The effects of proton irradiation on the properties and structure of poly(ethylene terephthalate) films were investigated. The results showed that mass loss was rapid with fluence and then tended to level off at higher fluence. The transmittance decreased obviously in the visible range. The relative intensity of C-1s with a binding energy of 284.6 eV increased with the dose and then tended to level off. 01, decreased with the dose and more rapidly at 533.5 eV. All this indicated that decarbonylation occurred on the surface. The Fourier transform infrared and X-ray photoelectron spectroscopy results demonstrated that the change in the substitution of phenyl was due to the, enrichment of the phenyl group on the surface; in other words, carbonification took place (in which C-1s was usually situated at 284.6-285 eV). The change in transmittance was considered to result from the change in the surface structure and morphology. (c) 2007 Wiley Periodicals, Inc.