Preparation And Characterization Of SiO₂-PDMS Hybrid Coatings

With the development of marine economy and the deterioration of marine environment in our country, a better durability of concrete used in oceaneering are required. There are some drawbacks of the commercial coatings what we used at present such as bad penetrability and low adhesion, and they will block the concrete holes so that the water inside it cannot volatilize, although they can provide som protective effects. Organic-inorganic hybrid materials combine the advantages of organic materials with those of inorganic materials, so they can offer a very excellent anti-corrosive effect.In this paper, the hydroxyl-terminated polydimethylsiloxane(PDMS) modified silicate hybrid sols and nanoparticles modified SiO2-PDMS hybrid sols were synthesized via sol-gel process, where PDMS acted as organic component precursor and tetraethoxysilane(TEOS) as inorganic component precursor in the presence of dibutyl tin dilaurate(DBTL) catalyst. The hybrid sols were coated on the concrete and glass slide. And by the measurements of infrared spectroscopy(FT-IR), contact angle and SEM, we characterized the coatings’properties. We tried to produce a kind of stable organic-inorganic hybrid coating with excellent properties in order to offer a reference for the actual concrete anti-corrosion.(1) The SiO2-PDMS hybrid sols had low viscosity and could penetrate into the concrete well, it kept the "respiration character" at the same time. The coatings had strong hydrophobicity compared with pure TEOS coating, but the more the PDMS content, the easier the hybrid sols gelled. In this experiment, the hybrid coating’s best overall properties were achieved when the PDMS content was43%.(2) We changed the water content in order to investigate the sol-gel process. And we found the rate of TEOS hydrolysis was slow and TEOS couldn’t hydrolyze completely, it tented to hydrolyze and polymerize step by step and produced linear polymer when the water content was small. If the water was enough, it would promote the hydrolysis of TEOS and tent to produce three-dimensional structure. But if the water was too much, there would produce some white precipitates and the amount of them increased with the increasing of water. The hybrid coating had the best performance when R was2, because it could make the precursor hydrolysis just completely.(3) We produced nano-SiO2modified SiO2-PDMS hybrid sols, and found nano-SiO2strengthened the coating’s hydrophobicity only if the amount were more than2%and the more the nano-SiO2content, the higher the contact angle was. But if we added too much nanaoparticle, it would weaken other properties. When adding5%nanoparticle, the nanoparticle-SiO2-PDMS owned the best properties.(4)The nano-Al2O3could strengthen the anti-UV-aging property of the SiO2-PDMS hybrid coating.