Highly Flame-Retarded Epoxy Thermoset Imparted by Bio-Based Phosphorus/Nitrogen-Containing Furan Derivative with Enhanced Mechanical Toughness

A bio-based phosphorus/nitrogen-containing furan derivative, 6,6′′,6′′′-((((1,3,5-triazine-2,4,6-triyl) tris(oxy))tris(benzene-4,1-diyl))tris(((furan-2-ylmethyl) amino)methylene)) tris(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (TFAD) is successfully synthesized and characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The introduction of TFAD clearly lowers the activation energy for diglycidyl ether of a bisphenol A (DGEBA)/4,4′-diaminodiphenyl methane (DDM) system. The DGEBA/DDM/ TFAD thermoset achieves UL-94 V-0 rating and possesses a limiting oxygen index (LOI) of 30.1% as the content of phosphorus is up to 0.41 wt.%. Further, compared with unmodified epoxy thermoset, its peak heat release rate and total heat release experience 42.0% and 14.8% decrement, respectively. The flame-retardant mechanism analysis confirms that TFAD exerts a fire-retardant effect in both gaseous and condensed phases. Meanwhile, the impact strength of the flame-retardant thermoset is enhanced by 35.6%, from 19.5 kJ m –2 for EP-0 to 26.5 kJ m –2 . This work provides a novel strategy to construct superior flame-retarded epoxy thermosets with admirable impact performance.