Thermal degradation auto-oxidation

In many types of degradation the interference of oxidative attack, which has an accelerating role, happens [56, 62-65], i.e., auto-oxidation. However, in oxidative degradation, the most commonly known phenomena are photo-oxidation and thermal oxidation T < 300°C), the effects of which are discoloration, hardening, and surface cracking or flaking. These two phenomena are mainly differentiated by the initiation step, since other aspects are similar. 

The kinetics of oxidative degradation has been developed by Emanuel and Buchachenko [13, 92], Tiidos et al. [115, 121, 141, 148], Shlyapnikov et al. [95, 127, 149], and others [84, 87-91, 133, 150, 151]. The thermal and photochemical degradation of solid PO has traditionally been studied within a kinetic framework developed for the auto-oxidation of liquid hydrocarbons. 

Superposition of mechanical degradation and thermal oxidation is expressed in increased radical concentration as compared with that for pure auto-oxidation. 

Allylic hydroperoxides (3.11) formed from auto-oxidation at low temperatures (50-90 °C) and thermal oxidation during processing (130-190 °C) differ substantially in the rates of decomposition, and initiation of degradation processes ... 

Keywords Auto-oxidation, thermal degradation, radiation, mechanisms, degradation rate, pyrolysis... 

F. Gugumus [21] provides an alternative view of the thermal oxidation reactions in polymers. Various possibilities arising from inter- and intramolecular reactions between hydroperoxide groups, peroxy radicals, and alkoxy radicals are postulated. The author underlines the plausible over-estimation of degradation attributed to -scissions in polypropylene (PP) and offers alternative (non (3-scission) routes that result in formation of 1,2-dioxetane which can account for auto-oxidation, chain scissions and enhanced chemiluminescence of PP oxidation products. An illustration of this proposed scheme is provided in Scheme 6.4. 

---