Fire properties of polystyrene-clay nanocomposites

Polystyrene-clay nanocomposites have been prepared using a bulk polymerizat ion technique. Three new "onium" salts have been used to prepare the nanoco mposites, two are functionalized ammonium salts while the third is a phosph onium salt. By TGA/FTIR, both ammonium and phosphonium treatments have been shown to degrade by a Hofmann elimination mechanism at elevated temperatur es. TGA/FTIR showed that the phosphonium treatment is the most thermally st able treatment when compared to the two ammonium salts. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, strength and elongation at break, as a measure of the mechanical properties , thermogravimetric analysis, and cone calorimetry. The onset temperature o f the degradation is increased by about 50 degreesC and the peak heat relea se rate is reduced by 27-58%, depending upon the amount of clay that is pre sent. The mass loss rates are also significantly reduced in the presence of the clay.