Use of oxide nanoparticles and organoclays to improve thermal stability and fire retardancy of poly(methyl methacrylate)

Nanocomposites of PMMA-oxide (oxide: nanoparticles of TiO2 or Fe2O3), PMMA-organoclays (organomodified montmorillonite: OMMT) and PMMA-oxide-OMMT were prepared by melt blending with different additive contents. These nanocomposites were studied by thermogravimetric analysis (TGA) and cone calorimetry. The experimental results obtained by TGA show that TiO2 and Fe2O3 nanoparticles improve the thermal stability of PMMA by about 50 °C from 5 wt% of fillers. Cone calorimeter measurements show that the peak of heat release rate is lowered in the presence of oxide nanoparticles in comparison to pure PMMA and that this decrease is higher when the filler content increases. The time to ignition increases in the case of TiO2, but remains constant for Fe2O3. A synergistic effect was also found by the combination of TiO2 and organoclays resulting mainly in an increase of the ignition time and the reinforcement of the barrier effect of the organoclays. A possible mechanism of improvement of the thermal stability and fire retardant properties of PMMA mixed with TiO2, Fe2O3, OMMT and oxide-OMMT is discussed.