Differences in polyene formation between polyethylene and polypropylene during photo-irradiation

During the photo-irradiation of polyethylene a new fluorescence emission spectrum with a peak at 420 nm and a corresponding excitation spectrum with distinguishable peaks at 298, 312 and 327 nm were observed; the intensities of these peaks increased with irradiation time. In the case of polypropylene no emission spectrum was observed in these regions. However, infrared spectra of both polymers showed formation of carbon-carbon double bonds during the photo-irradiation. These differences in the fluorescence emission spectra between two polymers indicate that the polyethylene forms polyene structures fairly easily during the photo-irradiation, while polypropylene forms only isolated double bonds or very short sequences of double bonds.