Quick answer: Flame retardant polyurethane foam is formulated at the moment the foam is made, not afterward — the flame retardant goes into the liquid isocyanate/polyol mix before it reacts and expands, not compounded into a solid resin like every other material on this site. The industry workhorse for decades has been TCPP, a chlorinated organophosphate liquid, but it’s a non-reactive additive that can migrate out of the foam, and it’s now under REACH substance evaluation. The replacements moving in are reactive phosphorus chemistries that bond into the polymer network, plus melamine and ATH as supporting additives.
“Flame retardant polyurethane” gets confused with “flame retardant TPU” constantly, and they are not the same conversation. TPU is a thermoplastic elastomer — pellets, melted, extruded or molded, flame retardant compounded in like any other plastic (we cover that on our flame retardant TPU page). PU foam is a thermoset: isocyanate and polyol react and expand in real time, in a mold or on a production line, and whatever additive is going to make it fire-safe has to already be dissolved in that liquid mix before the reaction starts. Once it foams and cures, there’s no melting it again to add anything.
Flexible vs rigid: two different foams, two different FR jobs
| Foam type | Typical use | Common FR route |
|---|---|---|
| Flexible foam | Furniture, mattresses, seating | Liquid TCPP, melamine powder for smoke |
| Rigid foam | Insulation boards, spray foam, refrigeration | TCPP, or ATH where filler loading is tolerable |
Why TCPP is under pressure
TCPP — tris(chloropropyl) phosphate — became the industry default because it’s liquid, miscible with the polyol stream, and cheap per kilogram of fire performance. The problem is built into that convenience: TCPP is non-reactive, meaning it sits physically dissolved in the cured foam rather than chemically bonded into it, and it can migrate out over the product’s life — into dust, into the air, into people. It’s currently under REACH substance evaluation in the EU, and its relative TDCP already carries tighter restriction in some consumer-facing markets, particularly furniture. Neither is banned outright as of 2026, but the regulatory direction is the same one-way trend we’ve tracked on other legacy flame retardants across this site.
What’s replacing it
Three directions, each with a different trade-off:
- Reactive phosphorus chemistries. Instead of dissolving in the mix, these bond into the polyurethane network as it forms — the same reactive-vs-additive logic we cover for flame retardant epoxy. Once bonded, it can’t migrate out, which is the whole point.
- Melamine. A nitrogen-based additive, common in flexible furniture foam specifically for its smoke-suppression contribution alongside a phosphorus component — the same nitrogen mechanism (heat absorption, inert gas dilution) behind the melamine cyanurate chemistry we supply for plastics, though the foam-grade material itself is a different formulation.
- ATH. Works in rigid foam where the density budget tolerates mineral loading — the same endothermic mechanism as our MDH & ATH line, dosed differently for a cellular structure than for a solid cable jacket.
None of these three is a drop-in swap for TCPP at the same phr — foam formulators re-balance the whole system (catalyst, surfactant, blowing agent) around whichever route they pick, which is part of why TCPP has stayed dominant despite the regulatory pressure: reformulating a qualified foam system is not a small project.
Where Rectivas fits — and where it doesn’t
Straight answer: PU foam formulation happens at the point of reaction — isocyanate, polyol, catalyst, blowing agent and flame retardant all measured and mixed by the foam producer in one shot. That is a different supply chain from our business, which is compounding flame retardant into solid thermoplastic resin and masterbatch after the fact. We don’t supply liquid TCPP-type foam additives. If your project is actually a thermoplastic elastomer part rather than a reacted foam — door seals, cable jacketing, footwear components — that’s flame retardant TPU territory, and that one we do supply. Worth double-checking which material your part actually is before sourcing.
Request a quote if your part turns out to be TPU, or if you need the ATH/mineral filler component for a rigid foam project on the compounding side.
FAQ
Is flame retardant polyurethane foam the same as flame retardant TPU?
No. PU foam is a thermoset made by reacting isocyanate and polyol in real time, with the flame retardant added to the liquid mix before it cures. TPU is a thermoplastic elastomer, melted and compounded like any other plastic, with the flame retardant added during that compounding step. Different chemistry, different supply chain.
What flame retardant is used in polyurethane foam?
Historically TCPP (tris(chloropropyl) phosphate), a liquid chlorinated organophosphate mixed into the reacting foam. It’s now facing regulatory pressure under EU REACH, and reactive phosphorus chemistries, melamine, and ATH are increasingly used as replacements or supplements.
Is TCPP banned in polyurethane foam?
Not as of 2026, but it is under REACH substance evaluation in the EU, and its relative TDCP already carries tighter restrictions in some consumer-facing markets, particularly furniture. The direction is toward reactive, non-migrating alternatives.
Why doesn’t Rectivas supply polyurethane foam flame retardants?
Foam FR additives are liquid components measured directly into the isocyanate/polyol reaction — a different supply chain from compounding flame retardant into solid thermoplastic resin, which is our business. We do supply the ATH/mineral filler family used in rigid foam, and the full flame retardant system for TPU, a genuinely different (thermoplastic) material sometimes confused with PU foam.
—— Rectivas Materials 团队 技术工程师老陈