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 a new high molecular weight siloxane 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–1 and 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 curing. However, the best barrier performance was obtained with a coating from non‐hydrolyzed Bayrecit. The lowest oxygen transmission rate (OTR) on PET obtained so far is 5 cm3 m–2 day–1 bar–1.