Paper surface modification by plasma deposition of double layers of organic silicon compounds

In this work, filter paper was coated with plasma depositions of hexamethyl disilazane (HMDS), and double layers of HMDS and n-hexane, and HMDS and tet raethyl orthosilicate (TEOS). In the case of double layers of HMDS and TEOS , TEOS deposition times of 2, 4 and 6 minutes were studied. The double laye rs were interfaced by an intermixing layer, in which both reagents were pre sent. All coating films formed adhered well to the substrate, and resulted in water repellent paper surfaces with apparent water contact angles above 100 degrees and water adsorption around 15 g m(-2). Apparent water contact angles were not affected by immersion in strong basic and acid solutions, o r by exposure to ultraviolet light for 106 hours. Water adsorption of HMDS, HMDS-n-hexane and HMDS-TEOS (6 min) coated samples was not significantly a ltered by these resistance tests, but HMDS-TEOS (2, 4 min) coated samples w ere hydrolysed by immersion in strong basic solution and by ultraviolet lig ht. These results seemed to indicate that the HMDS-TEOS intermixing layer w as fragile and malformed. This hypothesis was confirmed by Raman and atomic force microscopies, which showed heterogeneous structures with very high p eaks, and by XPS analysis, which indicated oxidation of carbonic species an d crosslinkings together with elimination of ethylene gas probably triggere d in the intermixing layer. The porosity of paper was not altered showing t hat all depositions were conformal. FTIR analysis of HMDS coatings indicate d that the films formed were crosslinked by ultraviolet light showing its p otential for outdoor applications.