without dye photobleaching. The subsequent photo-oxidation of the thermally
oxidized polyamide results in a distinct shift in phosphorescence at a shorter
wavelength and a shortening of the emission lifetime55. Thermal oxidation caused a
new longer wavelength phosphorescence bands in aliphatic polyamides. These
caused reduction in mean phosphorescence lifetime for new longer wavelength
bands and in original phosphorescence as well. Photo-irradiation to thermally
oxidized samples vanishes the emission maxima of longer wavelength. Also the
yellow discolouration caused by thermal oxidation was gradually decreased upon
photo-irradiation. Phosphorescence species can impart greater absorption of
sunlight in the near ultra-violet region and in turn reduces the photostability of the
substrate. Moreover, strain relieving in crystalline region can cause chain
restructuring upon thermal treatment. This will also contribute to make polymer
susceptible to photo-oxidation.