Photo-oxidation of poly(diethylene glycol terephthalate)

The photo-oxidation of poly(diethylene glycol terephthalate) (PDEGT) under accelerated aging conditions has been investigated. A weatherometer was used to expose samples to simulated sunlight under air, replicating outdoor exposure. Irradiations were also performed under air using UV lamps of wavelengths centred on 302 and 365 nm. After exposure, the extent of degradation was determined using attenuated total reflectance Fourier transform infrared spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy and UV–visible spectroscopy. Results show that in general PDEGT degrades to a greater extent than the closely-related polymer poly(ethylene terephthalate) due to the susceptibility of the ether linkage. Although the diethylene glycol sequences are not themselves photoactive over this wavelength range and are not acting as photochemical weak links they do serve as additional sites for secondary free radical chemistry.