The use of luminescence spectroscopy to evaluate oxidation processes in polyolefin films

Luminescence spectroscopy has been used for the investigation of oxidation in Low Density Polyethylene (LDPE) films without antioxidant which were subjected to laboratory thermal oxidation treatment at 90°C for periods of 15 and 30 days. Fluorescence spectra at room temperature and phosphorescence spectra at liquid nitrogen temperatures of the additive free 26 μm thick films were recorded and are compared with those of a non-oxidised reference sample. Fourier Transform Infra Red (FTIR) absorption spectroscopy was used to identify a carbonyl group absorption increase at 1725 cm^-1 indicating increased oxidation which coincided with a significant decrease in room temperature fluorescence intensity at 330 nm. Phosphorescence spectra at liquid nitrogen temperature are also shown to exhibit changes after oxidation. The possible mechanisms affecting luminescence are discussed with reference to the observations