Improvement Of Stability And Durability Research On The Superhydrophobic Biomass Materials

Superhydrophobic surfaces with water contact angle greater than 150° and contact angle hysteresis less than 10° have aroused considerable interest in scientific and industrial community due to their great importance in fundamental research and potential industrial applications. Generally speaking, superhydrophobic surfaces can be fabricated by creating a rough structure on a hydrophobic material surface or modifying a rough surface with a special low surface energy material.In this thesis, not only we fabricated the superhydrophobic surface on the biomass materials, but also the stability and durability of as-prepared superhydrophobic surface have a much better improvement.The superhydrophobic coating with an appropriate recipe contains PVA and SiO2 particles, followed by modification of OTS reagent, was fabricated on a wooden base surface. A simple drop-coating process enabled the formation of a superhydrophobic wood surface, exhibiting its commercial feasibility. The addition of SiO2 particles plays a critical role in improving the mechanical properties of the PVA/SiO2 composite polymer. This enhancement of the mechanical properties can be attributed to the fact that the SiO2 particles act as a solid plasticizer capable of enhancing the chemical and mechanical properties. The mechanical robustness of superhydrophobic wood surfaces has been investigated on several superhydrophobic wood surfaces by abrasion test. Based on our results, the mechanical robustness of the superhydrophobic wood surface by coating PVA/SiO2 composite polymer has a better improvement, and applying a mechanical robust superhydrophobic wood surface appears to be a promising commercial feasibility on various woodworks.The superhydrophobic/superoleophilic cotton, which could be used in field of water/oil separation, was fabricated via sol-gel process and an OTS treatment. The surface of cotton fibers was initially pretreated by NaOH aqueous solution, then coated with a film of SiO2 nanoparticlesvia sol-gel process and subsequently modified with octadecyltrichlorosilane through a simple solution-immersion step.Theas-prepared cotton could be used to selectively absorb various kinds of oils and organic solvents up to above 50 times of its own weight while repelling water completely. The cotton also showed good buoyancy on the water surface, and good reusability in oil/water separation cycle. The removal and the collection of the absorbed oils were easily achieved with the help of vacuum air pump.There was only a slight decrease of the maximal oil absorption capacity through the 10 cycle processes.When the pretreated cotton sample was immersing in the SiO2 sol, the SiO2 sol permeated the corrugations and interspaces and the SiO2 particles tightly adhered to the cotton fiber through the chemical bond, which generated between the hydroxyl groups from cotton fiber surface and hydrolyzed silane, and not easily fall off, indicating that the surface structure of as-prepared cotton was not easily changed after reutilization.So the as-prepared cotton has good reusability. From another perspective, the microstructures of as-prepared superhydrophobic/superoleophilic cotton have a preferable stability and durability.The three kinds of superhydrophobic biomass materials samples were prepared in three-steps (coating epoxy resin/anchoring silica particles/coating low surface energy layer), where the epoxy resin coating was first adhered to the superhydrophobic biomass materials surface by immersing samples into epoxy resin acetone solution, then silica particles were anchored onto the samples surface through the strong bond between epoxide group of epoxy resin and amino group of amino-functionalized silica particles to rough the surface microstructure by immersing samples into the solution of amino-functionalized silica particles. The prepared samples surfaces were further modified by OTS reagent. The mechanical stability of the resulting wood surfaces was investigated by the sand collision test and water wash test. Meanwhile, the sand collision test and water wash test revealed that the epoxy resin concentration was the key factor for preparing these kinds of relatively mechanical stable superhydrophobic biomass materials. On the basis of the results, the mechanical stability of the superhydrophobic biomass materials surface prepared by epoxy/silica coating has a much better improvement, so the relatively mechanical stable superhydrophobic biomass materials surface delivers a promising commercial feasibility on various woodworks.