Producing of high-transparent antiscratch nanohybrid thin films on polycarbonate substrate

Abstract In the present work, a new aqueous sol–gel procedure has been used for producing hard transparent organic–inorganic nanohybrid coatings on polycarbonate (PC) substrate for improving its optical and mechanical properties. Sol-gel thins films were prepared by mixing Si and Al aqueous precursors and applied them on the cold plasma treated PC substrate. TEOS, GPTMS and aluminum tri sec-butoxide were used as main precursors. In order to improve the adhesion strength onto polymer, PC substrates were treated by Dielectric Barrier Discharge (DBD) system being conducted at atmosphere pressure in open air. The effects of sol ratios, curing temperature and aging time on the prepared coatings properties were investigated. Chemical, structural, morphological, optical and mechanical characteristics of the samples were studied by ATR-FTIR, EDS, XRD, FE-SEM, TEM, UV/vis spectroscopy, pencil hardness and eraser scratch methods. The obtained results indicated that the water contact angle of PC (73.24°) decreased to 6.32° by 45 second plasma treatment due to added functional groups on the treated surfaces. All of the films showed higher optical transmittance (89%) than the raw PC (86%) that was stemmed from the lower refractive index of the prepared films. Films indicated good adhesion onto the plasma treated substrates (5B). The pencil hardness of the PC substrate (4B) improved to 3H (8 pencil grade increment) with just a single layer coating (about 200 nm thickness) due to the preparation of new hard structures of interlocked Si and Al atoms.