Improved durability of Bisphenol A polycarbonate by bilayer ceramic nano-coatings alumina-zinc oxide

Abstract Polycarbonate exposed to sunlight yellows, degrades and loses its usable properties. In order to increase its lifetime, it can be coated with nano-ceramic thin layers of ZnO and Al2O3 deposited by sputtering. The role of the ZnO is to absorb the UV photons that can damageable for the polycarbonate. However, one of the limitations in the use of ZnO is the photocatalytic oxidation that could occur at interface ZnO/PC as a consequence of the photocatalytic activity of this oxide. Insertion of Al2O3 between PC and ZnO could be a way to inhibit this interfacial oxidation. The photooxidation of the ceramic/polymer assemblies, in condition of artificial accelerated ageing, was measured by infra-red and UV-vis spectroscopies. The results show that the photocatalytic activity of ZnO occurring in monolayer coated substrates can be significantly reduced by insertion of Al2O3 and that, in addition, Al2O3 decreases the permeability to oxygen of the coating.