The kinetic order of decomposition of polymer hydroperoxides assessed by chemiluminescence

In response to critical comments expressed in the preceding paper, the kinetics of the weak chemiluminescence (CL) observed when partially oxidised polypropylene is heated in an inert atmosphere have been re-examined for samples oxidised at the same temperature for different times. It is unequivocally shown that the data for CL decay do not fit first-order kinetics, whether analysed by the integration, initial rate or half-life methods. The data are better fitted by second-order kinetics, though the apparent rate constant depends on the extent of oxidation. The CL decay can be fitted quite well by a second-order model at any given degree of oxidation but the apparent rate constant varies with the degree of oxidation. CL decay and peroxide decomposition can be correlated only by assuming that the emission arises from a fraction of reactive peroxides.