Fire properties of polystyrene-clay nanocomposites

Polystyrene-clay nanocomposites have been prepared using a bulk polymerization technique. Three new onium salts have been used to prepare the nanocomposites, two are functionalized ammonium salts while the third is a phosphonium salt. By TGA/FTIR, both ammonium and phosphonium treatments have been shown to degrade by a Hofmann elimination mechanism at elevated temperatures. TGA/FTIR showed that the phosphonium treatment is the most thermally stable 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 of the degradation is increased by about 50 degreesC and the peak heat release rate is reduced by 27-58%, depending upon the amount of clay that is present. The mass loss rates are also significantly reduced in the presence of the clay.