FRs for tomorrow: PIN, bio-based, safe

Materials expert Bob Howell says flame retardants of future will be bio-based organophosphorus, reactive or oligomeric. PIN phosphorus-based FRs are seen as the solution to ensure polymer compatibility and so material performance, fire safety, to avoid toxic and leaching halogenated substances and with accessible costs. Nitrogen PIN FRs can bring fire performance cooperative effects. The most effective P FRs are designed to include phosphorus with low level of oxygenation of the phosphorus and a structure conducive to release the phosphorus radical PO which can contribute to both charring, ensuring solid phase fire protection of the materials, and flame quenching in the gas phase. Sustainable organophosphorus PIN FRs can be produced by combining phosphorus derivates into bio-based compounds such as starch, cellulose, isosorbide (derived from carbohydrates), compounds recovered from wine or food processing. Tomorrow’s phosphorus PIN FRs must also be non-migrating (not leach out of materials) and this can be achieved by either covalent bonding into the polymer matrix (reactive PIN FR) or by developing oligomeric phosphorus PIN FRs (large, often highly branched molecules, which tangle with the polymer matrix preventing migration). Examples are given of innovative research proposing new PIN FR molecules in these directions.

“Flame retardants of the future: biobased, organophosphorus, reactive or oligomeric”, Bob A. Howell, Central Michigan University, USA, Front. Chem. 12:1500782, https://doi.org/10.3389/fchem.2024.1500782