Two DOPO-based phosphonamidates were synthesised (by Atherton-Todd reaction) and tested as PIN flame retardants in epoxy resin (80% DGEBA – 20% DDM). Loadings of 2.5% DDM-DOPO (total loading 0.25% phosphorus) or 5% MPL-DOPO (0.52%P) increased LOI from 26 (pure epoxy) to 30 – 31 and achieved UL94-V0 (3mm) compared to no rating for pure epoxy. Cone calorimeter tests show that lower emissions of hydrocarbons, aromatic compounds and ethers from the phosphorus PIN FR epoxy and significantly lower smoke production (TSP), up to 16.5% lower than pure epoxy. Analysis data leads to conclude that these DOPO-based phosphonamidates show a significant gas-phase flame retardant effect.
DOPO = 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The two phoshonamidate derivates studied: 4,4’-diamino-diphenyl methane (DDM)-DOPO and morpholine (MPL)-DOPO
“Two high-efficient DOPO-based phosphonamidate flame retardants for transparent epoxy resin”, P. Wang et al., High Performance Polymers 1–12, DOI: https://doi.org/10.1177/0954008318762037