The organophosphorus PIN FR DOPO-diamine was reacted into PLA and polyurethane, achieving UL94-V0 @ 0.8 mm. Tests covered simple addition of DOPO diamine (DOPOd) to PLA (poly lactic acid), DOPOd reacted into PLA at c. 2:5 ratio and a PLA-PU (polyurethane) polymer obtained by combining this DOPd-PLA with hexamethyl diisocyanurate. This DOPOd(PLA-PU polymer had 4% phosphorus, enabled extrusion of transparent film and achieved UL94-VO @ 0.8 mm. On the other hand, DOPOd simply added to PLA (not reacted) did not improve fire performance. The authors indicate that further work is needed to clarify the FR effect of DOPOd reacted into PLA only compared PLA-PU.
“Development of Inherently Flame-Retardant Phosphorylated PLA by Combination of Ring-Opening Polymerization and Reactive Extrusion”, R. Mincheva et al., Materials 2020, 13, 13; http://dx.doi.org/10.3390/ma13010013