The photo-oxidation of polypropylene/montmorillonite nanocomposites has been studied under irradiation at long wavelengths (λ > 300 nm) at 60 °C and in the presence of oxygen. The chemical modifications resulting from photo-oxidation were followed by IR and UVvisible spectroscopies for each component of these nanocomposites polypropylene (PP), organomodified montmorillonite (MMt), and the compatibilizing agent (maleic anhydride-graftedpolypropylene). We have found that the mechanism of photo-oxidation of the polypropylene component was not modified in the polymer-nanocomposite, but that the rates of oxidation were modified, leading to an unexpected decrease of the durability of the material.

The influence of stabilizing additives on the photooxidation of polypropylene/montmorillonite (PP/ MMt) nanocomposites exposed to UV light was studied. Two different stabilizers were used, a phenolic antioxidant and a redox antioxidant. A significant reduction in the induction period of oxidation was observed in the presence of MMt. This is believed to arise from interactions between the additives and the nanoclay. The interactions could involve the adsorption of additives onto the clay, the degradation of the alkylammonium cations exchanged in MMt, and the catalytic effect of iron impurities of the organomontmorillonite. Iron could catalyze the decomposition of the primary hydroperoxides formed by photooxidation of PP, which would in turn accelerate the additive consumption and decrease the length of the period before the permanent regime of oxidation is reached.