When polymers are oxidized, unstable alkyl radicals are formed which react further with oxygen to form peroxy bonds. The excitation and stabilization of the peroxy radical causes chemiluminescence. The light produced by this reaction is typically low wavelength infrared light. The amount of light emitted is used to determine the oxidation rate of an adhesive. 
Chemiluminescence (CL) light intensity can be measured at various isothermal oxidation cycles; however, the temperature need not be raised to high levels. Correlation of light intensity is made to oxidation process parameters such as Oxidation Induction Temperature (OIT). By obtaining measurements at different temperatures, an accelerated oxidation progression correlation can be established. The prediction of oxidation during service life can then be carried out.