Synthesis of a new flame retardant and performance study of flame retardant epoxy resin

This paper aims to study a new halogen-free flame-retardant curing agent, 6,6'-(1,5-bis((4-(4-aminobenzyl)phenyl)amino)pentane-1,5-diyl)bis(dibenzo-oxaphosphinine 6-oxide) (DOPO-DMG). The DOPO-DMG was synthesized using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 4,4-Diaminodiphenyl methane (DDM), and glutaric dialdehyde as raw materials in this paper. The chemical structures of DMG and DOPO-DMG were characterized by 1H NMR and FTIR. The results showed that the DOPO -DMG was successfully prepared. The thermal stability, mechanical and flame properties, as well as the morphology of the char layer in composite materials were investigated separately using TG (Thermogravimetric analysis), tensile and Charpy impact tests, LOI (Limiting Oxygen Index) and UL-94 (UL-94 HB flammability standard), and SEM (scanning electron microscope). When IFR (Intumescent Flame Retardants) was added to the EP, the LOI of the composite material improved. DOPO-DMG exhibited excellent flame-retardant properties and produced no toxic fumes when burned in case of fire. Under optimal conditions, it was found that adding DOPO-DMG with a phosphorus content of 2.01% to the epoxy resin resulted in an LOI of 28.8, UL 94 rating of V-0, tensile strength of 39.1 MPa, impact strength of 5.2 KJ/m2 respectively, and a char yield at 800°C of 25.63%. © The Author(s) 2024.