Branched oligomeric PIN FR shows flame retardant and smoke suppression, smoke toxicity reduction in epoxy. The synthesised aluminium branched oligo(phenylphosphonate) (AHPP) had average molecular weight of 2 100 g/mol and oligomeric structure. This was blended into DGEBA before curing of epoxy at 2.5 – 7.5% With AHPP at 7.5% loading UL 94 v-0 (3 mm) was achieved, peak heat release was reduced by nearly 70% and LOI was increased from 23.5% to 30%. Smoke density was considerably reduced for the first 15+ minutes of combustion, total smoke yield was significantly reduced, as were toxic emissions (HCN, NOx, carbon monoxide). Smoke reduction is considered to result from catalytic carbonisation of the polymers and formation of aluminium oxide layers on the surface of char residues.
“Facile synthesis of aluminum branched oligo(phenylphosphonate) submicroparticles with enhanced flame retardance and smoke toxicity suppression for epoxy resin composites”, Y. Yuan et al., Journal of Hazardous Materials 381 (2020) 121233 https://doi.org/10.1016/j.jhazmat.2019.121233