A piperazine – phytic acid compound showed to be an effective PIN FR in epoxy, passing UL 94 V-0 and reducing smoke. Phytic acid, a natural molecule with high P content which is widely present in plant seeds, was reacted in ethanol with piperazine, which contains nitrogen, and was then dispersed in epoxy resin before curing. At 15% loading, the P-N PIN FR enabled epoxy to achieve UL 94 V-0 (3 mm), increased LOI from 24% to 36% and decreased PHRR (peak heat release rate) by over 50%. Total smoke release was reduced by 45% and carbon monoxide release by 30%. Mechanical properties of the epoxy resin were somewhat reduced (e.g. tensile strength -14%). The authors conclude that the P-N FR acts by forming resistant, compact char and that this bio-based PIN flame retardant is economically viable and simple to synthesise.
“Synthesis of a bio-based piperazine phytate flame retardant for epoxy resin with improved flame retardancy and smoke suppression”, Z. Huang & Z. Wang, Polym Adv Technol. 2021;1–14, https://dx.doi.org/10.1002/pat.5429