People used asbestos and halogenated chemicals for fire protection through much of the twentieth century. After decades of heavy use and affordability, researchers realized that these chemicals brought long-term health and environment problems that just wouldn’t go away. Around the turn of the millennium, halogen-free alternatives started to grab the market’s attention, with phosphorus-based compounds like Exolit AP422 stepping into the spotlight. Unlike its predecessors, Exolit AP422 came through persistent research on safer, more stable flame retardants. Developers at Clariant, mixing a passion for materials science with industry pressure for safer chemicals, landed on ammonium polyphosphate as a backbone for the new flame retardant. The product built a reputation for combining real safety gains with lower toxicity. No silver bullet, but it certainly put distance between the past and a better future for fire prevention in plastics, coatings, foams, and more.
The chemical name looks intimidating: ammonium polyphosphate, phase II. Nobody outside a lab or a factory says that, though. Most users call it Exolit AP422. It’s a solid, white powder — no fancy colors, no hidden surprises. In this form, it’s easy to transport and blend into polymers, coatings, or foams. What makes Exolit AP422 notable comes down to its stability and behavior when heat climbs fast: the salt won’t melt or break down suddenly, and it releases phosphoric acid at a temperature high enough to avoid complications under normal usage but soon enough to protect when flames start licking at the surface.
Anyone handling Exolit AP422 gets used to its low solubility — it doesn’t dissolve much in water. The powder boasts a decomposition temperature above 275°C and keeps its shape right up to ignition points of most plastics where it gets used. With polymerization, the phosphate chain length boosts insulation properties, forming a char barrier once heat cranks up. Dustiness can be a concern for workers (it’s a powder, after all), but the fine particle size helps it distribute straightforwardly through the host material. What this means for end use: the flame retardant protects without changing texture or strength if blended well. The pH runs around 5.5 to 7 in water, avoiding unnecessary acid or base hazard in day-to-day handling.
Bags of Exolit AP422 show batch numbers, hazard pictograms, and full compliance labelling for REACH, RoHS, and many state-level regulations. Spec sheets list nitrogen content around 14% and phosphorus content about 31%. Preparation doesn’t take exotic chemicals or high-risk solvents. Manufacturers run a reaction of phosphoric acid and ammonia under heat, driving off water, building polymer chains, then chilling the slurry to crystallize the white powder. Proper drying protects the chemical from clumping, a factor in storage and mixing on factory floors. Material safety data sheets spell out every step for responsible use, from eye protection and respiratory masks for workers to recommended storage temperature and humidity.
Exolit AP422 steps up in fire safety because of its dramatic transformation during combustion. Under intense heat, the ammonium polyphosphate forms a thin glassy char, thanks to phosphoric acid release, sticking to surfaces and blocking oxygen. This keeps combustible vapors from escaping and starves the fire. Scientists keep playing with the molecule, grafting on silanes or tweaking polymer chain lengths. The aim: better compatibility with different plastics, stronger bonds, or improved weather resistance. These modifications might seem minor on paper but can change the fate of a cable or building panel in a fire.
Outside the official product name, it gets sold under technical aliases like “ammonium polyphosphate II,” “APP II,” or “APP phase II.” Some suppliers use their own brand variations, but most fire safety professionals recognize Exolit AP422 as the market leader, especially in Europe and North America.
Factories and laboratories rely on international standards to steer safe handling and storage. The powder can produce dust and slight irritation if mishandled. Gloves, goggles, and dust masks cut exposure to a minimum. Guidelines require spill containment systems, ventilation, and routine inspection of storage areas to prevent unexpected moisture contact or fire risk — it won’t start a fire, but the packaging or accidental powders in the air could pose an unrelated hazard. Regulatory frameworks like REACH and global GHS provide structure for labelling and safe transit. In my experience, keeping clear separation between food and chemical storage avoids plenty of headaches later.
Exolit AP422 turns up everywhere someone needs to slow fire without relying on environmentally tough chemicals. You’ll catch it in cable insulation, circuit boards, construction panels, ceiling tiles, and mass transit interior components. It gets praise for working inside both intumescent paints (coatings that bubble to protect steel beams during fires) and rigid polyurethane foams used in furniture. Electronics makers like its low impact on material properties, meaning a phone case or monitor housing stays durable even with fire resistance built in. In all these places, the basic goal remains: buy critical escape time or preserve life and property from sudden ignition.
