Rate of thermooxidation and polymer morphology

A model of the thermooxidation of semicrystalline polymers involving two processes simultaneously is described. The first process is initiated by oxygen dissolved in the interspherulitic amorphous pahse. The second is related to a slower rate of polymer chain scission m the interlamellar amorphous pahse, which is controlled by oxygen diffusion into the spherulite. The presented model describes an exampble of isotactic polypropylene and predicts the effect of polymer morphology on the process of thermooxidation. It leads to the conclusion that the initial rate of polymer chain scission depends on the amount of interspherulitic amorphous phase fraction but the slower rate, considered in steady state conditions of oxygen diffussion into the interlamellar amorphous phase, depends depends on spherulite size according to the derived equation.