Photoprotection of poly(ethylene-naphthalate) by zinc oxide coating

Zinc oxide coatings were deposited by sputtering on poly(ethylene-naphthalate) (PEN) films in order to protect the polymer against photodegradation. The main effects of the sputtering parameters (power, pressure, oxygen concentration) on the composition, structure and optical properties were studied. The adhesion of the ZnO coating on PEN films was evaluated by means of the 180° peeling test. Treatments by cold plasmas (Ar, Ar–O2, CO2) were used to increase the surface energy of PEN. The barrier properties of the ZnO coating to the oxygen diffusion were examined. The photo-protective properties of zinc oxide coatings deposited in various conditions on PEN films were studied by irradiating assemblies in artificial conditions (wavelength >300 nm). The rate of photo-oxidation of PEN was characterized by infrared measurements of the hydroxylated photoproducts (3100–3700 cm−1). The results indicate that the photodegradation of PEN was strongly reduced by the presence of ZnO coatings.