Thermal Analysis of Polymer-Clay Nanocomposites

In Section 3.2.2, data were presented which show that char formation, possibly from a catalytic reaction between the polymer (PS, PA6, or a polymer compati-bilizer, PP-g-MA) and the clay, is often present when low peak HRRs (or mass loss rates) are observed. However, data were also presented which show that in the absence of any substantial charring there can still be a 50 to 60% reduction in peak HRRs if synthetic mica is used in PP/PP-g-MA nanocomposites. It appears that at least two mechanisms may be important to the function of nanocomposites one involving char formation and a second involving the inorganic residue alone. This dual mechanism may explain why the effectiveness of clay nanocomposites varies from polymer to polymer. 

In an effort to fashion a unified mechanism for clay nanocomposites, Wilkie et al. have studied the effect that clay has on the thermal degradation behavior of more than 11 different polymers. This work also attempts to correlate the thermal analysis data with flammability properties measured in a cone calorimeter. In this work TGA degradation products were cryogenically trapped and analyzed using gas chromatography/mass spectroscopy (GC-MS) the thermal degradation pathways of the polymers with and without clay were investigated. Wilkie 

FLAME RETARDANT MECHANISM OF POLYMER-CLAY NANOCOMPOSITES 

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