Review of flame retardants for PU foam

Most new developments and research into flame retardants for flexible PU foams are PIN. Performance challenges remain. Flexible PU (polyurethane) foams are widely used in furniture, transport seats, anti-vibration and packaging materials, but are highly flammable (high heat release, toxic smoke). FRs most widely used to improve fire safety today include chlorinated compounds (TCEP, TCPP, TDCPP) but solutions are today available using inorganic or organic phosphorus PIN FRs, nitrogen-based FRs and PIN minerals such as nanoclays or expanded graphite. Coating of inorganic PIN FRs can improve their compatibility with polyurethane, so processing and foam characteristics. Fire performance achievable with some 60 different FRs and combinations of FRs is indicated. Reactive FRs are available, and offer durability and stability, but the polymerisation reactions of their inclusion are complicated. Surface coating methods are presented, offering the advantage of not deteriorating foam characteristics, but often limited durability. The authors suggest that future FR development should focus on FR mechanism synergies, impacts on foam characteristics, foam compatibility and selection of compounds which are safe, environmentally friendly and recyclable.

TCEP = tris 2-cloropropyl phosphate. TCPP = tris(2-chloropropyl) phosphate. TDCPP = tris(1,3- dichloro-2-propyl) phosphate (TDCPP) are typical chlorine-containing phosphate ester flame retardants [31].

“Progress of flame retardant research on flexible polyurethane foam”, C. Shen et al., European Polymer Journal 220 (2024) 113478 https://doi.org/10.1016/j.eurpolymj.2024.113478