Trifluoromethyl-containing phthalonitrile modified epoxy thermoset with improved flame retardancy and thermal stability

The phthalonitrile monomer (AFPN) containing trifluoromethyl was prepared and blended with the widely used bisphenol A diglycidyl ether (DGEBF)/diaminodiphenyl sulfone (DDS) system to prepare a series of thermosets. The incorporation of AFPN endowed the thermoset with obviously promoted thermal stability and flame retardancy. The glass transition temperature (T g ) and char yield at 800 °C in N 2 were 161 °C and 18.1 % respectively for the pure EP/DDS (EP0) which increased to 203 °C and 32.3 % for the thermoset containing 30 wt.% AFPN (EP/AF30). The detailed study on the mechanism of pyrolysis and flame retardancy was presented. The formation of graphite-like nitrogen-containing structure and •CF 3 free radicals during combustion in the solid phase and gaseous phase, respectively, was confirmed. It was confirmed that there was synergistic effect of phthalonitrile and trifluoromethyl on the flame retardancy of the thermoset. Moreover, the dielectric constant decreased from 2.39 to 1.45 at 1 MHz which is favorable for the application as low dielectric materials.