The high-temperature member of the nitrogen family: melamine polyphosphate survives glass-filled PA66 and PBT processing where melamine cyanurate cannot, and pairs with phosphinates to form the standard halogen-free V-0 package for connectors and electronics parts. Supplied as fine powder, alone or in pre-balanced phosphinate packages.
Fig. MPP01 — fine white powder at incoming QCMPP powder checked for particle size and moisture before formulation.
MPP is the salt of melamine and polyphosphoric acid — nitrogen and phosphorus bound into one thermally rugged molecule that stays intact past ~350 °C. That number is the whole story: it is what lets MPP ride through PA66 processing at 280–300 °C, the zone where most other nitrogen and intumescent chemistry decomposes in the barrel.
Glass fibers wick flame along a burning part like a candle wick, defeating additives that work in unfilled resin. The phosphinate-MPP pair is the industry’s standard halogen-free answer in GF-PA66 and GF-PBT.
MPP rarely works alone in engineering plastics — and phosphinates work measurably better with it. The ~2:1 DEPAL:MPP ratio is one of the best-documented synergies in halogen-free flame retardancy.
In intumescent terms MPP is acid source and blowing agent in one molecule — the option formulators reach for when an APP-based system can’t take the processing temperature.
Both halves of the salt earn their place: the polyphosphate half builds char in the condensed phase while the melamine half dilutes the flame in the gas phase.
On decomposition the polyphosphate releases phosphoric acid species that catalyze crosslinking and char formation — a protective barrier over the polymer and around the glass fibers.
The melamine fraction releases inert nitrogen gases and absorbs heat through its own endothermic breakdown and vaporization, thinning the fuel/oxygen mix below the flame.
Combined with DEPAL-type phosphinates, aluminum phosphate structures reinforce the char while gas-phase phosphorus and nitrogen work the flame — more rating per percent than either component alone.
Its home ground is glass-filled electronics polyamides — with honest signposts to the neighboring chemistries where they fit better.
| Application | Partner System | Typical Package | What It Delivers | Related Page |
|---|---|---|---|---|
| GF-PA66 connectors & E&E parts | DEPAL-type phosphinate | ~2:1 phosphinate:MPP, 15–20% total | Halogen-free V-0 at 0.4–0.8 mm; glow wire; CTI | Flame retardant nylon |
| GF-PBT connectors & bobbins | Phosphinate systems | Ratio tuned per wall thickness | Halogen-free V-0; electrical property retention | FR PBT guide |
| Unfilled PA6/PA66 housings | — (different chemistry wins) | MC at 5–15% instead | In unfilled nylon, melamine cyanurate is the economical answer | Melamine cyanurate |
| PP and general intumescent systems | — (different chemistry wins) | APP-based systems instead | Below ~250°C processing, APP intumescents are more economical | Ammonium polyphosphate |
| High-temp coatings, TPU & elastomers | Char formers, phosphinates | System-dependent | Intumescent action where APP can’t take the heat | — |
Two melamine salts, two different jobs. Picking the wrong one is the most common formulation error we see in polyamide RFQs.
The resin is glass-filled, the walls are thin, or the processing is hot.
The resin is unfilled and cost per part is the driver.
The phosphinate ratio, the total loading and the grade’s thermal stability are engineered to the part — resin, fill level, wall and test stack together.
Mostly as the engineered half of a package: the phosphinate ratio and loading are set against your part’s test stack and verified in our burn lab before quotation.
Fig. MPP02 — burn verification in our labEvery package ratio is burn-tested before we quote it.
Fig. MPP03 — export packagingBags, big bags and palletized supply for overseas buyers.Direct answers for formulators and procurement evaluating melamine polyphosphate before sampling.
Primarily as the synergist half of phosphinate packages in glass-filled PA66 and PBT — the standard halogen-free route to UL94 V-0 connectors and E&E parts — and as a high-temperature nitrogen-phosphorus source in intumescent systems that run too hot for APP.
Unfilled nylon: melamine cyanurate, cheaper and sufficient. Glass-filled nylon or PBT: MPP with a phosphinate — the fibers defeat MC’s mechanism, and MPP’s thermal stability survives the hotter processing. Fill level is the deciding line.
Around 2:1 phosphinate:MPP at 15–20% total loading is the well-documented starting point for V-0 in GF-PA66. The optimum shifts with wall thickness, fill level and the glow-wire clause, which is why we ladder the ratio on your resin and burn-test before quoting.
MPP is markedly less corrosive than red phosphorus and less water-soluble than APP, and it does not bloom the way small-molecule additives do. Standard precautions still apply: keep it dry, respect the ~350 °C stability ceiling, and verify color stability if the part is bright white.
Tell us the resin, glass-fill level, wall thickness at the test point and the full test stack — UL94, glow wire, CTI. We will design the phosphinate-MPP ratio and prove it in our burn lab before you commit a trial.