Effects of different laser and plasma treatments on the interface and adherence between evaporated aluminium and polyethylene terephthalate films: X-ray photoemission, and adhesion studies

Chemical functionalities, topography and adherence between Al and polyethylene terephthalate (PET) films, modified by laser treatment below the polymer ablation threshold fluence in air and in helium at different wavelengths, fluences, pulse numbers and by low pressure plasma treatment in He 95% with O2 5%, at 0.2 W/cm3 were investigated by XPS, AFM, water contact angle and adhesion measurements. XPS results revealed (i) formation of polar-oxygenated functional groups (C=O, O-C=O) by laser treatments in air and (ii) incorporation of ester and ether groups by plasma treatment in He 95% with O2 5%. After deposition of thermally evaporated Al on laser or plasma treated PET films, U-Peel tests indicated that laser treatment in air at 248 nm and 20 mJ/cm2, and plasma treatment improved Al/PET adhesion. XPS studies revealed the presence of an increasing number of Al-O-C stable and cohesive interfacial complexes formed by chemical interaction between aluminium and the laser treated in air or plasma treated in He 95% with O2 5% PET films. These interfacial compounds play an important role in the enhancement of the metal/polymer adhesion