Research shows that the PIN chemical NiNH4PO4.H2O can reduce flammability and smoke emission from epoxy resin. Three different nano-morphologies of nickel ammonia phosphate (NiAP) were synthesised in a one-step precipitation reaction, then tested in 0 – 7 % loading in epoxy. LOI (limiting oxygen index) was increased from 25% to 35% with 5% NiAP, peak heat release rate (PHRR) is decreased by more than two thirds and smoke production rate is reduced by 22 -34 %. Three morphologies were produced: needles, nanosheets (c 20 -40 µm sheet dimensions x 100 – 300 nm thickness), and agglomerates of the sheets. The authors suggest that the morphology of the NiAP is important, with the nanosheets being most effective as FRs: however, the differences for LOI and PHRR are (very) small, and somewhat larger only for smoke emission. pinfa notes that possible toxicity risk of nickel should be verified before development of such a use.
“Investigation of nickel ammonia phosphate with different morphologies as a new high-efficiency flame retardant for epoxy resin”, W. Zhang et al., High Performance Polymers 2020, 1–12 https://doi.org/10.1177/0954008319867369