A novel intumescent flame retardant imparts high flame retardancy to epoxy resin

Intumescent flame retardant (IFR) has received the considerable attention ascribed to the inherent advantages including non-halogen, low toxicity, low smoke release and environmentally friendly. In this work, a novel charring agent poly (piperazine phenylaminophosphamide) named as PPTA was successfully synthesized and characterized by Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS). Then, a series of flame-retardant EP samples were prepared by blending with ammonium polyphosphate (APP) and PPTA. Combustion tests include oxygen Index (LOI), vertical Burning Test (UL-94) and cone calorimeter testing，these test results showed that PPTA greatly enhances the flame retardancy of EP/APP. According to detailed results, EP containing 10 wt% APP had a LOI value of 30.2%，but had no enhancement on UL-94 rating. However, after both 7.5 wt% APP and 2.5 wt% PPTA were added, EP-7 passed UL-94 V-0 rating with a LOI value of 33.0%. Moreover, the peak heat release rate (PHRR) and peak of smoke product rate (PSPR) of EP-7 were greatly decreased. Meanwhile, the flame-retardant mechanism of EP-7 was investigated by scanning electron microscopy (SEM), thermogravimetric analysis/infrared spectrometry (TG-IR) and X-ray photoelectron spectroscopy (XPS). The corresponding results presented PPTA significantly increased the density of char layer, resulting in the good flame retardancy.