Influence of a treated kaolinite on the thermal degradation and flame retardancy of poly(methyl methacrylate)

Modified kaolinite poly(methyl methacrylate) nanocomposites were prepared using successively in situ polymerization and melt blending methods. Pristine kaolinite (Kaol) was intercalated using two organic molecules dimethyl sulfoxide (DMSO) and dodecylamine. This treated kaolinite (TKaol) was exfoliated via in situ polymerization of MMA. The prepared blends were extruded with a commercially available PMMA and then injection molded. The thermal degradation and flammability of TKaol PMMA nanocomposites was compared to pure PMMA and also to PMMA nanocomposites filled with untreated Kaol. Results showed the influence of Kaol morphology on fire behavior of these nanocomposites. The use of exfoliated Kaol allowed a better thermal stability to be achieved and the decrease of peak heat release rate (PHRR) as revealed by the cone calorimeter tests. Moreover, TKaol PMMA nanocomposite enabled to maintain time to ignition close to that of PMMA while it was largely reduced with PMMA nanocomposites filled with untreated Kaol. Finally, exfoliated Kaol led to an efficient barrier effect due to the formation of a cohesive residue as highlighted by its mechanical strength.

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► TGA test showed the stabilization effect of treated kaolin.
► Exfoliation of kaolin does not promote the charring of PMMA.
► During combustion treated kaolin platelets do not re-aggregate.
► Kaolin is not as efficient as MMT for improving the flammability of PMMA.