Study on flame retardant properties of epoxy composites using circular economy material hydroxyapatite combined with DOPO-HQ

In this study, hydroxyapatite (HA) was extracted from biological waste. HA was modified by N,N-diglycidylaniline (NDY) and DOPO-HQ to obtain the flame retardant which was added to epoxy resin (EP) to prepare the composite. The flame retardancy of the composites was measured by the horizontal and vertical combustion tester (UL-94) and the limiting oxygen index (LOI), the thermal property was carried out by the thermogravimetric analyzer (TGA), and the surface morphology was observed by the field emission scanning electron microscope (SEM). The UL-94 grade of pure EP is a fail grade, and the LOI value was 22%. After adding HA-NDY-DOPOHQ (weight ratio 1:2:1) 40[Formula: see text]wt.% flame retardant, the UL-94 grade of the composites was raised to V-1, and the LOI value promoted to 28%, a total increase of 6%. Composite materials had excellent thermal stability and flame retardancy and could be used in fireproof panels for energy storage systems to prevent thermal runaway, and could also be used in building materials.