P-functionalised polyethyleneimine with iron salt achieved UL 94 V-0 in epoxy and improved mechanical properties. The commercial nitrogen containing polymer polyethylenimine (PEI) was reacted with phosphoric acid, then combined with ferric (Fe3+) salt, giving an iron – phosphorus – nitrogen polymeric PIN FR (PEIP-Fe). At 3% loading in DGEBA epoxy, UL 94 fire performance was improved from NR to V-0 with no dripping (3 mm). LOI was increased from 25.6 to 27.8, peak heat release rate was reduced by nearly 50%, peak smoke production by 20%. Impact, tensile and flexural strength of the epoxy were improved. Fire performance improvement was considered to be the result of compact and continuous char generation (catalysis of charring and of cross linking) and of gas phase action (P., PO.). Mechanical benefits are considered to be related to intermolecular cavities, active amino groups and chelating effects in the epoxy.
“Simultaneously improving the fire safety and mechanical properties of epoxy resin with iron phosphonated grafted polyethylenimine”, X-H. Shi et al., Polymer Degradation and Stability 206 (2022) 110173 https://doi.org/10.1016/j.polymdegradstab.2022.110173