Experimental reactive PIN FR improves mechanical and fire performance of epoxy resin. DOPO (phosphorus) and triethylamine (nitrogen) were reacted with silane (silicon) to generate an N-P-phenylsiloxane macromolecule (PD-PPD) which could be reacted into DGEBA epoxy resin. PD-PPD was tested at 0 – 9 % w/w in epoxy (i.e. up to 0.3% phosphorus). Impact strength, flexural strength and flexural modulus were increased 100%, 13% and 39% with the 9% DP-PPD loading, and peak heat release rate was reduced by 31% and smoke release by 20%. At 3 mm, the neat resin failed UL-94 whereas IL94-V0 was achieved with 3% or more DP-PPD. The authors consider that the flexible phenylsiloxane units reacting into the epoxy resin improve mechanical properties and that the fire performance is improved by a combination of catalysis of charring, reduction of volatile organic compounds emissions in fire and flame inhibition by phosphorus.
“High strength, low flammability, and smoke suppression for epoxy thermoset enabled by a low-loading phosphorus-nitrogen-silicon compound”, W. Rao et al., Composites Part B 211 (2021) 108640 https://doi.org/10.1016/j.compositesb.2021.108640