Aerosol-assisted plasma deposition of barrier coatings using organic-inorganic sol-gel precursor systems

Hybrid organic-inorganic precursors and sol-gel systems thereof, obtained via wet-chemical hydrolysis, were atomized and introduced into an atmospheric pressure dielectric barrier discharge (DBD) in nitrogen. The precursors used are tetraethoxysilane (TEOS), glycidoxypropyltrimethoxysilane (GLYMO), methacryloxypropyltrimethoxysilane (MEMO), propyltrimethoxysilane (PTMO), and new high molecular weight siloxance precursor (Bayrecit). The obtained coatings were analyzed by means of Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and field emission scanning electron microscopy (FESEM). Deposition rates varied between 30 nm min-1and 175 nm min-1. Injection of hydrolized sol-gel precursor systems resulted in higher deposition rates. Films deposited on PET foil were tested for their oxygen barrier properties. Plasma-assisted coating deposition of the sol-gel systems proved to be superior to wet-chemical application and conventional thermal or UV curving. Howwever, the best barrier performance was obtained with a coating form non-hydrolyzed Bayrecit. The lowest oxygen transmission rate (OTR) on PET abtained so far is 5 cm3 m-2 day-1 bar-1.