Study On The Fabrication Of Superhydrophobic Wood Surface Based On Cuprous Oxide

Wood is widely used in daily production and life because of its various merits include high strength-to-weight ratio,easy processing and short regeneration cycle,etc.However,the presence of hydrophilic hydroxyl groups in the components makes wood have strong water absorption,resulting in dimensional instability,susceptible to microorganisms,dry shrinkage and wet expansion,and other drawbacks,which shorten and reduce the service life and performance of wood.The creation of superhydrophobic function on wood surface will significantly prolong the service life of wood.In this study,the copper chloride aqueous solutions with different concentrations were introduced in the synthesis process of phenol formaldehyde(PF)resin adhesive,in which different kinds of nano cuprous oxide(Cu₂O)were prepared.The superhydrophobic wood surface was constructed using simple coating method in combination with the immersion of stearic acid(STA)ethanol solution.Various properties of as-prepared superhydrophobic wood were tested and characterized.The main research results are as follows:(1)Cu₂O nanoparticles were prepared simultaneously in the synthesis system of PF resin adhesive with the 40%aqueous solution of copper chloride as the origin of copper.The size of as-prepared Cu₂O nanoparticles is evenly distributed between 9.56 nm and 51.58 nm,and the morphology of Cu₂O nanoparticles is concave octahedral.The crystal plane with the fastest growth rate is the(111)plane,and the lattice spacing is d=0.25 nm.The calculating result displayed that the average grain size is 44.34 nm.It can be confirmed by the results of TEM,XRD,XPS that the as-prepared particles are pure Cu₂O.(2)The STA@PF@Cu₂O core-shell structure was successfully formed on the surface of masson pine by the spray of nano-Cu₂O modified PF resin adhesive and subsequently immersion with STA ethanol solution.The changes of surface morphology of masson pine before and after modification were observed by SEM,and the hydrophobic properties,water permeability,surface free energy,acid and alkali resistance,wear resistance and corrosion resistance of the modified masson pine surface were tested.The results showed that the superhydrophobic function of modified masson pine was obtained.The contact angles of the three sections were all higher than 150°,and the maximum was153.3°.After being sprayed with nano-Cu₂O modified PF resin adhesive,a micro-nano surface was successfully constructed on masson pine substrate,subsequently the surface free energy of masson pine was greatly reduced from 47 J/m~2 to 20 J/m~2 after immersion with STA ethanol solution.Moreover,superhydrophobic masson pine has low water permeability,strong acid and alkali resistance and wear resistance,and the decay resistance against white rot was also improved with the mass loss of masson pine was lowered from 35.60%to 19.89%.(3)Two kinds of Cu₂O nanoparticles(Cu₂O NPs 1 and Cu₂O NPs 2)derived from 20%and 40%Cu Cl₂·2H₂O solutions were used for superhydrophobic modification of masson pine(softwood)and pecan wood(hradwood),respectively.The results showed that the two kinds of synthesized particles were Cu₂O nanoparticles and they have the same morphologies,while the size distribution of Cu₂O NPs 2 ranged from 122.4-164.2 nm is more uniform than that of Cu₂O NPs 1.A flower-like structure was obtained on the pecan wood surface after STA immersion,where the structure grew along the edge of nano Cu₂O particles.Both masson pine and pecan wood were endowed with superhydrophobic properties,both of them had a contact angle more than 155°and sliding angle less than 10°.Moreover,the modified surface possessed outstanding self-cleaning,low permeability,low free energy,strong acid and alkali resistance and wear resistance.The contact angle is still higher than 150°after soaking in strong acid(p H=2)and strong alkali(p H=12)solution for more than 12 h or wearing for more than 12 cycles by 1200 mesh sandpaper at vertical pressure of 2.2 k Pa.In conclusion,the low-cost superhydrophobic modification strategy developed in this study is simple and easy to implement,and the prepared superhydrophobic surface has good acid and alkali resistance,wear resistance and decay resistance,which has the potential to be applied industrially on a large scale.