Localization of oxidation in polypropylene

We review some of the available evidence to suggest that the oxidation of polypropylene is not a homogeneous process but is localised at several levels. Optical microscopy of oxidised polymer shows regions of high oxidation on the micron scale, sometimes associated with uneven distribution of catalyst residues. Atactic polymer is shown to oxidise more rapidly than isotactic and to be redistributed in the isotactic polymer during melt crystallization. Atactic polymer is shown by GPC to undergo random scission with the formation of terminal carbonyl groups; in contrast, the oxidation of isotactic polymers is non‐random. Finally, evidence is discussed to show that both the initiation of oxidation by peroxide decomposition and its termination by radical recombination follow complex kinetics.