Thermooxidative degradation of polyolefins in the solid state .3. Heterogeneous oxidation model

A model accounting for heterogeneous thermal oxidation of semicrystalline polymers is proposed. It is based on the spreading of oxidation from preoxidized amorphous domains in the polymer to surrounding amorphous domains not previously touched by oxidation. The corresponding mathematical model explains the kinetics of formation of free hydroperoxides in low density polyethylene samples of various origin. The model describes also the effect of sample thickness on formation of free hydroperoxides in PE-LD. The model can be used to understand the effect of various kinds of initiation. It explains the impact of random initiation in the bulk as well as of initiation in the superficial layers of the samples. (C) 1996 Elsevier Science Limited.