Flame retardancy and thermal properties of solid bisphenol A bis(diphenyl phosphate) combined with montmorillonite in polycarbonate

A series of flame retardant formulations of solid bisphenol A bis(diphenyl phosphate) (S-BDP) and organo-montmorillonite (OMMT) were prepared based on polycarbonate (PC) by a melt compounding procedure. OMMT was well dispersed into the matrix showing an intercalated-exfoliated morphology. S-BDP and OMMT exhibit a synergistic effect in the vertical burning test (UL-94) but an antagonistic effect in the limiting oxygen index (LOI) evaluation. Thermogravimetric analysis (TGA) of the flame retarded PC system both under nitrogen and air was performed. Migration of S-BDP and OMMT towards the surface occurs during combustion. The introduction of OMMT could especially enhance the thermal-oxidative stability of the material, which is further confirmed by the analysis of the char residues by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).