Development of new fluorinated polysilazanes via Si-H bonds activation for application as protective hydrophobic coatings

Reference Presenter Authors
(Institution)
Abstract
18-006 Plinio de Paula Furtat Furtat, P.d.(Federal University of Santa Catarina); Leite, M.L.(Universität Bayreuth); Ionescu, E.(Technical Universität Darmstadt); MACHADO, R.A.(Universidade Federal de Santa Catarina); Motz, G.(Universität Bayreuth); A new route to synthesize fluorine-modified polysilazanes for coating applications with improved hydrophobicity and excellent chemical resistance was developed by the reaction of the commercially available liquid oligosilazane Durazane® 1800 and the fluorinated alcohol 2,2,2-trifluoroethanol (TFE) using tetra-n-butylammoniumfluoride (TBAF) as selective catalyst to activate Si-H groups for simultaneous selective reactions with both N-H and O-H groups. The resulted reaction product is a solid and soluble fluorinated polysilazane, suitable for coating applications via simple dip-coating technique. The proposed reaction mechanisms and the resulting polymer structures confirm the attachment of the fluorinated groups on the polysilazane backbone, were investigated with 1H, 13C NMR, FTIR, XPS spectroscopy, GPC, GC and elemental analysis. It was also demonstrated that the absence of catalyst leads only to the expected decomposition of the silazane by the alcohol. Whereas the remaining silazane Si-H and Si-N bonds provide for an excellent adhesion of the coatings to the substrate, the CF3 groups decrease the surface energy leading to an increased contact angle of up to 15 % and 40 % to water and hexadecane, respectively, in comparison to fluorine-free polysilazane coatings. When tested as mold release coatings, the F-modified silazanes reduced the adhesion of a phenolic resin with an aluminum substrate from 12.7 to 2.8 MPa. Moreover, the chemical resistance of the fluorine-modified polysilazanes based coatings in contact with acids, bases (HCl and KOH) and also NaCl solutions is remarkably improved, offering a great potential to protect especially metals from corrosion.
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