OIT tests (Oxidative-induction time) are well-known for evaluating the oxidative resistance of polymers, in particular polyolefins.
In this example, two PP samples were heated to 200°C under a dynamic nitrogen atmosphere. The endothermic peak detected during heating illustrates the melting of the polypropylene. After 3 minutes at 200°C, the gas was switched to air. The resulting exothermic effect indicates the polymer degradation.
In the present case, oxidation occurs earlier for sample A than for sample B (OIT 6.6 min vs. 11.6 min).