Synthesis of a bio-based piperazine phytate flame retardant for epoxy resin with improved flame retardancy and smoke suppression

Piperazine phytate (PIPT), a bio-based nitrogen-phosphorus containing flame retardant, was feasibly synthesized by the reaction of piperazine (PI) with phytic acid (PA) in ethanol. The structure and chemical composition of PIPT were systematically characterized by NMR, FTIR, XRD, TEM and EDX. Epoxy resin (EP) composites with PIPT were prepared by utilizing 4, 4 '-diaminodiphenylmethane as a curing agent. The flame retardancy, mechanical performances and thermal decomposition of the EP composites were studied. The results show that the EP composite containing 15 wt% PIPT (sample EP/15PIPT) passes UL-94 V0 rating with a limiting oxygen index reaching 35.5%. The cone calorimetric tests results demonstrate the peak heat release rate and total smoke release of EP/15PIPT are about 51.4% and 44.9% reduced than which of pure EP, respectively. The morphology of residual char reveals that the EP/ PIPT composites can form good and compact char during the combustion. In comparison with pure EP, the mechanical performances of the EP/PIPT composites decrease slightly as PIPT content increases.