Chemiluminescence as a clear diagnostic tool of polymer oxidation

Chemiluminescence (CL) was applied to evaluate the oxidation of low density polyethylene and cross-linked polyethylene. The CL measurements done at a constant temperature revealed that the CL spectra always exhibit a clear incubation period or oxidation induction time during which no CL appears. The CL appearing in an early stage of oxidation seems to be due to excited carbonyls, while the CL due to singlet oxygen is only observable in the end stage. Skewness and kurtosis are effective parameters to analyze the change in CL intensity spectrum as a function of time.