P/N synergistic integrated flame retardants with instant cross-linking at high-temperature for flame retardancy and impact resistance of epoxy resins

Abstract

With the development of flame retardant technology, intumescent flame retardant (IFR) systems, and instant cross-linking in case of fire have become important directions for epoxy resin (EP) flame retardancy. A carbonized matrix containing a benzoxazine structure was constructed with the triazine structure, and the integrated flame retardant (TRBPO) was constructed by introducing the phosphorus source through a partial ring-opening reaction. It can maintain its structural characteristics during the curing process of EP. When EP materials are exposed to fire, TRBPO will cross-link in the EP matrix and work as the P/N synergistic IFR system to achieve excellent flame retardancy. The results showed that 5 wt% of TRBPO could make EP composites reach UL-94 rating of V-0 with a PHRR of 303.7 kW/m2, and the TSP and TSR were reduced by 48.5 % and 48.9 %, respectively, compared with pure EP. The introduction of TRBPO has a impact resistance effect on EP, and its excellent stress dispersion effect made the impact strength of 5-TRBPO/EP reached 36.49 KJ/m2. The analysis of the flame retardant mechanism proved that the rapid carbon formation function of IFR and the self-crosslinking flame retardancy of TRBPO in the fire are the main reasons for flame retardancy. In addition, the capture of flammable groups in the gas phase is an important source of flame retardant effect.