Over the last ten years, research on Exolit AP422 keeps shifting to new ideas — better dispersal in biopolymers, upgrades to char-forming ability, and ways to make it compatible with recycled materials. We see ongoing work optimizing particle surface treatment, using organic modifiers or nanoclays to help it blend smoothly into cutting-edge plastics. Scientists test new synergies: mixing APP with melamine compounds, zinc borate, or polyols. Some studies drive down smoke generation, others boost UV resistance or moisture stability. These strategies offer a future with smarter, safer, and more sustainable building and electronics products.
Safety claims carry weight only if tested again and again. Lab animal testing, cell studies, and eco-toxicology screenings suggest Exolit AP422 does not bioaccumulate and offers far lower toxicity compared to halogenated flame retardants. That said, workers still face risk with bulk powders, mostly from inhalation or eye contact. Waste disposal and run-off management remain real-world headaches, since any phosphorus-based product influences water chemistry if handled poorly. Watching for low-level chronic exposure, especially among workers, deserves close attention. Transparent reporting of all toxicity data keeps both industry users and the wider public better informed.
The future of Exolit AP422 depends on stronger safety rules, greener chemistry demands, and ongoing fire tragedies that put a spotlight on better protection. One of the biggest challenges comes from the circular economy: getting flame retardants that fit with recycling practices instead of causing breakdown or poisoning the loop. The demand for more bio-based, low-carbon footprints also impacts development. With regions outlawing older brominated flame retardants, attention and funding stay locked on upgrades to APP II chemistry. Research teams worldwide eye hybrids, smarter surface treatment, and nanotechnology to give builders, manufacturers, and fire professionals what they push for: honest-to-goodness safety gains without trading off other values we can’t afford to lose. Real progress will mean not just better products, but smarter systems, from product design through end-of-life treatment, with no corners cut along the way.
Exolit AP422 sounds like a fancy name, but really, it’s a tool chemists use to keep things from catching fire. It’s a powder loaded up with phosphorus compounds. And in the hands of manufacturers, it turns regular plastics or foams into materials less likely to burn or smoke heavily. You’ll find it in stuff all around the house—cushions, electrical appliances, even in wires running behind your walls.
I once helped my dad tear out old insulation from an attic after a small electrical fire. Melted plastic made a mess all over the support beams. Volunteers from the fire department said things might have gone worse if the foam hadn’t been treated. That moment made it real: when synthetic materials catch fire, the clock starts ticking fast.
Statistics give this a stark edge. The National Fire Protection Association tallies hundreds of thousands of home fires every year in the US, with electrical failures and malfunctioning devices as frequent spark points. Items made from plastics and PU foams—mattresses, cables, even car seats—burn hot and fast. Extra protection helps slow the spread, and Exolit AP422 taps into that need.
Imagine you’re making foam for seat cushions. You add Exolit AP422 straight into the mix, turning a flammable material into something much safer. If there’s ever a spark, the phosphorus triggers a sort of chemical “crust” on the surface of the foam. This layer blocks heat and stops oxygen from feeding the flames. Less smoke, less damage, fewer toxic gases. That’s a big deal for first responders and families caught in a fire. Some electrical cables get a dose too, so a short-circuit doesn’t become a disaster before anyone knows what happened.
One thing I’ve learned while working in both schools and tech offices is that safety upgrades also raise questions about side effects. People want safer products, but no one likes the idea of toxic chemicals around children or pets. Thankfully, Exolit AP422 stands out because it skips chlorine and bromine—two elements with a nasty reputation for toxic fumes and environmental pollution. Instead, it leans on phosphorus, which breaks down more cleanly and doesn’t hang around in the environment. REACH, the tough European chemical rulebook, gives it the green light. Mothers and builders worry less about what’s leaching out of foam or offgassing from new appliances.
Some folks in the industry push for less dependence on any fire retardant. They advocate smarter product design—secure wiring, well-vented electronics, and stricter codes. Others chase after green chemistry, hoping for fire protection from plant-based or mineral formulas. Product recalls remind us that shortcuts create dangers, so knowing what you’re putting into a home or office matters more than ever.
Phosphorus-based solutions like Exolit AP422 keep a lot of nightmares at bay, but manufacturers and standards bodies still hold the keys to safer living spaces. Every time safer fire protection nudges out older, dirtier chemicals, people get a little more breathing room if disaster strikes.
Exolit AP422 stands out as a flame retardant with a solid track record across industries dealing with plastics, coatings, and electronics. Its white, powdery form looks almost unassuming, yet it’s packed with features that make life easier for manufacturers and offer a layer of safety for end-users. Years ago, I walked through a plastics plant for an article, and folks there wouldn’t stop talking about how this additive had smoothed out their production headaches when fire standards grew stricter. It stuck with me because the benefits came straight from people on the line, not some sales sheet.
