Near edge X-ray absorption fine structure spectroscopic and infrared reflection absorption spectroscopic studies of surface modification of poly(butylene terephthalate) induced by UV irradiation

Surface modification of poly(butylene terephthalate) (PBT) induced by ultraviolet (UV) irradiation was investigated using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and infrared reflection absorption spectroscopy (IRAS). UV irradiation drastically altered carbon and oxygen K-edge NEXAFS spectra of PBT. NEXAFS spectra obtained after UV irradiation were compared with those of various molecules containing carbonyl, carboxylic, ester, and anhydride groups. UV-irradiated PBT surfaces had similar spectral features to pyromellitic dianhydride, which contains anhydride groups. IRAS spectra of PBT surfaces were also changed by UV irradiation. The changes indicate that UV irradiation destroyed alkyl chains and changed the ester bond structure. These results indicate that UV irradiation removes alkyl chains and ester bonds in PBT and forms anhydride groups on PBT surfaces. It was also suggested that anhydrides might be formed near PBT surfaces by UV irradiation.