The influence of N ion bombardment on the properties of PET surface and SiN x/PET complex

Abstract

The surfaces of polyethylene terephthalate (PET) substrates were bombarded by N ions at room temperature. Varying the working power of ion source, PET surfaces with different composition and properties were obtained. Characterization by X-ray photoelectron spectrometry showed that the ester bonds at PET surface, especially C–O bonds, were selectively destroyed. With increasing the working power of ion source, more N element chemically bonded with C and formed C–N bonds. But such change only happened at the PET surface and the influence depth was less than 5 nm. The contact angle results revealed that with increasing the working power of ion source, the static contact angle of PET surface to pure water increased from 51° to 95°. With these results, one conclusion could be deduced that the surface properties of PET could be influenced by the relative content of N element chemically bonded at surface, which in turn was controlled by the working power of ion source. Finally, the bombarded PET substrates were coated with same silicon nitride (SiN x) film. The static contact angle of SiN x/PET complex with PET surface bombarded with 150 W, displayed no obvious difference before and after the bending fatigue test, which was caused by the little difference in surface morphology before and after test. Combining the results of the static contact angle and surface morphology, PET surface bombarded with 150 W displayed better crosslink properties to form SiN x/PET complex.