Thermo-oxidation of isotactic polypropylene in O-32(2)-O-36(2): comparisonof the mechanisms of thermo- and photo-oxidation

The formation of gaseous products resulting from thermo-oxidation of isotac tic polypropylene (iPP) at 95 and 140 degreesC in an atmosphere composed of a blend of O-32(2) and O-36(2) has been investigated using mass spectrosco py (MS). In contrast to the results obtained previously in the case of phot ochemical oxidation, MS analysis shows that thermo-oxidation does not gener ate O-34(2). A possible interpretation is that, in thermo-oxidation, the me chanism involving the recombination of peroxy radicals POO. occurs only wit h a very low probability. As a consequence, it is suggested that, in thermo -oxidation conditions, the main pathway of oxidation involves the formation of hydroperoxides and not recombination of peroxy radicals as proposed in photo-oxidative conditions. (C) 2001 EIsevier Science Ltd. All rights reser ved.