The effects of several sulfonates on thermal and fire retardant properties of poly(methyl methacrylate) and polystyrene

Three different sulfonates (sodium diphenylamine-4-sulfonate [SDPAS], 3-(1-pyridino)-1-propane sulfonate [PPS], and ammonium sulfamate) have been melt blended with polystyrene (PS) or poly(methyl methacrylate) (PMMA) and with clay to make composites. All have been examined by X-ray diffraction to determine the morphology, by thermogravimetry to determine thermal stabilities, and by cone calorimetry to evaluate fire retardancy. All three sulfonates enhance the thermal stability of the PMMA composites, and SDPAS achieves the greatest improvement. SDPAS also seems to aid in the dispersion of the clay in the polymer. Combination of sulfonates (5 or 10wt% SDPAS, or 5wt% PPS) with an organically modified clay exhibit enhanced fire retardancy. The three sulfonates did not enhance the thermal stability of the PS composites; however, there is a reduction in the peak heat release rate. The presence of ammonium sulfamate in PS brings about a 52% reduction in the peak heat release rate. The combination of sulfonates (5 or 10wt% PPS, or 10wt% SDPAS) with an organically modified clay provides some fire retardancy to the PS composites.