A New Halogen‐Free Flame Retardant Based on 9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide for Epoxy Resins and their Carbon Fiber Composites for the Automotive and Aviation Industries

The pyrolysis and fire behavior of halogen-free flame-retarded DGEBA/DMC, RTM6 and their corresponding 60 vol.-% carbon fibers (CF) composites were investigated. A novel phosphorous compound (DOPI) was used. Its action is dependent on the epoxy matrix. DGEBA/DMC and DOPI decompose independently of each other. Only flame inhibition occurs in the gas phase. RTM6 shows flame inhibition and a condensed phase interaction increasing charring. Both mechanisms decrease with increasing irradiance, whereas in RTM6-CF charring is suppressed at low ones. RTM6 + DOPI shows a higher LOI (34.2%) than DGEBA/ DMC + DOPI and a V-0 classification in UL 94. Adding CF only enhances the LOI, DOPI + CF leads to a superposition in LOI for DGEBA/DMC-CF + DOPI (31.8%, V-0) and a synergism for RTM6-CF + DOPI (47.7%, V-0).