Plenty of flame retardants out there can get a bad rap—mainly ones relying on halogen chemicals. Exolit AP422 doesn’t follow that old script. It’s based on ammonium polyphosphate, which skips over toxic legacy additives. Instead of loading up the air and soil with stubborn pollution, it releases mostly harmless byproducts when exposed to fire. Regulatory agencies in both Europe and North America keep tightening screws on what goes into everyday goods, particularly anything touching kids or food. I’ve lost count of the news stories about recalls driven by chemical safety concerns. Products using Exolit AP422 tend to skirt this problem.
There’s real value in a flame retardant that can take the heat—literally. Plastics often run through machines at high temperatures, sometimes pushing up to 300°C (around 570°F). Exolit AP422 doesn’t break down or turn into a sticky mess under these conditions. That’s a big deal for factories. Melted wires and ruined batches waste both time and money. Because this additive stays stable, manufacturers don’t risk churning out subpar products or damaging expensive equipment. I remember a project where technicians pointed out the nasty cleanup from older additives; AP422 cut that frustration nearly overnight.
All the test results in controlled environments mean little if a flame retardant can’t hold up in real-life chaos. Exolit AP422 doesn’t just slow down flames; it works through intumescence—a fancy way of saying it swells and forms a char barrier when heated. In practice, that barrier buys extra moments in an emergency, letting people get clear and giving fire crews a fighting chance. Europe’s strict fire safety codes in train interiors, cable covers, and building panels pushed companies toward this additive years ago. Each time a piece using Exolit AP422 does its job out there, people get another day with one less reason to worry.
No one wants to deal with additives that mess with a material’s texture or processability. Exolit AP422’s fine particle size lets it blend smoothly into mixtures. Finished plastics and coatings don’t end up overloaded with grit or off-colors—a simple thing, but it’s huge on a busy floor that has quotas and deadlines. The stuff also resists clumping during storage, so it keeps its shelf life longer, staying reliable every step of the way from warehouse to shop floor.
There’s always a bit of tension between safety, cost, and usability. While some next-generation retardants have struggled to keep up, Exolit AP422 strikes a balance. It delivers strong fire protection at doses that don’t weigh down budgets or add steps to production. Even during lean periods, I’ve seen companies refuse to cut corners here, recognizing that the cost of a single accident dwarfs the investment in safer chemistry.
The future keeps moving toward better, safer materials. Exolit AP422 isn’t perfect—nothing is—but its blend of fire safety, low toxicity, and process simplicity means it continues to show up in new products each year. Every time someone innovates with it, we get a little closer to a world where fire hazards do less harm, and businesses can count on consistent, regulatory-friendly performance without over-complicating life on the line.
Anyone working in plastics or flame-retardant materials has likely run into the big shift away from halogenated additives. Halogens like chlorine and bromine have been the backbone of fire resistance for decades, but they leave behind toxic smoke, stubborn residues, and long-term environmental headaches. People want alternatives, especially as regulations keep getting tighter around the world.
Exolit AP422 often comes up in these conversations. The name pops up in data sheets, project specs, safety audits—just about anywhere companies want plastics that won’t burn quickly and won’t leave a mess behind. Clarity matters: Is Exolit AP422 halogen-free? Yes, it is. This isn’t marketing fluff. The chemistry behind AP422 steers clear of the chlorine and bromine compounds you’d see in the old guard fire retardants. You’re looking at an ammonium polyphosphate base—phosphorus in, halogens out.
My own jobs in plastics processing showed me one thing above all: people obsess about halogen-free status for good reason. I remember unpacking sample sheets from suppliers, running burn tests, and seeing what happened when wires or enclosures using old-style brominated flame retardants caught fire. Smoke would cloud up quick, with a sharp, choking smell and terrible residue. Designers and end users deal with that mess in the real world, turning even a small electronics fire into a huge cleanup.
Switching to true halogen-free fire retardants like Exolit AP422 can feel like night and day. The smoke clears faster, the toxic fumes aren’t nearly as bad, and the environmental impact slips way down. Some people focus on the European RoHS directive or California’s Proposition 65, but this isn’t just about laws or labels. Living standards count, too. In schools, homes, and transit systems, cutting those harmful gases translates to healthier air after accidents.
