Excimer laser (lambda=193nm) versus AlK alpha X-ray damages on polymer surfaces: An XPS (core and valence levels) analysis of polytetrafluoroethylene, polypropylene and polyethylene

The characterization of surface modifications of polymers, after irradiation with X-ray or UV photons, is abundant in the XPS literature, reporting from core level analysis the modification of surface chemical composition (loss of fluorine, or chlorine, or oxygen ... content). This work focuses on the use of XPS valence band spectra to show that irradiation can lead to superficial structural modification - lateral chain grafting, or crosslinking - of so-called ''reactive'' (polytetrafluoroethylene) and even more ''stable'' (polypropylene and polyethylene) polymers: this is best evidenced by modification of the typical shape of the C-2s valence band. This structural modification appears more pronounced for high fluence UV excimer laser irradiation in air, than for (more moderate) exposition to harder X-rays in vacuo.