The catalytic role of oxide in the thermooxidative degradation of poly(methyl methacrylate)-TiO2 nanocomposites

The influence of TiO2 nanoparticles on the thermal degradation of poly(methyl methacrylate) (PMMA) was investigated by TGA. The studied materials were characterized by Py-GC-MS, TEM, SEM, TGA, DSC and TGA-MS. The PMMA-TiO2 nanocomposites were prepared by melt blending with different (5, 10, 15 and 20 wt% TiO2) loadings. According to TGA results and to the activation energy (determined by the model-free isoconversional method of Vyazovkin), the incorporation of 5 wt% of TiO2 nanoparticles into PMMA stabilizes it by more than 40 °C. However, for higher loading contents, a catalytic effect on the thermal decomposition was observed which increased with the oxide content. The results obtained by Py-GC-MS showed clearly that TiO2 increases the formation of methanol, methacrylic acid and propanoic acid methyl ester during the degradation of PMMA. This catalytic effect could be explained through the interaction of the methoxy group of the methacrylate function with the hydroxyl groups present at the surface of the oxide particles.