It’s easy to get skeptical about “green” or “safe” alternatives actually working in harsh conditions. I’ve watched teams test cables and connectors, yanking them through heat cycles, bending them up, and then blasting them with flame. In the early days, halogen-free options used to let people down—too much dripping, weak after aging, color issues, price hikes. The story changed with advanced formulations like AP422.
This stuff manages to limit flame spread and reduce smoke without the old tradeoffs. It uses phosphorus as its backbone, so what you end up with is a char layer when things do go wrong instead of a toxic cloud and sticky residue. You can see the results for yourself in standardized tests—UL 94 ratings and the like. It gets used not just in cheap packaging but in automotive parts, trains, and high-rise building materials, where performance can’t take a back seat.
Some folks get stuck thinking the only path forward is swapping every chemical out for a natural one, but that’s rarely workable at scale. Materials like AP422 prove you can split the difference—ditch the worst offenders like halogens without losing out on safety. For folks designing consumer goods, circuit boards, or structural plastics, picking a halogen-free fire retardant isn’t just about ticking a box on a spec sheet. It’s about making sure that the safety story holds up both in tests and in real-life accidents.
The more we push for sustainable solutions that actually work, the better outcomes we get across the board—for users, workers, and the environments we all share. Exolit AP422 stands out as one of those rare “greener” choices that won’t let performance slip through our fingers.
Exolit AP422 gets a lot of attention for a good reason. This flame retardant works without boosting smoke or dumping toxic gases into the air. You’re talking about a chemical developed for real-life fire safety in plastics that end up right in the hands and homes of people everywhere.
Look at the inside of a car or the casing of household appliances and you’ll spot parts made from polypropylene. Now, most people think plastic burns easily. That’s true unless you mix in something like Exolit AP422. It bakes into the resin, keeps up the toughness, and lets makers skip chlorine or bromine, which always sparked health debates. I’ve worked with manufacturers who switched to AP422 to hit strict flammability codes without messing with mechanical properties or worrying about dioxins.
Cables, connectors, and switches crowd the electrical racks in factories I’ve toured. Most of those need consistent dimensions and strength under heat. Polyamides, especially PA6 and PA66, show up everywhere in these places because they won’t melt easily. Still, push them to high temperatures and you start worrying. Exolit AP422 steps in as a fire break, sidestepping all the hazards tied to old-school halogen options. Products stuff these compounds into wall sockets, tool housings, and circuit breakers so fire risk drops while reliability sticks around.
Flexible foams cushion car seats and beds. Rigid polyurethane insulates fridges and buildings. Both forms share one problem—they burn fast. Adding Exolit AP422 can be tricky, though, since it needs solid mixing procedures, and costs matter in huge production batches. People often hunt for the right balance: strong fire protection, stable material feel, and no greasy residue after months on the shelf. The companies that figure this out keep their recipes close.
Look at polyester in car under-the-hood bits and appliance frames and you’ll spot that same demand: don’t ignite, don’t lose structure, don’t threaten health. Exolit AP422 sinks right into PET or PBT. In my time working with processing teams, it’s clear—it doesn’t just stop fires, it doesn’t color plastics weirdly or make them brittle. This solves problems for parts that snap together and stay under stress.
People want safer, longer-lasting plastics for cars, electronics, and even everyday chargers. Exolit AP422 isn’t a silver bullet but it does more than chemicals from decades ago. If regulators keep pushing for non-halogenated choices, demand for this kind of technology will only get stronger.
Recycling complicates things—a flame retardant that plays nice in virgin resin may make things messy in recycled streams. More work from chemists and recyclers will set the next big leap. For now, picking Exolit AP422 in your product’s bill of materials can mean fewer trade-offs between safety, chemistry, and usability. And in my view, steering industrial change like this takes more than just rules—it runs on real-world testing and a willingness to invest early, even when the spreadsheet says wait.
Working with Exolit AP422 isn’t quite like tossing flour into a cake mix. Unlike other additives, this flame retardant asks for a decent amount of attention—and a little patience. Anyone who's ever spent a hot afternoon tending a plastic extrusion line knows how critical the processing window becomes for additives like this. If the setup isn’t just right, you can wind up with chunks or, even worse, gassing issues that mess with your final product. Experience teaches quick: it pays to mind the details.
Every plastics processor I’ve met has a horror story about their filler breaking down in the melt. Exolit AP422, being an ammonium polyphosphate, holds up well, but keep things around 200°C whenever possible. Too much heat above 240°C, especially for extended runs, often leads straight to decomposition—then you’re dealing with bubbles, grit, and a property drop that nobody wants to explain to a customer. I’ve run batches that barely edged over this limit and saw the difference in surface finish the moment we let standards slip.
