Research shows PIN flame retardant can achieve UL 94 V-0 (3 mm) and 65% smoke reduction at 4% loading in epoxy. The PIN FR was synthetised by reacting furfurylamine (containing N) with Thiophene-2-carbaldehyde (containing S) then DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, containing P) then included into DGEBA epoxy resin at 0, 2 or 4 % w/w loading. This resulted (at 4%) in contents of 0.3% P, 2.82% N and 0.31% S. At 4% loading, the peak heat release rate was reduced by 20% and total smoke production by 60%, achieving UL 94 V-0 (no dripping) and V-1 at 2%. Volatile, hydrocarbon and aromatic compounds in smoke were almost the same between pure epoxy and the PIN FR epoxy. Mechanical performance of the epoxy was improved with the PIN FR addition and optical properties were not deteriorated.
“A P/N/S containing flame retardant for epoxy resins with excellent optical, mechanical and flame retardant properties”, Z. Jiang et al., Polymer Degradation and Stability 225 (2024) 110783 https://doi.org/10.1016/j.polymdegradstab.2024.110783