-level roughness structures on superhydrophobic properties on wood surface were analyzed,and the hydrophobic mechanism was also analyzed.The main conclusions are as follows:(1)The low-energy component directly modifies the natural structure of the wood to achieve overall high hydrophobicity.The bulk highly hydrophobic wood was prepared by grafting long-chain alkyl groups onto the wood cell wall.The water contact angle of the cross-section was 150°,the sliding angle was 13°-38°,the water contact angle of the longitudinal section was 140°,and the sliding angle was greater than 90°.The hydrophobic property throughouts whole structure of wood,and exhibited excellent abrasion resistance and chemical durability.After abrasion and corrosion,the cross-section contact angle was greater than 145°.(2)The sol-gel synthesis of SiO2 nanoparticles assisted in the construction of surface micro-nanostructures,which can achieve the superhydrophobicity of the three-section of wood.The transverse section has a water contact angle of 155° and a sliding angle of 3°;the longitudinal section has a water contact angle of 1520 and a sliding angle of 5°.After corrosion by chemical reagents,the transverse section contact angle is greater than 150°.However,the synthesized SiO2 has a low deposition amount and uneven distribution in the inner layer of wood,and the prepared superhydrophobic wood has poor abrasion resistance.(3)Biomimetic mussel polydopamine(PDA)surface modification method can achieve chemically durable superhydrophobicity on wood surface.The PDA/Ag composite layer has a water contact angle of 1520 and a sliding angle of 8°.The polymerized PDA layer at 60? had a water contact angle of 153°and a sliding angle of 9°;the polymerized PDA/Cu composite layer at 600 C had a water contact angle of 1570 and a rolling angle of 5°.Coordination-driven multi-assembly technology constructs a polyphenol-metal ion superhydrophobic coating with controlled thickness on the surface of the wood.Compared the three times assembly with the one assembly,the thickness of the tannic acid(TA)-Fe? composite coating increased from 4.3 ?m to 8.9 ?m,contact angle increased from 146° to 154°,sliding angle decreased from 15°to 9°;TA-Fe?/Ag composite coating thickness increased from 5.6 ?m to 10.8 ?m,contact angle increased from 1520 to 157°,sliding angle reduced from 100 to 4°.After the above superhydrophobic coatings were tested by chemical solvents and harsh environments,the contact angles were all greater than 150°.(4)Based on the spray method of fluorinated hierarchical nanoparticles and epoxy resin,it can achieve superamphiphobicity with abrasion and corrosion resistance on a variety of substrate surfaces.The superamphiphobic coating exhibits excellent repellent ability to liquids having a surface tension of 20.1 mN/m or above.The contact angle of n-heptane is 1540 and the sliding angle is 10°.The coating has a scratch hardness of 1.05 GPa.After the sandpaper wears 3 m,the water contact angle is reduced from 175° to 160°,the sliding angle is increased from 1°to 8°,and the n-decane contact angle is reduced from 159° to 149°,the sliding angle is increased from 60 to 24°.After chemical corrosion of reagents,the contact angle of water and n-decane is greater than 150°,and the sliding angle is less than 10°.(5)Wood materials with selective oil/water separation function were prepared by using wood natural hierarchical porous structure template combined with superhydrophobic modification technology.The wood aerogel/PDMS composite material can realize the selective oil-water separation function,which combining the filtration and absorption functions into one.It can absorb oils with a weight of 9-20 times.The separation efficiency of the water/trichloromethane mixture is 99.5%,and the flux was 2.25×104 L/m2·h.Janus wood membrane material can achieve the dual-selective oil/water separation function.The separation flux for water/n-hexane mixtures is 2450 L/m2·h,and for water/trichloromethane mixtures is 4820 L/m2 h.The separation efficiency is higher than 99.3%.