Effect of compatibilizer and Irganox MD 1024 on the thermo-oxidative stability of PP/PP-g-MA/OMMT nanocomposites

The thermo-oxidative stability of polymeric materials reinforced with mineral fillers, such as clays, may be lower than that of pristine polymers, due to the presence of metallic ions and compatibilizing agents. In this paper, an effort was made to understand the influence that a compatibilizing agent and a metal deactivator bonded to a primary stabilizer has on the thermal stability of polypropylene/polypropylene-grafted maleic anhydride/organic montmorillonite (PP/PP-g-MA/OMMT) nanocomposites. At the first stage of this work, the organically modified montmorillonite clay is chemically analyzed by Inductively Coupled Plasma Atomic Emission Spectrometry to quantify the metals present in the clay. TGA, DSC, OIT, and dynamic OIT were used to assess the degradation of the nanocomposites. The results showed that the use of compatibilizing agents has a positive effect on the stability of nanocomposites in the initial steps of degradation, but has a degradative effect at higher temperatures, as indicated by the decreasing T_max for compatibilized nanocomposites. In relation to Irganox MD 1024, an increase in all the parameters for assessing the stability of nanocomposites was observed; however, the most significant change was the delay in the temperature at which the occurrence of exothermal reactions begins. Use of this additive is responsible for delaying the beginning of the exothermic reaction until a higher temperature, as a function of its concentration, as well the differences between the beginning of volatile release and the exothermal reactions. Also was discussed the influence of Irganox MD1024 concentration on T_max, and the difference of temperature between the beginning of heat releasing and the initial weight loss, which decreases as the stabilizer concentration is increased. Thanks to the association of dynamic OIT and TGA results from experiments performed with identical conditions. This complementary use of these techniques is a powerful tool for assessing the stability in the polymeric system.