Combustion and thermal degradation mechanism of a novel intumescent flame retardant for epoxy acrylate containing phosphorus and nitrogen

A novel phosphorus- and nitrogen-containing compound (POPHA) has been synthesized by allowing phosphorus oxychloride to react with piperazine and 2-hydroxyethyl acrylate (HEA). Its structure was characterized by FTIR, ¹H NMR, and ³¹P NMR. A series of UV-curable flame-retardant resins were obtained by blending POPHA with EA in different ratios. The flame-retardant properties were characterized by the limiting oxygen index (LOI) and microscale combustion calorimeter (MCC). The results showed that the incorporation of POPHA into EA can improve the flame retardancy of EA dramatically. The thermal properties of the resins were investigated by thermogravimetric analysis (TGA) in air atmosphere. Moreover, the thermal degradation mechanisms of the EA/POPHA were investigated by real-time Fourier transform infrared spectra (RTIR), thermogravimetric analysis/infrared spectrometry (TG-IR), and direct pyrolysis/mass (DP-MS). The morphologies of the formed chars were observed by scanning electron microscopy (SEM) demonstrating the most effective amount of POPHA is 20 wt %. © 2011 American Chemical Society.