Thin ZrO2 coatings on polymers: role of interfacial adhesion

The interfacial characteristics between thin layers of zirconium dioxide an d different thermostable polymers - polyimide, poly(ether ether ketone), an d poly(ethylene terephthalate) were studied. These layers, with a thickness ranging from a few nanometers to a few micrometers, were deposited by mean s of magnetron sputtering from a ZrO2 target. In some cases, the polymers w ere subjected to plasma treatment (in the presence of different gases: air, Ar, and CO2) prior to ZrO2 deposition. X-ray photoelectron spectroscopy (X PS) analyses indicated clearly that zirconia coatings can be considered uni form when their thickness exceeds c. 10 nm. No interfacial covalent bonds b etween zirconia and polymers, such as Zr-O-C, were demonstrated. The level of adhesion at the coating-substrate interface was determined by a fragment ation test. The interfacial shear strength, related to the thermodynamic as pects of the polymer surfaces, i.e. their surface energy, was estimated. Th e result was in good agreement with the existence of physical interactions only, like van der Waals interactions, as shown by the XPS investigation.