KINETIC-STUDY OF THE THERMAL-OXIDATION OF POLYPROPYLENE

The thermal oxidation of non-stabilized isotactic polypropylene was st udied in air at 80, 90, 100 and 150 degrees C using gravimetric and IR spectrophotometric determinations (hydroxyls and carbonyls). A kineti c model in which radical production results only from unimolecular hyd roperoxide decomposition was developed. This model predicts that: the induction time depends only on the rate constant of hydroperoxide deco mposition. It must be almost independent of the polypropylene source ( for low content of catalytic impurities and low initial hydroperoxide concentration) and its apparent activation energy must be about 100 kJ mol(-1); the induction times relative to, respectively, weight, carbo nyl and hydroxyl gain must be in the ratio 2:3:3; 'the steady state' o xidation rate must be independent of initiation rate constant. The exp erimental data on oxidation kinetics in the temperature range under st udy confirm all these predictions. (C) 1997 Elsevier Science Limited.