Flame-retarded polystyrene: Investigating chemical interactions between ammonium polyphosphate and MgAl layered double hydroxide

Potential flame retardants, MgAl-LDH and ammonium polyphosphate (APP), were added to neat polystyrene (PS) individually or in combinations at weight fractions no greater than 10%. Structural morphologies of MgAl-LDH and the corresponding PS nanocomposites were established via X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermogravimetric analysis (TGA) and cone calorimetry were used to study the thermal stability and fire performance of the composites. Time to ignition is greatly reduced for PS composites when compared to the virgin polymer. Synergistic effects were observed in both TGA and cone calorimetry for formulations containing both MgAl-LDH and APP. Physical and chemical interactions between MgAl-LDH and APP are responsible for the observed synergy in thermal stability and fire performance.