Depth profiles of photodegradation in films of aliphatic and aromatic polyesters

Depth profiles of photodegradation in the films of poly(butylene succinate) (PBSU) and poly(ethylene terephthalate) (PET) irradiated with ultraviolet (UV) light of wavelength 312 nm were investigated. FT-IR-ATR spectra were measured at 10, 25, 50, and 80 mu m in depth from the irradiated surface. In the case of PBSU, the IR bands were changed during irradiation, even at 80 mu m in the depth. On the other hand, in the case of PET, the IR spectra for the portion deeper than 10 mu m were nearly the same as that of the unirradiated film. The different depth profiles in photodegradation between PBSU and PET seem to be mainly caused by the different photodegradation mechanisms: the Norrish II type for PBSU and photo-Fries rearrangement-photooxidation reaction type for PET.