Comparison of Flame-retardancy Property and Mechanism between a Phosphate Ester and a Phosphoramine Flame-retardants

Abstract

A halogen-free flame-retardant (hydroquinone bis (N, N’-diarylphosphoramidate), 4N-HDP) containing phosphorus-nitrogen was synthesized. Its structure was characterized by infrared spectroscopy (IR), nuclear magnetic resonance (¹H-NMR and ³¹P-NMR). Thermogravimetric analysis (TG), limiting oxygen index (LOI), UL-94 vertical burning test (UL-94), thermogravimetric-infrared instrument (TG-IR) and scanning electron microscopy (SEM) were used to compare the flame-retarding performance and mechanism of hydroquinone bis (diphenyl phosphate) (HDP) and 4N-HDP. TG, IR and TG-IR were used for comparative analysis, indicating that both HDP and 4N-HDP are flame-retardants, and the gas phase and condensed phase act synergistically. In the pyrolysis process, it is divided into two steps: the first step is the breakage of large molecules to small molecules; the second step is the gasification and carbonization of small molecules, and eventually produces phosphate ester and non-flammable gases. Through the comparison of various results, it could be found that 4N-HDP has better flame-retarding performance compared to HDP in the composite with polycarbonate (PC).

Keywords

flame-retardant / phosphoramine / thermogravimetric analysis / polycarbonates / TG-IR