Thermal stability of nanoclay polypropylene composites by simultaneous DSC and TGA

The thermooxidative and thermal stability of polypropylene nanocomposite with fully exfoliated MMT was studied by simultaneous measurements by DSC and TGA methods in a wide range of temperature. By comparing both the mass loss from TGA and enthalpy changes from DSC in a temperature range from room temperature to 500 degrees C it was possible to identify precisely the specific mechanisms of polymer degradation. In oxygen-free atmosphere the thermal degradation of polypropylene in nanocomposites is strongly inhibited up to the temperature of 420 degrees C in contrast to pristine polypropylene degradation beginning with 300 degrees C. Simultaneous TGA and DSC made possible to show that exfoliated clay platelets modified with alkylammonium salt exhibit a strong stabilizing effect on polypropylene macromolecules in oxygen-free atmosphere. It was further shown that the lower sensibility to thermal oxidation of nanocomposites was correlated with lower oxygen permeability resulting from an increased diffusion path for oxygen as well as for volatile decomposition products. (C) 2007 Elsevier Ltd. All rights reserved.