CHEMILUMINESCENCE FROM POLYPROPYLENE .2. THE EMISSION WAVELENGTHS DURING PROLONGED OXIDATION

Using a CCD imaging detector of broad spectral sensitivity, the chemil uminescent (CL) emission wavelength of accelerated thermal oxidation o f polypropylene has been found to depend on the extent of oxidation of the material. Initial chemiluminescence occurs mainly below 385 mm, a nd this is consistent with a bimolecular peroxy radical termination as the source of the emitting triplet ketone. The maximum emission shift s to longer wavelengths as further oxidation of the primary products o f degradation results in phosphorescent carbonyl groups of lower energ y than an isolated ketone. Results indicate that this secondary emitti ng species is alpha,beta-unsaturated carbonyls, thought to be formed b y the same termination mechanism.