Humidity creeps into everything. Exolit AP422 acts like a sponge, so it pulls water right out of the air. If you ever jammed a humid sack of flame retardant into the hopper, you know the result: steam on the extruder, clumping, then a surprise in your melt pressure. People in the trade often dry the stuff below 100°C for a couple of hours—sometimes even less, if you’ve stored it decently. You get far fewer surprises that way, trust me.
Feeders love consistency, but Exolit clings and bridges if you let it sit. Vibration or forced feeding setups help a great deal. We once tried to shortcut this by dumping straight in at high rates and promptly spent an hour unclogging the line. Better to run at a steady pace, monitor the feed, and pay attention to flowability. High-shear mixing works well for dispersing it in polyolefins, and twin-screw extruders seem to do best—easy enough to check for yourself by pulling a sample at the die and cutting it open.
Dust from Exolit can get airborne pretty quickly, and not everyone enjoys wheezing after a shift. Wearing masks and keeping extraction on around the feeding point becomes second nature after a couple of dusty mornings. Keeping the workspace swept and unloading gently instead of dumping helps too. A clean work area not only keeps health risks down, but equipment runs longer without grit chewing up the feed screws.
If you spend enough time on the line, you spot the weak links. It’d help if bagged material included detailed reminders about pre-drying, moisture pickup, or even batch-specific best temperatures. Early warning alarms on feeders save a lot of product from being wasted. Some plants already use local hoppers with built-in dryers—worth the investment for anyone running big batches. Talking to suppliers and comparing notes across the company also uncovers tricks for smoother processing, and small changes often lead to fewer headaches and better results.
| Names | |
| Preferred IUPAC name | Ammonium polyphosphate |
| Other names |
Ammonium Polyphosphate APP Exolit AP 422 |
| Pronunciation | /ˈfleɪm rɪˈtɑːd(ə)nts ˈɛksəˌlɪt ˌeɪ piː fɔː ˈtuː/ |
| Identifiers | |
| CAS Number | 94516-09-3 |
| Beilstein Reference | 104937-15-7 |
| ChEBI | CHEBI:86462 |
| ChEMBL | CHEMBL1909017 |
| ChemSpider | 31241892 |
| DrugBank | DB11362 |
| ECHA InfoCard | 03a587da-d68d-448b-adaf-6d893c1516d4 |
| EC Number | 01-2119486772-26-0000 |
| Gmelin Reference | 146502 |
| KEGG | C16818 |
| MeSH | D05.385.385.175.250.300. |
| PubChem CID | 145896313 |
| RTECS number | WX8900000 |
| UNII | 7L3JQ04H55 |
| UN number | UN3077 |
| CompTox Dashboard (EPA) | DTXSID7020736 |
| Properties | |
| Chemical formula | (NH4PO3)n |
| Molar mass | 132.00 g/mol |
| Appearance | White powder |
| Odor | Odourless |
| Density | 1.3 g/cm³ |
| Solubility in water | insoluble |
| log P | 2.8 |
| Vapor pressure | <0.01 hPa (20 °C) |
| Acidity (pKa) | 13.2 |
| Basicity (pKb) | 8.0 |
| Magnetic susceptibility (χ) | <0 |
| Refractive index (nD) | 1.70 |
| Dipole moment | 1.44 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 15 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -258.5 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -5916 kJ/mol |
| Hazards | |
| GHS labelling | GHS labelling of product Flame Retardants Exolit AP422: "GHS05, Danger, Causes serious eye damage. |
| Pictograms | GHS07,GHS08 |
| Signal word | Warning |
| Hazard statements | H317: May cause an allergic skin reaction. |
| Precautionary statements | P261, P264, P272, P273, P280, P302+P352, P305+P351+P338, P362+P364 |
| NFPA 704 (fire diamond) | 1-0-0 |
| Flash point | > > 250 °C |
| Autoignition temperature | > 470 °C |
| Lethal dose or concentration | LD50 (oral, rat): > 2000 mg/kg |
| LD50 (median dose) | > 10,000 mg/kg (rat, oral) |
| PEL (Permissible) | PEL (Permissible): Not established |
| REL (Recommended) | 1,000 – 4,000 |
| Related compounds | |
| Related compounds |
Exolit AP422 EG Exolit AP423 Exolit AP452 Exolit AP462 Exolit AP 750 Exolit AP 760 |
