I ~~ R I -CHz-C-CH-CH z- I I \/ 0 0 0 I .
Initiation step: formation of free radicals. 2. Propagation step: reaction of free polymer radicals with oxygen, production of polymer oxy- and peroxy-radicals and secondary polymer radicals, resulting in chain scission. 3. Termination step: reaction of different free radicals with each other, resulting in crosslinking. 6) General mechanism of photo-oxidative degradation 25 po; + PH ~ p. + HO; + p. 7) HO; + PH ~ H· + HO; + p. 8) PO; ~ p. 9) PO· 2 H + CH =CH- + ·OH ~ _C/ ~O 2 (POOH). + PH ~ P=O + H 2 0 + PH (POOH)!