Study On Coating Modification And Hydrophobic Properties Of Architectural Membrane Materials

With the development of society, architectural membrane materials has beenwidely used. But, the degradation of the PVC building membranes were acceleratedby Ultraviolet light, while PVC plasticizer migration to the membrane surface.Membrane surface become sticky, was easy to tarnish and difficult to clean. Itspopularization and application greatly was affected in the field of architecturalmembrane. Many scholars did a large number of research in the antifoulingphenomenon of the nature, for example, the not stain of the moth wings, the not waterof the wings of securidaca, the not moth from the Silt of the Lotus leaf. They foundthat it was an effective way to achieve antifouling self-cleaning properties by buildingmaterials hydrophobic surface, and it is key steps that building the rough structure onthe surface of the material constructing for achieving. The study showed that it was asimple and effective method which used nanoSiO₂to modify the PVC architecturemembrane by coating. However, the surface of the SiO₂has a lot of hydroxy whichhas highly hydrophilic. It must be hydrophobically modified before coated on thePVC architecture membrane to reduce its hydroxyl content.The treatise was coating to the PVC architecture membrane using dedicated SiO₂then study its hydrophobic properties. While prepared nanoSiO₂, firstly the affect tothe nanoSiO₂was studied when the molar ratio of nNH₃H₂O/nTEOSwas changed.Secondly process parameters were optimized in the situ modification of KH-570toSiO₂by Sol-gel method. Lastly, its hydrophobic properties were studied after the PVCarchitecture membrane was surface treated by the nanoSiO₂.The thesis studied the particle size and distribution, hydroxyl content, surfacegroups, material structure of the nano-SiO₂which prepared in the different molar ratioof nNH₃H₂O/nTEOSby the particle size analyzer, thermal gravimetric analyzer, fourier transform infrared and XRD. The results showed that,（1） the particle size of thenanoSiO₂increased as the rise of the molar ratio of nNH₃H₂O/nTEOS, and the particlesize distribution become uneventful.（2） The surface of the nanoSiO₂has a lot ofhydroxy. The hydroxyl content firstly increased and then decreased, and it achievedthe highest when the molar ratio of （NH₃H₂O）/（TEOS）was1:1.（3） The gelation timeshortened with the addition of the molar ratio of （NH₃H₂O）/（TEOS）.Both the dosage of SiO₂coupling agent KH-570, the modification time and themodification temperature are important influence factors of the effect in nanoSiO₂insitu modification by SOL-GEL method. By using range analysis and variance analysisafter the orthogonal test, the research discussed the influences on modified silicaactivation index and grafting efficiency which made by different modificationprocesses. The results showed that: both the dosage of SiO₂coupling agent KH-570and the modification time have significant influence on activation index undersignificance level0.05, then in terms of the grafting efficiency, only the dosage ofSiO₂coupling agent KH-570has the significant influence which under significancelevel0.05.By comprehensive analysis, it got an optimizing process: the dosage ofSiO₂coupling agent KH-570is2%, the time of modification is3h, the temperature ofmodification is50℃. It proved out that the activation index and grafting efficiency ofmodified silica under the optimizing process are96%and19.1%respectively.The hydrophobicity of PVC architectural membrane material had vastlyimproved after treating with nanoSiO₂on the surface. The water contact angle hadincreased from82.9°to147°,and the rolling angle lowed to15°; Than after kept thematerial in natural environment for about three months, the hydrophobicity of PVCarchitectural membrane material had declined slightly.